JP7122977B2 - Mold material composition and mold manufacturing method using the same - Google Patents

Description

The present invention relates to a mold material composition and a method for manufacturing a mold using the same, and in particular, a mold material that allows the finally obtained mold to exhibit excellent strength and also excellent collapsibility. Compositions and methods of advantageously making molds using such mold material compositions.

Conventionally, as one of the molds used for casting molten metal, a mold material composition in which mold sand made of refractory aggregate is coated with a predetermined caking material is used to mold a desired shape. The material obtained through this process is used. Specifically, in "Casting Engineering Handbook" edited by the Japan Foundry Engineering Society, pp. 78-90, as a caking agent in such a mold material composition, in addition to an inorganic caking agent such as water glass, phenol Organic caking agents using resins such as resins, furan resins and urethane resins have been clarified, and techniques for forming self-hardening molds using these caking agents have also been clarified.

Further, in Japanese Patent Application Laid-Open No. 2012-076115 (Patent Document 1), as a caking agent-coated refractory using water glass as a caking agent, a solid coating layer containing water glass is used as a refractory aggregate. A caking agent-coated refractory (mold material composition) having good fluidity is disclosed. There, such a caking agent-coated refractory (mold material composition) with good fluidity is filled into the molding cavity of a mold for making a mold, and then is allowed to pass through water vapor. It has been clarified that solidification of such a caking agent-coated refractory (mold material composition) proceeds to give the desired mold.

By the way, in the case of molding a mold using a dry mold material composition having good fluidity, the mold material composition is wetted with moisture such as water vapor and then dried. By solidifying, the desired casting mold is formed. After that, a molten metal such as an aluminum alloy is poured into the obtained mold to form a casting. must be destroyed. However, in a mold made with a water glass caking material, the organic caking material cannot be burned or carbonized by the heat of the molten metal, as in the case of using an organic caking material such as phenol resin. So, it is not possible to eliminate the cohesive force and promote the collapse. In addition, in the case of organic caking additives, disintegration improvers and the like are sometimes used to promote combustion by generating oxygen by heat. It is not possible to think in the same way as in the case of materials. As a result, the cohesive force remains even after casting, which inherently poses a problem of poor collapsibility.

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 that the finally obtained mold exhibits excellent strength and is also disintegrable. To provide a mold material composition capable of giving a casting having an excellent and favorable casting surface. Another object of the present invention is to provide a mold manufacturing method using such an excellent mold material composition.

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) (a) a refractory aggregate;
(b) a caking additive containing water glass as an essential component;
(c) at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid.
(2) the nitrate is 100% solids of water glass in the mold material composition;
The mold material composition according to the aspect (1), characterized in that it is contained in a proportion of 0.5 to 30 parts by mass with respect to parts by mass.
(3) The mold material composition according to aspect (1) or aspect (2), wherein the nitrate is selected from the group consisting of potassium nitrate, sodium nitrate, calcium nitrate and magnesium nitrate.
(4) The mold material composition according to any one of the aspects (1) to (3), further comprising a hydrocarbon-containing compound.
(5) The mold material composition according to aspect (4), wherein the hydrocarbon-containing compound is a surfactant.
(6) the surfactant accounts for 1 part of the water glass solid content in the mold material composition;
The mold material composition according to the aspect (5), characterized in that it is contained in a ratio of 0.1 to 20 parts by mass with respect to 00 parts by mass.
(7) The mold material composition according to the aspect (4), wherein the hydrocarbon-containing compound is a lubricant.
(8) The aspect (7) characterized in that the lubricant is contained at a ratio of 0.1 to 10 parts by mass with respect to 100 parts by mass of the water glass solid content in the mold material composition. ).
(9) The mold material composition according to any one of the aspects (1) to (8), which further contains a carbonate and/or a borate.
(10) The carbonate and/or borate is contained at a ratio of 0.5 to 50 parts by mass with respect to 100 parts by mass of the water glass solid content in the mold material composition. The mold material composition according to the aspect (9), characterized in that:
(11) The refractory aggregate is spherical in the aspect (1) to the aspect (1)
0) The mold material composition according to any one of 1).
(12) The mold material composition is a mixture in a dry state having normal temperature fluidity, in which the surface of the refractory aggregate is covered with the coating layer containing the water glass, and the water content in the mixture is , 5 to the solid content of the water glass
The aspect (1) to the aspect (1) characterized by being 55% by mass
The mold material composition according to any one of 1).
(13) Preheated refractory aggregate with water glass as an essential component caking additive and at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid. and evaporating the water to form a coating layer of the caking additive on the surface of the refractory aggregate, and the water content thereof becomes 5 to 55% by mass of the solid content of the water glass. A method for producing a mold material composition, characterized in that it is taken out as a dry mixture having room temperature fluidity.
(14) Using the dry mold material composition obtained by the production method according to the aspect (13), filling it into a mold, and then allowing water vapor to pass through,
A mold manufacturing method characterized by obtaining a desired mold by holding it in such a mold and solidifying or hardening it.
(15) The mold manufacturing method according to the aspect (14), wherein the mold is heated to a temperature of 80°C to 200°C.
(16) Using the dry mold material composition obtained by the production method according to the aspect (13), water is added to make it wet, and the moist coated sand is put into a mold. A method of manufacturing a mold, characterized in that a desired mold is obtained by filling the inside of the mold with the material, holding the material in the mold, and solidifying or hardening the mold.
(17) The mold manufacturing method according to the aspect (16), wherein the mold is heated to a temperature of 80°C to 300°C.
(18) Any one of the aspects (14) to (17), wherein hot air or superheated steam is passed through the mold while the mold material composition is held in the mold. A method for manufacturing a mold according to claim 1.
(19) At least one selected from the group consisting of (a) a refractory aggregate, (b) a caking additive containing water glass as an essential component, and (c) an alkali metal salt and an alkaline earth metal salt of nitric acid By mixing with one nitrate,
A method for producing a mold material composition, characterized in that it is taken out as a wet mixture.
(20) Using a mold material composition in a wet state formed by the manufacturing method according to the aspect (19), filling it into a heated mold, and then holding it in the mold. and solidifying or hardening to obtain a desired mold.
(21) The mold manufacturing method according to the aspect (20), wherein the mold is heated to a temperature of 80°C to 300°C.
(22) A method for manufacturing a mold, comprising forming a desired mold by lamination molding using the mold material composition according to any one of the above aspects (1) to (12). .

As described above, since the molding material composition according to the present invention contains water glass as a caking additive and a predetermined nitrate, it is possible to mold using such a molding material composition. When casting a predetermined molten metal in a mold, the nitrates dispersed in the mucosa on the surface of the refractory aggregate formed of water glass are decomposed by the heat of the molten metal to generate oxygen, nitrogen dioxide gas, etc. By doing so, the gas generated in the mucous membrane of the water glass causes cracks to occur, and the mucous membrane of the water glass is destroyed, so that the mold can be easily collapsed. be. In addition, such nitrogen dioxide gas combines with the moisture remaining in the water glass to generate nitric acid, which neutralizes the sodium silicate in the water glass and vitrifies it, thereby embrittlement of the water glass. is obtained, and thus the mold can be easily collapsed by impact or the like. Moreover, due to the film effect of the generated gas, a gas film is formed between the mold and the molten metal, which advantageously increases the smoothness of the mold surface, thereby advantageously improving the casting surface of the resulting casting. The improved characteristics will also be exhibited. Furthermore, by combining nitrates with carbonates and/or borates, it is possible to further improve the collapsibility of the mold, improve the moisture resistance of the mold, and suppress strength deterioration due to moisture absorption. Become.

