JP7252897B2 - Mold material and method for manufacturing the same, mold and method for manufacturing the same, and method for regenerating foundry sand - Google Patents

Description

The present invention relates to a mold material and its manufacturing method, a mold and its manufacturing method, and a method of regenerating foundry sand.

Conventionally, as one of the molds used for casting molten metal, coated sand (mold material) made by coating casting sand made of refractory aggregate with a predetermined binder is used to obtain the desired shape. The one obtained by molding is used. Specifically, in "Casting Engineering Handbook" edited by the Japan Foundry Engineering Society, pp. 78-90, as a binder for such coated sand, inorganic binders such as water glass, phenol resins, Organic binders using resins such as furan resin and urethane resin have been clarified, and techniques for forming self-hardening molds using these binders have also been clarified.

For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-76115), a solid coating layer containing a predetermined water-soluble inorganic compound such as water glass as a binder is formed on the surface of a refractory aggregate (foundry sand). A coated binder-coated refractory (coated sand) with good fluidity is disclosed. In addition, in the same document, after filling such a binder-coated refractory (coated sand) with good fluidity into a molding cavity of a mold for making a mold, steam is introduced into the mold. A technique has also been clarified in which the aeration promotes solidification of the binder-coated refractory (coated sand) to obtain the desired mold.

Here, the coated sand (mold material) composed of an inorganic binder such as water glass has a higher organic content than the coated sand (mold material) using an organic binder. It is conventionally known that, due to the low content, the generation of various gases due to heat during molding and casting is advantageously suppressed, and problems such as odor are less likely to occur. However, in the case of coated sand (mold material) composed of conventional inorganic binders, including the one disclosed in Patent Document 1, casting sand (refractory aggregate ) is recovered and the recovered sand is regenerated by roasting, the inorganic binder remaining on the surface of the recovered sand does not burn and instead sinters, resulting in foundry sand (refractory aggregate ), it has an inherent problem that it is difficult to reproduce. In particular, coated sand (mold material) using water glass as an inorganic binder causes the water glass to vitrify due to the heat during casting. Even if it is practiced, there is a problem that it is very difficult to remove the vitrified water glass on the sand surface. In addition, the conventional coated sand (mold material) using an inorganic binder does not have sufficient collapsibility of the mold obtained by using it, and there is still room for improvement in this respect as well. There is.

JP 2012-76115 A

"Casting Engineering Handbook" pp.78-90

Here, the present invention has been made against the background of such circumstances, and the problem to be solved is to provide a mold material that is excellent in mold collapsibility and that facilitates regeneration of foundry sand. to provide. In addition, the present invention provides a method for advantageously producing a mold material having such excellent properties, a mold using such a mold material, a method for manufacturing the same, and a method for regenerating foundry sand. is also a problem to be solved.

In order to solve the above-described problems, the present invention can be suitably implemented in various aspects as listed below, and each aspect described below can be employed in any combination. It is possible. It should be noted that the aspects and technical features of the present invention are not limited to those described below, and can be recognized based on the inventive idea that can be grasped from the description of the entire specification. should be understood.

(1) Foundry sand coated with a solid coating layer containing a crosslinked curable resin and/or a cured product thereof and a coupling agent is a liquid binder composition containing a water-soluble inorganic binder. Wet mold material, characterized in that it is coated.
(2) The mold material according to the aspect (1), wherein the solid coating layer has a thickness of 0.1 to 6 μm.
(3) The mold material according to the aspect (1) or the aspect (2), wherein the cross-linking curable resin is a phenolic resin.
(4) The mold material according to any one of the aspects (1) to (3), wherein the crosslinked curable resin has a weight average molecular weight of 300 or more .
(5) The mold material according to any one of the aspects (1) to (4) , wherein the crosslinking curable resin and its cured product have a solubility of 1% by mass or less in 100 g of water at 25°C.
(6) The mold according to any one of the aspects (1) to (5), wherein the solid content of the water-soluble inorganic binder in the liquid binder composition is 10 to 80% by mass. material.
(7) The mold material according to any one of aspects (1) to (6), wherein the liquid binder composition comprises a coupling agent.
(8) The mold material according to any one of the aspects (1) to (7), wherein the liquid binder composition contains inorganic oxide particles.
(9) The mold material according to aspect (8), wherein the inorganic oxide particles are silicon dioxide particles.
(10) The mold material according to any one of the aspects (1) to (9), wherein the liquid binder composition contains a moisture resistance improver.
(11) The mold material according to any one of the aspects (1) to (10), wherein the water-soluble inorganic binder is water glass.
(12) The mold material according to any one of the aspects (1) to (11), wherein the liquid binder composition contains water.
(13) A mold made using the mold material according to any one of the aspects (1) to (12) .
(14) The mold according to the aspect (13), which generates 3 to 30 ml of gas per 1 g when heated at 1000° C. for 240 seconds.
(15) A step of forming a solid coating layer containing a cross-linkable curable resin and/or a cured product thereof and a coupling agent on the surface of the foundry sand;
a step of adding a liquid binder composition containing a water-soluble inorganic binder to the foundry sand on which the solid coating layer is formed, and kneading or mixing the mixture;
A method for producing a wet mold material comprising:
(16) The solid coating layer contains a cross-linking curable resin , and after the solid coating layer is formed on the surface of the foundry sand, the cross-linking curable resin contained in the solid coating layer is The method for producing a mold material according to the aspect (15), which comprises a step of curing.
(17) The method for producing a mold material according to the aspect (15) or the aspect (16), wherein the water-soluble inorganic binder is water glass.
(18) The method for producing a mold material according to any one of the aspects (15) to (17), wherein the liquid binder composition contains water.
(19) After filling the mold material according to any one of the above aspects (1) to (12) , it is held in the mold, and a) heating the mold. b) by adding a curing agent into the mold, or c) by reducing the pressure in the mold to solidify or harden the mold material filled in the mold to achieve the purpose A method for producing a mold, characterized in that a mold is obtained.
(20) The mold manufacturing method according to the above aspect (19) , wherein hot air or superheated steam is passed through the mold while the mold is being held.
(21) The aspect (19) or the aspect (20) , wherein a carrier gas comprising at least one of carbon dioxide, argon, nitrogen, helium and air is passed into the mold while the mold is held. A method for manufacturing the described mold.
(22) The mold manufacturing method according to any one of the aspects (19) to (21), wherein the mold is heated to a temperature of 80°C to 300°C.
(23) After casting using a mold made of the solidified or hardened mold material according to any one of the aspects (1) to (12) , casting sand is removed from the mold. A method for reclaiming foundry sand, comprising recovering and subjecting the sand to dry reclaiming treatment to obtain reclaimed sand.

According to such a wet mold material according to the present invention, various effects as listed below can be exhibited.
(A) When casting is performed using a mold made of the mold material in a wet state according to the present invention (hereinafter simply referred to as the mold in this paragraph), the heat produced by the molten metal causes the surface of the foundry sand to The organic compounds contained in the solid coating layer are effectively thermally decomposed, so that the mold after casting has good collapsibility. In addition, in the foundry sand recovered from the mold after casting, the solidified or hardened water-soluble inorganic binder is in a state where it is easy to separate from the surface of the foundry sand due to the thermal decomposition of the above-mentioned organic compounds. Therefore, it is possible to easily reclaim sand by subjecting the collected sand to a dry reclaiming process including a polishing process.
(B) Gas is generated by thermal decomposition of the organic compounds contained in the coating layer during casting using the mold, so the gas suppresses the penetration of the molten metal into the spaces between the particles (sand grains) of the foundry sand that make up the mold. A layer is advantageously formed between the mold surface and the cast product, resulting in a good casting surface in the final cast product.
(C) In the wet mold material according to the present invention, since the organic compound exists in a solid state, the problem of odor caused by volatilization of the organic compound is less likely to occur.
(D) In the wet mold material according to the present invention, if the liquid binder composition contains inorganic oxide particles or a moisture resistance improver, the decrease in strength of the moisture-absorbed mold is advantageously suppressed. Therefore, it is possible to improve the moisture resistance strength of the mold.
(E) In the mold material of the present invention, when a coupling agent is contained in the solid coating layer and/or in the liquid binder composition, wettability and adhesiveness are improved, The bond between the foundry sand and the coating layer and/or the bond between the coating layer on the surface of the foundry sand and the water-soluble inorganic binder,
It becomes strong and can improve the strength of the mold.

FIG. 2 is a longitudinal cross-sectional explanatory view of a sand mold for casting test used in a collapsibility test in Examples. FIG. 2 is a vertical cross-sectional explanatory view of an aluminum alloy casting containing a waste core in an example.

By the way, the wet molding material (coated sand) according to the present invention is obtained by coating molding sand coated with a solid coating layer containing an organic compound with a liquid binder composition containing a water-soluble inorganic binder. It is composed of As described above, in the foundry material (coated sand) of the present invention, foundry sand particles coated with a solid coating layer are covered with a liquid binder composition containing a water-soluble inorganic binder. Because of its construction, it exhibits a wet state (appearance) as a whole, that is, a wet state.

Here, in the present specification and claims, the wet mold material (coated sand) means a mold material (coated sand) that does not have normal temperature fluidity. More specifically, a mold material (coated sand) for which a dynamic repose angle cannot be measured according to the following method is defined as a wet mold material (coated sand). The dynamic angle of repose is defined as the mold material (coated sand) placed in a cylinder with one transparent flat surface (for example, a container with a diameter of 7.2 cm and a height of 10 cm filled with half the volume of the mold material (coated sand). Sand) is inserted), rotated at a constant speed (e.g., 25 rpm), the slope of the layer of the mold material (coated sand) flowing in the cylinder becomes planar, and the angle formed between the slope and the horizontal surface is Measured. In such a measurement method, if the mold material (coated sand) does not flow in the cylinder and the slope of the layer of the mold material (coated sand) is not formed as a plane, and therefore the dynamic angle of repose cannot be measured, it is called a wet state. of mold material (coated sand). The wet mold material (coated sand) is superior to the dry mold material (coated sand) in that it requires less labor and is easier to manufacture.

