CN113646107A - Mold material composition and method for producing mold using same - Google Patents

Mold material composition and method for producing mold using same Download PDF

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Publication number
CN113646107A
CN113646107A CN202080025084.8A CN202080025084A CN113646107A CN 113646107 A CN113646107 A CN 113646107A CN 202080025084 A CN202080025084 A CN 202080025084A CN 113646107 A CN113646107 A CN 113646107A
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mold
water glass
composition
material composition
casting
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CN113646107B (en
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海川善久
高间智宏
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Asahi Yukizai Corp
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Asahi Yukizai Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B22C1/10—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for influencing the hardening tendency of the mould material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/12—Treating moulds or cores, e.g. drying, hardening

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)

Abstract

Provided is a mold material composition which can advantageously form a mold having good disintegratability and can easily recycle a refractory aggregate (sand) recovered after casting. A mold material composition was prepared using the following components as essential constituent components: (a) a refractory aggregate, (b) a binder containing water glass as an essential component, and (c) a neutralizing agent which causes a neutralization reaction between a decomposition product generated by heating during casting and an alkali component of the water glass.

Description

Mold material composition and method for producing mold using same
Technical Field
The present invention relates to a mold material composition and a method for producing a mold using the same, and particularly to a mold material composition which can provide a mold having excellent disintegration properties after casting and easy recycling of recycled refractory aggregate, and a method for advantageously producing a mold exhibiting such excellent properties.
Background
Conventionally, as one of the molds used for casting molten metals such as iron and aluminum, the following molds have been known: a mold is obtained by molding a precoated sand (mold material composition) obtained by covering a refractory aggregate with a predetermined binder into a desired shape. As a binder used for forming a covering layer in such a mold material composition, in addition to water-soluble inorganic binders such as water glass and sodium phosphate, organic binders using resins such as phenol resins, furan resins, and urethane resins have been elucidated, and various methods for molding a self-hardening mold using the binder have been proposed.
Further, as a mold composition using an inorganic binder such as water glass, it is known that: since the content of organic components is small as compared with a molding composition using an organic binder, generation of various gases due to heat during molding and casting is advantageously suppressed, and problems such as odor are less likely to occur. However, in the case of a conventional mold material composition using an inorganic binder, when it is desired to recover a refractory aggregate (sand) from a cast mold and to recycle the recovered sand by a baking treatment, the inorganic binder remaining on the surface of the recovered sand is not burned, but rather is sintered and adheres hard to the surface of the refractory aggregate (sand), and therefore, there is a problem that recycling thereof is difficult. In particular, a mold composition using water glass as an inorganic binder has the following problems: since the water glass is vitrified by heat at the time of casting, it is very difficult to remove the water glass vitrified on the sand surface even if the recovered sand is subjected to baking treatment and grinding treatment after casting. Further, the conventional mold material composition using an inorganic binder has a problem that the mold obtained by using the composition is insufficient in disintegratability.
Under such circumstances, various techniques have been proposed as measures for improving the disintegration property of the mold after casting and techniques related to the recycling of the recovered refractory aggregate (sand). For example, patent document 1 (jp 2016-. However, even when the water glass mold is disintegrated using the mold disintegrating agent composition disclosed in the patent document, there is a concern that water glass remains on the surface of the recovered refractory aggregate (sand), and when such recovered sand is subjected to a baking treatment, re-fusion occurs between particles of the recovered sand, and it is difficult to regenerate the sand. Further, since the mold disintegrator composition disclosed in this patent document is an acidic solution, there is a concern that a metal casting device and a casting obtained therefrom may be corroded.
In addition, patent document 2 (japanese patent application laid-open No. 2015-51446) proposes a method including, as a method for regenerating casting sand, a mixing step of: the crushed material of the foundry sand is mixed and stirred in water at 5 to 70 ℃, whereby the binder adhering thereto is separated from the foundry sand. However, there are problems as follows: when the reclamation treatment method disclosed in the patent document is applied to a foundry sand mold using water glass as a binder (binder), for example, treated water containing a large amount of alkali components derived from water glass is generated, and further labor is required for treatment and division (treatment) of the treated water.