FIG. 2 is a vertical cross-sectional explanatory view of a sand mold for casting test used to measure the collapsibility of cores 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 molding material composition according to the present invention is generally prepared by: 1) mixing a refractory aggregate with a caking additive containing water glass as an essential component and a nitrate, and evaporating water from the mixture; , in other words, it is produced by evaporating the water content of the water glass in the state of an aqueous solution. 2) Manufactured by mixing a caking additive containing water glass as an essential component and nitrate with refractory aggregate, which is formed on the surface of aggregate. Specifically, it may be in a wet state formed by kneading water glass in the state of an aqueous solution and a refractory aggregate, and in a dry state it has good fluidity at room temperature. However, in the wet state, it does not have such room temperature fluidity. The mold material composition according to the present invention can be applied in either a dry state or a wet state. can be said to be desirable.

Here, the "dry mold material composition having normal temperature fluidity" in the present invention means a mold material composition that gives a measured value when the dynamic angle of repose is measured, regardless of the water content. It is something to do. This dynamic angle of repose is obtained by housing the mold material composition in a cylinder whose one end in the axial direction is closed with a transparent plate (for example, in a container with a diameter of 7.2 cm and a height of 10 cm, Fill the mold material composition to half of its volume), hold the axis in the horizontal direction, and rotate around the horizontal axis at a constant speed (e.g., 25 rpm) to flow in the cylinder. The slope of the mold material composition layer on which the surface is formed is flat, and the angle formed between the slope and the horizontal plane. The dynamic angle of repose is preferably 80° or less, more preferably 45° or less, and even more preferably 30° or less. Especially when the refractory aggregate is spherical, a dynamic angle of repose of 45° or less can be easily achieved. In addition, when the mold material composition is wet and does not flow in the cylinder, the slope of the mold material composition layer is not formed as a flat surface, and as a result, the dynamic angle of repose cannot be measured. is classified as a wet mold material composition.

In the dry mold material composition having room temperature fluidity according to the present invention, the water content is An amount corresponding to a proportion of 5 to 55% by mass is desirable, more preferably 10 to 50% by mass, and most preferably 20 to 50% by mass. When the water content in this mold material composition is less than the amount corresponding to 5% by mass with respect to the solid content of the water glass in the coating layer, the water glass vitrifies and water is added again during mold making. However, if the amount is more than 55% by mass, the mold material composition may not reach a dry state. The method for measuring the water content in the mold material composition is not particularly limited, and a known method suitable for the type of water glass, nitrate, or the like can be appropriately employed. Specifically, the measuring method described in the section of Examples below can be exemplified.

On the other hand, in the wet mold material composition according to the present invention, the water content should correspond to a ratio of 70 to 400% by mass with respect to the solid content of the water glass used as the caking additive. is preferable, and 80 to 300% by mass is more preferable, and 90 to 200% by mass is most preferable. When the water content in the mold material composition is less than the amount corresponding to 70% by mass of the solid content of the water glass, the viscosity of the water glass increases, making it difficult to mix uniformly during kneading. A good template cannot be obtained. On the other hand, if it exceeds the amount corresponding to 400% by mass, the mold material composition may become slurry, and as a result, it may not be possible to fill the mold. Moreover, even if it can be filled, it may take a long time to dry in the mold.

Here, the refractory aggregate constituting the mold material composition of the present invention is a refractory substance functioning as a base material of the mold, and various refractory granular or Any powdery material can be used, specifically silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag. , slag-based particles such as converter slag; artificial particles such as alumina-based particles and mullite-based particles, and regenerated particles thereof; alumina balls, magnesia clinker, and the like. It should be noted that these refractory aggregates may be new sand, or recycled or recovered sand that has been used as foundry sand once or several times for molding molds, and furthermore, such recycled sand may be used. Mixed sand obtained by adding new sand to sand or recovered sand and mixing them may be used without any problem. Such refractory aggregates are generally used with a particle size of about 40 to 200, preferably about 50 to 150 in terms of AFS index. Further, the refractory aggregate is preferably spherical, and specifically, it is desirable that the particle shape coefficient is 1.2 or less, more preferably 1.0 to 1.1. By using a refractory aggregate with a particle shape factor of 1.2 or less, fluidity and filling properties are improved, and the number of contact points between aggregates increases. It is possible to reduce the amount of caking additive and the amount of additives. The particle shape index of the aggregate used here is generally adopted as a measure of the outer shape of the particles, and is also referred to as the particle shape index. It means to approach a (perfect sphere). Such a grain shape factor is represented by a value calculated using a sand surface area measured by various known methods, such as a sand surface area measuring instrument (manufactured by George Fischer). means the value obtained by measuring the surface area of the actual sand grain per gram and dividing it by the theoretical surface area. The theoretical surface area is the surface area when all sand grains are assumed to be spherical.

In addition, in the mold material composition according to the present invention, water glass is used as an essential component as the caking additive to be mixed with the refractory aggregate as described above. Here, water glass is a water-soluble silicic acid compound, and examples of such silicic acid compounds include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and silicic acid. Among these, sodium silicate (sodium silicate) is particularly advantageously used in the present invention. As the caking agent, as long as water glass is used as an essential component, various water-soluble binders such as thermosetting resins, sugars, proteins, synthetic polymers, salts and inorganic polymers can be used in combination. It is possible. When another water-soluble binder is used in combination with water glass, the proportion of water glass in the entire caking additive is preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably 80% by mass or more, based on the solid content. Preferably, it is 90% mass or more.

Further, the above sodium silicate is usually classified into types 1 to 5 according to the molar ratio of SiO ₂ /Na ₂ O and used. Specifically, sodium silicate No. 1 has a 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. In the present invention, these various sodium silicates may be used singly or in combination. By mixing, the molar ratio of SiO ₂ /Na ₂ O can be adjusted. It is possible.

In the present invention, in order to advantageously obtain the desired mold material composition, the sodium silicate constituting the water glass used as the caking additive generally has a SiO ₂ /Na ₂ O molar ratio of 1.5. It is desirably 9 or more, preferably 2.0 or more, more preferably 2.1 or more, and sodium silicates corresponding to Nos. 1 and 2 in the above sodium silicate classification are particularly advantageously used. It will happen. Such sodium silicates No. 1 and No. 2, respectively, provide mold material compositions that are stable and have good properties even in 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. , 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, the viscosity of the water glass becomes low, especially in the dry state, and unless the water content is considerably reduced, the mold material composition becomes On the other hand, if it is more than 3.5, the solubility in water decreases, the adhesion area cannot be increased, and the strength of the finally obtained mold decreases. There is fear.

In addition, the water glass used in the present invention means a solution of a silicic acid compound dissolved in water. It will be added and used in a diluted state. Then, 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 above-mentioned soluble silicate compound such as sodium silicate. It is something to do. Also, the higher the proportion of such solids (non-volatiles), the higher the silicic acid compound concentration in the water glass. Therefore, the solid content of the water glass used in the present invention corresponds to the amount excluding the water content in the concentrate when the water glass is composed only of the concentrate. When a diluted solution obtained by diluting with becomes.

Furthermore, the solid content in such water glass is set to an appropriate proportion depending on the type of the water glass component (soluble silicic acid compound), etc., and is preferably 20 to 50% by mass. It is desirable to contain in. By allowing the water glass component corresponding to this solid content to exist in the aqueous solution appropriately, when mixing (kneading) with the refractory aggregate, the refractory aggregate is evenly and uniformly in a dry state. It is possible to form a coating of the water glass component, and to mix the aggregate and the water glass evenly and uniformly in a wet state, thereby advantageously forming the desired mold. It becomes possible. If the concentration of the water glass components in the water glass becomes too low and the total amount of solid content becomes less than 20% by mass, the heating temperature is raised in order to dry the mold material composition in the dry state. Also, it is necessary to lengthen the heating time, which causes problems such as energy loss. In a wet state, the time required for heating in the mold becomes longer, causing the problem of a prolonged molding cycle of the mold. In addition, if the proportion of solids in the water glass becomes too high, it becomes difficult to evenly coat the surface of the refractory aggregate with the water glass component in the dry state, and the viscosity of the water glass in the wet state increases. is too high, it becomes difficult to evenly and uniformly mix the aggregate and the water glass, which causes problems in improving the properties of the desired mold. Therefore, it is desirable to prepare the water glass in the form of an aqueous solution so that the water content is 50% by mass or more.