First, the foundry sand constituting the wet mold material according to the present invention is a refractory substance functioning as a base material for molds, and various refractory granular or powdery materials conventionally used for molds. Specifically, silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag, Slag-based particles such as furnace slag; artificial particles such as alumina-based particles and mullite-based particles, and regenerated particles thereof; alumina balls, magnesia clinker, and the like. These foundry sands may be fresh sand, or recycled sand or recovered sand that has been used once or several times in the molding of a mold. There is no problem even if it is a mixed sand obtained by adding new sand to and mixing it. Such foundry sand is generally used with a grain size of about 40 to 130, preferably about 60 to 110 in terms of AFS index. Further, the foundry sand is preferably spherical, and specifically, it is desirable that the grain size coefficient is 1.2 or less, more preferably 1.0 to 1.1. By using foundry sand with a grain shape factor of 1.2 or less, the fluidity and filling properties during mold production are improved, and the number of contact points between foundry sand materials increases, so that the same strength is exhibited. It is possible to reduce the amount of binder and additives required for this purpose. The particle shape index of foundry sand used here is generally adopted as a measure of the outer shape of the particles, and is also called the particle shape index. It means to approach a (perfect sphere). Such a grain shape factor is expressed by a value calculated using the surface area of foundry sand (sand surface area) measured by various known methods. (manufactured by George Fisher Co.) to measure the surface area of actual foundry sand grains (sand grains) per gram, and divide it by the theoretical surface area. The theoretical surface area is the surface area assuming that all foundry sand particles (sand grains) are spherical.

The surface of the foundry sand constituting the mold material of the present invention is coated with a solid coating layer containing an organic compound. Due to the presence of the predetermined coating layer on the surface of the foundry sand, the water-soluble inorganic binder, which will be described later, does not come into direct contact with the foundry sand. In addition, since the solid coating layer contains an organic compound, when a molten metal is poured into a mold using the mold material of the present invention (hereinafter simply referred to as a mold), the organic compound contained in the coating layer The compound is thermally decomposed and gasified, and the generated gas advantageously destroys the solidified or hardened material of the water-soluble inorganic binder at the joints between the foundry sand particles. will be excellent. Furthermore, when the organic compound contained in the coating layer is thermally decomposed and gasified, the internal pressure of the gas causes the solidified or hardened water-soluble inorganic binder present on the foundry sand particles to move from the inside (casting (from the sand particle side), for example, in the polishing process when regenerating the foundry sand recovered from the mold after casting, the solidified or hardened water-soluble inorganic binder is peeled off from the surface of the foundry sand particles. This makes it easy to recycle foundry sand. In addition, during casting using the mold, gas is generated by thermal decomposition of the organic compounds contained in the coating layer, so the gas layer that suppresses the penetration of the molten metal into the molding sand particles that make up the mold. It is advantageously formed between the mold surface and the cast product, so that the finally obtained cast product has a good casting surface.

In the present invention, the film thickness of the solid coating layer formed on the foundry sand surface is 0.1 to 6 μm, preferably 0.2 to 5 μm, more preferably 0.3 to 3 μm, further preferably 0.5 μm. ~2 μm. If the film thickness is less than 0.1 μm, it may be difficult to form a coating layer, and it may be difficult to gasify the inside of the layer composed of the binder composition containing the water-soluble inorganic binder. On the other hand, if it is thicker than 6 μm, there is a possibility that an odor may be generated by the organic compound. As a method for measuring the film thickness of the coating layer, the foundry sand particles with the coating layer formed thereon are embedded in epoxy resin or the like, and the cross section of the foundry sand particles cut using a cutting device such as an ion cutter is examined using an optical microscope or the like. Observation is performed using an optical instrument such as an electron microscope, 10 cross-sectional grains are randomly selected, and the film thickness of the coating layer is measured. Further, when the molding sand particles are spherical, the film thickness may be calculated from the average particle diameter of the molding sand particles and the amount of the molding sand particles and the organic compound added.

The organic compound used in the present invention is not only capable of forming a solid coating layer on the surface of foundry sand particles, but also can be contained in a solid coating layer. If so, it is preferably at least one selected from the group consisting of crosslinked curable resins and cured products thereof, thermoplastic resins, and carbohydrates, although it is not particularly limited.

The cross-linking curable resin is, for example, hexamethylenetetramine, organic ester, organic acid, carbon dioxide gas, peroxide, metal ion, in the presence or absence of a curing agent or curing catalyst such as amine, heated or unheated (normal temperature ), the molding sand particles are bound together to form a mold. Specific examples of such crosslinked curable resins include phenol resins, phenol urethane resins, epoxy resins, melamine resins, unsaturated polyester resins, polyfunctional acrylamide resins (see JP-B-7-106421). ), unsaturated alkyd resins, unsaturated fatty acid-modified alkyd resins, diallyl phthalate resins, and resins obtained by combining these resins as necessary. Among these, novolak-type or resol-type phenol-based resins and phenol-urethane-based resins used in mixture with a polyisocyanate compound are particularly preferred from the viewpoint of being able to enjoy the effects of the present invention more advantageously.

Moreover, the cured product of the crosslinked curable resin is obtained by subjecting a low-molecular compound to a curing reaction to increase the molecular weight of the polymer compound. After coating the surface of the foundry sand particles with a low-molecular-weight material with low melt viscosity, it is hardened by heating or adding a hardening agent to prevent alkali deterioration and provide a high-molecular-weight material with good surface stability. A coating layer can be formed, and both coatability and surface stability can be achieved. In addition, compared with an uncured crosslinked curable resin, the cured product of the crosslinked curable resin has 1) suppression of softening of the coating layer due to heat and improved mold strength, and 2) pre-curing necessary Since the amount of heat is consumed, the heat is effectively used for pyrolysis, and the pyrolysis is accelerated, so that the collapsibility of the mold is further improved. 3) Gas accompanying hardening is released in advance Therefore, there is also the advantage that the amount of gas generated during casting can be suppressed.

Furthermore, specific examples of thermoplastic resins include polyvinyl alcohol, polyvinyl acetate, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, ethylene-vinyl acetate copolymer, polymethyl methacrylate, methacrylic- Resins such as styrene copolymer, cellulose acetate, polycarbonate, and polyvinyl chloride can be mentioned. Among them, polyvinyl alcohol, polyvinyl acetate, polystyrene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, cellulose acetate, and polycarbonate are particularly preferred from the viewpoint of solvent solubility (film formability).

Furthermore, specific examples of carbohydrates include those composed of glucose, fructose, galactose, lactose, sucrose, maltose, trehalose, starch, glycogen, and cellulose. Among them, trehalose, starch, and glycogen are particularly preferred from the viewpoint of film-forming properties. Additionally, other organic compounds include acrylamide, N-methylolacrylamide, diacrylamide dimethyl ether, methylenebisacrylamide, ethylenebisacrylamide, ethyleneglycol diacrylamide, and the like.

In the present invention, the organic compound contained in the coating layer on the surface of the foundry sand is preferably a high-molecular compound (polymer, multimer) from the viewpoint of covering the foundry sand particles. Specifically, a polymer compound (polymer, multimer) having a weight average molecular weight of 300 or more, preferably 300 to 100000000, more preferably 500 to 50000000, and even more preferably 800 to 20000000 is advantageously used. Even organic compounds that are not included in the category of high-molecular compounds (polymers, multimers) preferably have a molecular weight of 300 or more from the viewpoint of surface stability of the solid coating layer. 100000000 or less is preferable from the viewpoint of coverage.

Further, in the present invention, poorly water-soluble or water-insoluble organic compounds are advantageously used, and particularly water-insoluble organic compounds are suitable as the organic compound contained in the solid coating layer. This is because if a readily water-soluble organic compound is used, it will dissolve in the water contained in the liquid binder composition containing the water-soluble inorganic compound coated on the surface of the coating layer, resulting in a solid state. This is because there is a possibility that the coating layer cannot be maintained. Specifically, in the present invention, the solubility in 100 g of water at 25° C. is 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0.1% by mass. The following organic compounds are used as the organic compounds contained in the solid coating layer. The solubility means the amount of the organic compound dissolved in the solvent (water) when 10 g of the organic compound is added to 100 g of water at 25° C., stirred for 1 hour, and allowed to stand still for 1 hour. It is. Moreover, the water-insoluble organic compound is an organic compound that does not dissolve in water.

Furthermore, in the wet mold material according to the present invention, the coating layer provided on the surface of the foundry sand may contain a coupling agent. By incorporating a coupling agent into the coating layer, the wettability and adhesiveness of the coating layer can be improved, and the bond between the foundry sand and the coating layer can be strengthened. As the coupling agent contained in the coating layer, for example, a silane coupling agent, a zircon coupling agent, a titanium coupling agent and the like can be mentioned as suitable ones. The content of the coupling agent in the coating layer is generally 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass, and more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the organic compound. is assumed to be the ratio of

On the other hand, the wet mold material according to the present invention is constructed by coating the foundry sand coated with the predetermined coating layer described above with a liquid binder composition containing a water-soluble inorganic binder. . As the water-soluble inorganic binder contained in the liquid binder composition, any one conventionally used in mold materials (coated sand) can be used. Examples of water-soluble inorganic binders include water glass, sodium chloride, sodium phosphate, sodium carbonate, sodium vanadate, sodium borate, sodium aluminum oxide, potassium chloride, potassium carbonate, and Those containing two or more selected from among them as main components can be mentioned. Among these, water glass and those containing water glass as a main component are preferable from the viewpoint of ease of handling and the strength of the finally obtained mold. Here, water glass is an aqueous solution of a soluble silicate compound, and examples of such silicate compounds include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, Ammonium silicate and the like can be mentioned, but sodium silicate (sodium silicate) is particularly advantageously used in the present invention. In addition, water glass may be used as a main component, and water-soluble binders such as thermosetting resins, sugars, proteins, synthetic polymers, salts and inorganic polymers may be blended. When water glass and another water-soluble binder are used together, the ratio of water glass to the total amount of the binder is 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more.

