JP6841695B2 - Improved manufacturing method for laminated molds - Google Patents

Description

The present invention relates to an improved method for manufacturing a laminated mold, in particular, forming a thin sand layer, repeatedly curing the thin sand layer one by one into a predetermined shape, and laminating a plurality of the formed sand layers. It relates to a method of manufacturing a target three-dimensional sand mold by integrating them.

In recent years, laminating molding technology using a three-dimensional printing method has been actively researched and put into practical use. In addition, by applying such laminating molding technology to mold molding, trial production of molds and production of molds for high-mix low-volume production are being studied all over the world, and among them, laminating by laser method or inkjet method. A method for forming a mold has been proposed. Among these laser methods and inkjet methods, the inkjet method manufacturing apparatus has an advantage that the apparatus is cheaper than the laser type.

By the way, as a conventional method for laminating molds by a laser method, for example, a method for forming a sand mold by a laminating method as clarified in Japanese Patent Application Laid-Open No. 9-168840 (Patent Document 1) has been proposed. ing. Then, in that method, a sand layer forming step of spraying resin-coated sand (resin coated sand) to form a thin sand layer and a curing step of curing a predetermined portion of the thinly stratified sand layer by irradiation with a laser are performed. Including, thereby forming one layer of the sand mold, and repeating these steps in sequence, the hardened sand layers corresponding to each cross-sectional shape of the target sand mold are sequentially laminated, and the sand is formed in a three-dimensional shape. It is designed to form a certain sand mold.

However, in the method of forming a sand mold by such a laser laminating method, the resin-coated sand is heat-cured by heating by laser irradiation, so that when heating by laser irradiation is performed. In addition, there is an inherent problem that the odor of organic substances is generated. 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 be generated, and there is a problem that the sand mold is warped or distorted when stored for a long period of time. Furthermore, in order to irradiate a predetermined part with a laser and cure it by heating, high output and precise control are required, an expensive laser irradiation device is required, and a very large amount of energy is required for heating. There is also an inherent problem of becoming.

On the other hand, as a method for laminating molds by an inkjet 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 the layer forming are performed. A production step of forming a layer having a product produced by dissolving the three-dimensional modeling powder in the modeling liquid by ejecting a modeling liquid using water as a solvent into the layer formed in the step from an inkjet head. The manufacturing method of the three-dimensional model to be provided has been clarified.

Then, there, a thickening wetting agent that suppresses the evaporation of water and thickens the modeling liquid and a surfactant are contained in the modeling liquid to be used, and the pH is further adjusted to 7 to 9. It is said that the target three-dimensional model can be formed according to the desired shape. However, when the modeling solution is discharged from the inkjet head onto the three-dimensional model powder, the three-dimensional model powder is produced. There is a problem that bleeding of the modeling liquid occurs in the layer of the three-dimensional modeling powder during dissolution. Then, in the case of laminated modeling with such bleeding occurring, the contour portion of the obtained modeled object becomes uneven and the dimensional accuracy deteriorates. In particular, FIG. 7 shows. When the spraying range of the modeling liquid is wider in the upper layer than in the lower layer, as in the case of obtaining the target mortar-shaped model 2 shown, the modeling liquid sprayed on the upper layer soaks into the lower layer. For the sake of ease, the obtained laminated product 4 has a problem of changing the shape of the model as shown in the drawing.

Japanese Unexamined Patent Publication No. 9-168840 Japanese Unexamined Patent Publication No. 2011-230421

Here, the present invention has been made against the background of such circumstances, and the problem to be solved thereof is the bleeding of the spray liquid at the time of forming the two-dimensional pattern of each sand layer at the time of laminated molding. It is an object of the present invention to provide an improved manufacturing method of a laminated mold capable of advantageously suppressing or preventing the above, and another problem is deterioration, deformation, and dimensional accuracy of the shape of the obtained laminated mold. It is an object of the present invention to provide an improved method for producing a laminated mold, which can advantageously suppress or prevent the deterioration of the laminated mold.

Under such circumstances, as a result of diligent studies on the laminated molding method by the present inventors, as casting sand, a coated sand formed by coating a refractory aggregate with a coating layer containing water glass and a moisturizing agent is used. The present invention has been completed by finding that the above-mentioned problems can be solved by solidifying or curing the formed mold layer by spraying and heating an aqueous medium.

The present invention can be preferably carried out in various aspects as listed below in order to solve the above-mentioned problems. Each aspect described below can be adopted in any combination, and the aspect or technical feature of the present invention is not limited to those described below, and the description and drawings of the entire specification are not limited to those described below. It should be understood that it is recognized based on the invention idea described in.

(1) A thin sand layer is formed using a coated sand formed by coating a refractory aggregate with a binder, and then a solidified layer having a predetermined two-dimensional pattern is formed by spraying an aqueous medium on the sand layer and heating the sand layer. In a method of producing a laminated mold having a three-dimensional shape of interest by repeating the work of forming the hardened layer and laminating the solidified layer or the hardened layer, the surface of the refractory aggregate is used as the coated sand. An improved method for producing a laminated mold, which comprises using a dry coated sand obtained by forming a coating layer containing a moisturizing agent together with water glass as a binder.
(2) The above-described aspect (1), wherein the moisturizing agent is selected from the group consisting of polyhydric alcohols, water-soluble polymer compounds, hydrocarbons, saccharides, proteins and inorganic compounds. Improved manufacturing method of laminated molds.
(3) The aspect (3), wherein the content of the moisturizer is 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 coated sand.
1) Or the improved manufacturing method of the laminated mold according to the above aspect (2).
(4) The improved manufacturing method of the laminated mold according to any one of the above-described aspects (1) to (3), wherein the aqueous medium contains a moisturizer.
(5) The laminated mold according to the above aspect (4), wherein the aqueous medium further contains at least one of a curing accelerator, a surfactant, a drying accelerator and a preservative. Improved manufacturing method.
(6) In any one of the above-described aspects (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. An improved method of manufacturing the described laminate mold.
(7) Improved production of the laminated mold according to any one of the above aspects (1) to (6), wherein the coated sand further contains a lubricant on its surface. Method.
(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 the water glass in the coated sand. ) To the improved manufacturing method of the laminated mold according to any one of the above aspects (7).
(9) The layer according to any one of the above-described aspects (1) to (8), wherein the water content in the coated sand is 5 to 55% by mass of the solid content of the water glass. An improved method of making molds.
(10) The laminated casting according to any one of the above-described aspects (1) to (9), wherein the spraying of the aqueous medium on the sand layer is performed using an inkjet spraying device. Improved mold manufacturing method

According to such an improved manufacturing method of the laminated mold according to the present invention, various effects listed below can be achieved.
(A) Since the coated sand has good water retention when wet with water, the bleeding of the aqueous medium sprayed on the sand layer can be effectively suppressed or prevented.
(B) It is possible to advantageously obtain a laminated mold having excellent dimensional accuracy by suppressing deterioration and deformation of the shape of the mold obtained by the laminated molding.
(C) A sufficient amount of the aqueous medium for developing the strength can be sprayed on the sand layer without worrying about the permeation of the sprayed aqueous medium.
(D) When molding a large laminated mold, the spraying range of the aqueous medium sprayed on the sand layer is widened, but because the sand layer has good water retention, drying due to a time lag in the spraying area can be satisfactorily prevented. Molding unevenness can be suppressed.