Further, patent documents 3 (japanese patent application laid-open No. 2017-77570) and 4 (japanese patent application laid-open No. 2010-519042) disclose, as a method for regenerating foundry sand recovered from a mold molded from foundry sand using an inorganic binder (water glass): the recovered foundry sand is fired at a high temperature, whereby water glass is vitrified to be inactivated. However, in order to vitrify the water glass, it is necessary to perform firing at a high temperature of 900 ℃ or higher, and it is difficult to say that the firing is an efficient method from the viewpoint of energy efficiency in regeneration.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2016-
Patent document 2: japanese patent laid-open publication No. 2015-51446
Patent document 3: japanese patent laid-open publication No. 2017-77570
Patent document 4: japanese Kokai publication No. 2010-519042
Disclosure of Invention
Problems to be solved by the invention
In view of the above, the present invention is made in the light of the above circumstances, and the problems to be solved are: provided is a mold material composition which can advantageously form a mold having good disintegratability and can easily recycle a refractory aggregate (sand) recovered after casting. In addition, the problems to be solved by the present invention are: provided is a method whereby a useful mold can be advantageously produced using a mold material composition having such excellent properties.
Means for solving the problems
In the present invention, in order to solve the above-described problems, various embodiments described below can be appropriately implemented, and the various embodiments described below can be adopted in any combination. It should be noted that: the embodiments and technical features of the present invention are not limited to the following description, and can be recognized based on the idea of the invention that can be grasped from the entire description of the specification.
(1) A casting mold material composition, comprising at least: (a) a refractory aggregate; (b) a binder containing water glass as an essential component; and (c) a neutralizing agent that neutralizes the alkali component of the water glass with a decomposition product generated by heating during casting.
(2) The mold material composition according to the aspect (1), wherein the neutralizing agent is an organic halogen compound or a phosphate ester.
(3) The mold material composition according to the aforementioned mode (1) or the aforementioned mode (2), wherein the aforementioned neutralizing agent is contained in a quantitative ratio as follows: the alkali component of the water glass is neutralized by the decomposition product generated by heating during casting, so that the proportion of the alkali component of the water glass after casting is 15 mass% or less.
(4) The mold material composition according to any one of the above-described aspects (1) to (3), wherein a coating layer containing the binder and the neutralizer is formed so as to cover the surface of the refractory aggregate.
(5) The mold material composition according to any one of the above-described aspects (1) to (3), wherein the solid first coating layer containing the neutralizing agent is formed so as to cover the surface of the refractory aggregate, and the second coating layer containing the binder composition containing the binder is formed so as to cover the first coating layer.
(6) The mold material composition according to the mode (5), wherein the first coating layer contains an organic compound.
(7) The mold material composition according to any one of the above-described aspects (1) to (6), wherein the refractory aggregate is spherical.
(8) The mold material composition according to any one of the above-mentioned aspects (1) to (7), which has no room-temperature fluidity and is in a wet state.
(9) The mold material composition according to any one of the above-mentioned aspects (1) to (7), which has room-temperature fluidity and is in a dry state.
(10) A method for producing a mold, characterized in that the mold material composition in the wet state according to the above aspect (8) is used, and after being filled into a mold, the mold material composition is held in the mold and cured or hardened, thereby obtaining a target mold.
(11) A method for producing a mold, characterized in that the mold material composition in the dry state according to the above-mentioned aspect (9) is used, and after filling the mold with the composition, water vapor is allowed to pass through the composition, and the composition is held in the mold and cured or hardened, thereby obtaining a target mold.
(12) A method for producing a mold, characterized in that the mold material composition in a dry state described in the above-mentioned embodiment (9) is used, water is added thereto to wet the composition, the wet mold material composition is filled into a mold, and then the mold material composition is held in the mold and cured or hardened, thereby obtaining a target mold.
ADVANTAGEOUS EFFECTS OF INVENTION
As described above, the mold composition of the present invention comprises, as essential components, (a) a refractory aggregate, (b) a binder containing water glass as an essential component, and (c) a neutralizing agent that neutralizes a decomposition product generated by heating during casting and an alkali component of water glass. Therefore, when casting is carried out using a mold formed from the above-mentioned mold material composition, the mold is heated by molten metal (usually heated to a temperature exceeding 300 ℃), and the decomposition product generated from the neutralizing agent by the heating is neutralized with the alkali component of the water glass, whereby the water glass becomes physically fragile, and therefore the mold after casting has good disintegratability. Further, since a part or all of the alkali component of the water glass is neutralized by heating accompanying pouring of the molten metal, the mold material composition containing the refractory aggregate (precoated sand) covered with the coating layer can effectively prevent the dissolution of the coating layer on the surface of the precoated sand caused by the alkali component that has become high temperature, and as a result, the re-fusion (sintering) between the precoated sand particles caused by heating at the time of pouring can be favorably suppressed.