It is desirable that such water glass be used at a ratio of 0.1 to 5.0 parts by mass in terms of solid content when considering only the non-volatile content with respect to 100 parts by mass of the refractory aggregate. , from 0.3 to 4.0 parts by weight are particularly advantageously employed. Here, the measurement of solid content is carried out 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 dish is inverted and left on the heating plate for an additional 20 minutes. Thereafter, the sample dish is taken out from the heating plate, allowed to cool in a desiccator, weighed, and the solid content (% by mass) is calculated 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 water glass used is too small, it becomes difficult to form a coating layer on the surface of the refractory aggregate in a dry state, and the aggregate is covered with an aqueous solution of water glass in a wet state. There is a possibility that solidification or hardening of the mold material composition during mold making will not proceed sufficiently. In addition, even if the amount of water glass used is too large, an excessive amount of water glass will adhere to the surface of the refractory aggregate in a dry state, making it difficult to form a uniform coating layer and increasing the amount of the mold material. There is also a risk that the composition will adhere to each other and form nodules (composite particles), and in a wet state, an excessive amount of water glass will cause unevenness during mold molding, and there is a risk that uniform physical properties of the mold will be hindered. As a result, the physical properties of the finally obtained mold are adversely affected, and in addition, there is a risk of causing the problem of difficulty in removing sand from the core after casting the metal.

A major technical feature of the molding material composition according to the present invention is that the predetermined nitrate is present in the water glass (coating layer) that covers the surface of the refractory aggregate. It exists. That is, since the predetermined nitrate is dispersed in the water glass, the nitrate in the water glass is decomposed by the heat of the molten metal to produce nitrogen oxide gas such as nitrogen dioxide gas and oxygen. The generated gas causes cracks in the mucous conjunctiva made of water glass existing on the surface of the refractory aggregate, and breaks the mucous membrane of water glass, thereby facilitating the collapse of the mold. I can. Furthermore, the sodium silicate in the water glass is neutralized by the nitric acid generated by the reaction with the moisture in the water glass, vitrification, and the effect of making the mold brittle is obtained. It becomes possible to make it easy to collapse. Furthermore, the film effect of the generated gas creates a gas film between the mold and the molten metal, which advantageously enhances the smoothness of the mold surface, thereby effectively improving the casting surface of the resulting casting. It will also be possible.

Here, the amount of the above-described predetermined nitrate contained in the mold material composition in the present invention is desirably 0.5 to 30 parts by mass with respect to 100 parts by mass of the solid content of the water glass. , Among them, 1 to 25 parts by mass is preferable, and 3 to 20 parts by mass is particularly preferable. If the amount of nitrate contained is too small, there is a risk that the above-mentioned effects cannot be advantageously obtained. Not permitted, and furthermore, it is not advisable from a cost-effectiveness point of view. In the present invention, the predetermined nitrate includes sodium nitrate and potassium nitrate which are alkali metal nitrates, and calcium nitrate and magnesium nitrate which are alkaline earth metal nitrates. It is possible to mix and use the above. In particular, sodium nitrate and potassium nitrate are recommended because of their high solubility in water glass. Since these nitrates have the property of being easily mixed with water glass, the nitrates can be uniformly dispersed in the cococonjunctiva of the water glass during molding of the mold.

By the way, in the mold material composition of the present invention, in addition to the above-described nitrates and the like, it is also possible to appropriately contain various known additives as necessary. In particular, it is preferable to use a nitrate in combination with a hydrocarbon-containing compound, and the reaction between the organic content of the hydrocarbon-containing compound and the nitrate reduces the collapsibility of the mold formed using the mold material composition. , can be further improved. Any compound containing a hydrocarbon group may be used as the hydrocarbon-containing compound, but preferred examples include surfactants and lubricants.

When a surfactant as such an additive is added to the mold material composition, it reacts with oxygen generated from the nitrate and burns, thereby further improving the disintegration property. of. In addition, the presence of the surfactant provides excellent water permeability, in other words, excellent wettability with water. For this reason, when water is supplied to a dry mold material composition during molding, the surfactant mediates between the supplied water and the water glass, so that even a small amount of water can be used. Even if there is, the entire mold material composition will be effectively moistened. , water vapor ventilation time) can be minimized, and 2) the amount of water supplied to the mold (molding cavity) can be suppressed to a small amount. In addition to being excellent in releasability from the mold, it is possible to advantageously enjoy effects such as exhibiting excellent strength.

In the present invention, the amount of surfactant contained in the mold material composition is desirably 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of the water glass. 0.5 to 15.0 parts by mass is preferable, and 0.75 to 12.5 parts by mass is particularly preferable. If the amount of the surfactant to be contained is too small, there is a risk that the above effects cannot be advantageously enjoyed. No improvement in effectiveness is observed, and furthermore, it is not a good plan from the viewpoint of cost effectiveness.

Examples of such surfactants include cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, silicone surfactants and fluorosurfactants. , can be used. Specific examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, and benzethonium chloride. 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 ethoxy sulfate, 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. Among them, 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. be done. In addition, fluorine-based surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, 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 water glass and their surface activity may decrease or disappear over time. Polysurfactants and silicone-based surfactants are particularly advantageously used in the mold material composition of the present invention.

Further, in the present invention, it is preferable to add a lubricant as an additive so that it exists on the surface of the refractory aggregate of the mold material composition. The presence of such a lubricant can advantageously improve the fluidity of the mold material composition. Moreover, the combination of the lubricant and the nitrate causes the organic matter of the lubricant to react with the oxygen generated from the nitrate and burn, thereby further improving the collapsibility of the mold.

Here, the amount of the lubricant contained in the mold material composition according to the present invention is desirably 0.1 to 10 parts by mass, preferably 0.3 parts by mass, per 100 parts by mass of the solid content of the water glass. 8 parts by mass is preferable, and 0.5 to 5 parts by mass is particularly preferable. If the amount of the lubricant to be contained is too small, the above-mentioned effects may not be advantageously obtained. , is not a good idea from a cost-effectiveness point of view.

Lubricants used in the present invention include, for example, waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; fatty acid amides such as stearamide, oleic acid amide, and erucic acid amide; Alkylene fatty acid amides such as ethylene bisstearic acid amide; stearic acid, stearyl alcohol; stearic acid metal salts such as lead stearate, zinc stearate, calcium stearate, magnesium stearate; stearic acid monoglyceride, stearyl stearate, hydrogenated oil, etc. can be used. Among these, calcium stearate and the like are particularly advantageously used. It is to be noted that a hydrocarbon-free lubricant such as graphite, talc, mica, and molybdenum disulfide may be used in combination with the hydrocarbon-containing compound lubricant.

In addition, in the mold material composition of the present invention, it is preferable to use nitrate in combination with at least one of carbonate and/or borate. Further useful effects can be obtained by using together. That is, like nitrates, carbonates release carbon dioxide due to the heat generated by molding and casting, causing cracks in the mucous membrane of the water glass, breaking the mucous membrane of the water glass, and easily collapsing the mold. At the same time, the generated carbon dioxide becomes carbonated water of a weak acid due to the water content in the water glass, and can accelerate the neutralization reaction, although the effect is lower than that of nitrate. On the other hand, borate reacts with OH in the water glass and tetraborate ions or metaborate ions generated from the borate due to the heat of molding and casting, blocking the OH in the water glass and regenerating. It becomes difficult to dissolve, thereby preventing the softening of the mucous conjunctiva of water glass and promoting the effect of nitrate. From these facts, the collapsibility of a mold molded using the mold material composition can be further improved, the moisture resistance of the mold can be improved, and strength deterioration due to moisture absorption can be suppressed. .