The above-mentioned water-soluble inorganic binders are usually handled in a solid form or a liquid form, and the solid form is used in the form of an aqueous solution. Advantageously, the liquid binder composition containing the water-soluble inorganic binder has a viscosity of 5 to 2000 cP, preferably 7 to 1200 cP, more preferably 7 to 800 cP at 25°C. be done. In such preparation, even a liquid water-soluble inorganic binder such as water glass can be diluted with water to adjust the viscosity of the binder composition. It is also possible to separately add a solid or liquid water-soluble inorganic binder and water to the refractory aggregate or the like during kneading or mixing with the foundry sand.

Here, the water glass sodium silicate that is advantageously used in the present invention will be described in detail. Sodium silicate is usually classified into types 1 to 5 according to the molar ratio of SiO ₂ /Na ₂ O. used 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 has a SiO ₂ /Na ₂ O molar ratio of 2.0 to 2.3. 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 of is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. These sodium silicates may be used singly or in combination, and two or more of them may be mixed to adjust the SiO ₂ /Na ₂ O molar ratio. is also possible.

In order to advantageously obtain the wet mold material according to the present invention, the sodium silicate constituting the water glass used as the binder generally has a SiO ₂ /Na ₂ O molar ratio of 1.9 or more, It is preferably 2.0 or more, more preferably 2.1 or more, and sodium silicates corresponding to Nos. 1 and 2 in the above-described sodium silicate classification are particularly advantageously used. . Such sodium silicate Nos. 1 and 2 provide mold materials that are stable and have good properties even over a wide range of sodium silicate concentrations in water glass. Also, the upper limit of the molar ratio of SiO ₂ /Na ₂ O in such sodium silicate is appropriately selected according to the properties of the 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 SiO ₂ /Na ₂ O molar ratio is less than 1.9, a large amount of alkali is present in the water glass, so the solubility of the water glass in water increases, and the mold material deteriorates due to moisture absorption. It may become easier. On the other hand, sodium silicate having a molar ratio of SiO ₂ /Na ₂ O of more than 3.5 has low solubility in water, so that the finally obtained mold cannot increase the bonding area between the molding sand particles. There is a possibility of causing a problem that the strength of the mold is lowered.

Further, the water glass used in the present invention means a solution of a silicic acid compound dissolved in water. In addition to being used, water is added to such a stock solution to be used in a diluted state. The non-volatile content (water glass component) obtained by removing volatile substances such as water and solvents from such water glass is called solid content, which corresponds to the soluble silicate compound such as sodium silicate described above. It is. Also, the higher the proportion of such solids, the higher the silicic acid compound concentration in the water glass. Therefore, the solid content of the water glass used in the present invention, when it is composed only of the undiluted solution, corresponds to the ratio excluding the water content in the undiluted solution. When a diluted solution obtained by diluting with becomes.

In the present invention, sodium chloride (NaCl), which can be used as a water-soluble inorganic binder, is edible, harmless to the human body, and inexpensive and easy to use. It is possible. Further, since it is easily dissolved in water, a mold material using sodium chloride as a binding agent can be used to manufacture molds that are easily disintegrated by water. The amount of sodium chloride dissolved in 100 g of water is 35.9 g (20°C). Furthermore, since the melting point of sodium chloride is 1413° C., which is relatively high, a mold with high heat resistance can be produced.

Examples of sodium phosphate include monosodium phosphate hydrate (NaH ₂ PO ₄ ·xH ₂ O; x is a known integer), disodium phosphate hydrate (Na ₂ HPO ₄ ·x'H ₂ O x' is a known integer), trisodium phosphate hydrate (Na ₃ PO ₄ ·x"H ₂ O; x" is a known integer). Sodium phosphate is soluble in water, as typified by the fact that the amount of trisodium phosphate hydrate dissolved in 100 g of water is 25.8 g (20° C.). The melting point of sodium phosphate is relatively high, as typified by the melting point of 1340° C. of the hydrate. Therefore, a mold material using sodium phosphate as a water-soluble inorganic binder is easily disintegrated by water, and a mold with high heat resistance can be produced.

Further, sodium carbonate (Na ₂ CO ₃ ) has a solubility of 17.4 g (at 20° C.) in 100 g of water, and is easily dissolved in water and inexpensive. Also, the melting point is relatively high at 851°C. Therefore, a mold material using sodium carbonate as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

Also, sodium vanadate (Na ₃ VO ₄ ) is soluble in water and has a relatively high melting point of 866°C. Therefore, a mold material using sodium vanadate as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

Furthermore, sodium aluminum oxide (NaAlO ₂ ) is soluble in water and has a high melting point of 1700° C. or higher. Therefore, a mold material using sodium aluminum oxide as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

In addition, potassium chloride (KCl) is easily dissolved in water, and is inexpensive, with a dissolution amount of 34.2 g (20° C.) per 100 g of water. Also, the melting point is relatively high at 776°C. Therefore, a mold material using potassium chloride as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

Potassium carbonate (K ₂ CO ₃ ) dissolves easily in water, with a dissolution amount of 111.9 g (20° C.) per 100 g of water, and has a relatively high melting point of 891° C. Therefore, a mold material using potassium carbonate as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

The content ratio of such a water-soluble inorganic binder in the liquid binder composition is set appropriately according to the type of the water-soluble inorganic binder used. From the viewpoint of molding speed and strength of the mold finally obtained, the solid content of the water-soluble inorganic binder is advantageously 10 to 80% by mass, preferably 15 to 70% by mass, more preferably 20 to 50%. It is desirably contained in the liquid binder composition in a mass % ratio. By using the liquid binder composition containing the solid content of the water-soluble inorganic binder in such a ratio, such castings can be obtained when mixed (kneaded) with foundry sand particles having a predetermined solid coating layer. The sand particles can be evenly and uniformly coated with the water-soluble inorganic binder component, which makes it possible to advantageously mold the desired mold according to the present invention. . In addition, the concentration of the water-soluble inorganic binder component (solid content) in the liquid binder composition is too low, specifically a liquid binder with a solid content of less than 10% by mass. When the composition is used, it is necessary to raise the heating temperature and lengthen the heating time in order to dry the mold material during molding, which causes problems such as energy loss. Become. On the other hand, if a liquid binder composition with an excessively high solids content is used, it becomes difficult to evenly coat the surfaces of the foundry sand particles with the binder composition, resulting in problems in mold properties. Since there is a risk of causing such a liquid, the solid content is 80% by mass or less, so that the solvent such as water is 20% by mass or more (water content is 10% by mass or more). It is desirable to prepare a binder composition.

In addition, the water-soluble inorganic binding agent in the wet mold material according to the present invention is the weight of the solid in the case of solid and the solid content in the case of liquid with respect to 100 parts by weight of the foundry sand. It is used in a proportion of 0.1 to 5 parts by mass, preferably 0.2 to 2.5 parts by mass, more preferably 0.5 to 2.0 parts by mass in terms of solid content. desirable. By using the water-soluble inorganic binder in such a quantitative ratio, the surface of the solid coating layer provided on the surface of the foundry sand particles becomes a liquid binder containing the water-soluble inorganic binder. A wet mold material of the invention coated with the composition will advantageously be constructed. In addition, the measurement of solid content is implemented as follows. That is, 10 g of the sample was placed in an aluminum foil sample dish (length: 9 cm, width: 9 cm, height: 1.5 cm), weighed, placed on a heating plate maintained at 180 ± 1 ° C. After standing for 20 minutes, the sample pan is inverted and left on the heating plate for an additional 20 minutes. Next, 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 according to the following equation.
Solid content (% by mass)
= {[mass of sample dish after drying (g) - mass of sample dish (g)]
/ [mass of sample dish before drying (g) - mass of sample dish (g)]} x 100

In the present invention, if the amount of the water-soluble inorganic binder used is too small, a sufficient amount of the water-soluble inorganic binder does not exist on the solid coating layer provided on the surface of the foundry sand. A problem may occur in which the mold material cannot be sufficiently solidified or hardened. Moreover, even if the amount of the water-soluble inorganic binder used is too large, an excessive amount of the water-soluble inorganic binder is present on the solid coating layer provided on the surface of the foundry sand. There is a risk that the foundry sand particles will adhere to each other and become agglomerates (composite particles), which will adversely affect the physical properties of the mold and also cause the problem of difficulty in removing the sand from the core after casting the metal. become provocative.

Here, in the mold material according to the present invention, it is possible to incorporate a coupling agent into the liquid binder composition containing the water-soluble inorganic binder described above. By incorporating a coupling agent into such a binder composition, the wettability and adhesiveness are improved, and the bond between the coating layer on the foundry sand surface and the water-soluble inorganic binder can be strengthened. Such an effect can be obtained by including the coupling agent in either the coating layer or the binder composition. By containing the agent, the binding force between the two is further improved, and the strength of the finally obtained mold is further improved, which is further preferable. As the coupling agent to be contained in the liquid binder composition, those listed above as coupling agents that can be contained in the coating layer can be exemplified. In addition, the content of the coupling agent in the liquid binder composition is generally 0.5 to 10 parts by mass, preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder contained therein. The ratio is 1 to 5 parts by mass, more preferably 1 to 3 parts by mass.

Moreover, the liquid binder composition containing a water-soluble inorganic compound may contain inorganic oxide particles. When the binder composition contains the inorganic oxide particles, it is effective in improving the fluidity and filling properties of the mold material and the moisture resistance of the finally obtained mold. The size of the inorganic oxide particles used in the present invention is preferably smaller than the foundry sand particles constituting the mold material. Inorganic oxide particles having a size of 0.3 μm or more and 200 μm or less, particularly preferably 0.5 μm or more and 100 μm or less are used. The average particle diameter can be obtained from the particle size distribution measured by a laser diffraction particle size distribution analyzer or the like. The content of the inorganic oxide particles in the binder composition is generally 5 to 200 parts by mass, preferably 10 to 100 parts by mass, based on 100 parts by mass of the solid content of the water-soluble inorganic binder contained therein. It is assumed to be a ratio of parts by mass.