It is a schematic explanatory drawing which shows the 1st step adopted in the example of the manufacturing method of the laminated mold according to this invention, (a) is the state which coated sand is sprayed, (b) is the plane of the sprayed coated sand. The expanded state is shown respectively. It is a schematic explanatory drawing which shows the 2nd step adopted in the example of the manufacturing method of the laminated mold according to this invention. It is a schematic explanatory drawing which shows the 3rd process adopted in the example of the manufacturing method of the laminated mold according to this invention. It is schematic explanatory drawing which shows the form after the process of 1 turn which consists of the process shown in FIGS. 1 to 3. FIG. It is a schematic explanatory drawing which shows the state which formed the laminated mold layer of a plurality of layers by repeating each step of the manufacturing method of the laminated mold according to this invention. It is schematic explanatory drawing which shows the laminated mold obtained in embodiment of the manufacturing method of the laminated mold according to this invention shown in FIGS. 1 to 5. It is a schematic explanatory drawing which shows an example of the sand mold (stacking mold) obtained by the conventional layered manufacturing method in comparison with the modeled product of a target shape.

Hereinafter, in order to clarify the configuration of the present invention more concretely, a typical embodiment of the present invention will be described in detail with reference to the drawings.

First, the coated sand (coated sand) used in the present invention is generally mixed with water glass in an aqueous solution as a binder with a refractory aggregate, and further mixed with a moisturizing agent, and the like. Water, which is a binder and is produced by evaporating water from the obtained mixture, in other words, by evaporating the water in water glass in an aqueous solution or the water brought in by a moisturizer. A dry coating layer containing a solid content of glass and a moisturizing agent is formed on the surface of the refractory aggregate at a predetermined thickness, and is in a dry state and has good room temperature fluidity. Is what you are doing.

Here, the "dry coated sand having normal temperature fluidity" in the present invention means a coated sand from which a measured value can be obtained when the dynamic angle of repose is measured regardless of the water content. This dynamic angle of repose means that the coated sand to be measured is housed in a cylinder (for example, 7.2 cm in diameter × 10 cm in height) in which one end in the axial direction is closed with a transparent plate material. Fill the container with coated sand up to half its volume), hold it so that the axis is horizontal, and rotate it around the horizontal axis at a constant speed (eg, 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 becomes flat. On the other hand, for example, in a wet state of the coated sand, the slope of the coated sand layer is not formed as a flat surface without flowing in the cylinder, and as a result, the dynamic angle of repose can be measured. Those that cannot be called wet coated sand.

The dry coated sand having room temperature fluidity according to the present invention has a water 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. It is desirable that the amount corresponds to the proportion of mass%, more preferably 10 to 50% by mass, and most preferably 20 to 50% by mass. When the water content in this coated sand becomes 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 at the time of molding. On the other hand, if the amount exceeds 55% by mass, the coated sand may not be in a dry state. The method for measuring the water content in the coated sand is not particularly limited, and a method according to the type of water glass, a moisturizer, or the like can be appropriately adopted. Specifically, the measurement 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 that have been conventionally used for a mold. Any kind of material can be used. Specifically, special sands such as alumina sand, olivine sand, zircon sand, and chromate sand, as well as ferrochrome slag and ferronickel slag, including silica sand and recycled silica sand, Examples thereof include slag-based particles such as rotary furnace slag; artificial particles such as alumina-based particles and murite-based particles and their regenerated particles; alumina balls, magnesia clinker and the like. It should be noted that these fire-resistant aggregates may be fresh sand, or recycled sand or recovered sand that has been used once or multiple times as casting sand for molding a mold, and further, such regeneration. There is no problem even if it is mixed sand made by adding new sand to sand or recovered sand and mixing them. Then, such a refractory aggregate is generally used as having a particle size of about 40 to 200 in AFS index, preferably about 50 to 150.

Further, in the coated sand used in the present invention, a binder containing water glass as a main component is used as the binder for coating the refractory aggregate as described above. Here, the water glass is a water-soluble silicic acid compound, and examples of such a silicic acid compound include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and silicic acid. Ammonium and the like can be mentioned, but among them, sodium silicate (sodium silicate) is particularly advantageously used in the present invention. Further, as the binder, as long as water glass is used as the main component, other known water-soluble binders such as thermosetting resins, sugars, proteins, synthetic polymers, salts and inorganic polymers are used in combination. It is possible to do. When such another water-soluble binder is used in combination with water glass, the proportion of water glass in the entire binder is preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably 80% by mass or more. 90% or more mass.

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

In the present invention, sodium silicate, which constitutes water glass used as a binder, generally has a molar ratio of _{SiO 2} / Na _{2 O of 1.9 or more in order to obtain a dry coated sand advantageously.} It is preferably 2.0 or more, more preferably 2.1 or more, and in the above-mentioned classification of sodium silicate, sodium silicate corresponding to Nos. 1 and 2 is used particularly advantageously. Become. Such sodium silicate No. 1 and No. 2 respectively provide a dry coated sand having good characteristics and being stable even in a wide range of sodium silicate concentration in water glass. _{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 water glass in the form of an aqueous solution, but is generally 3.5 or less. It is 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 becomes low, and it becomes difficult to dry the coated sand unless the water content is considerably lowered. On the other hand, if it is larger than 3.5, the solubility in water may decrease, the adhesive area may not be increased, and the strength of the finally obtained mold may decrease.

Here, the water glass used in the present invention means a solution of a silicic acid compound in a state of being dissolved in water, and is used in the state of a stock solution as purchased on the market, or water in such a stock solution. It is also possible to add and use it in a diluted state. The non-volatile content (water glass component) obtained by removing volatile substances such as water and solvent from such water glass is called a solid content, which corresponds to the above-mentioned soluble silicic acid compound such as sodium silicate. To do. Further, the higher the proportion of such solid content (nonvolatile content), the higher the concentration of the silicic acid 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 undiluted solution when it is composed only of the undiluted solution, while the undiluted solution is converted into water. When a diluted solution obtained by diluting 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.