In the present invention, the amount of carbonate and/or borate contained in the mold material composition should be 0.5 to 50 parts by mass with respect to 100 parts by mass of the solid content of the water glass. , preferably 1 to 20 parts by mass, particularly preferably 2 to 15 parts by mass. If the amount of carbonate and/or borate to be contained is too small, the above-described effects may not be advantageously obtained. Even if it is too long, the improvement of the effect according to the amount used is not recognized, and furthermore, it is not a good idea from the viewpoint of cost effectiveness. Carbonate and borate may be used in combination.

Examples of such carbonates include 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, and the like. mentioned. Also, such borates include sodium tetraborate, potassium tetraborate, lithium tetraborate, ammonium tetraborate, calcium tetraborate, strontium tetraborate, silver tetraborate, sodium metaborate, Potassium metaborate, lithium metaborate, ammonium metaborate, calcium metaborate, silver metaborate, copper metaborate, lead metaborate, magnesium metaborate, and the like. Among them, basic zinc carbonate, sodium tetraborate, and potassium metaborate can more advantageously improve disintegration and moisture resistance when used in combination with nitrates.

In the present invention, a moisture resistance improver may be added as another additive. By adding a moisture resistance improver to the water glass, the moisture resistance of the finally obtained mold can be improved. As the moisture resistance improver used in the present invention, any agent conventionally used in coated sand can be used as long as it does not inhibit the effects of the present invention. Specifically, sulfates such as sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, titanium sulfate, aluminum sulfate, zinc sulfate, 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, Hydroxides such as calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide and zinc hydroxide, oxides such as silicon, zinc, magnesium, aluminum, calcium, lithium, copper, iron, boron and zirconium , can be exemplified. Among them, lithium sulfate and lithium hydroxide can more advantageously improve moisture resistance. Moisture resistance improvers such as those mentioned above may be used alone, or may be used in combination of two or more.

The total amount of such a moisture resistance improver to be used is generally about 0.5 to 50 parts by mass with respect to 100 parts by mass of the solid content of the water glass. 20 parts by weight is more preferred, and 2 to 15 parts by weight is even more preferred. 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. It is desirable that the amount is 50 parts by mass or less, since there is a risk of causing problems such as deterioration of the strength of the finally obtained mold.

In addition, as other additives, it is also effective to contain a coupling agent that strengthens the bond between the refractory aggregate and the water glass. Examples include silane coupling agents, zircon coupling agents, and titanium coupling agents. etc. can be used. Furthermore, release agents include 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-based release agent, silicone-based release agent. Agents and the like can also be used. These other additives are generally contained in an amount of 5% by mass or less, preferably 3% by mass or less, relative to the solid content of the water glass.

By the way, in the production of the dry mold material composition having normal temperature fluidity according to the present invention, water glass as a caking agent and a predetermined nitrate are generally added to the refractory aggregate, if necessary. The refractory aggregate is kneaded or mixed together with the additives used in the method to be uniformly mixed so that the surface of the refractory aggregate is coated with the water glass composition containing nitrate and the like, and such water glass A method of forming a coating layer of the water glass composition on the surface of the refractory aggregate by evaporating the water content of the composition is adopted. In such a method, water glass in the form of an aqueous solution is used for refractory aggregates because it is necessary to quickly evaporate water from the coating layer before solidification or hardening of the water glass proceeds. Generally within 5 minutes, more preferably within 3 minutes after adding (mixing), it is desirable to evaporate the contained moisture to obtain a dry powdery molding material composition. If the _time for such transpiration becomes longer, the mixing (kneading) cycle becomes longer, and the productivity of the mold material composition decreases. This is because the risk of causing problems increases.

In the manufacturing process of the mold material composition described above, as one of the effective means for rapidly evaporating the water content in the water glass, the refractory aggregate is heated in advance, and the aggregate is prepared in the form of an aqueous solution. A method of kneading or mixing a certain water glass, a predetermined nitrate, etc., and mixing them is preferably employed. By kneading or mixing the water glass with the preheated refractory aggregate, the water in the water glass is very quickly evaporated by the heat of the refractory aggregate. As a result, the water content of the resulting mold material composition can be effectively reduced, and a dry powder having room temperature fluidity can be advantageously obtained. Here, the preheating temperature of the refractory aggregate is appropriately selected according to the amount of water contained in the water glass, the amount of the water glass, and the like. A temperature of about 100 to 140° C. is adopted. If the preheating temperature is too low, the water cannot evaporate effectively and drying takes a long time. If the temperature is too high, the solidification or hardening of the water glass component will proceed when the resulting mold material composition is cooled, and in addition, the formation of composite particles will proceed. It causes problems in the physical properties such as the strength of the mold obtained in the first step.

On the other hand, in the production of the wet mold material composition according to the present invention, in general, water glass as a caking agent and a predetermined nitrate are added to the refractory aggregate, and additives are used as necessary. At the same time, a method of kneading or mixing at room temperature and uniformly mixing them to form a coating layer of a water glass composition with a high water content on the surface of the refractory aggregate is adopted.

In the mold material composition of the present invention, the nitrate contained in the coating layer of water glass or a water glass composition containing a predetermined nitrate, and other additives used as necessary, such as surfactants, The lubricant or the like may be added to the refractory aggregate in a state of being mixed with the water glass in advance and then kneaded, or may be added separately from the water glass during kneading and kneaded, or may be further kneaded. In some cases, the water glass may be added with a time lag between the addition and kneading. Therefore, the coating layer in the dry mold material composition of the present invention is formed, for example, in a state in which water glass and nitrate or the like are blended together, or in which water flows outward from the surface of the refractory aggregate. While the concentration of the solid content (non-volatile content) of the glass gradually decreases or increases, the concentration of nitrate or the like gradually increases or decreases. Furthermore, water glass as a binder may be diluted with water in order to adjust its viscosity. Also, water glass and water may be added separately during kneading or mixing.

By the way, the following two methods, for example, can be employed in forming a mold using the dry mold material composition according to the present invention. The first of these methods involves kneading a dry mold material composition with water at a molding site where molds are manufactured, thereby moistening the mold material composition to a wet state. The conditioned mold material composition is filled into the molding cavity of a mold that provides the desired mold, and the mold is heated to a temperature of 80 to 300° C. to convert the filled mold material composition into It is a method of holding until it dries in the mold. In the second method, steam is blown into the molding cavity of the mold that provides the desired mold, after the mold material composition is filled, and the filled phase of the mold material composition is moistened by the aeration of the steam. It is a method in which it is heated to a wet state and then held in a mold heated to 80 to 200° C. until it is dried.

In such molding, it is desirable that the mold, such as a metal mold or a wooden mold, to be filled with the dry mold material composition having normal temperature fluidity is preliminarily kept warm by heating, so that the composition can be kneaded with water. Advantageously, the drying of the mold material composition moistened by the water vapor can be allowed to proceed. The heat retention temperature by preheating is generally 80 to 300° C., preferably 90 to 250° C., more preferably 100 to 200° C. in the first method, and 80 to 200° C. in the second method. C., preferably 90-150.degree. C., more preferably about 100-140.degree. If the heat retention temperature is too high, it will be difficult for the steam to pass through the surface of the mold, while if the temperature is too low, it will take time to dry the molded mold.

In addition, the dry mold material composition to be filled into such molds is also advantageously preheated. In general, by filling the molding die with the molding material composition heated to a temperature of 30° C. or higher, the bending strength of the resulting mold can be more advantageously increased. The heating temperature of such a mold material composition is preferably about 30 to 100° C., and particularly a mold material composition heated to a temperature of about 40 to 80° C. is advantageously used. Become.

