JP7345596B2 - 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 final mold to exhibit excellent strength and collapsibility. The present invention relates to compositions and methods of advantageously manufacturing molds using such mold material compositions.

Conventionally, as one of the molds used for casting molten metal, a mold material composition made of molding sand made of refractory aggregate and coated with a predetermined caking agent is used to mold it into the desired shape. The resulting product is used. Specifically, pages 78 to 90 of "Casting Engineering Handbook" compiled by the Japan Foundry Engineering Society states that in addition to inorganic caking agents such as water glass, phenol is used as a caking agent in such mold material compositions. Organic binders using resins such as resins, furan resins, and urethane resins have been revealed, and methods for molding self-hardening molds using these binders have also been revealed.

Furthermore, in JP-A No. 2012-076115 (Patent Document 1), as a caking agent coated refractory using water glass as a caking agent, refractory aggregate is coated with a solid coating layer containing water glass. A binder-coated refractory (mold material composition) with good fluidity and whose surface is coated has been disclosed. Therefore, such a binder-coated refractory (mold material composition) with good fluidity is filled into the molding cavity of a mold for mold making, and then steam is aerated through it. It has been revealed that the solidification of such a caking agent-coated refractory (mold material composition) progresses and that a desired mold can be obtained.

By the way, when molding a mold using a dry mold material composition with good fluidity, the mold material composition is wetted with moisture such as steam and then dried. By solidifying it, the intended mold is formed. Thereafter, a molten metal such as aluminum alloy is poured into the resulting mold to form a casting.The heat of the molten metal is used to remove the casting from the mold. needs to be destroyed. However, in a mold made with a caking agent using water glass, the organic caking agent may be burned or carbonized by the heat of the molten metal, as is the case when an organic caking agent such as phenol resin is used. Therefore, it is not possible to eliminate cohesion and promote disintegration. In addition, in the case of organic caking materials, disintegration improvers may be used that promote combustion by generating oxygen through heat, but water glass does not burn or carbonize due to the heat of the molten metal, so organic caking materials You cannot think of it in the same way as with wood. For this reason, even after casting, caking force remains, resulting in the problem of poor disintegration properties.

JP2012-76115A

“Casting Engineering Handbook” pp. 78-90

The present invention has been made against this background, and the problem to be solved is to ensure that the mold finally obtained has excellent strength and is also low in collapsibility. It is an object of the present invention to provide a mold material composition that can provide a casting having an excellent and good casting surface. Another object of the present invention is to provide a method for manufacturing a mold using such an excellent mold material composition.

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

(1) (a) refractory aggregate;
(b) a caking agent containing water glass as an essential component;
(c) A wet state that contains at least one nitrate selected from the group consisting of alkaline earth metal salts of nitric acid, and that does not have fluidity at room temperature and does not allow for the measurement of a dynamic angle of repose. A mold material composition characterized in that it is constituted as a mixture of.
(2) The mold material composition according to aspect (1), wherein the nitrate is selected from the group consisting of calcium nitrate and magnesium nitrate.
(3) (a) refractory aggregate;
(b) a caking agent 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;
(d) A mold material composition characterized in that it contains at least a surfactant and is constituted as a wet mixture that does not have fluidity at room temperature and whose dynamic angle of repose cannot be measured. thing.
(4) The mold material composition according to aspect (3), wherein the nitrate is selected from the group consisting of potassium nitrate, sodium nitrate, calcium nitrate, and magnesium nitrate.
(5) The above embodiment, characterized in that the surfactant is contained in a proportion of 0.1 to 20 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition ( 3) or the mold material composition according to aspect (4).
(6) Aspect (1) characterized in that the nitrate is contained in a proportion of 0.5 to 30 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition. The mold material composition according to any one of the above aspects (5) to 1.
(7) The mold material composition according to any one of aspects (1) to (6), further comprising a lubricant.
(8) Aspect (7) characterized in that the lubricant is contained in a proportion of 0.1 to 10 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition. The mold material composition described in .
(9) The mold material composition according to any one of aspects (1) to (8), further comprising a carbonate and/or a borate.
(10) The carbonate and/or borate is contained in a proportion of 0.5 to 50 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition. The mold material composition according to aspect (9).
(11) The mold material composition according to any one of aspects (1) to (10), wherein the refractory aggregate is spherical.
(12) The mold material composition is a wet mixture having no room-temperature flowability, which is formed by covering the surface of the refractory aggregate with a coating layer containing the water glass, and the water content of the mixture is is 70 to 400% by mass of the solid content of the water glass, the mold material composition according to any one of aspects (1) to (11).
(13) A method for producing the mold material composition according to aspect (1), comprising (a) a refractory aggregate, (b) a caking material containing water glass as an essential component, and (c) nitric acid. and at least one nitrate selected from the group consisting of alkaline earth metal salts. Production method.
(14) A method for producing the mold material composition according to aspect (3), comprising: (a) a refractory aggregate; (b) a caking material containing water glass as an essential component; and (c) nitric acid. By mixing at least one nitrate selected from the group consisting of alkali metal salts and alkaline earth metal salts with (d) a surfactant, it is possible to extract it as a wet mixture that does not have room temperature flowability. A method for producing a mold material composition, characterized in that:
(15) Using the wet mold material composition formed by the manufacturing method according to the above aspect (13) or the above aspect (14), filling this into a heated mold, and then performing such molding. A method for manufacturing a mold, which comprises obtaining a desired mold by holding it in a mold and solidifying or hardening it.
(16) The method for manufacturing a mold according to aspect (15), wherein the mold is heated to a temperature of 80°C to 300°C.
(17) A method for manufacturing a mold, comprising forming a desired mold by additive manufacturing using the mold material composition according to any one of aspects (1) to (12). .

As described above, since the mold material composition according to the present invention contains water glass as a binding agent and a predetermined nitrate, molding using such a mold material composition is possible. When a predetermined molten metal is cast using a mold, nitrates dispersed in the caking membrane on the surface of the refractory aggregate formed from water glass are decomposed by the heat of the molten metal, producing oxygen, nitrogen dioxide gas, etc. By doing so, the gas generated in the cohesive conjunctiva of this water glass will cause cracks, and the cocoon conjunctiva of the water glass will be destroyed, making the mold more likely to collapse. be. In addition, such nitrogen dioxide gas combines with the moisture remaining in the water glass, generates nitric acid, neutralizes the sodium silicate in the water glass, and vitrifies it, thereby making the water glass brittle. This makes it possible to make the mold more likely to collapse due to impact or the like. Furthermore, due to the film effect caused by the generated gas, a gas film is formed between the mold and the molten metal, which advantageously improves the smoothness of the mold surface, thereby improving the casting surface of the resulting casting. Improved characteristics will also be exhibited. Furthermore, by combining nitrate with carbonate and/or borate, it is possible to further improve the disintegration properties of the mold, and also to improve the moisture resistance of the mold and suppress strength deterioration due to moisture absorption. Become.

FIG. 2 is an explanatory longitudinal cross-sectional view of a sand mold for casting tests used to measure the disintegration properties of cores in Examples. FIG. 2 is an explanatory longitudinal cross-sectional view of an aluminum alloy casting containing a waste core in an example.