The inorganic oxide particles used in the present invention may be spherical particles or non-spherical particles, but spherical particles are more advantageous in exhibiting the effects of the present invention, and in particular, provide a better casting surface. It is preferable in that it is possible to obtain a casting product having a Such spherical particles may have a spherical shape that is generally recognized, and are not necessarily required to have a true spherical shape, but usually have a sphericity of 0.5 or more. is preferably 0.7 or more, more preferably 0.9 or more, is advantageously used. Here, the sphericity is defined as the aspect ratio (ratio of minor axis/major axis) obtained from the projection shape of 10 randomly selected single particles in observation using a scanning electron microscope. It means the average value. When non-spherical inorganic oxide particles are used, projections and depressions are present on the surface of the inorganic oxide particles, and therefore, for example, the inorganic oxide particles are dissolved by the supplied moisture. When trying to flow between the particles of the molding sand together with the hard water glass, the projections on the surface of the inorganic oxide particles collide with the particles of the molding sand and other inorganic oxide particles, resulting in an anti-slip effect. The flow of water glass and inorganic oxide particles between particles is hindered, and as a result, there is a possibility that the filling property and strength of the finally obtained mold are lowered.

In addition, the material constituting such inorganic oxide particles is not particularly limited, but inorganic metal oxides are preferable. As particles of inorganic metal oxides, particles of silicon dioxide, aluminum oxide, titanium oxide, etc. are advantageously used. It can react with the silanol groups formed on the surface, and when the water evaporates, a strong bond is formed between the silicon dioxide and the solidified water glass, which can improve the mold strength. is preferred. There are two types of silicon dioxide: crystalline and amorphous. Amorphous silicon dioxide is preferable. Silica produced by thermal decomposition of ₄ , silicon dioxide produced by oxidizing metallic silicon with gas containing oxygen, quartz glass powder of spherical particles produced from crystalline quartz by melting and then rapid cooling, etc. can be exemplified. . These can of course be used alone, and can also be used in combination of two or more. In the present invention, silicon dioxide is treated as an inorganic metal oxide.

Furthermore, the liquid binder composition constituting the present invention may contain a moisture resistance improver. By including a moisture resistance improver in the binder composition, the moisture resistance of the finally obtained mold can be improved. As the moisture resistance improver used in the present invention, any agent that has been conventionally used in mold materials can be used as long as it does not hinder the effects of the present invention. Specifically, carbonates such as zinc carbonate, basic zinc carbonate, iron carbonate, manganese carbonate, copper carbonate, aluminum carbonate, barium carbonate, magnesium carbonate, calcium carbonate, lithium carbonate, potassium carbonate, sodium carbonate, tetraborate Sodium, potassium tetraborate, lithium tetraborate, ammonium tetraborate, calcium tetraborate, strontium tetraborate, silver tetraborate, sodium metaborate, potassium metaborate, lithium metaborate, ammonium metaborate, metaboric acid Calcium, silver metaborate, borate salts such as copper metaborate, lead metaborate, magnesium metaborate, sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, titanium sulfate, aluminum sulfate, sulfuric acid Sulfates such as zinc, copper sulfate, sodium phosphate, sodium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, aluminum phosphate, Phosphates such as zinc phosphate, lithium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide, hydroxides such as zinc hydroxide, silicon, zinc, magnesium, aluminum, Examples include oxides of calcium, lithium, copper, iron, boron, zirconium, and the like. Among them, basic zinc carbonate, sodium tetraborate, potassium metaborate, lithium sulfate, and lithium hydroxide improve moisture resistance more advantageously when water glass is used as the water-soluble inorganic binder. Is possible. Moisture resistance improvers such as those mentioned above may be used alone, or may be used in combination of two or more. Some of the moisture resistance improvers listed above include compounds that can be used as water-soluble inorganic binders. When used, it can act as a moisture resistance improver.

The total amount of such a moisture resistance improver used is generally 0.5 to 0.5 parts per 100 parts by mass of the solid content of the water-soluble inorganic binder in the liquid binder composition. It is preferably about 50 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 2 to 15 parts by mass. In order to enjoy the effect of adding the moisture resistance improver advantageously, it is desirable that the amount used is 0.5 parts by mass or more. is desirably set to 50 parts by mass or less because there is a risk of causing problems such as a decrease in the strength of the mold finally obtained.

Furthermore, in the foundry material according to the present invention, a surfactant may be contained in the liquid binder composition that coats the surface of the foundry sand particles. By including a surfactant in a binder composition containing a water-soluble inorganic binder, the wet mold material according to the present invention can: 1) be prepared (manufactured) due to the presence of the surfactant; 2) the surface tension of water is suppressed to improve the fluidity of the mold material; It is possible to advantageously enjoy effects such as that the mold exhibits excellent strength in addition to excellent releasability from the mold. In the present invention, the content of the surfactant in the liquid binder composition is 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder contained therein. part, preferably 0.5 to 15.0 parts by mass, particularly preferably 0.75 to 12.5 parts by mass.

In the present invention, surfactants added to the liquid binder composition include cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, and silicone surfactants. Both active agents and fluorosurfactants can be used. Specific examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, and imidazolinium salts. Examples of anionic surfactants include fatty acid soaps, N-acyl-N-methylglycine salts, N-acyl-N-methyl-β-alanine salts, N-acylglutamates, alkyl ether carboxylates, acyl peptide, alkylsulfonate, alkylbenzenesulfonate, alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkylsulfoacetate, α-olefinsulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol Sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxysulfate, polyoxyethylene alkylphenyl ether sulfate, monoglysulfate, fatty acid alkylolamide sulfate, alkyl ether phosphorus acid ester salts, alkyl phosphate salts, and the like. Furthermore, amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine, and the like. In addition, nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, polyoxyethylene alkylphenyl ethers (e.g., Emulgen 911), polyoxyethylene sterol ethers, polyoxyethylene lanolin derivatives. , polyoxyethylene polyoxypropylene alkyl ether (e.g. 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 fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetylene glycol, Acetylene alcohol etc. are mentioned.

Among various surfactants, those having a siloxane structure as a non-polar site are called silicone-based surfactants, and those having a perfluoroalkyl group are called fluorine-based surfactants. Examples of silicone-based surfactants include polyester-modified silicones, acrylic-terminated polyester-modified silicones, polyether-modified silicones, acrylic-terminated polyether-modified silicones, polyglycerin-modified silicones, aminopropyl-modified silicones, and the like. In addition, fluorine-based surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyltrimethylammonium salts, perfluoroalkylethylene oxide adducts, and perfluoroalkyl groups. containing oligomers, and the like.

In the present invention, various surfactants as described above can be used alone or in combination of two or more. However, some surfactants may react with the water-soluble inorganic binder and may lose or lose their surfactant ability over time. is used, anionic surfactants, nonionic surfactants and silicone surfactants that do not react with such water glass are particularly advantageously used in the mold material of the present invention.

In addition, in the wet mold material according to the present invention, a polyhydric alcohol may be contained in the liquid binder composition that covers the surfaces of the foundry sand particles on which the coating layer is formed. In this way, the polyhydric alcohol is contained in the binder composition containing the water-soluble inorganic binder. It can be stably maintained until it is solidified or cured by In the present invention, the content of the polyhydric alcohol in the binder composition is 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder contained therein. 0.5 to 15.0 parts by mass is more desirable, and 0.75 to 12.5 parts by mass is most desirable.

Specific examples of polyhydric alcohols that can be used in the present invention include 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- Examples include octanediol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane and the like.

Furthermore, in the wet mold material according to the present invention, various known additives are optionally added to the liquid binder composition surrounding the foundry sand particles, together with the above-described coupling agent or the like, or alone. It is also possible to contain additives as appropriate. In addition, in order to include such an additive in the binder composition, when preparing the liquid binder composition, it is added to the composition together with a water-soluble inorganic binder and the like. In addition, a method of kneading or mixing a binder composition containing additives with the foundry sand, or a method of adding a predetermined additive to the foundry sand separately from the binder composition to obtain a total A method of kneading or mixing uniformly is adopted.

As one of such additives, in the present invention, a lubricant that contributes to improving the fluidity of the mold material is advantageously used. Lubricants that can be used in the present invention include waxes such as paraffin wax, synthetic polyethylene wax and montanic acid wax; fatty acid amides such as stearamide, oleamide and erucamide; Alkylene fatty acid amides such as 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, etc. can do In addition, as a release agent, paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, vermiculite, fluorine release agent, silicone release agent. Agents and the like can also be used. These other additives are generally 0.5 to 10 parts by mass, preferably 1 part by mass, per 100 parts by mass of the solid content of the water-soluble inorganic binder contained in the liquid binder composition. To 5 parts by mass, more preferably 1 to 3 parts by mass.

By the way, the wet mold material according to the present invention is prepared by: 1) first forming a solid coating layer containing an organic compound on the surface of the foundry sand; Then, a liquid binder composition containing a water-soluble inorganic binder is added and kneaded or mixed.

In producing the wet mold material of the present invention according to such a production method, first, a solid coating layer containing an organic compound is formed on the surface of foundry sand. Therefore, one suitable for the characteristics of the organic compound is appropriately selected and employed. For example, dry hot coating, cold coating, etc. can be exemplified as methods for forming a solid coating layer containing an organic compound on the surface of foundry sand. If so, the method is not particularly limited.

In the dry hot coating method, a solid organic compound is added to and mixed with foundry sand heated to 130 to 180° C., the solid organic compound is melted by the heat of the foundry sand, and the melted organic compound is In this method, the surface of the refractory aggregate is coated with a compound, and then cooled while the mixture is maintained to form a solid coating layer on the surface of the foundry sand. In the cold coating method, an organic compound is used as it is or dissolved in a solvent such as methanol to form a liquid, and the liquid is added to and mixed with the foundry sand to evaporate the solvent. It is a method of forming a solid coating layer on the surface.