In the first method described above, the step of adding water to the dry mold material composition to make it wet is simply adding the dry mold material composition and a predetermined amount of water to a suitable mixer. Since it can be carried out by mixing and mixing, it can be carried out in a very simple work, and there is an advantage that it can be carried out very simply and easily even at a molding site where the work environment is bad. . It is also possible to add other additives when adding water.

On the other hand, in the above-described second method, after filling the mold heated as described above, specifically, the mold cavity thereof with the dry mold material composition according to the present invention, Vapor is passed under pressure into the formed filled phase through vents provided in the mold to moisten (moisten) the mold material composition that constitutes the filled phase, thereby forming the mold. The water glass contained in the coating layer of the material composition binds and connects the mold material compositions to form an integral mold-shaped mold material composition assembly (bond). Water glass usually hardens by evaporating water to dryness if no additives are added, and if oxides, salts, esters, etc. It will be done. When the hardening agent is added, the filled phase becomes hardened, but there is no problem even if it is simply hardened.

Here, the temperature of the water vapor that is blown through the vent hole of such a mold and allowed to pass through the filled phase of the mold material composition is generally about 80 to 150°C, more preferably about 95 to 120°C. It is said that If a high steam temperature is employed, a large amount of energy is required for its production. As the pressure of the water vapor to be ventilated, a gauge pressure of about 0.01 to 0.3 MPa, more preferably about 0.01 to 0.1 MPa is advantageously adopted. In the case where the mold material composition has good air permeability, if the pressure for passing water vapor is about the above-mentioned gauge pressure, water vapor can be passed evenly through the mold formed in the mold. In addition, the steam ventilation time and the drying time of the mold can be shortened, and the molding speed can be shortened. Further, with such a gauge pressure, there is an advantage that molding can be performed even when the mold material composition has poor air permeability. If the gauge pressure is too high, there is a risk that staining will occur near the vents. may not be sufficiently wetted.

In addition, as a method for venting water vapor as described above, a technique is adopted in which water vapor is blown in from a vent provided in the mold to vent the inside of the mold material composition (phase) filled in the molding cavity of the mold. Furthermore, as the aeration time, water vapor is supplied to the surface of the filled mold material composition to sufficiently wet the water glass as the binder contained in the coating layer on the surface, and the mold material composition is dried. The time required for mutual bonding (bonding) is appropriately selected depending on the size of the mold and the number of ventilation holes. will be adopted. This is because if the ventilation time of the water vapor is too short, it becomes difficult to sufficiently wet the surface of the mold material composition. This is because there is a possibility that the will dissolve or flow out. As described above, the mold material composition of the present invention is excellent in wettability with water. It is possible to make In addition, the air permeability of water vapor in the mold material composition filled in the mold can be further improved by ventilating water vapor while sucking the atmosphere in the mold from the exhaust port of the mold. is possible.

Additionally, in making molds using the mold material composition of the present invention, the filled phase of the wet mold material composition formed by either of the first and second methods described above is actively dried. For this purpose, a method of blowing dry air, heated dry air, superheated steam, or nitrogen gas to aerate such a packed phase is preferably adopted. By passing such dry air, heated dry air, superheated steam, or nitrogen gas, the inside of the filling phase of the mold material composition is sufficiently and quickly dried to solidify or harden the filling phase. It is possible to accelerate the process more advantageously, thereby advantageously increasing the solidification or hardening speed, and also advantageously improving the characteristics such as the bending strength of the resulting mold. It can contribute to your advantage. It should be noted that hot air such as heated dry air or superheated steam is particularly advantageously used for ventilation for promoting such drying.

Further, a curing agent may be added in the mold as an additive for accelerating the curing of the water glass while it is held in the mold. By neutralizing the caking agent (water glass) with a curing agent, it is possible to further promote its solidification. The curing agent may be ventilated at any time as long as it is held in the molding die, and it does not matter if it is ventilated simultaneously with the ventilating of water vapor or dry air or the like.

As a curing agent, inorganic acids such as carbon dioxide (carbonated water), sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic acids such as oxalic acid, carboxylic acid, and paratoluenesulfonic acid; Esters such as γ-butyrolactone, β-propiolactone, ethylene glycol diacetate, diethylene glycol diacetate, glycerin diacetate, triacetin, propylene carbonate, and monohydric alcohols such as methanol, ethanol, butanol, hexanol, octanol, etc. I can give an example. These curing agents can be used alone, and can also be used in combination of two or more. These curing agents should be gaseous or misted while the mold is held, and should be passed through the mold. There is no problem even if a hardening agent is added together with the water.

On the other hand, in molding a mold with a wet mold material composition according to the present invention, it is advantageous to first place such a mold material composition in the molding cavity of a heated mold which provides the desired mold. Solidification or hardening of the filled mold material composition is effected by filling it into a mold and holding it in the mold until it dries.

In this case, the mold to be filled with the wet mold material composition is desirably preliminarily kept warm by heating, so that the mold material composition filled in the wet state can be dried. Advantageously, it can be allowed to proceed. The temperature to be maintained by preheating is generally 80 to 300.degree. C., preferably 90 to 250.degree. C., more preferably 100 to 200.degree. If the heat retention temperature is too high, the filling of the mold with sand will be poor, while if the temperature is too low, it will take time to dry the molded mold.

Furthermore, when manufacturing a mold using the mold material composition of the present invention, dry air, heated dry air, superheated steam are used to actively dry the filling phase of the mold material composition in the wet state described above. Alternatively, a method of blowing in nitrogen gas to aerate such a filled phase may be adopted. In addition to aeration of dry air or the like, it is also possible to aerate carbon dioxide, an organic acid, a monohydric alcohol, or the like in gaseous or mist form as a curing agent.

Furthermore, when producing the desired mold using the mold material composition according to the present invention, various known methods can be used in addition to the above-described method of filling the mold with the mold material composition and molding. It goes without saying that the molding method of can be appropriately adopted.

In addition, in the production of the mold, as described above, in addition to the method of filling the mold with the mold material composition and molding, various known molding methods can be appropriately employed. It is also possible to employ a layered molding technique in which layers of the composition are sequentially laminated while the portion corresponding to the desired mold is cured to directly mold a three-dimensional mold. It should be noted that a dry state is preferred as the mold material composition used for such laminate molding.

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. The water content, disintegration property, and casting surface of the mold material compositions (CS) obtained in Examples and Comparative Examples were evaluated as follows.