By the way, the mold material composition according to the present invention is generally produced by: 1) mixing a caking agent containing water glass as an essential component with a nitrate into a refractory aggregate, and then evaporating water from the mixture. In other words, it is manufactured by evaporating the moisture of water glass in the state of an aqueous solution, and the dry coating layer made of solid water glass as a caking agent has such fire resistance at a predetermined thickness. 2) It is produced by mixing fire-resistant aggregate with a caking agent containing water glass as an essential component and nitrate. Specifically, it may be a wet form formed by kneading water glass in the state of an aqueous solution and fire-resistant aggregate, but in a dry state it has good flowability at room temperature. However, in a 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 or wet state, but from the viewpoint of ease of handling on site and good disintegration properties, it is preferable to use the mold material composition in a dry state. It can be said that it is desirable.

Here, the term "dry mold material composition having room temperature fluidity" as used in the present invention means a mold material composition from which a measured value can be obtained when the dynamic angle of repose is measured, regardless of the water content. It is something to do. This dynamic angle of repose is determined by storing the mold material composition in a cylinder whose one axial end 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 up to half of its volume), hold the axis horizontally, and rotate it around the horizontal axis at a constant speed (e.g., 25 rpm) to cause it to flow inside the cylinder. The slope of the mold material composition layer formed by the mold material composition layer is flat and the angle formed between the slope and the horizontal plane. This dynamic angle of repose is preferably 80° or less, more preferably 45° or less, and even more preferably 30° or less. In particular, 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 within the cylinder, the slope of the mold material composition layer does not form a flat surface, and as a result, the dynamic angle of repose cannot be measured. shall be classified as a wet mold material composition.

The dry molding material composition having room-temperature fluidity according to the present invention has a moisture content that is equal to or less than the solid content of water glass constituting the binding agent contained in the coating layer that covers the surface of the refractory aggregate. The amount is preferably 5 to 55% by weight, more preferably 10 to 50% by weight, most preferably 20 to 50% by weight. When the water content in this mold material composition becomes less than an amount equivalent to 5% by mass based on the solid content of water glass in the coating layer, the water glass becomes vitrified and water is added again during mold making. However, if the amount exceeds 55% by mass, the mold material composition may not be in a dry state. Note that the method for measuring the water content in the mold material composition is not particularly limited, and any known method depending on the type of water glass, nitrate, etc. can be adopted as appropriate. Specifically, the measurement method described in the Examples section below can be exemplified.

On the other hand, in the wet mold material composition according to the present invention, the water content thereof is an amount corresponding to a ratio of 70 to 400% by mass based on the solid content of water glass as a binding agent. The content is preferably 80 to 300% by mass, more preferably 80 to 300% by mass, and most preferably 90 to 200% by mass. If the water content in this mold material composition is less than the amount equivalent to 70% by mass based on the solid content of the water glass, the viscosity of the water glass will increase, making it difficult to mix uniformly during kneading. It becomes impossible to obtain a suitable mold. On the other hand, if the amount exceeds 400% by mass, the mold material composition may become slurry-like, and as a result, it may not be possible to fill it into the mold. Moreover, even if the filling is possible, it may take a long time to dry within the mold.

Here, the refractory aggregate constituting the mold material composition of the present invention is a refractory substance that functions as a base material for molds, and includes 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, etc. , slag-based particles such as converter slag; artificial particles such as alumina-based particles and mullite-based particles; and recycled particles thereof; alumina balls, magnesia clinker, and the like. Furthermore, these refractory aggregates may be new sand, recycled sand or recovered sand that has been used once or multiple times in mold making as foundry sand, and furthermore, such recycled sand may be There is no problem with mixed sand made by adding new sand to sand or recycled sand. Such refractory aggregate is generally used with a particle size of about 40 to 200 in AFS index, preferably about 50 to 150. 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 refractory aggregates with a grain size coefficient of 1.2 or less, fluidity and filling properties are improved, and the number of points of contact between aggregates increases, which is necessary to achieve the same strength. The amount of binder and additives can be reduced. The particle shape coefficient of the aggregate used here is generally adopted as a measure of the external shape of particles, and is also referred to as a particle shape index, and the closer the value is to 1, the more spherical it is. This means approaching a perfect sphere. Such grain shape coefficient is expressed as a value calculated using the sand surface area measured by various known methods, such as a sand surface area measuring device (manufactured by George Fisher). It means the value obtained by measuring the actual surface area of sand grains per gram and dividing it by the theoretical surface area. Note that the theoretical surface area is the surface area assuming that all sand grains are spherical.

Furthermore, in the mold material composition according to the present invention, a binder containing water glass as an essential component is used as a caking agent mixed with the above-mentioned refractory aggregate. Here, water glass is a water-soluble silicate compound, and examples of such silicate compounds include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and silicate. Among them, sodium silicate (sodium silicate) is particularly advantageously used in the present invention. Furthermore, 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 as the caking agent. It is possible. When using other water-soluble binders together with water glass, the proportion of water glass in the entire binder is preferably 60% by mass or more, more preferably 80% by mass or more, most preferably 80% by mass or more, based on solid content. Preferably it is 90% or more by mass.

Further, the above-mentioned 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 3.3 to 3.5. is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also specified in JIS-K-1408. In the present invention, these various sodium silicates may be used alone or in a mixture, and 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 intended mold material composition, the sodium silicate constituting the water glass used as the caking agent generally has a molar ratio of SiO ₂ /Na ₂ O of 1. 9 or more, preferably 2.0 or more, more preferably 2.1 or more, and in the above-mentioned sodium silicate classification, sodium silicates corresponding to No. 1 and No. 2 are particularly advantageously used. That will happen. Such sodium silicate No. 1 and No. 2 each provide a mold material composition that is stable and has good properties even in a wide range of sodium silicate concentrations in water glass. In addition, the upper limit of the molar ratio of SiO ₂ /Na ₂ O in such sodium silicate will be appropriately selected depending on the characteristics of 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 molar ratio of SiO ₂ /Na ₂ O is smaller than 1.9, the viscosity of the water glass becomes low, especially in the dry state, and the mold material composition cannot be used unless the water content is significantly lowered. On the other hand, if it is larger than 3.5, the solubility in water decreases, the adhesion area cannot be increased, and the strength of the mold ultimately obtained decreases. There is a fear.

Furthermore, the water glass used in the present invention refers to a solution of a silicic acid compound dissolved in water, and can be used in the form of a undiluted solution as purchased on the market, or by adding water to such a undiluted solution. It is added and used in a diluted state. The non-volatile content (water glass component) after removing volatile substances such as water and solvents from such water glass is called the solid content, and this corresponds to the soluble silicate compounds such as sodium silicate mentioned above. It is something to do. Moreover, the higher the proportion of such solid content (non-volatile content), the higher the concentration of silicic acid compounds in water glass. Therefore, when the water glass used in the present invention is composed of only a stock solution, the solid content of the water glass corresponds to the amount excluding the water content in the stock solution. If a diluted solution obtained by dilution is used, the amount of water in the stock solution minus the amount of water used for dilution must correspond to the solid content of the water glass used. becomes.