Further, when a crosslinked curable resin is used as the organic compound, for example, after forming a solid coating layer according to the above-described coating method, further heating and/or by adding a curing agent or a curing catalyst, The crosslinkable curable resin may be cured to increase the molecular weight of the crosslinkable curable resin contained in the coating layer. When the cross-linking curable resin is cured by heating, for example, it is placed in a constant temperature bath at 120°C to 300°C for 5 to 60 minutes for reaction hardening, or casting sand is heated to 150°C to 300°C and heated to 120°C. There is a method of kneading for about 5 to 60 minutes in a kneader heated to 300° C. for reaction hardening. In addition, the mold material in which the cross-linked curable resin contained in the coating layer has hardened has strong necks between molding sand particles (sand grains), and there is a possibility that it will form a single lump or form composite particles. In order to improve the surface condition of the foundry sand coated with , it is preferable to carry out reaction hardening with a high-speed kneader (speed muller) which has kneading and a high rotational speed. Further, if kneaded for a long time, peeling may occur and fine powder may be generated, so it is preferable to carry out the reaction at a high temperature for a short time. On the other hand, when a curing agent or curing catalyst is used to cure the crosslinked curable resin, the curing agent or curing catalyst includes, for example, hexamethylenetetramine, organic ester, organic acid, carbon dioxide gas, peroxide, metal ion, Amine or the like is used. Moreover, when the crosslinkable curable resin is a phenol urethane resin, it can be cured by mixing a phenol resin and a polyisocyanate resin. Even when a curing agent is used to cure the crosslinked curable resin, it is desirable to carry out reaction curing while kneading with a kneader.

Next, when the foundry sand having a solid coating layer containing an organic compound on its surface is coated with a liquid binder composition containing a water-soluble inorganic binder, for example, the coating layer is Solids containing organic compounds are obtained by kneading or mixing a water-soluble inorganic binder as a binder with the provided foundry sand, together with additives as necessary, by kneading or mixing. A wet foundry material according to the invention is obtained which consists of an admixture of a foundry sand provided with a crystalline coating layer and a liquid binder composition containing a water-soluble inorganic binder. Various conditions for mixing are appropriately determined according to the type and water content of the water-soluble inorganic binder, and the temperature for mixing is generally normal temperature to 40°C. degree. When producing the wet mold material according to the present invention, the water content is adjusted so that the resulting mold material exhibits an appropriate wet state. When water glass is used, the water content in the mold material is more than 55% by mass, preferably 70 to 900% by mass, more preferably 95 to 500% by mass of the solid content of the water glass. adjusted to In the wet mold material according to the present invention, the moisture content of which is adjusted in this way, the wet mold material is prevented from drying and blocking due to blowing air when the mold is filled during mold making. In addition to being able to maintain the wettability of the mold material in a wet state, the mold made using such a mold material is also endowed with excellent properties. . The water content of the mold material can be measured by the Karl Fischer method or by weight change when heated in a dryer or the like.

The wet mold material (coated sand) according to the present invention thus obtained can be used to form the desired mold using various conventionally known techniques. For example, the wet mold material (coated sand) described above is filled into the mold cavity of the mold that provides the desired mold, and the mold is heated to a temperature of 80 to 300°C, preferably 100 to 200°C. Heat and hold in the mold until the filled mold material (coated sand) is dry. By holding the heat in the mold, solidification or hardening of the filled wet mold material (coated sand) proceeds.

That is, by filling and holding the wet mold material (coated sand) in the cavity of the heated mold, the foundry sand particles constituting the mold material are mixed with the surrounding binder composition. An assembly (combination) of the template material is formed, which is linked to each other via the included water-soluble inorganic binder and presents an integral template shape. At this time, a curing agent may be added into the cavity as an additive for accelerating the curing of the water-soluble inorganic binder. Incidentally, the water-soluble inorganic binder is usually solidified by evaporation of water to dryness if no additives are added, and if a hardening agent is added, it will be hardened. be. In the present invention, the mold made of an aggregate (bonded body) of the mold material may be either a mold material (coated sand) that is simply solidified (solidified product) or a mold material that is hardened with a curing agent (hardened product). includes.

As a curing agent, organic acids such as carbon dioxide (carbonated water), sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, carboxylic acid, paratoluenesulfonic acid, methyl formate, ethyl formate, propyl formate, γ- Esters such as butyrolactone, γ-propionlactone, ethylene glycol diacetate, diethylene glycol diacetate, glycerin diacetate, triacetin, propylene carbonate, and monohydric alcohols such as methanol, ethanol, butanol, hexanol, octanol, etc. can be done. These curing agents can be used alone, and can also be used in combination of two or more.

In addition, when heating the wet mold material (coated sand) in the cavity of the mold, it is advantageous to heat (preheat) to a predetermined temperature in advance and heat the mold at that temperature. It is preferred to prepare, fill the mold material into the cavities of such molds, and heat the mold material. By preheating the mold in this way, it is possible to speed up the drying of the mold material and shorten the molding time. The heat retention temperature for this preheating is 80 to 300.degree. C., preferably 100 to 200.degree. C., more preferably 120 to 180.degree. From the viewpoint of speeding up drying and shortening molding time and improving moisture resistance strength by additives, the temperature is preferably 80°C or higher, and moisture evaporates before sufficient bonding between molding sand particles is formed. However, it is preferably 300° C. or less from the viewpoint of preventing the occurrence of the problem that the mold strength is not developed. By heating the mold at a temperature within such a temperature range, the moisture resistance strength of the finally obtained mold can be improved, and the drying of the mold material can be advantageously promoted.

Furthermore, while the mold material is held in the mold, hot air or superheated steam is blown into the mold in order to promote the evaporation of water so that the filled phase (mold material) in the mold is ventilated. method is preferably employed. Such ventilation of hot air or superheated steam quickly dries even the inside of the filled phase made of the mold material, and further advantageously accelerates the solidification or curing of the filled phase, thereby solidifying (hardening). In addition to advantageously increasing the speed, the properties of the resulting mold such as bending strength can be advantageously improved, and the molding time of the mold can be advantageously shortened. In addition, a carrier gas comprising at least one of carbon dioxide, argon, nitrogen, helium, and air is added to facilitate solidification or hardening of the mold material while the mold material is held in the mold. Blowing into the mold to allow the filling phase to aerate is preferably employed. Carbon dioxide then acts as a curing agent, and argon, nitrogen, helium and air as solidification accelerators. The air is preferably air from which some or all of the water vapor has been removed (dry air), and dry air with a humidity of 50% or less, more preferably dry air with a humidity of 30% or less is used. By neutralizing the water-soluble inorganic binder with a carrier gas, it is possible to further accelerate the solidification or hardening of the mold material. Only one of the hot air or superheated steam ventilation and the carrier gas ventilation may be performed, but it is also possible to perform both. The hot air or superheated steam ventilation and the carrier gas ventilation may be performed. It is possible to carry out simultaneously, to vent hot air or superheated steam followed by carrier gas, or to vent hot air or superheated steam after carrier gas. After filling the cavity of the mold with the mold material in a wet state, as long as it is held in the mold, it does not matter at what timing the hot air and/or carrier gas is vented. do not have.

In order to further promote solidification or curing by heating, a gaseous or atomized organic acid, ester, monohydric alcohol, or the like, which was exemplified as the curing agent, is used as a carrier gas in the mold. can be ventilated.

On the other hand, regarding the molding of a mold using the wet mold material (coated sand) according to the present invention, in addition to the method of heating in the mold as described above, by adding a curing agent in the mold, A method of solidifying or hardening the mold material, or a method of solidifying or hardening the mold material by reducing the pressure in the mold filled with the mold material can also be employed.

The method of adding a curing agent into the mold promotes curing through a reaction between the water-soluble inorganic binder and the curing agent. As a method of adding the curing agent, the curing agent is added to the mold material before filling the mold, and the mold material to which the curing agent is added is filled into the mold. It is also possible to add the hardener as a carrier gas by bubbling into the filled mold material. Curing by the curing agent progresses while it is held in the molding die, and hot air or superheated steam may be blown into the molding die in order to accelerate the evaporation of water. Furthermore, in order to promote solidification or hardening of the mold material more advantageously, a carrier gas consisting of at least one of carbon dioxide, argon, nitrogen, helium and air may be blown into the mold. When the curing agent is added, heating of the mold is not necessarily required, but it is preferable to heat the mold in order to promote solidification or curing more advantageously. Examples of curing agents that can be used here include organic acids such as carbon dioxide (carbonated water), esters such as methyl formate, and monohydric alcohols such as methanol, which were previously listed as curing agents. can do

On the other hand, the method of depressurizing the inside of the mold is to dry and solidify the mold material filled in the cavity of the mold by such decompression. Examples of the depressurizing method include depressurizing the inside of the mold using a known suction means. In addition, when decompressing the mold, hot air or superheated steam may be blown into the mold in order to promote the evaporation of water. Furthermore, in order to promote solidification or hardening of the mold material more advantageously, a carrier gas consisting of at least one of carbon dioxide, argon, nitrogen, helium and air may be blown into the mold. When the mold is depressurized, it is not always necessary to heat the mold, but it is preferable to heat the mold in order to promote solidification or curing more advantageously.

Using the wet mold material according to the present invention, both the mold obtained according to the above-described manufacturing method and the mold obtained according to other manufacturing methods can advantageously enjoy the following excellent effects. It is possible to That is, when casting is performed using such a mold, the organic compounds contained in the solid coating layer on the surface of the foundry sand are effectively thermally decomposed by the heat produced by the molten metal, and gas is generated by such thermal decomposition. As a result, the disintegrability of the mold after casting is improved. The wet mold material of the present invention contains an organic compound in the solid coating layer on the surface of the foundry sand. Since the amount is very small compared to the mold material used in the present invention, when casting is performed using a mold made of the wet mold material of the present invention, the amount of gas generated at that time is This has the advantage of being much less than when using a mold made of mold material. In particular, the mold material is used so that the amount of gas generated when the finally obtained mold is heated at 1000° C. for 240 seconds is 3 to 30 ml, preferably 4 to 28 ml, more preferably 6 to 20 ml per 1 g of the mold. It is preferred to prepare

Further, casting is performed using a mold made of the mold material in a wet state according to the present invention, and in the foundry sand recovered from the mold after such casting (recovered sand), organic compounds present on the surface of the foundry sand Due to the gas generated by the thermal decomposition of the water-soluble inorganic binder, the solidified or hardened water-soluble binder is in a state where it is easy to separate from the surface of the foundry sand. can be easily reproduced.

Here, the dry regeneration treatment for the collected sand can be any method as long as it is a conventionally known dry regeneration treatment method as a method for regenerating the collected sand. In general, a method of treating recovered sand, which includes at least polishing treatment and, if necessary, baking treatment, classification treatment, etc., is called dry recycling treatment.