-Measurement of water content to solid content of water glass-
10 g of each CS was weighed and placed in a crucible that had been air-fired and weighed, and the mass loss (%) after exposure to heat at a temperature of 900 ° C. for 1 hour was used to determine the amount of water in CS and the heat of nitrate. The total amount of the decomposition amount and the organic amount (hereinafter referred to as "(moisture + nitrate decomposition amount + organic content) amount" and referred to as "W1") is calculated by the following formula (1). Here, the nitrate thermally decomposed amount is the amount of weight loss due to the decomposition of nitrate, and the organic amount is the total amount of the surfactant and other organic additives (hereinafter referred to as organic content). In addition, the weighing amount is measured to the fourth decimal place. Next, the solid content (B1) of water glass in CS is calculated using the following formula (2). Then, the amount of (moisture + nitrate decomposition amount + organic matter) in CS (W1), the solid content of water glass in CS (B1), the amount of nitrate added to 100 parts of water glass solid content (A), The weight loss rate (C) during nitrate decomposition measured according to the method described later, the amount (D) of the organic component added to 100 parts of the solid content of the water glass, and the dry CS required according to the method described later. From the solid content (E) in the measured organic content, the water content relative to the solid content of water glass (the water content of CS relative to the solid content of water glass in the coating layer: W2) is calculated by the following formula (3a) or (3b ). W2 calculated as described above is shown as "water content (% by mass)" in Tables 1 and 2 below.
W1=[(M1−M2)/M3]×100 (1)
[W1: (moisture + nitrate decomposed content + organic content) amount (%) in CS, M1: total mass (g) of crucible and CS before firing, M2: crucible and CS after firing
total mass (g), M3: mass of CS before firing (g)]
B1=[B2/(100+B2)]×(100−W1) (2)
[B1: Solid content (%) of water glass in CS, B2: Solid content (parts) of water glass added to 100 parts of sand, W1: (moisture + nitrate decomposed content + organic content) content in CS (%)]
For dry:
W2=[(W1/B1)×100]−(A×C)/100
-(D×E)/100 (3a)
[W2: the water content of CS with respect to the solid content of water glass in the coating layer (%
), W1: amount (%) of (moisture + organic content) in CS, B1: amount of solid content of water glass in CS (%), A: amount of nitrate added to 100 parts of solid content of water glass (parts ), C: nitrate decomposition weight loss rate (kneading temperature ~ 9
00° C.) (%), D: Addition amount (parts) of organic content per 100 parts of solid content of water glass, E: Solid content percentage of organic content in CS (%)]
For wet conditions:
W2=[(W1/B1)×100]−(A×F)/100−D
(3b)
[W2: the water content of CS with respect to the solid content of water glass in the coating layer (%
), W1: amount (%) of (moisture + organic content) in CS, B1: amount of solid content of water glass in CS (%), A: amount of nitrate added to 100 parts of solid content of water glass (parts ), F: nitrate decomposition weight loss rate (normal temperature ~ 900
° C) (%), D: Amount (parts) of organic component added to 100 parts of solid content of water glass]

-Measurement of pyrolysis weight loss rate of nitrate-
Using a differential differential thermal balance (TG-DTA Thermoplus2 TG8120 manufactured by Rigaku Corporation; air flow rate: 500 ml/min, heating rate: 10° C./min, Pt pan: φ5 mm × 5 mm), the nitrate sample was heated from room temperature. Heat up to 930°C. At this time, the weight loss rate from kneading temperature to 900 ° C. is obtained, and the thermal decomposition weight loss rate of nitrate (kneading temperature to 900 ° C.) (C) is calculated, while the weight loss rate from room temperature to 900 ° C. Then, the thermal decomposition weight loss rate of nitrate (normal temperature to 900° C.) (F) is calculated.

-Measurement of solid content in organic content-
First, a sample is prepared which consists of a surfactant and other organic additives in the same mixing ratio as the sand (refractory aggregate). Next, 10 g of the previously prepared sample was placed in an aluminum foil dish (length: 9 cm, width: 9 cm, height: 1.5 cm), weighed, and placed on a heating plate maintained at 100 ± 1 ° C. After placing an aluminum foil plate and leaving it for 20 minutes, it is allowed to cool in a desiccator. Then, the aluminum foil plate after standing to cool is weighed, and the solid content (E) in the organic content is calculated from the following formula (4).
E = [{mass of aluminum foil plate after drying (g) - mass of aluminum foil plate (g
)} / {mass of aluminum foil plate before drying (g) - mass of aluminum foil plate (g)}
]×100 (4)

-Core casting test-
First, as shown in FIG. 1, a molten metal injection port 2 and a core baseboard fixing portion 4 (this portion is a discharge port for waste cores from castings) are provided in the upper portion and the lower portion, respectively, which are made of room-temperature self-hardening sand. ) having a half-split hollow main mold 6 (cavity diameter: 6 cm, height: 6 cm). 5 cm) is adhered and fixed by the baseboard fixing part 4, and then the half-split hollow main mold 6 is further adhered and fixed to each other to prepare a sand mold 12 for casting test. Next, a molten aluminum alloy (temperature: 710±5° C.) is poured from the molten metal injection port 2 of the sand mold 12 for casting test and allowed to solidify. A casting 16 having a core outlet 14 (diameter: 1.6 cm) is taken out. Then, when the temperature reaches a predetermined temperature, the casting 16 thus obtained is subjected to impact for 3 seconds at a time with an air hammer at a pressure of 0.2 MPa, and discharged from the discharge port 14 . If the core is 100% sand-discharged, the number of times is recorded, and if the core is not discharged by 10 times, the sand-discharge rate is obtained. The mass of the sand discharged up to 10 times is measured, and the core sand is completely discharged with an air hammer or the like to measure the total mass of the core sand. The sand discharge rate is indicated by mass % obtained by dividing the mass of the discharged core sand by the total mass of the discharged core sand.

-Evaluation of casting surface-
The casting obtained in the above core casting test was cut and the condition of the casting surface on the core side surface was visually evaluated. Evaluation criteria are as follows.
◎: Good ○: Slightly rough casting surface, but no problem for use △: Needs correction by post-processing ×: Poor casting surface

-Production Example 1a of Dry CS-
As a refractory aggregate, Lunamos #60 (trade name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, was prepared, and as a caking agent, a commercially available product: No. 2 sodium silicate (product Name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.5, solid content: 41.3%) was prepared. Then, after heating the above Lunamos #60 to a temperature of about 120° C., it is put into a whirl mixer (manufactured by Enshu Iron Works Co., Ltd.), and the water glass is added to 100 parts of Lunamos #60 at a rate of 2.4. (solid content: 1.0 part), and potassium nitrate is added at a rate of 0.03 part per 100 parts of Lunamos #60 (3 parts per 100 parts of solid content of water glass). Then, kneading was carried out for 3 minutes to evaporate the moisture, and the sand grains were stirred and mixed until the lumps of sand grains collapsed. 1 part to 1 part), stirred and mixed, and then taken out to obtain a dry mold material composition: CS1a having normal temperature fluidity. When the water content of CS1a after kneading was calculated, it was an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 2a of Dry CS-
Dry CS2a having normal temperature fluidity was prepared in the same manner as in Production Example 1a above, except that the amount of potassium nitrate added was 0.1 parts (ratio of 10 parts to 100 parts of the solid content of the water glass). got The water content of CS2a thus obtained was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 3a of Dry CS-
Dry CS3a having normal temperature fluidity was prepared in the same manner as in Production Example 1a above, except that the amount of potassium nitrate added was 0.3 parts (ratio of 30 parts to 100 parts of the solid content of the water glass). got The water content of the obtained CS3a was calculated and found to be equivalent to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 4a of Dry CS-
Except that potassium nitrate was replaced with 0.1 part of sodium nitrate (ratio of 10 parts per 100 parts of solid content of water glass), a dry state having room temperature fluidity was produced in the same manner as in Production Example 1a above. of CS4a was obtained. The water content of the obtained CS4a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Dry CS Production Example 5a-
Except that potassium nitrate was replaced with 0.03 parts of calcium nitrate (ratio of 3 parts per 100 parts of solid content of water glass), the same procedure as in Production Example 1a was performed to obtain a dry state having room temperature fluidity. of CS5a was obtained. The water content of CS5a thus obtained was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Dry CS Production Example 6a-
Except that potassium nitrate was replaced with 0.03 parts of magnesium nitrate (ratio of 3 parts per 100 parts of solid content of water glass), the same procedure as in Production Example 1a above was performed to obtain a dry state having room temperature fluidity. of CS6a was obtained. The water content of the obtained CS6a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 7a of Dry CS-
Commercial product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ /Na ₂ O molar ratio: 2.1, solid content: 48.5%) was used as the water glass of the caking additive. , Also, the same procedure as in Production Example 2a above, except that the amount added was 2.1 parts (solid component: 1.0 parts) per 100 parts of the refractory aggregate (Lunamos #60) According to the method, a dry CS7a having room temperature fluidity was obtained. The water content of the obtained CS7a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 8a of Dry CS-
Commercially available product: No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ /Na ₂ O molar ratio: 3.2, solid content: 38%) is used as the water glass of the caking agent, and , According to the same procedure as in Production Example 2a above, except that the amount added was 2.6 parts (solid component: 1.0 part) per 100 parts of the refractory aggregate (Lunamos #60), A dry CS8a having fluidity at room temperature was obtained. The water content of the obtained CS8a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Dry CS Production Example 9a-
Commercially available anionic surfactant (anionic surfactant) as a surfactant: Olfine PD-301 (trade name: manufactured by Nissin Chemical Industry Co., Ltd.) was used, and it was added to 100 parts of Lunamos #60. 0.12 parts (12 parts per 100 parts of the solid content of the water glass) was added to the water glass in the same manner as in Production Example 2a, except that dry CS9a having room temperature fluidity was added. Obtained. The water content of the obtained CS9a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 10a of Dry CS-
A dry state CS10a having fluidity at room temperature was obtained in the same manner as in Production Example 1a except that no nitrate (potassium nitrate) was added. The water content of the obtained CS10a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 11a of Dry CS-
Dry state CS11a having normal temperature fluidity was obtained according to the same procedure as in Production Example 7a, except that no nitrate was added. When the water content of the obtained CS11a was calculated, it was an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 12a of Dry CS-
Dry CS12a was obtained according to the same procedure as in Production Example 8a above, except that no nitrate was added. The water content of the obtained CS12a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 13a of Dry CS-
Except that basic zinc carbonate was used as a carbonate, and that it was further added at a rate of 0.05 parts per 100 parts of Lunamos #60 (5 parts per 100 parts of solid content of water glass). obtained dry CS13a following the same procedure as in Production Example 2a above. The water content of the obtained CS13a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production Example 14a of Dry CS-
As a borate, sodium tetraborate decahydrate is used, and it is added in a ratio of 0.05 parts to 100 parts of Lunamos #60 (5 parts to 100 parts of solid content of water glass), A dry CS14a was obtained according to the same procedure as in Production Example 2a, except for the additional addition. The water content of the obtained CS14a was calculated and found to be an amount corresponding to 30% by mass of the solid content of the water glass in the coating layer.