Furthermore, the solid content in such water glass will be set at an appropriate ratio depending on the type of water glass component (soluble silicic acid compound), etc., but advantageously a ratio of 20 to 50% by mass. It is desirable that it be contained in. By having an appropriate amount of water glass component corresponding to this solid content in the aqueous solution, when mixed (kneaded) with the refractory aggregate, the refractory aggregate can be evenly and uniformly mixed in the dry state. , it is possible to form a coating of the water glass component, and in a wet state, the aggregate and water glass can be evenly and uniformly mixed, thereby making it possible to advantageously form the desired mold. It becomes possible. In addition, if the concentration of water glass components in water glass becomes too low and the total solid content becomes less than 20% by mass, the heating temperature may be raised to dry the mold material composition in the dry state. It is necessary to increase the heating time or increase the heating time, which causes problems such as energy loss. In a wet state, the heating time within the mold becomes longer, causing the problem of prolonging the molding cycle. Furthermore, if the proportion of solids in water glass becomes too high, it becomes difficult to uniformly cover 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. If the solid content becomes too high, it becomes difficult to evenly and uniformly mix the aggregate and water glass, and this also causes problems in improving the properties of the mold. Therefore, the solid content should be 50% by mass or less. Therefore, it is desirable to prepare 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 is used in a proportion of 0.1 to 5.0 parts by mass in terms of solid content when considering only non-volatile content, with respect to 100 parts by mass of the refractory aggregate. , 0.3 to 4.0 parts by weight are particularly preferably 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, and heated for 20 minutes. After being left for a minute, the sample dish is inverted and left on the heating plate for an additional 20 minutes. Thereafter, the sample plate is taken out from the heating plate, left to cool in a desiccator, and then weighed to calculate the solid content (mass %) using the following formula.
Solid content (mass%) =
{[Mass of sample plate after drying (g) - Mass of sample plate (g)]
/[mass of sample plate before drying (g) - mass of sample plate (g)]}×100

In addition, 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 the dry state, and in the wet state, the aggregate is covered with water glass in an aqueous solution. This may make it difficult for the mold material composition to sufficiently solidify or harden during mold making. Furthermore, even if the amount of water glass used is too large, an excess amount of water glass will adhere to the surface of the refractory aggregate in the dry state, making it difficult to form a uniform coating layer, and making it difficult to form a uniform coating layer. There is a risk that the compositions will stick to each other and form agglomerates (composite particles), and in a wet state, an excess amount of water glass may cause unevenness during mold formation, which may interfere with the uniform physical properties of the mold. This may have an adverse effect on the physical properties of the mold that is finally obtained, and may also cause the problem of making it difficult to remove sand from the core after casting the metal.

A major technical feature of the mold material composition according to the present invention is that a predetermined amount of nitrate is present in the water glass (coating layer) that covers the surface of the refractory aggregate through its adjustment. It exists. In other words, by dispersing the predetermined nitrates in the water glass, the nitrates in the water glass are decomposed by the heat of the molten metal, producing nitrogen oxide gas such as nitrogen dioxide gas, oxygen, etc. Then, the generated gas causes cracks in the cohesive conjunctiva made of water glass present on the surface of the refractory aggregate, and by breaking the cocoon conjunctiva of the water glass, the mold can easily collapse. I can do it. Furthermore, the nitric acid generated by the reaction with the water in the water glass neutralizes the sodium silicate in the water glass and vitrifies it, making it more brittle. This makes it easier to collapse. Furthermore, the film effect of the generated gas creates a gas film between the mold and the molten metal, which advantageously increases the smoothness of the mold surface, thereby effectively improving the casting surface of the resulting casting. This will also be possible.

Here, the amount of the above-described predetermined nitrate to be contained in the mold material composition in the present invention is preferably 0.5 to 30 parts by mass based on 100 parts by mass of the solid content of water glass. Among them, 1 to 25 parts by weight is preferable, and 3 to 20 parts by weight is particularly preferable. If the amount of nitrate contained is too small, there is a risk that the above-mentioned effects cannot be enjoyed advantageously.On the other hand, even if the amount of nitrate is too large, the effect will not improve according to the amount used. This is not acceptable, and furthermore, it is not a good idea from a cost-effectiveness perspective. In the present invention, preferred examples of the predetermined nitrate include alkali metal nitrates such as sodium nitrate and potassium nitrate, and alkaline earth metal nitrates such as calcium nitrate and magnesium nitrate, which may be used singly or in combination. It is possible to use a mixture of the above. In particular, it is recommended to use sodium nitrate or potassium nitrate because of their high solubility in water glass. Since these nitrates have the property of being easily mixed with water glass, it is possible to uniformly disperse the nitrates in the cacoconjunctiva of the water glass when molding.

By the way, in the mold material composition of the present invention, in addition to the above-mentioned nitrates, etc., various known additives can be appropriately included as needed. 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 a mold molded using the mold material composition. , it can be further improved. The hydrocarbon-containing compound may be any compound containing a hydrocarbon group, but preferred examples include surfactants and lubricants.

By adding a surfactant as such an additive to the mold material composition, it reacts with the oxygen generated from the nitrate and burns, thereby further improving the disintegration property. It is. Furthermore, the presence of the surfactant provides excellent water permeability, in other words, water wettability. Therefore, when water is supplied to a dry mold material composition during mold making, the surfactant acts as an intermediary between the supplied water and the water glass. Even if moisture is supplied to the mold material composition, the entire mold material composition will be effectively moistened. , steam ventilation time) can be kept to the necessary minimum, and 2) the amount of water supplied to the mold (molding cavity) can be kept to a small amount. In addition to being excellent in releasability from the mold, it is also possible to advantageously enjoy the effects of 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 based on 100 parts by mass of the solid content of water glass. The amount is preferably from 0.5 to 15.0 parts by weight, particularly preferably from 0.75 to 12.5 parts by weight. If the amount of surfactant contained is too small, there is a risk that the above-mentioned effects cannot be enjoyed advantageously.On the other hand, even if the amount of surfactant is too large, No improvement in effectiveness has been observed, and furthermore, it is not a good idea from a cost-effectiveness perspective.

Such surfactants include cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, silicone surfactants, and fluorine surfactants. , can be used. Specifically, examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, and the like. In addition, examples of anionic surfactants include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acylglutamate, alkyl ether carboxylate, acyl peptide, alkyl sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, dialkyl sulfosuccinate salt, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol Sulfate ester salt, secondary higher alcohol sulfate ester salt, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglysulfate, fatty acid alkylolamide sulfate ester salt, alkyl ether phosphorus Examples include acid ester salts and alkyl phosphate ester salts. Furthermore, examples of the amphoteric surfactant include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine, and the like. In addition, nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkyl phenyl ether (e.g., Emulgen 911), polyoxyethylene sterol ether, polyoxyethylene lanolin derivatives. , polyoxyethylene polyoxypropylene alkyl ether (e.g. Newport 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, Examples include acetylene alcohol.

Furthermore, among various surfactants, those that have a siloxane structure as a nonpolar moiety are called silicone surfactants, and those that have a perfluoroalkyl group are called fluorine surfactants. However, examples of silicone surfactants include polyester-modified silicones, acrylic-terminated polyester-modified silicones, polyether-modified silicones, acrylic-terminated polyether-modified silicones, polyglycerin-modified silicones, and aminopropyl-modified silicones. It will be done. In addition, examples of fluorosurfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl trimethylammonium salts, perfluoroalkyl ethylene oxide adducts, and perfluoroalkyl groups. Examples include containing oligomers.

In the present invention, the various surfactants described above can be used alone or in combination of two or more. However, some surfactants may react with water glass and cause their surfactant ability to decrease or disappear over time, so anionic surfactants and nonionic surfactants that do not react with water glass Polymer surfactants and silicone 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 and make it exist on the surface of the refractory aggregate of the mold material composition. The presence of such lubricants can advantageously improve the flowability of the mold material composition. Moreover, by combining this lubricant with nitrate, the organic content of the lubricant reacts with the oxygen generated by the nitrate and burns, making it possible to further improve the collapsibility of the mold.