In the polishing process in the dry reclaiming process, deposits remaining on the surface of the recovered sand particles are scraped off. Specifically, by putting the recovered sand into a rotating rotor, it crushes the foundry sand into individual grains there, and furthermore, deposits on the surface of the foundry sand particles (water-soluble inorganic binder solidified or hardened material) is scraped off. The polishing method is not particularly limited, but examples include polishing using a rotary reclaimer, a sand fresher, a sand shiner, or the like. In addition, various polishing conditions such as polishing time in the polishing process are appropriately determined according to the state of adherence of deposits on the surface of the collected sand.

Further, the firing treatment is performed for the purpose of burning and removing organic compounds, dust, impurities, etc. of the coating layer adhering to the collected sand. For such firing treatment, a roasting furnace such as a rotary kiln or a tunnel kiln is used, and the recovered sand is fired in the furnace while the recovered sand is fed into the roasting furnace at any time. The firing temperature in the roasting furnace is 200 to 700°C, preferably 300 to 700°C, more preferably 350 to 650°C, still more preferably 400 to 600°C. If the firing temperature is lower than 200° C., there is a risk that dust and the like adhering to the collected sand will not be sufficiently burned. On the other hand, if the firing temperature exceeds 700° C., the water-soluble inorganic binder remaining on the surface of the collected sand is sintered and may become difficult to separate from the surface of the sand particles. Such baking treatment may be performed before or after the polishing treatment described above, or may be performed before or after the polishing treatment.

The classification treatment is generally performed after the above-described polishing treatment, or after the baking treatment if the baking treatment is performed after the polishing treatment, and the foundry sand taken out from the above-described treatment steps. A dust collection step in which fine powder contained in the treated molding sand is removed by a dust collector while the treated material is made to flow by an air flow, and a sieving step in which foreign matter contained in the treated foundry sand is removed by a sieve. have. Specifically, in the dust collection step, the treated foundry sand is fluidized by an air flow, and fine particles such as shavings, dust, and fine powder contained in the treated foundry sand that could not be removed in the previous steps are removed. The bodies are removed with a dust collector in an active state, which effectively removes fine residues from the foundry sand treatment. In the sieving step, a sieve is used to classify the particle size of the treated foundry sand, thereby removing foreign matter contained in the treated foundry sand that could not be removed in the previous steps. Thereby, sand with an appropriate particle size is selectively taken out.

In addition, the classification process employed in the present invention is not limited to the one having the dust collection process and the sieving process as described above, and for example, the classification process having only one of the dust collection process and the sieving process. There is no problem even if the dust collection process is performed after the sieving process is performed. Furthermore, any other known method can be adopted for the classification process as long as it is a method capable of classifying the foundry sand into a predetermined size.

As described above, the foundry sand reclaimed by the recovered foundry sand reclaim method according to the present invention is again supplied to the mold material manufacturing process and the mold making process to provide the foundry sand with excellent properties. As such, it will be used advantageously.

The present invention will be clarified more specifically below using several examples, but the present invention should not be construed in any limited way by the description of such examples. should be understood. In the following examples and comparative examples, "%" and "parts" are expressed on a mass basis unless otherwise specified. In addition, measurement of the viscosity of the liquid binder composition, measurement of the solubility of organic compounds in water, measurement of the amount of gas generated in molds made of mold materials (coated sand: CS) obtained in Examples and Comparative Examples, Evaluation of the casting surface, disintegration property, and polishing removability was performed as follows.

-Measurement of viscosity of liquid binder composition-
JIS-Z-8803-2011 "Method for measuring the viscosity of a liquid" stipulated in "9. Method for measuring viscosity with a single cylindrical rotary calorimeter", using a device with the same principle as the device described therein. Then, the viscosity (cP) at 25° C. of the liquid binder composition used in Examples and Comparative Examples is measured. The liquid binder composition means an aqueous solution of water glass or an aqueous solution of potassium carbonate itself when additives such as silicon dioxide particles are not used in the production of CS. When manufactured, it means a liquid product obtained by adding an additive to an aqueous solution of water glass or the like.

-Measurement of water solubility of organic compounds-
10 g of an organic compound is put into a flask, and 100 g of water at 25° C. is put into the flask and stirred for 1 hour. After that, it is allowed to stand still for 1 hour. Exactly 10 ml of the supernatant liquid in the flask after standing is sampled with a whole pipette or the like, and transferred to an evaporating dish (mass: W1 (g)) with a known mass. Evaporate, dry and solidify with a gas burner or the like so as not to cause bumping. Next, the dried and solidified sample is sufficiently dried together with the evaporating dish in a drier at 110° C. for 3 hours or more, and the mass (W2 (g)) is measured. Considering the mass of the evaporating dish, the dissolved amount of the organic compound (W3 (g)) is obtained from the following formula.
W3(g) = (W2-W1) x 10
Using W3 calculated above, the solubility of the organic compound in water at 25° C. is calculated from the following formula.
Solubility (mass%)
= {dissolved amount / water volume} x 100 = {W3/100} x 100

－Measurement of gas generation amount－
Using each CS, a cylindrical test piece with a diameter of 3 cm and a length of 5 cm was molded, and the test piece was placed in a quartz glass tube with a diameter of 4.5 cm and a length of 45 cm. Seal with silicone rubber. Using a horizontal molding sand dilatometer EOS-3 (product name, manufactured by Ozawa Kagaku Co., Ltd.), the test piece together with the glass tube is exposed to heat at 1000° C. for 4 minutes. The amount of generated gas is measured every 30 seconds with a W-NK type wet gas meter (product name, manufactured by Shinagawa Co., Ltd.). The total amount of gas generated in 4 minutes from the start of heat exposure (total amount of gas generated) was divided by the mass of the test piece to obtain the amount of gas generated.
Gas generation amount (ml/g)
= [Total amount of gas generated after 4 minutes (ml)]/[Specimen mass (g)]

-Disintegration test-
First, as shown in FIG. 1, a half-split hollow main mold 6 (cavity diameter: 6 cm, height: 6 cm), a circular airless element 10 (diameter: 5 cm, height: 5 cm) having a baseboard part 8 made using each CS is adhesively fixed by a baseboard fixing part 4. After that, the half-split hollow main molds 6 are further adhesively fixed to each other to produce a sand mold 12 for casting test. In addition, in order to prevent molten metal from leaking during casting, the bonded main mold is clamped with a vise or the like, or tightly fixed by winding a wire. Next, molten iron FC150 (at a temperature of 1350±50° C.) is poured from the pouring port 2 of the sand mold 12 for casting test and allowed to solidify. 16 is taken out, and an air hammer is used to hit the casting 16 that has reached room temperature, thereby ejecting the circular airless element 10 . During this discharge, the chipping pressure is set at 0.3 MPa, and the casting 16 is hit with an air hammer every 3 seconds. Then, the easiness of discharging the CS (hereinafter referred to as core CS) constituting the circular non-aerial element 16 from the casting 16 is evaluated in five grades according to the following criteria. In the present invention, A to C are accepted.
A: All the cores CS were discharged within 10 hits.
B: All the cores CS were discharged within 30 hits.
C: All the cores CS were discharged within 60 hits.
D: 50% or more to less than 100% of the core CS was discharged after 60 impacts.
E: 0 to less than 50% of the core CS was discharged at 60 impacts.

-Evaluation of casting surface-
The casting obtained in the collapsibility test described above is cut in half, and the condition of the casting surface (casting surface) is visually and tactilely checked, and evaluated according to the following four-grade criteria. In the present invention, ⊚ and ∘ are regarded as acceptable.
⊚: No seizure was observed and the surface was smooth.
◯: No seizing is observed, but surface roughness is observed.
Δ: Seizure is observed in part of the casting surface, and roughness is also observed on the surface.
x: Seizure is observed on the entire surface of the casting surface, and roughness is also observed on the surface.

- Polishing peelability test -
100 g of the sand (recovered sand) constituting the circular aneurons taken out in the aforementioned collapsibility test was placed in a ball mill and ground for 1 hour. Thereafter, the sand is sieved with 200 mesh for 1 minute to separate the foundry sand from the exfoliated fine powder. Evaluate with In the present invention, A to C are regarded as acceptable.
A: The amount of fine powder is 2% by mass or more with respect to the mass of foundry sand.
B: The amount of fine powder is 1% by mass or more and less than 2% by mass with respect to the mass of the foundry sand.
C: The amount of fine powder is 0.5% by mass or more and less than 1% by mass with respect to the mass of the foundry sand.
D: The amount of fine powder is 0.25% by mass or more and less than 0.5% by mass with respect to the mass of the foundry sand.
E: The amount of fine powder is less than 0.25% by mass relative to the mass of foundry sand.

In addition, the novolak-type phenolic resins and the like used in the production of each CS were prepared according to the following procedures or commercially available products.

(1) Novolac Phenolic Resin Into a reaction vessel equipped with a thermometer, a stirrer and a condenser were charged 940 parts of phenol, 479 parts of 47% formalin and 2.8 parts of oxalic acid. Next, the inside of the reaction vessel is gradually heated to reach the reflux temperature, and the mixture is refluxed for 90 minutes for reaction. A novolak-type phenolic resin having a weight average molecular weight (Mw) of 2900 was obtained.

(2) Resol type phenolic resin A
As the resol-type phenolic resin A, SP400 (trade name, Mw: 2100) manufactured by Asahi Organic Chemicals Co., Ltd., which is an ammonia resol-type phenolic resin, was used.

(3) Resol type phenolic resin B
A reaction vessel equipped with a thermometer, stirrer and condenser was charged with 940 parts of phenol, 957 parts of 47% formalin and 20 parts of potassium hydroxide. Then, the inside of the reaction vessel was gradually heated up to 75° C. in 60 minutes, and the reaction was carried out at that temperature for 5 hours. Thereafter, dehydration was carried out to 80° C. under reduced pressure to obtain a resol-type phenolic resin B having a weight average molecular weight (Mw) of 1,500.

(4) Phenolic urethane resin A benzylic ether type phenol resin (manufactured by Asahi Organic Chemicals Co., Ltd., trade name: CBP-160EH, Mw: 1200) and a polymeric MDI (manufactured by Asahi Organic Chemicals Co., Ltd.; CB- MT3) was prepared, and a mixture in which these two resins were mixed at a ratio of 1:1 (mass ratio) was used when forming a coating layer on the surface of the foundry sand.