The solid content in such water glass will be set to an appropriate ratio depending on the type of the water glass component (soluble silicic acid compound) and the like, but is preferably a ratio of 20 to 50% by mass. It is desirable that it is contained in. By appropriately allowing the water glass component corresponding to this solid content to be present in the aqueous solution, the water glass component is evenly and uniformly applied to the refractory aggregate when mixed (kneaded) with the refractory aggregate. Can be coated, which makes it possible to advantageously form the desired mold. If the concentration of the water glass component in the water glass becomes too low and the total amount of solids is less than 20% by mass, the heating temperature is raised or the heating time is lengthened for drying the coated sand. Therefore, problems such as energy loss will be caused. In addition, if the proportion of solids in the water glass becomes too high, it becomes difficult to uniformly cover the surface of the refractory aggregate with the water glass component, which also causes a problem in improving the characteristics of the target mold. From the point of view, 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 therefore the water content is 50% by mass or more.

Further, in the present invention, the water glass as described above is used at a ratio of 0.1 to 5.0 parts by mass in terms of solid content when considering only the non-volatile content with respect to 100 parts by mass of the refractory aggregate. Among them, a ratio of 0.3 to 4.0 parts by mass is particularly advantageously adopted, and a predetermined coating layer is formed on the surface of the refractory aggregate. Here, the measurement of the solid content is carried out as follows. That is, 10 g of the sample was weighed and contained in an aluminum foil dish (length: 90 mm, width: 90 mm, height: 15 mm), placed on a heating plate held at 180 ± 1 ° C., and left for 20 minutes. The sample dish is inverted and left on the heating plate for another 20 minutes. Then, the sample dish is taken out from the heating plate, allowed to cool in a desiccator, weighed, and the solid content (mass%) is calculated by the following formula.
Solid content (mass%) = [mass after drying (g) / mass before drying (g)] × 100

If the amount of water glass used in the present invention is too small, it becomes difficult for a coating layer to be formed on the surface of the refractory aggregate, and it may be difficult for the coated sand to solidify or harden sufficiently during molding. is there. Further, even if the amount of water glass used is too large, an excess amount of water glass adheres to the surface of the refractory aggregate, making it difficult to form a uniform coating layer, and the coated sands adhere to each other. There is also a risk of agglomerating (composite particles), which adversely affects the physical properties of the final mold, and in addition, there is also the problem of making it difficult to remove sand from the core after casting the molten metal. May cause.

By the way, the coated sand used in the present invention has a great feature in that a moisturizer is further contained in the coating layer covering the surface of the refractory aggregate together with water glass. is there. By further impregnating the coating layer containing water glass with a moisturizer in this way, when the coated sand gets wet with water, water retention is satisfactorily performed based on its swelling property. Therefore, it is possible to effectively suppress or prevent the sprayed aqueous medium from exuding outside the sprayed range. Further, due to this water retention effect, it is possible to spray a sufficient amount of the aqueous medium on the sand layer without worrying about the permeation of the water-based medium to be sprayed, and also to care about the permeation of the water-based medium to be sprayed. There is an advantage that a sufficient amount of an aqueous medium for developing strength can be sprayed on the sand layer without using. In particular, when molding a large laminated mold, the range of the aqueous medium sprayed on the sand layer becomes wide, but since the water retention is good, drying due to the time difference of the spraying area can be prevented and molding unevenness can be suppressed. The characteristics are demonstrated.

Further, in the present invention, the amount of the moisturizing agent contained in the coating layer containing water glass is 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the 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. If the amount of the moisturizer contained is too small, the above-mentioned effects may not be enjoyed advantageously, while if the amount of the moisturizer is too large, blocking due to moisture absorption may occur. In addition, the improvement of the effect according to the amount used is not recognized, and it is not a good idea from the viewpoint of cost effectiveness. Examples of the moisturizer that can be used in the present invention include known moisturizers such as polyhydric alcohols, water-soluble polymers, hydrocarbons, saccharides, proteins, and inorganic compounds.

Specifically, polyhydric alcohols, which are one of these moisturizers, include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, propylene glycol, butylene glycol, and 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 Examples thereof include -octanediol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane and the like. The water-soluble polymer compound particularly refers to a compound having 5 to 25 alcoholic hydroxyl groups per 1000 molecular weight, and such water-soluble polymer compounds include polyvinyl alcohol and its above. Vinyl alcohol-based polymers such as various modified products; cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; starch derivatives such as alkyl starch, carboxylmethyl starch, and oxidized starch. ; Examples include water-absorbing polymers such as sodium polyacrylate. Further, examples of the hydrocarbons include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum ethers, petroleum benzyls, tetralins, decalins, tertiary amylbenzenes, dimethylnaphthalin and the like, and examples of saccharides include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum ethers, petroleum benzyls, tetralins, decalins, dimethylnaphthalins and the like. , Monosaccharides, oligosaccharides, polysaccharides such as dextrin, etc. Among them, monosaccharides are saccharides that are not decomposed into simpler saccharides by hydrolysis, and are preferably tricarbonate sugars (preferably tricarbonate sugars). It is a monosaccharide having 3 carbon atoms) to a dextrin sugar (monosaccharide having 10 carbon atoms), more preferably a hexacarbon sugar (monosaccharide having 6 carbon atoms). Examples of the protein include gelatin and the like. In addition, examples of the inorganic compound include salt, sodium sulfate, calcium chloride, magnesium chloride, silicate and the like. Then, these various moisturizers will be used alone or in combination of two or more.

Various conventionally known moisturizers include those that are water-soluble to those that are poorly water-soluble, but in the present invention, the viscosity increases when the moisturizer is put into water at room temperature (25 ° C.). Moisturizers with a low viscosity will be used advantageously. Specifically, in the case of a water-soluble moisturizer, a moisturizer in an amount corresponding to 20% of the mass of water is added to water at room temperature and stirred for 1 hour, and the viscosity of the solution after such stirring is 0. Moisturizers with 8-10 cP, preferably 0.8-5 cP, are advantageously used. On the other hand, a poorly water-soluble moisturizer exerts an effect as a moisturizer when dispersed in water. However, even a poorly water-soluble moisturizer can be added to water at room temperature to 20% of the mass of water. After adding a moisturizer in an amount corresponding to the above and stirring for 1 hour, the solution (mixture of water and moisturizer) after the stirring is filtered, and the viscosity of the obtained filtrate is within the above range. However, it can be used advantageously. Based on the above, examples of the moisturizing agent advantageously used in the present invention include cellulose derivatives such as glycerin and hydroxypropylmethylcellulose, water-absorbing polymers such as sodium polyacrylate, polysaccharides such as dextrin, and polyvinyl alcohol. Examples thereof include vinyl alcohol-based polymers and polyethylene glycol (polyethylene oxide) having a weight average molecular weight of 50,000 or more.

Further, in the coated sand used in the present invention, various additives can be appropriately contained in the coating layer in addition to the above-mentioned moisturizer, if necessary.