Here, the amount of lubricant contained in the mold material composition according to the present invention is desirably 0.1 to 10 parts by mass, particularly 0.3 parts by mass, based on 100 parts by mass of the solid content of water glass. The amount is preferably 8 parts by weight, particularly 0.5 to 5 parts by weight. If the amount of lubricant contained is too small, the above-mentioned effects may not be advantageously enjoyed, while if the amount of lubricant is too large, mold strength may decrease or even worse. , it is not a good idea from a cost-effectiveness perspective.

Examples of the lubricant used in the present invention include waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; fatty acid amides such as stearamide, oleic acid amide, and erucic acid amide; methylene bisstearic acid amide; Alkylene fatty acid amides such as ethylene bisstearamide; 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. It is possible to use Among these, calcium stearate and the like are particularly advantageously used. Note that there is no problem in using a lubricant such as graphite, talc, mica, molybdenum disulfide, etc., which does not contain hydrocarbons, in combination with the above-mentioned lubricant which is a hydrocarbon-containing compound.

Furthermore, in the mold material composition of the present invention, it is preferable to use nitrate in combination with at least one of carbonate and borate; such carbonate and/or borate and nitrate are preferably used in combination. Further useful effects can be achieved by using them together. In other words, carbonates, like nitrates, release carbon dioxide due to the heat generated during molding and casting, causing cracks in the cohesive conjunctiva of the water glass, and by breaking the cocoon conjunctiva of the water glass, making the mold more likely to collapse. At the same time, the generated carbon dioxide becomes carbonated water, which is a weak acid, due to the moisture in the water glass, and although it is less effective than nitrates, it can promote the neutralization reaction. On the other hand, borates are produced by the reaction of OH in water glass with tetraborate ions or metaborate ions generated from borates due to the heat generated during molding and casting, which blocks the OH in water glass. It becomes difficult to dissolve, thereby preventing the softening of the conjunctiva of water glass and further promoting the effect of nitrate. From these facts, it is possible to further improve the collapsibility of a mold molded using the mold material composition, and also to improve the moisture resistance of the mold and suppress strength deterioration due to moisture absorption. .

In the present invention, the amount of carbonate and/or borate as described above contained in the mold material composition is 0.5 to 50 parts by mass based on 100 parts by mass of the solid content of water glass. The amount is preferably 1 to 20 parts by weight, particularly preferably 2 to 15 parts by weight. If the amount of carbonate and/or borate contained is too small, the above-mentioned effects may not be advantageously enjoyed; on the other hand, if the amount of carbonate and/or borate is too large, Even if the amount is exceeded, the effect will not improve in proportion to the amount used, and furthermore, it is not a good idea from a cost-effective point of view. Note that carbonate and borate may be used in combination.

Here, 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, etc. Can be mentioned. In addition, such borates include sodium tetraborate, potassium tetraborate, lithium tetraborate, ammonium tetraborate, calcium tetraborate, strontium tetraborate, silver tetraborate, sodium metaborate, Examples include 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 be used in combination with nitrates to more advantageously improve disintegrability and moisture resistance.

In the present invention, a moisture resistance improver may be further included as another additive. By incorporating a moisture resistance improver into the water glass, it is possible to improve the moisture resistance of the mold ultimately obtained. As the moisture resistance improver used in the present invention, any moisture resistance improver that has been conventionally used in coated sand can be used as long as it does not impede 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, and sodium hydrogen phosphate. , potassium phosphate, potassium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, aluminum phosphate, zinc phosphate and other phosphates, lithium hydroxide, magnesium hydroxide, Hydroxides such as calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide, zinc hydroxide, oxides of silicon, zinc, magnesium, aluminum, calcium, lithium, copper, iron, boron, zirconium, etc. , can be exemplified. Among them, lithium sulfate and lithium hydroxide can particularly advantageously improve moisture resistance. The moisture resistance improvers including those mentioned above can of course be used alone or in combination of two or more.

The amount of such moisture resistance improver to be used is generally preferably about 0.5 to 50 parts by mass based on 100 parts by mass of solid content of water glass, and among them, 1 It is more preferably 20 parts by weight, and particularly preferably 2 to 15 parts by weight. In order to advantageously enjoy the effects of adding a moisture resistance improver, it is desirable to use an amount of 0.5 parts by mass or more. On the other hand, if the amount added is too large, the bonding of aggregates by water glass may be inhibited. It is desirable that the amount be 50 parts by mass or less, since this may cause problems such as a decrease in the strength of the final mold obtained.

In addition, it is also effective to include coupling agents that strengthen the bond between the refractory aggregate and water glass as other additives, such as silane coupling agents, zircon coupling agents, titanium coupling agents. etc. can be used. Furthermore, as a mold 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 mold release agent, silicone mold release agent. Agents etc. can also be used. Each of these other additives is contained in an amount that is generally 5% by mass or less, preferably 3% by mass or less, based on the solid content of water glass.

By the way, when producing the dry molding material composition having room-temperature fluidity according to the present invention, generally water glass as a caking agent and a prescribed nitrate are added to the refractory aggregate as necessary. The water glass composition is kneaded or mixed with the additives used in the refractory aggregate, so that the surface of the refractory aggregate is coated with the water glass composition containing nitrates, etc. A method will be adopted in which a coating layer of the water glass composition is formed on the surface of the refractory aggregate by evaporating the water in the composition. In such a method, water glass in the form of an aqueous solution must be evaporated quickly in the coating layer before the water glass solidifies or hardens. It is desirable to evaporate the moisture contained therein generally within 5 minutes, more preferably within 3 minutes, to obtain a dry powder mold material composition after adding (mixing). If the transpiration time becomes longer, the mixing (kneading) cycle will become longer, which will reduce the productivity of the mold material composition, and will also cause the water glass to be exposed to _CO2 in the air for a longer time, resulting in deactivation, etc. This is because there is a high possibility that problems will occur.

In addition, in the manufacturing process of the above-mentioned mold material composition, one of the effective means for quickly evaporating the water in the water glass is to heat the refractory aggregate in advance and convert it into an aqueous solution. A method of kneading or mixing a certain water glass, a certain nitrate, etc. to make them mix is preferably adopted. By kneading or mixing water glass with this pre-heated refractory aggregate, the water in the water glass can be evaporated extremely quickly by the heat of such refractory aggregate. Therefore, the moisture content of the resulting mold material composition can be effectively reduced, and a dry powder having room temperature flowability can be advantageously obtained. Here, the preheating temperature of the refractory aggregate will be appropriately selected depending on the water content of water glass and its blending amount, but generally a temperature of about 100 to 160°C is preferable. A temperature of about 100 to 140°C is used. If this preheating temperature is too low, water cannot evaporate effectively and drying will take longer. Therefore, it is desirable to use a temperature of 100°C or higher. 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 progress, which may affect the function of the mold material composition, especially the final Problems arise in the physical properties such as the strength of the mold obtained.

On the other hand, when manufacturing the wet mold material composition according to the present invention, generally water glass as a caking agent and a prescribed nitrate are added to the refractory aggregate, and additives are added as necessary. At the same time, a method will be adopted in which a coating layer of a water glass composition with a high moisture content is formed on the surface of the refractory aggregate by kneading or mixing at room temperature to ensure uniform mixing.