(5) Polyvinyl Acetate Polyvinyl acetate solution of Gohsenyl M35-X6 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., 35% methanol solution) was used as polyvinyl acetate.

(6) Starch A starch solution (concentration: 25%) obtained by dissolving starch manufactured by Wako Pure Chemical Industries, Ltd. in hot water at 70°C was used.

-Production example 1 of wet CS-
Lunamos #60 (trade name, manufactured by Kao-Quaker Co., Ltd.), which is commercially available artificial sand for casting, was prepared as foundry sand, and a novolac-type phenolic resin was prepared as an organic compound. Then, after heating Lunamos #60 to a temperature of about 130° C., it is put into a whirl mixer (manufactured by Enshu Iron Works), and further, 0.3 parts of novolac type phenolic resin is added to 100 parts of Lunamos #60. and kneaded for 3 minutes to evaporate the moisture, while stirring and mixing until the sand grain lumps collapsed, and then taken out, so that a solid novolak phenolic resin was applied to the surface of the molding sand grains. A coating layer was formed. The film thickness of the formed solid coating layer was calculated to be 0.2 μm from the average particle diameter of spherical foundry sand particles and the amount of the foundry sand and organic compound (novolak type phenolic resin) added.

Next, commercially available product No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ /Na ₂ O molar ratio: 2.0) was prepared as water glass as a water-soluble inorganic binder. was used to prepare an aqueous water glass solution having a solid content (concentration) of 31% and a viscosity of 11 cP at 25°C. Then, the previously prepared foundry sand having a solid coating layer on the surface is put into a Shinagawa-type universal stirrer (5DM-r type, manufactured by Dalton Co., Ltd.) at room temperature, and then a water glass aqueous solution is added. , 2.5 parts (solid component: 0.775 parts) per 100 parts of Lunamos #60, kneaded for 3 minutes, stirred and mixed until uniform, and then taken out. Thus, a wet mold material (CS1) composed of a mixture of foundry sand having a coating layer on its surface and an aqueous solution of water glass was obtained. When the water content of CS1 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production Examples 2 to 5 of Wet CS-
In Production Example 1 of wet state CS, the amount of the novolac-type phenolic resin used in forming the coating layer was set to 0.5 parts, 1 part, 2 parts, and 5.5 parts, respectively. Wet mold materials (CS2-CS5) were obtained following a similar procedure. When the water contents of the obtained CS2 to CS5 were calculated from the added amounts of the added materials, all of them corresponded to 223% by mass of the solid content of the water glass.

-Production example 6 of wet CS-
In Production Example 4 of Wet CS, a wet mold material ( CS6) was obtained. When the water content of the obtained CS6 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 7 of wet CS-
In wet state CS production example 1, the amount of novolac-type phenolic resin used in forming the coating layer was 0.8 parts, and silicon dioxide particles 971U (trade name, manufactured by Elkem Co., Ltd., average particle diameter: 0 A wet mold material (CS7) was obtained by following the same procedure as in Preparation Example 1 above, except that 1 part of 0.15 μm) was added to the aqueous water glass solution. When the water content of the obtained CS7 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 8 of wet CS-
In Production Example 3 of Wet CS, except that 0.01 part of KBE903 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silane coupling agent, was added to the novolac-type phenolic resin at the time of forming the coating layer, the above production was performed. Following a procedure similar to Example 3, a wet mold material (CS8) was obtained. When the water content of the obtained CS8 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 9 of wet CS-
In Production Example 3 of Wet CS, the procedure was the same as in Production Example 3 above, except that 0.025 parts of KBE903 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silane coupling agent, was added to the water glass aqueous solution. A wet mold material (CS9) was obtained according to When the water content of the obtained CS9 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 10 of wet CS-
In Production Example 8 of Wet CS, the procedure was the same as in Production Example 8 above, except that 0.025 parts of KBE903 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silane coupling agent, was added to the water glass aqueous solution. A wet mold material (CS10) was obtained according to When the water content of the obtained CS10 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 11 of wet CS-
Wet CS Production Example 3 was the same as Production Example 3 above, except that 0.075 parts of a borate (sodium tetraborate decahydrate) as a moisture resistance improver was added to the aqueous solution of water glass. A wet mold material (CS11) was obtained following a similar procedure. When the water content of the obtained CS11 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 12 of wet CS-
A wet mold material (CS12 ). When the water content of the obtained CS12 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 13 of wet CS-
Except that in Production Example 3 of Wet CS, resol-type phenolic resin B was used instead of novolac-type phenolic resin, and the amount used was 1.6 parts (solid content: 1.0 part) to form a coating layer. obtained a wet mold material (CS13) following the same procedure as in Production Example 3 above. When the water content of the obtained CS13 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 14 of wet CS-
In Production Example 3 of Wet CS, the same procedure as in Production Example 3 was followed except that the coating layer was formed according to the following procedure in order to replace the organic compound forming the coating layer from the novolak phenolic resin to the phenol urethane resin. , to obtain a wet mold material (CS14). That is, Lunamos #60 was put into a whirl mixer (manufactured by Enshu Iron Works Co., Ltd.) at 130 ° C., and a benzylic ether type phenol resin and a polyisocyanate resin for constituting a phenol urethane resin were mixed at a mass ratio of 1:1. They are added in an amount such that the total amount thereof is 1.4 parts, kneaded in a mixer, and the benzylic ether type phenol resin and the polyisocyanate resin react to form a phenol urethane resin (solid content: 1.0 parts). ), and the mixture was stirred and mixed until it hardened and solidified, and then it was taken out. When the water content of the obtained CS14 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 15 of wet CS-
In wet state CS production example 3, the novolak type phenolic resin was replaced with a polyvinyl acetate solution (35% methanol solution), the amount used was 1.54 parts (solid content: 1.0 parts), and when the coating layer was formed, A wet mold material (CS15) was obtained following the same procedure as in Production Example 3 above, except that the solvent was evaporated. When the water content of the obtained CS15 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Production example 16 of wet CS-
In wet CS production example 3, a starch solution (concentration: 25%) obtained by dissolving starch in hot water at 70°C was used in place of the novolak-type phenolic resin, and the amount used was 4 parts (solid content: 1 A wet mold material (CS16) was obtained according to the same procedure as in Production Example 3 above, except that the content was changed to .0 parts. When the water content of the obtained CS16 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Wet CS Production Example 17-
In Production Example 3 of Wet CS, commercial product No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.0) was used as the aqueous solution of water glass. A wet mold material (CS17 ). When the water content of the obtained CS17 was calculated from the added amount of the added material, it was an amount corresponding to 117% by mass of the solid content of the water glass.

-Wet CS Production Example 18-
In Wet CS Production Example 3, 0.15 part of hexamethylenetetramine was added during kneading to form a solid coating layer made of a novolak-type phenolic resin on the surface of the foundry sand, and then such a coating layer was formed. A wet mold material (CS18) was obtained according to the same procedure as in Production Example 3 above, except that the foundry sand was placed in a constant temperature bath at 180° C. for 30 minutes to accelerate the curing of the novolak-type phenolic resin. When the water content of the obtained CS18 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Wet CS Production Example 19-
In Wet CS Production Example 12, after forming a solid coating layer made of resol-type phenolic resin A on the surface of the foundry sand, the foundry sand having the coating layer formed thereon was placed in a constant temperature bath at 180°C for 30 minutes. A wet mold material (CS19) was obtained in the same manner as in Production Example 12, except that the curing of the resol-type phenolic resin A was accelerated. When the water content of the obtained CS19 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Wet CS Production Example 20-
In wet CS production example 3, instead of the aqueous solution of water glass, an aqueous potassium carbonate solution having a potassium carbonate solid content (concentration) of 50% and a viscosity of 8 cP at 25° C. was used. A wet mold material (CS20) was obtained according to the same procedure as in Production Example 3 above, except that the amount used was changed to 3 parts. When the water content of the obtained CS20 was calculated from the added amount of the added material, it was an amount corresponding to 100% by mass of the solid content of potassium carbonate.

-Production Examples 21 to 24 of Wet CS-
Wet CS production examples 1, 7, 8, and 11 were prepared according to the same procedure as in production examples 1, 7, 8, and 11 above, except that the step of forming a solid coating layer was not performed. A mold material (CS21 to CS24) in the form of When the water content of the obtained CS21 to CS24 was calculated from the added amount of the added material, all of them were equivalent to 223% by mass of the solid content of the water glass.

- Production example 25 of wet CS -
A wet mold material (CS25) was obtained in the same manner as in Production Example 20 except that the step of forming a solid coating layer was not carried out in Production Example 20 of Wet CS. When the water content of the obtained CS25 was calculated from the added amount of the added material, it was an amount corresponding to 100% by mass of the solid content of potassium carbonate.

-Wet CS Production Example 26-
In Wet CS Production Example 25, the same procedure as in Production Example 25 above, except that 0.03 part of a silane coupling agent KBE903 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the aqueous potassium carbonate solution. A wet mold material (CS26) was obtained according to When the water content of the obtained CS26 was calculated from the added amount of the added material, it was an amount corresponding to 100% by mass of the solid content of potassium carbonate.

-Wet CS Production Example 27-
In Wet CS Production Example 25, except that 0.09 parts of sodium tetraborate decahydrate as a moisture resistance improver was added to the aqueous potassium carbonate solution, wet A mold material (CS27) in the form of When the water content of the obtained CS27 was calculated from the added amount of the added material, it was an amount corresponding to 100% by mass of the solid content of potassium carbonate.

-Molding examples of molds (Examples 1 to 20, Comparative Examples 1 to 7)-
After filling CS1 to 27 produced according to the above procedures into a molding die heated to 150° C., they are held in the molding die, and each CS filled in the molding die is cured. Thus, a mold used as a test piece (diameter: 5 cm×height: 5 cm) of a circular aneuron was produced. Tables 1 to 4 below show the CS used in producing the molds (test pieces) for Examples 1 to 20 and Comparative Examples 1 to 7.