-Production example 1b of wet CS-
As a refractory aggregate, Lunamos #80 (trade name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, was prepared. Name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.5, solid content: 41.3%) was prepared. Then, the above Lunamos #80 is put into a Shinagawa type universal stirrer (5DM-r type) (manufactured by Dalton Co., Ltd.) at room temperature, and the water glass is added to 100 parts of Lunamos #80 at 2.4. part (solid component: 1.0 part), and potassium nitrate is added at a rate of 0.03 part per 100 parts of Lunamos #80 (3 parts per 100 parts of solid content of water glass). Then, the mixture was kneaded for 3 minutes, stirred and mixed until uniform, and then taken out to obtain a wet mold material composition: CS1b. When the water content of CS1b after such kneading was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Wet CS Production Example 2b-
According to the same procedure as in Production Example 1b above, except that the amount of potassium nitrate added was 0.1 parts per 100 parts of Lunamos #80 (10 parts per 100 parts of solid content of water glass). , to obtain wet CS2b. The water content of the obtained CS2b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 3b of wet CS-
According to the same procedure as in Production Example 1b above, except that the amount of potassium nitrate added was 0.3 parts per 100 parts of Lunamos #80 (30 parts per 100 parts of solid content of water glass). , to obtain wet CS3b. The water content of the obtained CS3b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass.

-Wet CS Production Example 4b-
Wet CS4b was obtained according to the same procedure as in Production Example 1b above, except that potassium nitrate was replaced with 0.1 part of sodium nitrate (10 parts per 100 parts of solid content of water glass). . When the water content of CS4b obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Wet CS Production Example 5b-
Wet CS5b was obtained according to the same procedure as in Production Example 1b above, except that potassium nitrate was replaced with 0.03 parts of calcium nitrate (ratio of 3 parts to 100 parts of solid content of water glass). . The water content of the obtained CS5b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass.

-Wet CS Production Example 6b-
Wet state CS6b was obtained according to the same procedure as in Production Example 1b above, except that potassium nitrate was replaced with 0.03 parts of magnesium nitrate (ratio of 3 parts to 100 parts of solid content of water glass). . When the water content of CS6b obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Wet CS Production Example 7b-
Commercial product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ /Na ₂ O molar ratio: 2.1, solid content: 48.5%) was used as the water glass of the caking additive. , Also, the same as in Production Example 2b above, except that the amount added was 2.1 parts (solid component: 1.0 parts) per 100 parts of the refractory aggregate (Lunamos #80). Wet CS7b was obtained according to the procedure of . When the water content of CS7b obtained was calculated, it was an amount corresponding to 110% by mass of the solid content of water glass.

-Wet CS Production Example 8b-
Commercially available product: No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ /Na ₂ O molar ratio: 3.2, solid content: 38%) is used as the water glass of the caking agent, and , The same procedure as in Production Example 2b above, except that the amount added was 2.6 parts (solid component: 1.0 part) per 100 parts of the refractory aggregate (Lunamos #80). Wet CS8b was obtained according to When the water content of the obtained CS8b was calculated, it was an amount corresponding to 160% by mass of the solid content of the water glass.

-Wet CS Production Example 9b-
Commercially available anionic surfactant (anionic surfactant) as a surfactant: Olfine PD-301 (trade name: manufactured by Nissin Chemical Industry Co., Ltd.) is used, and the amount added is 100% of Lunamos #80. Dry CS9b having room temperature fluidity was prepared in the same manner as in Production Example 2b above, except that the ratio was 0.12 parts per part (12 parts per 100 parts of the solid content of water glass). Obtained. The water content of the obtained CS9b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass in the coating layer.

-Wet CS Production Example 10b-
Wet CS10b was obtained following the same procedure as in Preparation 1b above, except that no nitrate was added. The water content of the obtained CS10b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass.

-Wet CS Production Example 11b-
Wet CS11b was obtained following the same procedure as in Preparation 7b above, except that no nitrate was added. The water content of the obtained CS11b was calculated and found to be an amount corresponding to 110% by mass of the solid content of the water glass.

-Wet CS Production Example 12b-
Wet CS11b was obtained following the same procedure as in Preparation 8b above, except that no nitrate was added. The water content of the obtained CS12b was calculated and found to be equivalent to 160% by mass of the solid content of water glass.

-Wet CS Production Example 13b-
Except that basic zinc carbonate was used as a carbonate, and that it was further added at a rate of 0.05 parts per 100 parts of Lunamos #80 (5 parts per 100 parts of solid content of water glass). obtained dry CS13b following the same procedure as in Production Example 2b above. The water content of the obtained CS13b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass in the coating layer.

-Wet CS Production Example 14b-
As a borate, sodium tetraborate decahydrate is used, and it is added in a ratio of 0.05 parts to 100 parts of Lunamos #80 (5 parts to 100 parts of solid content of water glass), Dry CS14b was obtained according to the same procedure as in Production Example 2b above, except for the addition. The water content of the obtained CS14b was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass in the coating layer.

-Molding example 1 (Examples 1 to 9, Comparative examples 1 to 3)-
CS1a to CS12a (temperature: 20° C.) produced according to the procedures described above are each blown into a molding die heated to 110° C. at a gauge pressure of 0.3 MPa, and then filled. Further, under a gauge pressure of 0.05 MPa, water vapor at a temperature of 99° C. was blown for 4 seconds to allow air to pass through the mold material composition phase filled in the mold. Then, after such ventilation of steam is completed, hot air at a temperature of 150°C is blown for 2 minutes under a gauge pressure of 0.03 MPa to solidify or harden the CS filled in the mold. A mold used as a test piece [φ5 cm × 5 cm] was produced by each. In such a mold manufacturing process, the molding time from the start of steam ventilation to the end of hot air ventilation was 125 seconds. Table 1 below shows the composition of the CS and the molding conditions used to prepare the molds (test pieces) for Examples 1 to 9 and Comparative Examples 1 to 3. In addition, the above-mentioned core casting test was performed on the circular airless cores (10) produced from CS used in each of Examples 1 to 9 and Comparative Examples 1 to 3, and the collapsibility and yield of the core were evaluated. The casting surface of the casting thus obtained was evaluated, and the results are also shown in Table 1 below.