One such additive is a lubricant, and it is particularly desirable that such a lubricant be contained and present on the sand surface of the coated sand. In the present invention, since it is necessary to develop the coated sand thinly to a certain thickness in a plane to form a thin sand layer, it is desirable to add a lubricant in order to improve the fluidity of the coated sand. .. Further, since the lubricant has water repellency, when the aqueous medium is sprayed on the dry sand layer, the water repellency of the lubricant makes it difficult for the dry coated sand and the aqueous medium to become compatible with the conventional coated sand. The problem that it takes time for the aqueous medium to penetrate into the coated sand is likely to occur, but in the configuration of the present invention, the water repellency of the lubricant is suppressed by the water retention of the moisturizer, so that the flow of the coated sand It is possible to improve the property and the water retention at the same time.

As the lubricant used in the present invention, for example, waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; fatty acid amides such as stearic acid amide, oleic acid amide, and erucate amide; methylenebisstearic acid amide. , Alkylene fatty acid amides such as ethylene bisstearic acid amide; stearic acid, stearyl alcohol; stearic acid metal salts such as lead stearate, zinc stearate, calcium stearate, magnesium stearate; , Graphite, molybdenum disulfide, talc, mica, and the like. In particular, among these, calcium stearate and the like are preferably used.

The amount of the lubricant used as described above is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid content of the water glass in the coating layer, particularly 0.3 to 8 parts by mass. Parts are preferable, and 0.5 to 5 parts by mass is particularly preferable. If the amount of the lubricant contained is too small, the above-mentioned effects may not be enjoyed advantageously. On the other hand, if the amount of the lubricant is too large, the mold strength may decrease or the mold strength may decrease. Furthermore, it is not a good idea from the viewpoint of cost effectiveness.

Furthermore, as one of the above-mentioned additives, a surfactant can be mentioned. In the present invention, by impregnating the coating layer of the coated sand with a surfactant, the water permeability of the coated sand, in other words, the wettability of the coated sand to water can be effectively improved. Even when a small amount of water is sprayed, the entire coated sand sprayed can be advantageously moistened, resulting in a moist state. Thus, since the amount of water sprayed on the coated sand is suppressed to a small amount, the drying time in the subsequent drying operation can be shortened, which can contribute to the shortening of the molding time.

As such surfactants, various conventionally known surfactants such as cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, and silicone-based surfactants Any of these, fluorine-based surfactants, etc. can be used as long as the object of the present invention is not impaired. Here, the silicone-based surfactant refers to a surfactant having a siloxane structure as a non-polar moiety, and the fluorine-based surfactant refers to a surfactant having a perfluoroalkyl group. The content of the surfactant in the present invention is preferably 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, particularly 0.5. It is preferably ~ 15.0 parts by mass, and particularly preferably 0.75 to 12.5 parts by mass. If the amount of the surfactant used is too small, the above-mentioned effects may not be enjoyed advantageously. On the other hand, if the amount of the surfactant used is too large, the effect according to the amount used may not be enjoyed. No improvement is observed, and depending on the surfactant, the water glass may not solidify by drying and the coated sand may become wet, and further, it is not a good idea from the viewpoint of cost effectiveness.

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

The spherical particles used in the present invention may be spherical particles, and are not necessarily spherical particles. However, spherical particles having a sphericity of 0.5 or more are preferable. Those having a value of 0.7 or more, more preferably those having a value of 0.9 or more, are advantageously used. Here, the sphericity is the aspect ratio (minor axis / major axis ratio) obtained from the projected shape of 10 single particles randomly selected in the observation using a scanning electron microscope. It means the average value. The material constituting the spherical particles is not particularly limited, but advantageously, spherical particles such as silicon dioxide, aluminum oxide, and titanium oxide are preferably used.

Further, in the present invention, solid oxides and salts are also advantageously used as one of the additives to the coating layer. The moisture resistance of the coated sand can be advantageously improved by the inclusion of these solid oxides and salts. Among them, as the solid oxide, for example, the use of oxides of silicon, zinc, magnesium, aluminum, calcium, lead and boron is effective. In particular, among them, it is desirable to use silicon dioxide, zinc oxide, aluminum oxide, and boron oxide. Further, among silicon dioxide, precipitated silicic acid and exothermic silicic acid are preferably used. On the other hand, examples of salts include siliceous salts, silicates, phosphates, borates, tetraborates, carbonates, etc. Among them, zinc carbonate, basic zinc carbonate, potassium metaborate, tetraborate, etc. The use of sodium phosphate and potassium tetraborate is desirable. Then, these solid oxides and salts are generally used at a ratio of about 0.5 to 5% by mass with respect to the solid content in the water glass in the coating layer of the coated sand.

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

By the way, in producing the dry coated sand having room temperature fluidity used in the present invention, in general, water glass as a binder is used as a binder for refractory aggregates, and if necessary, a moisturizing agent is used. It is kneaded or mixed with the additives used and mixed uniformly so that the surface of the refractory aggregate is covered with water glass containing an additive such as a moisturizing agent, and such water is used. A method is adopted in which a coating layer containing an additive such as water glass or a moisturizing agent is formed on the surface of a refractory aggregate by evaporating the water content of the glass. In such a method, the evaporation of water in the coating layer needs to be carried out rapidly before the solidification or hardening of the water glass progresses. Therefore, the water glass in the form of an aqueous solution is used as opposed to the refractory aggregate. It is desirable to remove the water content within 5 minutes, more preferably within 3 minutes after adding (mixing) the mixture to obtain a dry powdered coated sand. If the evaporation time becomes long, the mixing (kneading) cycle becomes long, the productivity of the coated sand decreases, and the time that the water glass comes _{into contact with CO 2} in the air becomes long, causing problems such as deactivation. This is because the risk of occurrence increases.

Further, in the above-mentioned manufacturing process of coated sand, as one of the effective means for rapidly evaporating the water content in the water glass, the refractory aggregate is preheated, and water in the form of an aqueous solution is added. A method of kneading or mixing additives such as glass and a moisturizer to mix them is preferably adopted. By kneading or mixing water glass and additives with this preheated refractory aggregate, the moisture in the water glass can be very quickly removed by the heat of such refractory aggregate. Since it can be evaporated, the water content in the obtained coated sand can be effectively reduced, and a dry powder having room temperature fluidity can be advantageously obtained. is there. Further, in order to quickly evaporate the water content at this time, it is also effective to adopt a method of blowing hot air into the kneading container, a method of heating the kneading container, and a method of depressurizing the inside of the kneading container. Here, the preheating temperature of the refractory aggregate is appropriately selected according to the water content of the water glass, the blending amount thereof, and the like, but in general, a temperature of about 100 to 200 ° C. is preferable. A temperature of about 120 to 180 ° C. is adopted. If this preheating temperature is too low, it will not be possible to effectively evaporate the water and it will take time to dry. Therefore, it is desirable to adopt a temperature of 100 ° C. or higher, and the preheating temperature is high. If it is too high, the water glass component will harden when the obtained coated sand is cooled, and in addition, composite particle formation will proceed. Therefore, the function as a coated sand, especially the strength of the final obtained mold. It will cause problems with physical properties such as.