In addition, in the mold material composition of the present invention, the nitrate contained in the coating layer of the water glass composition containing water glass and a predetermined nitrate, and other additives used as necessary, such as surfactants, etc. The lubricant etc. may be added to the refractory aggregate in advance in a state mixed with water glass and kneaded, or it may be added separately from water glass during kneading and kneaded, and furthermore, it may be kneaded. Sometimes, the water glass may be added and kneaded with a time lag between the additions. Therefore, the coating layer in the dry molding material composition of the present invention is formed, for example, in a state in which water glass and nitrate etc. are harmoniously integrated, or in a state where water glass and nitrate etc. The glass is configured such that the concentration of solid content (non-volatile content) of the glass gradually decreases or increases, while the concentration of nitrates, etc. gradually increases or decreases. Furthermore, water glass as a caking agent may be diluted with water in order to adjust its viscosity. Moreover, there is no problem even if water glass and water are added separately at the time of kneading or mixing.

By the way, when molding a mold using the dry mold material composition according to the present invention, the following two methods can be adopted, for example. The first method is to knead the dry mold material composition with water at the molding site where the mold is manufactured, to moisten the mold material composition and make it wet. The mold material composition thus prepared is filled into the molding cavity of a mold that provides the desired mold, while the mold is heated to a temperature of 80 to 300°C, so that the filled mold material composition is In this method, the material is held in the mold until it is dried. In addition, in the second method, water vapor is blown into the molding cavity of the mold that provides the desired mold after filling the molding material composition, and the filling phase of the molding material composition is moistened by the ventilation of this steam. In this method, the material is heated to a wet state, and then held in a mold heated to 80 to 200° C. until dry.

During such molding, it is preferable that the mold, such as a metal mold or wooden mold, into which the dry molding material composition having room temperature flowability is filled, is kept warm by heating in advance, so that the mold material composition is not mixed with water. The drying of the mold material composition moistened by water vapor or water vapor can advantageously proceed. In general, the preheating temperature is preferably 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. ℃, preferably about 90 to 150 degrees Celsius, more preferably about 100 to 140 degrees Celsius. If this insulating temperature is too high, it will be difficult for steam to reach the surface of the mold, while if the temperature is too low, it will take time to dry the mold.

In addition, the dry molding material composition filled into such molds is also advantageously preheated. Generally, by filling a mold with a mold 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 in particular, a mold material composition heated to a temperature of about 40 to 80°C is advantageously used. Become.

In addition, 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 an appropriate mixer. Since it can be carried out by mixing the two, it has the advantage that it can be carried out in an extremely simple operation, and it can be carried out extremely simply and easily even in a molding site with a poor working environment. . Note that when adding water, it is also possible to add other additives.

On the other hand, in the second method described above, the dry mold material composition according to the present invention is filled into the mold heated as described above, specifically, into the mold cavity thereof, and then Water vapor is passed under pressure into the formed filling phase through a vent provided in the mold to moisten (moisten) the mold material composition constituting the filling phase, and then the mold is made into a mold. The mold material compositions are bonded and connected to each other by the water glass contained in the coating layer of the material composition, and a mold material composition aggregate (combination) in the shape of an integral mold is formed. Note that water glass usually solidifies by evaporating water to dryness if no additives are added, and if hardening agents such as oxides, salts, or esters are added, it will not harden. I will do it. When a curing agent is added, the filling phase becomes hardened, but there is no problem even if the filling phase is simply solidified.

Here, the temperature of the water vapor that is blown through the vent of such a mold and aerated through the filling 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 production, so a steam temperature of around 100° C. is particularly advantageously employed. Furthermore, the pressure of the steam to be vented is advantageously a gauge pressure of about 0.01 to 0.3 MPa, more preferably about 0.01 to 0.1 MPa. When the mold material composition has good air permeability, if the pressure for passing water vapor is about the gauge pressure mentioned above, the water vapor can be evenly passed through the mold formed in the mold. Moreover, the time required for steam ventilation and drying of the mold is short, and the molding speed can be shortened. Further, such a gauge pressure has the advantage that molding can be performed even when the mold material composition has poor air permeability. Note that if the gauge pressure is too high, staining may occur near the vent, while if the gauge pressure is too low, the entire filling phase of the mold material composition will not be aerated, and the mold material composition will There is a possibility that it may not be possible to moisten the area sufficiently.

In addition, as a method for aerating water vapor as described above, a method has been adopted in which water vapor is blown into the mold material composition (phase) filled in the molding cavity of the mold by blowing it through a vent provided in the mold. Furthermore, the aeration time is such that water vapor is supplied to the surface of the filled mold material composition to sufficiently moisten the water glass, which is a caking agent contained in the coating layer on the surface, and the mold material composition is The time required for mutual bonding (bonding) will be appropriately selected depending on the size of the mold, the number of vents, etc., but generally the ventilation time is from about 2 seconds to about 60 seconds. It will be adopted. If the ventilation time of this water vapor is too short, it will be difficult to sufficiently moisten the surface of the mold material composition, and if the ventilation time is too long, the caking agent (water glass) will form on the surface of the mold material composition. This is because there is a risk that the liquid will dissolve or flow out. As mentioned above, the mold material composition of the present invention has excellent water wettability, so there is no problem even if the steam ventilation time is short, and the mold material composition can be kept sufficiently wet. It is possible to make it a reality. In addition, the permeability of water vapor in the mold material composition filled in the mold can be further improved by venting the water vapor while sucking the atmosphere inside the mold from the exhaust port of the mold. is possible.

Furthermore, when manufacturing a mold using the mold material composition of the present invention, the filling phase of the wet mold material composition formed by either of the first and second methods described above is actively dried. In order to do this, a method is preferably adopted in which dry air, heated dry air, superheated steam, or nitrogen gas is blown into the packed phase. By aeration of 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 prevent solidification or hardening of the filling phase. In addition to advantageously increasing the solidification or hardening rate and advantageously increasing the properties such as the bending strength of the resulting mold, it also reduces the molding time. This can make a beneficial contribution. Note that hot air such as heated dry air or superheated steam is particularly advantageously used for ventilation to promote drying.

Furthermore, a curing agent may be added to the mold as an additive for promoting hardening of the water glass while it is held in the mold. By neutralizing the caking agent (water glass) with a hardening agent, it is possible to further accelerate its solidification. Note that the curing agent may be vented at any timing while it is being held in the mold, and there is no problem even if it is done simultaneously with the venting of water vapor, dry air, etc.

Hardening agents include carbon dioxide (carbonated water), inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic acids such as oxalic acid, carboxylic acid, and para-toluenesulfonic acid; methyl formate, ethyl formate, propyl formate, Esters such as γ-butyrolactone, β-propiolactone, ethylene glycol diacetate, diethylene glycol diacetate, glycerin diacetate, triacetin, propylene carbonate, monohydric alcohols such as methanol, ethanol, butanol, hexanol, octanol, etc. I can give an example. These curing agents can be used alone or in combination of two or more. It is best to use these curing agents in a gaseous or mist form while the mold is being held, and then ventilate them into the mold.If water is added to dry coated sand to make it wet, There is no problem even if a hardening agent is added together with water.

On the other hand, when molding a mold using a wet mold material composition according to the invention, it is advantageous to first introduce such mold material composition into the molding cavity of a heated mold providing the desired mold. The filled molding material composition is solidified or hardened by filling the molding material into the molding material and holding the molding material in the mold until dry.