- Molding Example 2 (Examples 10 to 20, Comparative Examples 4 to 6) -
CS1a to 14a (temperature: 20° C.) produced according to the above procedures are charged into a Shinagawa universal stirrer (type 5DM-r, manufactured by Dalton Co., Ltd.) at room temperature, and water is added to the CS. CS (molding material) was prepared by adding 1.0 part to 100 parts in a stirrer and stirring to moisten each. Next, various types of wet CS taken out from the stirrer are blown into a molding die heated to 150° C. at a gauge pressure of 0.3 MPa to fill the mold, and then held in the molding die. While, under a gauge pressure of 0.03 MPa, hot air at a temperature of 150 ° C. is blown for 2 minutes to solidify or harden the CS filled in the mold, thereby obtaining a test piece [φ5 cm × 5 cm]. The molds used were made individually. Here, the molding time from the start of holding in the molding die to the end of hot air ventilation was 180 seconds. Table 2 below shows the composition of the CS and the molding conditions used to prepare the molds (test specimens) of Examples 10 to 20 and Comparative Examples 4 to 6. In addition, the above core casting test was performed on the circular airless core (10) produced from CS used in each of Examples 10 to 20 and Comparative Examples 4 to 6, and the disintegration property and yield of the core were evaluated. The casting surface of the casting thus obtained was evaluated, and the results are also shown in Table 2 below.

-Molding Example 3 (Examples 21 to 31, Comparative Examples 7 to 9)-
CS1b to 14b (temperature: 20° C.) produced according to each of the procedures described above are filled in a molding die heated to 150° C., and then held as they are in the molding die. Molds used as test pieces [φ5 cm×5 cm] were prepared by solidifying or hardening each of the obtained CSs. Here, the molding time from the start to the end of holding in the molding die was 180 seconds. Table 3 below shows the composition and molding conditions of the CS used to prepare the molds (test pieces) for Examples 21 to 31 and Comparative Examples 7 to 9. In addition, the above-mentioned core casting test was performed on the circular airless core (10) produced from CS used in each of Examples 21 to 31 and Comparative Examples 7 to 9, and the disintegration property and yield of the core were evaluated. The casting surface of the casting thus obtained was evaluated, and the results are also shown in Table 3 below.

As is clear from Tables 1 to 3 above, the molds obtained using CS1a to 9a, 13a to 14a and CS1b to 9b, 13b to 14b according to the present invention have improved collapsibility and casting surface. improvement was observed. In addition, it can be seen that the same effects are obtained in both the dry state and the wet state of CS .

Furthermore, with respect to the test piece obtained according to Mold Making Example 2 using each of CS2a, CS13a, and CS14a, and the test piece obtained according to Mold Making Example 3 using each of CS2b, CS13b, and CS14b, According to the procedure shown below, the hygroscopic strength retention rate was measured (Examples 32 to 37). The measurement results are shown in Table 4 below.

-Measurement of 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 using this measured breaking load, The bending strength was calculated by the following formula. For the measurement of the breaking load, a room-temperature test piece was used after 1 hour from 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, a mixed solution of water and glycerol and a wire mesh with clogs at 4 points are placed in a container, and each test piece is placed on the wire mesh so that the test piece does not touch the mixed solution of water and glycerol (20% glycerol concentration). As a state, 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 determined in the same manner as described above. Then, the hygroscopic strength retention rate was calculated based on the following formula from the flexural strength before moisture absorption and the flexural strength after moisture absorption.
Moisture absorption strength retention rate (%) = (transverse strength after moisture absorption/transverse strength before moisture absorption) x 100

As is clear from Table 4, by adding (in combination with) carbonate or borate to the caking additive together with nitrate, the disintegration improving effect shown in Tables 2 and 3, It is recognized that the hygroscopic strength retention rate of the mold is greatly improved.

2 Molten metal injection port 4 Baseboard fixing part 6 Main mold 8 Baseboard part 10 Circular airless core 12 Sand mold for casting test 14 Waste core discharge port 16 Casting

Claims (19)

(a) a refractory aggregate;
(b) a caking additive containing water glass as an essential component;
(c) at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid, and having a dynamic angle of repose of 80° or less, in a dry state having fluidity at room temperature A mold material composition characterized in that it is constituted as a mixture of The mold material according to claim 1, wherein the nitrate is contained in a ratio of 0.5 to 30 parts by mass with respect to 100 parts by mass of the water glass solid content in the mold material composition. Composition. A mold material composition according to claim 1 or claim 2, wherein said nitrate is selected from the group consisting of potassium nitrate, sodium nitrate, calcium nitrate and magnesium nitrate. 4. The mold material composition according to any one of claims 1 to 3, further comprising a hydrocarbon-containing compound. 5. The mold material composition of claim 4, wherein said hydrocarbon-containing compound is a surfactant. 6. The surfactant according to claim 5, wherein the surfactant is contained in a proportion of 0.1 to 20 parts by mass with respect to 100 parts by mass of the water glass solid content in the mold material composition. Mold material composition. 5. The mold material composition of claim 4, wherein said hydrocarbon-containing compound is a lubricant. The mold material according to claim 7, wherein the lubricant is contained in a proportion of 0.1 to 10 parts by mass with respect to 100 parts by mass of the water glass solid content in the mold material composition. Composition. 9. The mold material composition according to any one of claims 1 to 8, further comprising a carbonate and/or a borate. The carbonate and/or borate is contained in a ratio of 0.5 to 50 parts by mass with respect to 100 parts by mass of solid content of water glass in the mold material composition. 10. A mold material composition according to Item 9. 11. The mold material composition according to any one of claims 1 to 10, wherein the refractory aggregate is spherical. The mold material composition is a mixture in a dry state having room temperature fluidity, in which the surface of the refractory aggregate is covered with the coating layer containing the water glass, and the water content in the mixture is the water 12. The mold material composition according to any one of claims 1 to 11, which is 5 to 55% by mass of the solid content of the glass. 13. A method for producing a mold material composition according to any one of claims 1 to 12, wherein a caking material containing water glass as an essential component is added to the preheated refractory aggregate; A coating layer of the caking material is formed on the surface of the refractory aggregate by mixing with at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts of nitric acid and evaporating water. A method for producing a mold material composition, characterized in that it is formed and taken out as a dry mixture having normal temperature fluidity and a dynamic angle of repose of 80° or less . Using the dry mold material composition obtained by the production method according to claim 13 , fill it in a mold, pass water vapor, hold it in the mold, solidify or A method of manufacturing a mold, characterized in that the desired mold is obtained by curing. The mold manufacturing method according to claim 14 , wherein the mold is heated to a temperature of 80°C to 200°C. Using the dry mold material composition obtained by the production method according to claim 13 , water is added to make it wet, and the moist coated sand is filled in the mold, A mold manufacturing method characterized by obtaining a desired mold by holding it in the mold and solidifying or hardening it. The mold manufacturing method according to claim 16 , wherein the mold is heated to a temperature of 80°C to 300°C. 18. A mold according to any one of claims 14 to 17 , characterized in that hot air or superheated steam is passed through the mold during holding of the mold material composition in the mold. manufacturing method. A method for producing a mold, comprising forming a desired mold by lamination molding using the mold material composition according to any one of claims 1 to 12 .

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