In the coated sand used in the present invention, a moisturizer contained in a coating layer containing water glass and other additives used as necessary, such as spherical particles and a surfactant, are previously added to water glass. It may be added to the refractory aggregate in a mixed state and kneaded, or it may be added and kneaded separately from the water glass at the time of kneading, and further, at the time of kneading, between the addition of the water glass. May be added with a time lag and kneaded. Therefore, the coating layer in the coated sand according to the present invention is, for example, in a state where the water glass and the additive such as a moisturizer are completely integrated, or from the surface of the refractory aggregate to the outside. The concentration of the solid content (nonvolatile content) of the above is gradually decreased or increased, while the concentration of the additive such as a moisturizer is gradually increased or decreased.

(Laminate modeling method)
By the way, the method for producing a laminated mold according to the present invention will be carried out using the coated sand obtained as described above, for example, as shown in FIGS. 1 to 6. That is, first, as shown in FIG. 1, in the mold molding apparatus used there, a rectangular table 12 slidable vertically in the vertical direction in a container-shaped frame 10 having a quadrangular planar shape is provided. Have been placed. Further, as shown in FIGS. 1 to 3, the modeling apparatus includes a storage tank 16 for supplying the coated sand 14 located above the frame 10, and a discharge tank 16 provided below the storage tank 16. The coated sand 14 supplied from the outlet 18 to the upper surface of the table 12 is thinly developed in a plane to a certain thickness to form a thin sand layer 20, and a predetermined liquid is sprayed on the sand layer 20 by an inkjet method. It is provided with an inkjet spraying device 26 as a selective spraying means for spraying on a site, and a heater 30 provided with a heating wire 32 as a heating element, and these are selectively selected according to each step of mold layer manufacturing. It is switched and placed.

There, the inkjet 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 the aqueous medium to be used can be sprayed. It has become. Further, a predetermined two-dimensional pattern (planar shape) of a predetermined mold layer 34 (see FIG. 5) formed in each sand layer 20 is stored in the storage device as an image signal, and the nozzle 28 is stored in the control device. It is possible to eject (spray) a predetermined aqueous medium in a predetermined planar shape (pattern) for each sand layer 20 while controlling the operation of the above in accordance with an image signal. Here, the equipment is automatically switched in each process, but of course, it is also possible to switch the equipment manually or semi-automatically.

Further, the heater 30 shown in FIG. 3 uses a heating wire 32 as a heating element so that it can be heated. As a heating element for such a heating wire 32, various known heating elements are used. Those can be appropriately selected and used. For example, in addition to metal heating elements (nichrome wire, cantal wire, platinum wire, etc.), silicon carbide, molybdenum dissilicate, lantern chromite, molybdenum, carbon, etc. are used. It is also possible to heat it. 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 be used.

In the above-described embodiment, the selective spraying means configured by the inkjet spraying device 26 is a device capable of selectively spraying a predetermined aqueous medium at a predetermined position on the sand layer 20. Therefore, an inkjet spraying device as illustrated is preferably used, but in addition, a mask is used so that a predetermined aqueous medium is sprayed only on a necessary portion of the sand layer 20. A type of spraying device or the like can also be appropriately adopted.

Then, as one method for manufacturing the target laminated mold according to the present invention using the above-mentioned apparatus, the following manufacturing procedure is adopted to manufacture the mold layer 34, and further, the mold layer is manufactured. By laminating and integrating 34, a three-dimensionally shaped laminated mold 36 (target mold) is formed.

<First process>
First, in the pre-manufacturing stage, 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 one layer of the sand layer 20. Next, the coated sand 14 stored in the storage tank 16 is supplied so as to be evenly distributed on the table 12 with a substantially uniform thickness while controlling the supply amount from the discharge port 18 [FIG. 1 (a). ) State]. At this time, the height of the sand layer 20 per layer is formed as a step corresponding to the distance that the table 12 slides downward, for example, a step of 0.3 mm. It should be noted that this step is formed so as to always have a uniform height for each layer to be laminated, and it is generally desirable that the step is about 0.1 to 3 mm.

Then, when the supply of the coated sand 14 onto the table 12 is completed, the extension 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. As a result, the sand layer 20 thinly and flatly developed on the table 12 is formed at a predetermined thickness [state of FIG. 1 (b)].

<Second process>
Then, as shown in FIG. 2, droplets, liquid or mist-like aqueous medium 22 is sprayed from the nozzle 28 of the inkjet spraying device 26 toward the sand layer 20 in a predetermined planar shape for each minute region. Will be done. Here, the defined planar shape is a shape obtained by horizontally dividing the shape of the manufactured mold into a plurality of regions at equal intervals corresponding to the wall thickness of the sand layer, depending on the mold to be manufactured. The aqueous medium 22 is sprayed on each sand layer in order from the bottom based on the planar shape of each layer. For example, by obtaining the shape data of the sand mold from the CAD data of the product shape and converting it into the cross-sectional shape data for each wall thickness of the sand layer, it is possible to set a predetermined planar shape of each layer. In the inkjet spraying device 26, the nozzle diameter of the nozzle 28 for injecting the aqueous medium 22 is, for example, about 20 to 100 μm, which is an extremely small diameter. However, since the liquid to be ejected is an aqueous medium, the nozzle It does not cause problems such as clogging.

By moistening the coated sand 14 with the aqueous medium 22 sprayed on the specific region of the sand layer 20 in this way, the water glass of the coating layer in the coated sand 14 is melted into the aqueous medium 22 and has fire resistance. It covers the aggregate and the water glass becomes agglomerated between the sand grains. At this time, when the coated sand 14 is wet with water, effective water retention is performed due to the swelling property based on the moisturizer existing in the coating layer, so that the water-based medium to be sprayed is in the spraying range. Exuding other than that can be effectively suppressed or prevented. Further, due to this water retention effect, there is an advantage that an aqueous medium in a sufficient amount for developing strength can be sprayed on the sand layer without worrying about the permeation of the water-based medium to be sprayed. In particular, when molding a large laminated mold, the range of the aqueous medium sprayed on the sand layer becomes wide, but since the water retention is good, drying due to the time difference of the spraying area can be effectively prevented, and molding unevenness can be prevented. The characteristics that can be suppressed will be exhibited.

Here, as a method of spraying 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 to the extent that the amount does not become too large. For example, in addition to a method of injecting an 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 adopted. ..