In addition, at this time, it is desirable that the mold to be filled with the wet mold material composition be kept warm by heating in advance, so that the mold material composition filled in the wet state can be dried. This can be advantageously advanced. The preheating temperature is generally 80 to 300°C, preferably 90 to 250°C, more preferably 100 to 200°C. If this insulating temperature is too high, sand will not be filled into the mold, while if the temperature is too low, it will take time to dry the mold.

Furthermore, when manufacturing a mold using the mold material composition of the present invention, in order to actively dry the filling phase of the mold material composition in a wet state, dry air, heated dry air, superheated steam, etc. Alternatively, a method may be adopted in which nitrogen gas is blown into the packed phase to aerate it. In addition to aeration with dry air or the like, a gas or mist of carbon dioxide, organic acid, monohydric alcohol, etc. may be aerated as a curing agent.

Furthermore, when manufacturing a target mold using the mold material composition according to the present invention, in addition to the above-mentioned method of filling the mold material composition into a mold and molding, various known methods can be used. It goes without saying that the following molding methods can be adopted as appropriate.

In addition, when manufacturing a mold, in addition to the method of filling a mold material composition into a mold and molding it as described above, various known molding methods can be adopted as appropriate. It is also possible to employ an additive manufacturing method in which layers of the composition are sequentially laminated while parts corresponding to the intended mold are hardened to directly create a three-dimensional mold. The mold material composition used in such layered molding is preferably in a dry state.

The present invention will be explained in more detail below using some examples, but the present invention is not to be construed in any way limited by the description of such examples. should be understood. In the following Examples and Comparative Examples, "%" and "part" are all expressed on a mass basis unless otherwise specified. In addition, the moisture content, disintegration properties, and casting surface of the mold material compositions (CS) obtained in Examples and Comparative Examples were evaluated as follows.

-Measurement of water content relative to solid content of water glass-
Weighed and stored 10 g of each CS in a weighed crucible and heated it at a temperature of 900°C for 1 hour. Using the mass loss (%), we calculated the water content in the CS and the nitrate heat. The total amount of the decomposed amount and the organic amount (hereinafter referred to as "(moisture + nitrate decomposed amount + organic content) amount" and referred to as "W1") is calculated from the following formula (1). Here, the nitrate thermal decomposition amount is the amount of nitrate decomposed and reduced in weight, and the organic amount is the total amount of surfactant and other organic additives (hereinafter referred to as organic content). Note that the weight 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 (W1) of (moisture + nitrate decomposition amount + organic content) in the CS, the solid content of water glass in the CS (B1), and the amount of nitrate added to 100 parts of the water glass solid content (A), The weight loss rate (C) during nitrate decomposition measured according to the method described below, the amount of organic content added to 100 parts of solid content of water glass (D), and the method necessary for dry CS according to the method described below. From the solid content rate (E) of 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 using the following formula (3a) or (3b). ). W2 calculated as above is shown as "water content (mass %)" in Tables 1 and 2 below.
W1=[(M1-M2)/M3]×100...(1)
[W1: Amount (%) of (moisture + nitrate decomposition content + organic content) in CS, M1: Total mass of crucible and CS before firing (g), M2: Total mass of crucible and CS after firing (g) , M3: mass of CS before firing (g)]
B1=[B2/(100+B2)]×(100-W1)...(2)
[B1: Amount of solid content of water glass in CS (%), B2: Amount of solid content of water glass added to 100 parts of sand (parts), W1: Amount of (moisture + nitrate decomposition content + organic content) in CS (%)]
In dry state:
W2=[(W1/B1)×100]-(A×C)/100
-(D×E)/100...(3a)
[W2: Moisture content (%) of CS relative to the solid content of water glass in the coating layer, W1: (moisture + organic content) content (%) in CS, B1: solid content (%) of water glass in CS, A: Addition amount of nitrate (parts) per 100 parts of solid content of water glass, C: Nitrate decomposition weight loss rate (kneading temperature ~ 900°C) (%), D: Per 100 parts of solid content of water glass Amount of organic content added (parts), E: solid content percentage of organic content in CS (%)]
In wet condition:
W2=[(W1/B1)×100]-(A×F)/100-D...(3b)
[W2: Moisture content (%) of CS relative to the solid content of water glass in the coating layer, W1: (moisture + organic content) content (%) in CS, B1: solid content (%) of water glass in CS, A: Addition amount of nitrate (parts) per 100 parts of solid content of water glass, F: Nitrate decomposition weight loss rate (room temperature to 900°C) (%), D: Per 100 parts of solid content of water glass Amount of organic content added (parts)]

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

-Measurement of solid content percentage in organic content-
First, a sample is prepared which is made of a surfactant and other organic additives and whose blending ratio is the same as that of 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. An aluminum foil plate was placed on the plate, left for 20 minutes, and then allowed to cool in a desiccator. Then, the aluminum foil plate after being left to cool is weighed, and the solid content (E) in the organic content is calculated from the following equation (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, the molten metal inlet 2 is made in advance from room-temperature self-hardening sand, and the baseboard fixing part 4 for the core is in the lower part (this part is the outlet for waste cores from castings). In a half-split hollow main mold 6 (cavity diameter: 6 cm, height: 6 cm) having a half-split hollow main mold 6 (cavity diameter: 6 cm, height: 6 cm), a circular hollow core 10 (diameter: 5 cm, height) having a baseboard portion 8 made using each CS was placed. 5 cm) are adhesively fixed with the baseboard fixing part 4, and then the half-split hollow main molds 6 are further adhesively fixed to each other to produce a sand mold 12 for casting test. Next, molten aluminum alloy (temperature: 710±5°C) is poured from the molten metal inlet 2 of the sand mold 12 for casting tests, and after solidifying, the main mold 6 is broken and the circular waste shown in FIG. A casting 16 having a core outlet 14 (diameter: 1.6 cm) is taken out. Then, when the temperature reaches a predetermined value, the obtained casting 16 is subjected to impact for 3 seconds at a time at a pressure of 0.2 MPa with an air hammer, and is discharged from the discharge port 14. If 100% of the cores have been ejected, record the number of times, and if the cores have not been ejected within 10 times, calculate the sand removal rate. The mass of sand discharged up to 10 times is measured, and the core sand is completely discharged using an air hammer or the like, and the total mass of the core sand is measured. The sand discharge rate is expressed as mass %, which is the mass of the discharged core sand divided by the total mass of the discharged core sand, and the larger the value, the better the collapsibility of the core is judged to be.