As is clear from Tables 1 to 4, the molds (Examples 1 to 20) obtained by using the mold materials in a wet state according to the present invention are excellent in disintegration property after casting, It is recognized that the casting surface of the cast product obtained is also good. In addition, with respect to the sand recovered after casting, it is recognized that the solidified or hardened material of the water-soluble inorganic binder adhering to the sand can be easily removed by polishing. It is also confirmed that the wet mold material facilitates regeneration of the foundry sand.

-Wet CS Production Examples 28 and 29-
In wet state CS production example 7, silicon dioxide particles 971U (trade name, manufactured by Elkem, average particle size: 0.15 μm) as a filling improver, and silicon dioxide particles HS312 (trade name, Nippon Steel & Sumikin Materials Co., Ltd.) company, average particle size: 9.5 μm), aluminum oxide particles AZ-75 (trade name, Nippon Steel & Sumikin Materials Co., Ltd., average particle size: 2.5 μm). Wet mold materials (CS28, CS29) were obtained according to the procedure of . The water content of the obtained CS28 and CS29 was calculated from the added amount of the added material, and the amount was equivalent to 226% by mass of the solid content of the water glass.

-Production Examples 30 and 31 of Wet CS-
Production Example 11 above except that borate (sodium tetraborate decahydrate) in Production Example 11 of wet CS was replaced with sulfate (lithium sulfate) and carbonate (basic zinc carbonate), respectively. Wet mold materials (CS30, CS31) were obtained according to the same procedure. When the water content of the obtained CS30 and CS31 was calculated from the added amount of the added material, the amount was equivalent to 226% by mass of the solid content of the water glass.

-Production example 32 of wet CS-
In wet state CS production example 11, the above production was performed except that 1 part of silicon dioxide particles 971U (trade name, manufactured by Elkem, average particle size: 0.15 μm) as a filling improver was added to the water glass aqueous solution. Following a procedure similar to Example 11, a wet mold material (CS32) was obtained. When the water content of the obtained CS32 was calculated from the added amount of the added material, it was an amount corresponding to 226% by mass of the solid content of the water glass.

- Production example 33 of wet CS -
In wet state CS production example 30, the above production was carried out except that 1 part of silicon dioxide particles 971U (trade name, manufactured by Elkem, average particle size: 0.15 μm) as a filling improver was added to the water glass aqueous solution. Following a procedure similar to Example 30, a wet mold material (CS33) was obtained. When the water content of the obtained CS33 was calculated from the added amount of the added material, it was an amount corresponding to 226% by mass of the solid content of the water glass.

-Production example 34 of wet CS-
In Production Example 31 of Wet CS, except that 1 part of silicon dioxide particles 971U (trade name, manufactured by Elkem, average particle size: 0.15 μm) as a filling improver was added to the aqueous solution of water glass. Following a procedure similar to Example 31, a wet mold material (CS34) was obtained. When the water content of the obtained CS34 was calculated from the added amount of the added material, it was an amount corresponding to 226% by mass of the solid content of the water glass.

Using each of CS3, CS7, CS8, CS9, CS10, CS11 and CS28 to CS34, each CS was blown into a mold heated to 150 ° C. at a gauge pressure of 0.3 MPa, and then 90 A test piece (width: 1 cm x height: 1 cm x length: 8 cm) for strength test was prepared by holding for 2 seconds. The hygroscopic strength retention rate of the obtained test pieces was calculated according to the procedure shown below (Examples 21 to 33). The results are shown in Tables 5 and 6 below.

-Hygroscopic strength retention-
For the test piece obtained using each CS, the breaking load was measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd., digital casting sand strength tester), and then using this measured breaking load , the bending strength was calculated by the following formula. The breaking load was measured using a room temperature test piece 1 hour after molding.
Bending strength (N/cm ² )=1.5×LW/ab ²
[However, L: distance between fulcrums (cm), W: breaking load (N), a: width of test piece (cm), b: thickness of test piece (cm). ]
Next, put water, a glycerol mixed solution, and a wire mesh with four clogs in a container, and place each test piece on the wire mesh so that the test piece does not come into contact with the water and glycerol mixed solution (20% concentration). The container was placed in a temperature controller and held at 40° C. for 24 hours to cause moisture absorption deterioration of each test piece. The bending strength of each test piece after the moisture absorption deterioration was measured in the same manner as described above. From the bending strength before moisture absorption and the bending strength after moisture absorption, the hygroscopic strength retention rate was calculated based on the following formula.
Moisture absorption strength retention rate (%) = (transverse strength after moisture absorption/transverse strength before moisture absorption) x 100

As is clear from Tables 5 and 6, by adding moisture resistance improvers such as borates, sulfates, and carbonates to the binder composition, and by adding silicon dioxide particles, , it is recognized that the hygroscopic strength retention rate of the finally obtained mold is greatly improved. Further, although it is recognized that the hygroscopic strength retention rate of the mold is improved by incorporating a coupling agent into either the solid coating layer or the liquid binder composition, It is recognized that the hygroscopic strength retention rate of the mold is further improved by including the coupling agent in both of the binding agent compositions.

- Production example 35 of wet CS -
In Production Example 8 of Wet CS, a wet mold material ( CS35) was obtained. When the water content of the obtained CS35 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Wet CS Production Example 36-
In Production Example 9 of Wet CS, a wet mold material (CS36 ). When the water content of the obtained CS36 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

-Wet CS Production Example 37-
In wet state CS production example 10, the amount of the silane coupling agent added to the novolak-type phenolic resin was set to 0.03 parts, and the amount of the silane coupling agent added to the water glass aqueous solution was set to 0.075 parts. A wet mold material (CS37) was obtained in the same manner as in Production Example 10 except that the procedure was followed. When the water content of the obtained CS37 was calculated from the added amount of the added material, it was an amount corresponding to 223% by mass of the solid content of the water glass.

Using each of CS3, CS8, CS9, CS10 and CS35 to CS37, each CS is blown into a mold heated to 150° C. at a gauge pressure of 0.3 MPa, and then held for 90 seconds. Thus, a test piece for strength test (width: 1 cm x height: 1 cm x length: 8 cm) was produced. The bending strength of the obtained test pieces was calculated according to the procedure shown below (Examples 34 to 40). The results are shown in Table 7 below.

- Bending strength -
For the test piece obtained using each CS, the breaking load was measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd., digital casting sand strength tester), and then using this measured breaking load , the bending strength was calculated by the following formula. The breaking load was measured using a room temperature test piece 1 hour after molding.
Bending strength (N/cm ² )=1.5×LW/ab ²
[However, L: distance between fulcrums (cm), W: breaking load (N), a: width of test piece (cm), b: thickness of test piece (cm). ]

As is clear from Table 7, in the mold material according to the present invention, the final It is recognized that strength is improved in the mold obtained by the method. In particular, it is recognized that by incorporating a coupling agent into each of the solid coating layer and the water-soluble inorganic binder, a mold exhibiting very high mold strength can be obtained due to a synergistic effect.

2 Molten metal injection port 4 Baseboard fixing part 6 Main mold 8 Baseboard part 10 Core 12 Sand mold 14 Waste core discharge port 16 Casting

Claims (23)

A foundry sand coated with a solid coating layer containing a crosslinked curable resin and/or a cured product thereof and a coupling agent is coated with a liquid binder composition containing a water-soluble inorganic binder. A wet mold material characterized by: The mold material according to claim 1, wherein the solid coating layer has a thickness of 0.1 to 6 µm. 3. A mold material according to claim 1 or 2, wherein said crosslinked curable resin is a phenolic resin. The mold material according to any one of claims 1 to 3, wherein the crosslinked curable resin has a weight average molecular weight of 300 or more . The mold material according to any one of claims 1 to 4, wherein the crosslinked curable resin and its cured product have a solubility of 1% by mass or less in 100 g of water at 25°C. The mold material according to any one of claims 1 to 5, wherein the solid content of the water-soluble inorganic binder in the liquid binder composition is 10 to 80 mass%. A mold material according to any one of claims 1 to 6, wherein the liquid binder composition comprises a coupling agent. 8. The mold material of any one of claims 1 to 7, wherein the liquid binder composition comprises inorganic oxide particles. 9. The mold material of claim 8, wherein said inorganic oxide particles are silicon dioxide particles. 10. The mold material of any one of claims 1-9, wherein the liquid binder composition comprises a moisture resistance improver. The mold material according to any one of claims 1 to 10, wherein the water-soluble inorganic binder is water glass. 12. The mold material of any one of claims 1-11, wherein the liquid binder composition comprises water. A mold made using the mold material according to any one of claims 1 to 12 . 14. The mold according to claim 13, wherein the amount of gas generated when heated at 1000° C. for 240 seconds is 3 to 30 ml per 1 g. a step of forming a solid coating layer containing a crosslinked curable resin and/or a cured product thereof and a coupling agent on the surface of foundry sand;
a step of adding a liquid binder composition containing a water-soluble inorganic binder to the foundry sand on which the solid coating layer is formed, and kneading or mixing the mixture;
A method for producing a wet mold material comprising: The step of forming the solid coating layer on the surface of the foundry sand , and then curing the cross-linking curable resin contained in the solid coating layer. The method for producing a mold material according to claim 15 , comprising: 17. The method for producing a mold material according to claim 15 or 16, wherein the water-soluble inorganic binder is water glass. 18. The method for producing a mold material according to any one of claims 15 to 17, wherein the liquid binder composition contains water. After filling the mold material according to any one of claims 1 to 12 , it is held in the mold, a) heating the mold, b) the mold or c) reducing the pressure in the mold to solidify or harden the mold material filled in the mold to obtain the desired mold. A method of manufacturing a mold, characterized in that: 20. The mold manufacturing method according to claim 19 , wherein hot air or superheated steam is passed through the mold while the mold is being held. 21. The mold manufacturing method according to claim 19 or 20 , wherein a carrier gas comprising at least one of carbon dioxide, argon, nitrogen, helium and air is passed into the mold while the mold is being held. The mold manufacturing method according to any one of claims 19 to 21 , wherein the mold is heated to a temperature of 80°C to 300°C. After casting using a mold made of the solidified or cured product of the mold material according to any one of claims 1 to 12 , the foundry sand is recovered from the mold and subjected to dry recycling treatment. A method for reclaiming foundry sand, comprising:

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