Further, since it is necessary to moisten the coated sand 14 with the aqueous medium 22 and then dry it, it is desirable that the aqueous medium 22 to be sprayed has a temperature of room temperature to higher than room temperature. Therefore, 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. When steam of an aqueous medium is used, it is preferably steam at 80 to 100 ° C.

In the present invention, water is typically used as the aqueous medium 22, and such water must be contaminated with pure water, tap water, distilled water, industrial water, dust, dust, and the like. For example, although not particularly limited, pure water or distilled water is preferable from the viewpoint of preventing nozzle clogging. Further, it is preferable to add a moisturizer to the aqueous medium 22. By adding a moisturizer to the aqueous medium 22, in addition to improving the water retention of the moisturizer contained in the coated sand 14, the action of the moisturizer in the aqueous medium 22 further improves the compatibility with the coated sand 14. improves. The water-retaining agent added to the aqueous medium 22 is not particularly limited, but it is particularly preferable to use the same water-retaining agent contained in the coated sand 14.

Further, the water may contain an acid or an ester as a curing agent or a curing accelerator. Among them, the acid is preferably sulfuric acid, hydrochloric acid, carbonic acid or sulfonic acid, and the ester is γ-butyrolactone or ε. -Lactones such as caprolactone and esters derived from alcohols having 1 to 10 carbon atoms and carboxylic acids having 1 to 10 carbon atoms such as ethylene glycol diacetate, triacetin, diethylene glycol diacetate and triethylene glycol diacetate are preferable. The alcohol having 1 to 10 carbon atoms at this time may be monovalent or multivalent. In addition, curing agents and curing accelerators such as acids and esters, the above-mentioned surfactants, alcohols such as methanol which are organic solvents, and drying accelerators such as ketones such as acetone and diacetone alcohol, Ronza Japan Co., Ltd. It is also possible to add and contain a small amount of an antiseptic such as PROXEL GXL (1,2-benzoisothiazole-3 (2H) -on) and PROXEL IB (polyhexamethylene biguanidine). In that case, the viscosity of the aqueous medium is generally 0.1 to 50 cP, and more preferably 0.3 to 40 cP, because problems such as clogging from the nozzle occur as the viscosity increases. Further, in order to facilitate the compatibility of the aqueous medium 22 with the sand layer 20, the surface tension may be 15 to 50 mN / m, more preferably 20 to 40 mN / m.

<Third process>
A heater 30 provided with a heating wire 32 is placed above the sand layer 20 after spraying the aqueous medium 22 at regular intervals, and the sand layer 20 is heated by the heat of the heater 30. Thereby, the damp coated sand 14 is dried (the state of FIG. 3). As a result, 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 water of the coated sand 14 moistened in the third step is evaporated from the state of being adhered to each other. Therefore, one mold layer 34 is formed by solidifying or hardening the refractory aggregates to which water glass is applied in a state of being bonded to each other. Further, since the portion moistened with the aqueous medium 22 has better heat conductivity than the portion not moistened, by heating, only the portion moistened with the aqueous medium 22 of the coated sand 14 is efficiently solidified or cured. It will be possible to make it. At this time, the heating by the heater 30 dries the coated sand 14 and solidifies or hardens it. Therefore, the sand layer 20 is heated at 30 to 180 ° C., preferably 60 to 150 ° C., more preferably 80 to 140 ° C. More preferably, it suffices if it can be heated to about 100 to 120 ° C., so that a temperature difference does not occur so much in the sand layer 20, so that warpage of the hardened sand layer (20) can be effectively suppressed. Further, 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.) can be effectively suppressed. You can do it. Therefore, the heater 30 does not need to have a high output, and exhibits features such as a small amount of energy consumption for heating.

Here, when the sand layer 20 is heated and dried, such drying can be promoted by performing the drying in an atmosphere of heated air. As another method, curing can be promoted by heating and drying in an atmosphere containing carbon dioxide or a gasified ester, or in an atmosphere of an inert gas such as nitrogen. The method for carrying out the above-mentioned promoting means is not particularly limited as long as it can be heated and dried in an atmosphere of a predetermined gas, but for example, the inside of the apparatus is sealed to create an internal atmosphere. There are methods such as substituting with heated air, carbon dioxide, gasified ester, or an inert gas, and modeling in the replaced atmosphere. It is also possible to control the temperature inside the device by heating.

Further, gas such as air, heated air, superheated steam, carbon dioxide gas, gasified ester, or inert gas may be sprayed or aerated at the same time as or before and after heating. Further, by flowing the gas, the drying of the coated sand 14 can be promoted. The method of spraying or aerating the gas is not particularly limited as long as the coated sand 14 can be carried out so as not to be blown off by the sprayed gas or aeration, but for example, a laminated portion. There is a method of ventilating by blowing gas from a spout installed at the upper part of the device or by circulating the atmosphere inside the device.

Further, in order to prevent water vapor from remaining in the device, a step of sucking the gas in the device and exhausting it to the outside of the system may be included. It is preferable that the gas is sucked after the sand layer is heated and dried in the third step, but it may be sucked during the third step or during the whole step as long as it does not adversely affect each step. Good.

<Repeat process>
Then, the series of mold layer 34 forming steps including the above-mentioned first step, second step, and third step is regarded as one turn (cycle), and the table 12 is continuously slid downward by the height of one sand layer. After the mold layer 34 is formed (the state shown in FIG. 4), the turn of the mold layer 34 forming step is repeated, so that a new mold layer 34 is integrally formed on the one mold layer 34 that has already been formed. Therefore, a laminated structure is realized. Further, the water-retaining effect of the coated sand in the present invention prevents the aqueous medium from seeping into the sand layer below during the laminated molding, so that deterioration and deformation of the mold shape can be suppressed, and a laminated mold having excellent dimensional accuracy can be obtained. It can be obtained in an advantageous manner. Further, by repeating the formation of the mold layer 34 several times, the mold layers 34 are sequentially laminated and integrated (as shown in FIG. 5), and thus the mold layers 34 are composed of an appropriate number of layers. A model 36 that provides a mold with a desired three-dimensional shape is manufactured. After that, the target mold (36) is taken out by removing the sand that has not been solidified or hardened from the molding apparatus (frame 10) (state of FIG. 6). Further, the obtained mold (36) may be further subjected to secondary firing in order to suppress variations in strength. The conditions for this secondary firing are 5 minutes to 2 hours, preferably 10 minutes to 1 hour in a constant temperature bath heated to about 100 to 200 ° C., preferably 120 to 180 ° C.

In the mold layer forming step including the first step, the second step, and the third step described above, the equipment is automatically switched in each step, but of course, a manual or semi-automatic method is used. , Even if the switching is performed, there is no problem.