-Evaluation of casting surface-
The casting obtained in the above core casting test was cut and the state of the casting surface on the core side surface was visually evaluated. The evaluation criteria are as follows.
◎: Good ○: There is some roughness on the casting surface, but there is no problem in use △: Correction by post-processing is necessary ×: Poor casting surface

-Production example 1a of dry CS-
Lunamos #60 (product name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, was prepared as a refractory aggregate, and commercially available sodium silicate No. 2 (product name: water glass) was prepared as a caking agent. (name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.5, solid content: 41.3%) was prepared. After heating the above Lunamos #60 to a temperature of about 120°C, it was put into a whirl mixer (manufactured by Enshu Tekko Co., Ltd.), and 2.4 parts of the water glass was added to 100 parts of Lunamos #60. (solid content: 1.0 part), and potassium nitrate was added at a ratio of 0.03 parts to 100 parts of Lunamos #60 (3 parts to 100 parts of solid content of water glass). Then, kneading was carried out for 3 minutes to evaporate the moisture, while stirring and mixing until the sand grains collapsed, and then added 0.01 part of calcium stearate to 100 parts of Lunamos #60 (solid content of water glass 100 parts). 1 part to 1 part), stirred and mixed, and then taken out to obtain a dry mold material composition: CS1a having room temperature fluidity. When the water content of CS1a after such kneading was calculated, it was found to be an amount equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 2a of dry CS-
Dry CS2a having room 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 part (ratio of 10 parts to 100 parts of solid content of water glass). I got it. The calculated water content of the obtained CS2a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 3a of dry CS-
Dry CS3a having room 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 (30 parts per 100 parts of solid content of water glass). I got it. The calculated water content of the obtained CS3a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 4a of dry CS-
The same procedure as in Production Example 1a above was followed except that potassium nitrate was replaced with 0.1 part of sodium nitrate (at a ratio of 10 parts to 100 parts of the solid content of water glass) to produce a dry state having room temperature fluidity. CS4a was obtained. The calculated water content of the obtained CS4a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 5a of dry CS-
The same procedure as in Production Example 1a above was followed except that potassium nitrate was replaced with 0.03 parts of calcium nitrate (at a ratio of 3 parts to 100 parts of solid content of water glass). of CS5a was obtained. The calculated water content of the obtained CS5a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 6a of dry CS-
A dry state fluid having room temperature fluidity was prepared by following the same procedure as in Production Example 1a above, except that potassium nitrate was replaced with 0.03 parts of magnesium nitrate (3 parts per 100 parts of solid content of water glass). CS6a was obtained. The calculated water content of the obtained CS6a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

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

-Production example 8a of dry CS-
Commercial product No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 3.2, solid content: 38%) was used as water glass as a 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), Dry CS8a having room temperature fluidity was obtained. The calculated water content of the obtained CS8a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

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

-Production example 10a of dry CS-
Dry CS10a having room temperature fluidity was obtained by following the same procedure as in Production Example 1a above, except that nitrate (potassium nitrate) was not added. The calculated water content of the obtained CS10a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Production example 11a of dry CS-
Dry CS11a having room temperature fluidity was obtained by following the same procedure as in Production Example 7a above, except that nitrate was not added. The calculated water content of the obtained CS11a was found to be equivalent to 30% by mass of the solid content of 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 nitrate was not added. The calculated water content of the obtained CS12a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

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

-Production example 14a of dry CS-
As the borate, sodium tetraborate decahydrate was used at a ratio of 0.05 parts to 100 parts of Lunamos #60 (5 parts to 100 parts of solid content of water glass). Dry CS14a was obtained by following the same procedure as in Production Example 2a above, except for adding more. The calculated water content of the obtained CS14a was found to be equivalent to 30% by mass of the solid content of water glass in the coating layer.

-Wet CS production example 1b-
Lunamos #80 (product name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, was prepared as a refractory aggregate, and commercially available sodium silicate No. 2 (product name) was prepared as water glass, which is a caking agent. (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 was put into a Shinagawa type universal stirrer (model 5DM-r) (manufactured by Dalton Co., Ltd.) at room temperature, and 2.4 parts of the water glass was added to 100 parts of Lunamos #80. (solid content: 1.0 parts), and potassium nitrate was added at a ratio of 0.03 parts to 100 parts of Lunamos #80 (3 parts to 100 parts of solid content of water glass). 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 found to be an amount equivalent to 140% by mass of the solid content of water glass.

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

-Wet CS production example 3b-
The same procedure as in Production Example 1b was followed 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). , wet CS3b was obtained. The calculated water content of the obtained CS3b was found to be equivalent to 140% by mass of the solid content of 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). . The calculated water content of the obtained CS4b was found to be equivalent 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 (3 parts per 100 parts of solid content of water glass). . The calculated water content of the obtained CS5b was found to be equivalent to 140% by mass of the solid content of water glass.

-Wet CS production example 6b-
Wet 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 (3 parts per 100 parts of solid content of water glass). . The calculated water content of the obtained CS6b was found to be equivalent to 140% by mass of the solid content of water glass.

-Wet CS production example 7b-
Commercially available sodium silicate No. 1 (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.1, solid content: 48.5%) was used as water glass as a caking agent. , Also, the same as in Production Example 2b above, except that the amount added was 2.1 parts (solid component: 1.0 part) per 100 parts of the refractory aggregate (Lunamos #80). Wet CS7b was obtained according to the procedure. The calculated water content of the obtained CS7b was found to be equivalent to 110% by mass of the solid content of water glass.

-Wet CS production example 8b-
Commercial product No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 3.2, solid content: 38%) was used as water glass as a 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). Accordingly, wet CS8b was obtained. The calculated water content of the obtained CS8b was found to be equivalent to 160% by mass of the solid content of water glass.

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

-Wet CS production example 10b-
Wet CS10b was obtained according to the same procedure as in Production Example 1b above, except that nitrate was not added. The calculated water content of the obtained CS10b was found to be equivalent to 140% by mass of the solid content of water glass.

-Production example 11b of wet CS-
Wet CS11b was obtained according to the same procedure as in Production Example 7b above, except that nitrate was not added. The calculated water content of the obtained CS11b was found to be equivalent to 110% by mass of the solid content of water glass.

-Production example 12b of wet CS-
Wet CS11b was obtained according to the same procedure as in Production Example 8b above, except that nitrate was not added. The calculated water content of the obtained CS12b was found to be equivalent to 160% by mass of the solid content of water glass.

-Production example 13b of wet CS-
Basic zinc carbonate was used as the carbonate, and it was further added at a ratio of 0.05 parts to 100 parts of Lunamos #80 (5 parts to 100 parts of solid content of water glass). obtained dry CS13b according to the same procedure as in Production Example 2b above. The calculated water content of the obtained CS13b was found to be equivalent to 140% by mass of the solid content of water glass in the coating layer.

-Production example 14b of wet CS-
As the borate, sodium tetraborate decahydrate was used at 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 by following the same procedure as in Production Example 2b above, except that additional addition was made. The calculated water content of the obtained CS14b was found to be equivalent to 140% by mass of the solid content of water glass in the coating layer.

- Mold molding example 1 (Examples 1 to 9, Comparative examples 1 to 3) -
CS1a to 12a (temperature: 20°C) manufactured according to each of the above procedures were blown and filled into a mold heated to 110°C at a gauge pressure of 0.3 MPa, and then Further, under a gauge pressure of 0.05 MPa, steam at a temperature of 99° C. was blown for 4 seconds to aerate the mold material composition phase filled in the mold. Next, after such steam ventilation 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. Accordingly, molds to be used as test pieces [φ5 cm×5 cm] were respectively produced. 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. The composition and molding conditions of the CS used in producing the molds (test pieces) for each of Examples 1 to 9 and Comparative Examples 1 to 3 are as shown in Table 1 below. In addition, the above-mentioned core casting test was carried out on the circular airless core (10) manufactured from CS used in each of Examples 1 to 9 and Comparative Examples 1 to 3, and the disintegration property and yield of the core were evaluated. The casting surface of the cast product was evaluated, and the results are shown in Table 1 below.