Hereinafter, the present invention will be clarified more concretely by using some examples, but the present invention shall not be construed in any way by the description of such examples. Should be understood. In the following examples and comparative examples, "%" and "part" are all shown on a mass basis unless otherwise specified. In addition, the water content of the coated sand (CS) obtained in Examples and Comparative Examples, the solid content ratio in organic content, the measurement of dimensional accuracy, and the evaluation of water permeability and appearance are as follows. went.

-Measurement of water content with respect to solid content of water glass-
10 g of each CS is weighed and stored in a crucible that has been air-baked and weighed, and the amount of mass loss (%) after heating at 900 ° C. for 1 hour is used to determine the amount of water and the amount of organic matter in the CS. The total amount (hereinafter referred to as "(moisture + organic content) amount" and referred to as "W1") is calculated from the following formula (1). Here, the organic content is the total amount of the moisturizer 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 water glass with respect to CS is calculated using the following formula (2). Then, the amount of (moisture + organic content) in CS (W1), the amount of solid content of water glass with respect to CS (B1), and the amount of organic content added to 100 parts of solid content of water glass (A) will be described later. 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 (the water content of CS with respect to the solid content of the water glass in the coating layer: W2) is calculated by the following formula (3). Calculate using. W2 calculated as described above is shown as "moisture content (mass%)" in Tables 1 and 2 below.
W1 = [(M1-M2) / M3] × 100 ... (1)
[W1: (moisture + organic content) amount (%) in CS, M1: total mass of crucible and CS before firing (g), M2: total mass of crucible and CS after firing (g), 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 of water glass added to 100 parts of sand (parts), W1: Amount of (moisture + organic content) in CS (%) ] W2 = [(W1 / B1) x 100]-(A x C / 100) ... (3)
[W2: Water content (%) of CS with respect to the solid content of water glass in the coating layer, W1: (Moisture + organic content) amount (%) in CS, B1: Solid content of water glass with respect to CS (
%), A: Amount of organic matter added to 100 parts of solid content of water glass (parts), C: Solid content ratio of organic matter in CS (%)]

-Measurement of solid content in organic matter-
First, a sample is prepared, which comprises a moisturizer and other liquid additives, and the mixing ratio thereof is the same as the addition ratio to sand (refractory aggregate). Next, 10 g of the previously prepared sample was placed in an aluminum foil plate (length: 90 mm, width: 90 mm, height: 15 mm) and weighed.
An aluminum foil dish is placed on a heating plate held at 180 ± 1 ° C., left for 20 minutes, and then allowed to cool in a desiccator. Then, the aluminum foil plate after such 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)

-Evaluation of water permeability in coated sand-
A simple column is made by filling a glass cylinder with an outer diameter of 10 mmφ and an inner diameter of 9 mmφ with cotton. 22 g of CS is put therein and vibrated for 1 minute to densely fill it. Next, 2 g of the liquid (water) to be permeated is put into the sand-filled column, and when the liquid permeates to 20 mm from the upper surface of the filled sand, the measurement is started. Five minutes after the start of this measurement, the distance (mm) of further penetration is measured from the position of 20 mm, and that distance is taken as the penetration amount.

-Measurement of dimensional accuracy-
Using each CS, a test piece (laminated model) having a size of width 30 mm × height 10 mm × length 85 mm was molded, and the width was measured three times with a caliper, and the obtained measured value was measured. With the average value, the dimensional accuracy is calculated by "measured average value" ÷ "design value". The closer the dimensional accuracy is to 1, the better the accuracy.

-Appearance judgment-
The appearance of the obtained laminated model is evaluated by visually observing the test pieces obtained by laminating and modeling each CS into a size of width 30 mm × height 10 mm × length 85 mm. Then, in such a laminated model, when the surface is flat and the corners are firmly formed, ○, some unevenness of the surface is observed, but when the corners are formed, △, the surface is uneven. If the corners are also rounded, it is evaluated as x.

− Production example of dry CS 1-
As a refractory aggregate, Lunamos # 110 (trade name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, is prepared, and as a water glass as a binder, a commercially available product: sodium silicate (product). Name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.5, solid component: 41.3%) was prepared. Then, after heating the above-mentioned Lunamos # 110 to a temperature of about 180 ° C., it is put into a whirl mixer (manufactured by Enshu Iron Works Co., Ltd.), and further, the water glass is added to 100 parts of Lunamos # 110. After adding 26 parts (solid component: 3.0 parts), 0.09 parts (water) of commercially available hydroxyethyl cellulose as a moisturizing agent: HEC-AL-15F (product name: Sumitomo Seika Co., Ltd.) By adding at a ratio of 3 parts to 100 parts of the solid content of the glass and kneading for 3 minutes, the water is evaporated, and the mixture is stirred and mixed until the sand granules collapse, and the calcium stearate is 0. By adding 03 parts (0.01 part with respect to 100 parts of solid content of water glass), stirring and mixing, and then taking out, a dry coated sand having normal temperature fluidity: CS1 was obtained. When the water content of CS1 after such kneading 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 2-
It has room temperature fluidity according to the same procedure as in Production Example 1 above, except that the amount of hydroxyethyl cellulose added as a moisturizer was 0.3 parts (10 parts with respect to 100 parts of solid content of water glass). Dry coated sand: CS2 was obtained. When the water content of the obtained CS2 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

− Production example of dry CS 3-
It has room temperature fluidity according to the same procedure as in Production Example 1 above, except that the amount of hydroxyethyl cellulose added as a moisturizer was 0.9 parts (30 parts with respect to 100 parts of solid content of water glass). Dry coated sand: CS3 was obtained. When the water content of the obtained CS3 was calculated, it was an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

− Production example of dry CS 4-
As a moisturizer, glycerin is used instead of hydroxyethyl cellulose, and this is 0.3 part with respect to 100 parts of the refractory aggregate (Lunamos # 110) (10 parts with respect to 100 parts of solid content of water glass). A dry coated sand: CS4 having room temperature fluidity was obtained according to the same procedure as in Production Example 1 except that the mixture was added in the ratio of. When the water content of the obtained CS4 was calculated, it was an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 5-
As a moisturizer, instead of hydroxyethyl cellulose, commercially available hydroxypropyl methylcellulose: Metrose 60SH-50 (product name: Shin-Etsu Chemical Co., Ltd.) was used, and this was applied to 100 parts of refractory aggregate (Lunamos # 110). A dry coated sand having room temperature fluidity according to the same procedure as in Production Example 1 above, except that 0.3 part (10 parts with respect to 100 parts of solid content of water glass) was added. Obtained CS5. When the water content of the obtained CS5 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 6-
As a moisturizer, a commercially available polyvinyl alcohol: PVA220 (product name: Kuraray Co., Ltd.) was used instead of hydroxyethyl cellulose, and 0.3 part of this was applied to 100 parts of the refractory aggregate (Lunamos # 110). A dry coated sand having normal temperature fluidity: CS6 was obtained according to the same procedure as in Production Example 1 above, except that the mixture was added at a ratio of (10 parts to 100 parts of solid content of water glass). When the water content of the obtained CS6 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 7-
As a moisturizing agent, a commercially available polyethylene oxide: Alcox R-150 (product name: Meisei Chemical Works, Ltd.) was used instead of hydroxyethyl cellulose, and this was applied to 100 parts of a refractory aggregate (Lunamos # 110). A dry coated sand having room temperature fluidity according to the same procedure as in Production Example 1 above, except that 0.3 part (10 parts with respect to 100 parts of solid content of water glass) was added. I got CS7. When the water content of the obtained CS7 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 8-
As a water glass as a binder, a commercially available product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.1, solid component: 48.5%) is used. In addition, the same procedure as in Production Example 1 was followed except that the amount added was 6.19 parts (3.0 parts of solid component) with respect to 100 parts of the refractory aggregate (Lunamos # 110). , A dry coated sand having normal temperature fluidity: CS8 was obtained. When the water content of the obtained CS8 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 9-
As a water glass as a binder, a commercially available product: sodium silicate No. 3 (trade name: manufactured by Fuji Chemical Co., Ltd., _{molar ratio of SiO 2} / Na ₂ O: 3.2, solid component: 38%) is used, and also. , The normal temperature according to the same procedure as in Production Example 1 above, except that the amount added was 7.89 parts (3.0 parts of solid component) with respect to 100 parts of the refractory aggregate (Lunamos # 110). A fluid, dry coated sand: CS9 was obtained. When the water content of the obtained CS9 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 10-
A dry coated sand having normal temperature fluidity: CS10 was obtained according to the same procedure as in Production Example 1 except that hydroxyethyl cellulose as a moisturizer was not added. When the water content of the obtained CS10 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 11-
A dry coated sand: CS11 having room temperature fluidity was obtained according to the same procedure as in Production Example 8 except that hydroxyethyl cellulose as a moisturizer was not added. When the water content of the obtained CS11 was calculated, it was an amount corresponding to 31% by mass of the solid content of the water glass in the coating layer.

-Production example of dry CS 12-
A dry coated sand: CS12 having room temperature fluidity was obtained according to the same procedure as in Production Example 9 except that hydroxyethyl cellulose as a moisturizer was not added. When the water content of the obtained CS12 was calculated, it was an amount corresponding to 29% by mass of the solid content of the water glass in the coating layer.

Next, using the dry CS1 to CS10 obtained above, the above-mentioned permeability evaluation was carried out in Examples 1 to 9 and Comparative Examples 1 to 3, respectively, 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 CS1 prepared above, a predetermined laminated mold was formed by the laminated mold manufacturing apparatus according to the embodiments 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 the CS1 is thinly flattened on the table (12) to form a sand layer (20), and then the second In the step, such an aqueous medium (22) is sprayed by an inkjet method for each minute region so as to give a predetermined planar shape of 203 mm × 254 mm. After wetting the sand layer (20) of the predetermined planar shape portion sprayed with), the portion was hardened or solidified to obtain a mold layer (34) having a shape corresponding to the portion. The aqueous medium (22) used there has a composition of water: 93% by mass, a moisturizer: 6% by mass, and a surfactant: 1% by mass (viscosity: 1.1 mPa · s / 25 ° C., surface). Tension: 31.5 mN / m) and was used at a temperature of 25 ° C.

Then, with the series of steps including the above first step and the second step as one turn, the mold layer (34) is formed until the wall thickness (height) of the laminated mold (modeled object 36) becomes 10 mm. The laminating molding operation of was repeated. Then, CS1 which was not solidified or hardened was removed from the laminated mold manufacturing apparatus, the modeled product was taken out, and the product was fired at a temperature of 150 ° C. for 10 minutes to produce the desired laminated mold (36). Then, the dimensional accuracy of the obtained laminated mold was measured and the appearance was judged, and the results are shown in Table 1 below.

− Examples 2 to 8, Comparative Examples 1 to 3−
CS1 is replaced with CS2 to CS10, respectively, and the mold is laminated in the same manner as in Example 1, and the obtained model is fired at a temperature of 150 ° C. for 10 minutes to achieve the desired lamination. A mold (36) was manufactured. Then, the dimensional accuracy of the obtained laminated mold was measured and the appearance was judged, and the results are shown in Table 1 below.

As is clear from the results in Table 1, CS1 to CS9, in which a coating layer containing water glass and a predetermined moisturizer is formed according to the present invention, have a low amount of water permeation and are excellent in water retention. It is recognized that all of the laminated molds obtained by laminating molding using these CS1 to CS9 are excellent in dimensional accuracy and appearance.

2 Modeled product 4 Laminated product 10 Frame 12 Table 14 Coated sand 16 Storage tank 18 Discharge port 20 Sand layer 22 Aqueous medium 24 Stretching member 26 Inkjet spraying device 28 Nozzle 30 Heater 32 Heating wire 34 Mold layer 36 Modeled object (laminated mold)

Claims (10)

A thin sand layer is formed using coated sand formed by coating a refractory 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 a method of manufacturing a laminated mold having a desired three-dimensional shape by laminating the solidified layer or the cured layer by repeating the work of forming the above.
As the coated sandwich, a laminate obtained by forming a coating layer containing a moisturizer on the surface of the refractory aggregate together with water glass as a binder is used. An improved method of making molds. The improved laminate template according to claim 1, wherein the moisturizer is selected from the group consisting of polyhydric alcohols, water-soluble polymer compounds, hydrocarbons, sugars, proteins and inorganic compounds. Production method. 1 or 2 according to claim 1, wherein the content of the moisturizer is 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 coated sand. An improved method for manufacturing a laminated mold according to the above. The improved method for producing a laminated mold according to any one of claims 1 to 3, wherein the aqueous medium contains a moisturizer. The improved method for producing a laminated mold according to claim 4, wherein the aqueous medium further contains at least one of a curing accelerator, a surfactant, a drying accelerator, and a preservative. .. The improved 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. Manufacturing method. The improved manufacturing method of a laminated mold according to any one of claims 1 to 6, wherein the coated sand further contains a lubricant on its surface. The laminated mold according to claim 7 , 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 the water glass in the coated sand. Improved manufacturing method.
The improved method for producing a laminated mold according to any one of claims 1 to 8, wherein the water content in the coated sand is 5 to 55% by mass of the solid content of the water glass. The improved manufacturing method of the laminated mold according to any one of claims 1 to 9, wherein the spraying of the aqueous medium on the sand layer is performed by using an inkjet spraying device.

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