- Mold molding example 2 (Examples 10 to 20, Comparative Examples 4 to 6) -
CS1a to 14a (temperature: 20°C) produced according to the above-mentioned procedures were put into a Shinagawa universal stirrer (Model 5DM-r, manufactured by Dalton Co., Ltd.) at room temperature, and water was added to the CS. A moistened CS (mold material) was prepared by adding it into a stirrer at a ratio of 1.0 parts to 100 parts and stirring it. Next, various types of wet CS taken out from the stirrer were blown into a mold heated to 150°C at a gauge pressure of 0.3 MPa, filled, and then held in the mold. Meanwhile, under a gauge pressure of 0.03 MPa, hot air at a temperature of 150°C was blown for 2 minutes to solidify or harden the CS filled in the mold, thereby forming a test piece [φ5 cm x 5 cm]. The molds used were each made. Here, the molding time from the start of holding in the mold to the end of hot air ventilation was 180 seconds. The composition and molding conditions of the CS used in producing the molds (test specimens) of Examples 10 to 20 and Comparative Examples 4 to 6 are as shown in Table 2 below. In addition, the aforementioned core casting test was conducted on the circular airless core (10) manufactured from CS used in each of Examples 10 to 20 and Comparative Examples 4 to 6, and the core disintegration property and yield were evaluated. The casting surface of the cast product was evaluated, and the results are shown in Table 2 below.

- Mold molding example 3 (Examples 21 to 31, Comparative examples 7 to 9) -
After filling CS1b to 14b (temperature: 20°C) manufactured according to each of the above steps into a mold heated to 150°C, the filling is performed by holding the CS1b to 14b (temperature: 20°C) in the mold as it is. By solidifying or hardening the obtained CS, molds to be used as test pieces [φ5 cm×5 cm] were respectively produced. Here, the molding time from the start to the end of holding in the mold was 180 seconds. The composition and molding conditions of the CS used in producing the molds (test pieces) of Examples 21 to 31 and Comparative Examples 7 to 9 are as shown in Table 3 below. In addition, the above-mentioned core casting test was conducted on the circular airless cores (10) manufactured from the CS used in each of Examples 21 to 31 and Comparative Examples 7 to 9, and the disintegration properties and yields of the cores were evaluated. The casting surface of the cast product was evaluated, and the results are shown in Table 3 below.

As is clear from Tables 1 to 3 above, molds obtained using CS1a to 9a, 13a to 14a and CS1b to 9b, and 13b to 14b according to the present invention have improved disintegrability and casting surface. Improvement was observed. Furthermore, it is recognized that similar effects are obtained when CS is in either dry or wet form.

Furthermore, regarding 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, The hygroscopic strength retention rate was measured in accordance with the procedure shown below (Examples 32 to 37). The measurement results are shown in Table 4 below.

-Measurement of moisture absorption strength retention rate-
The breaking load of the test piece obtained using each CS was measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd., digital foundry sand strength tester), and using this measured breaking load, The bending strength was calculated using the following formula. In addition, for the measurement of the breaking load, a test piece at room temperature after 1 hour had passed after molding was used.
Transverse 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 (cm) of the test piece. ]
Next, put a mixed solution of water and glycerol and a wire mesh with four clogs in the container, and place each test piece on the wire mesh so that the test piece does not touch the mixed solution of water and glycerol (20% glycerol concentration). The container was placed in a temperature controller and kept at 40° C. for 24 hours to deteriorate each test piece by absorbing moisture. The bending strength of each test piece after moisture absorption and deterioration was determined in the same manner as above. Then, the moisture absorption strength retention rate was calculated from the bending strength before moisture absorption and the bending strength after moisture absorption based on the following formula.
Hygroscopic strength retention rate (%) = (flexural strength after moisture absorption/flexural strength before moisture absorption) x 100

As is clear from Table 4, by adding (combining) carbonate or borate together with nitrate to the binder, the effect of improving disintegration shown in Tables 2 and 3, It is recognized that the moisture absorption strength retention rate of the mold is significantly improved.

2 Molten metal inlet 4 Baseboard fixing part 6 Main mold 8 Baseboard part 10 Circular hollow core 12 Sand mold for casting test 14 Waste core outlet 16 Casting

Claims (17)

(a) refractory aggregate;
(b) a caking agent containing water glass as an essential component;
(c) at least one nitrate selected from the group consisting of alkaline earth metal salts of nitric acid, including starch, dextrin, glucose, cellulose, gum, resin, wood materials, sugar, polyethylene, polystyrene, coal tar, A mold that does not contain charcoal tar, pitch, coal, or cane sugar, and is composed of a wet mixture that does not have fluidity at room temperature, and does not allow measurement of the dynamic angle of repose. Material composition.
The mold material composition of claim 1, wherein the nitrate is selected from the group consisting of calcium nitrate and magnesium nitrate. A mold material composition that is not a material for CO2 gas _mold ,
(a) refractory aggregate;
(b) a caking agent 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;
(d) A mold material composition characterized in that it contains at least a surfactant and is constituted as a wet mixture that does not have fluidity at room temperature and whose dynamic angle of repose cannot be measured. thing.
4. The molding material composition of claim 3, wherein the nitrate is selected from the group consisting of potassium nitrate, sodium nitrate, calcium nitrate and magnesium nitrate. 3. The surfactant is contained in a proportion of 0.1 to 20 parts by mass based on 100 parts by mass of solid water glass in the mold material composition. 4. The mold material composition according to 4. Claims 1 to 4, wherein the nitrate is contained in a proportion of 0.5 to 30 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition. The mold material composition according to any one of the items. The mold material composition according to any one of claims 1 to 4, further comprising 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 based on 100 parts by mass of solid water glass in the mold material composition. Composition. The mold material composition according to any one of claims 1 to 4, further comprising a carbonate and/or a borate. A claim characterized in that the carbonate and/or borate is contained in a proportion of 0.5 to 50 parts by mass based on 100 parts by mass of the solid content of water glass in the mold material composition. Item 9. The mold material composition according to Item 9. The mold material composition according to any one of claims 1 to 4, wherein the refractory aggregate is spherical. The mold material composition is a wet mixture having no room-temperature fluidity, which is formed by covering the surface of the refractory aggregate with the coating layer containing the water glass, and the water content of the mixture is as follows: The mold material composition according to any one of claims 1 to 4, wherein the mold material composition is 70 to 400% by mass of the solid content of water glass. A method for producing a mold material composition according to claim 1, comprising (a) a refractory aggregate, (b) a caking agent containing water glass as an essential component, and (c) an alkaline earth metal of nitric acid. A method for producing a mold material composition, characterized in that the composition is mixed with at least one nitrate selected from the group consisting of salts, and the composition is extracted as a wet mixture that does not have flowability at room temperature. A method for producing a mold material composition according to claim 3, comprising (a) a refractory aggregate, (b) a caking material containing water glass as an essential component, (c) an alkali metal salt of nitric acid, and At least one nitrate selected from the group consisting of alkaline earth metal salts and (d) a surfactant are mixed together to be extracted as a wet mixture that does not have room temperature fluidity. A method for producing a mold material composition. A wet mold material composition formed by the manufacturing method according to claim 13 or 14 is used, and after being filled into a heated mold, the composition is held in the mold and solidified. A method for manufacturing a mold, characterized in that a desired mold is obtained by curing or curing. 16. The mold manufacturing method according to claim 15, wherein the mold is heated to a temperature of 80°C to 300°C. 5. A method for manufacturing a mold, comprising forming a desired mold by additive manufacturing using the mold material composition according to any one of claims 1 to 4.

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