Furthermore, in the refractory aggregate (sand) which is cast using the mold made of the mold material composition of the present invention and then recovered, the whole amount of the alkali component of the water glass or a part thereof is neutralized and deactivated, and therefore, in regenerating the recovered sand, a firing treatment at a high temperature for removing the alkali component, a neutralization treatment using an acid, or the like is not necessary. Further, by neutralizing the alkali component of the water glass, the aggregate of the recycled refractory aggregate becomes brittle, and therefore, the advantage of easy recycling by grinding can be enjoyed.
Drawings
Fig. 1 is a longitudinal sectional explanatory view of a sand mold for a casting test used in a disintegration test in examples.
FIG. 2 is a longitudinal sectional explanatory view of a casting containing a waste core in the embodiment.
Detailed Description
Therefore, the mold composition of the present invention is roughly classified into a wet mold composition and a dry mold composition depending on the state of a layer (coating) containing a binder containing water glass as an essential component. The mold composition in a dry state has good room temperature fluidity, whereas the mold composition in a wet state does not have such room temperature fluidity.
The "mold composition having room-temperature fluidity and being in a dry state" in the present invention means a mold composition which can obtain a measured value when a dynamic repose angle is measured, regardless of the water content. The dynamic repose angle is an angle formed between a slope of a layer of a mold composition flowing in a cylinder and a horizontal plane by housing the mold composition in the cylinder in which one end in the axial direction is closed by a transparent plate (for example, by placing the mold composition in a container having a diameter of 7.2cm × a height of 10cm to half of its volume), rotating the cylinder around the horizontal axis at a constant speed (for example, 25rpm) while keeping the axis horizontal, and making the slope flat. The dynamic repose angle is preferably 80 ° or less, more preferably 45 ° or less, and further preferably 30 ° or less. In particular, when the refractory aggregate is spherical, a dynamic repose angle of 45 ° or less can be easily achieved. In addition, the mold composition did not flow in the cylinder in a wet state, and the inclined surface of the mold composition layer was not formed into a flat surface, and as a result, the dynamic repose angle could not be measured, and this was classified as a mold composition in a wet state.
In the dry casting mold composition having room temperature fluidity of the present invention, the water content is preferably 5 to 55% by mass, more preferably 10 to 50% by mass, particularly preferably 20 to 50% by mass, based on the solid content of the water glass constituting the binder contained in the coating layer covering the surface of the refractory aggregate. If the water content in the mold material composition is less than an amount corresponding to 5 mass% of the solid content of the water glass in the covering layer, the water glass is vitrified, and there is a possibility that the water glass cannot be returned to a solution state even if water is added again at the time of mold formation, while on the other hand, if the water content is more than an amount corresponding to 55 mass%, the mold material composition cannot be brought into a dry state. However, even a mold composition containing water in an amount exceeding 55 mass% relative to the solid content of the water glass may be in a dry state depending on the type of the water glass. The determination of whether the composition is a dry mold composition or a wet mold composition is determined by the presence or absence of the above-mentioned room-temperature fluidity. The method for measuring the moisture content in the mold composition is not particularly limited, and a known method can be suitably used.
On the other hand, in the wet casting mold composition having no room temperature fluidity of the present invention, the water content is preferably an amount corresponding to a ratio of 70 to 400 mass%, more preferably 80 to 300 mass%, most preferably 90 to 200 mass% with respect to the solid content of the water glass as the binder. If the water content in the mold material composition is less than an amount corresponding to 70 mass% relative to the solid content of the water glass, the viscosity of the water glass increases, and uniform mixing becomes difficult during kneading, and a uniform mold cannot be obtained. On the other hand, if the amount is more than 400% by mass, the molding material composition may be in the form of slurry, and as a result, the molding die may not be filled with the molding material composition. Even if filling is possible, there is a concern that drying in the mold takes time.
Here, as the refractory aggregate constituting the mold material composition of the present invention, there can be used: any of various refractory granular or powdery materials conventionally used for casting mold applications, which are refractory substances functioning as a base material of a casting mold, specifically, silica sand and regenerated silica sand, as typified by special sand such as alumina sand, olivine sand, zircon sand and chromite sand, slag-based granules such as ferrochrome-based slag, ferronickel-based slag and converter slag; artificial particles such as alumina-based particles and mullite-based particles, and regenerated particles thereof; alumina spheres, magnesium frit, and the like. The refractory aggregate may be fresh sand, reclaimed sand or reclaimed sand used once or more times as foundry sand in the molding of a mold, or mixed sand obtained by adding fresh sand to the reclaimed sand or reclaimed sand and mixing the same, without limitation. The refractory aggregate is generally an aggregate having a particle size of about 40 to 200 in terms of AFS index, and preferably an aggregate having a particle size of about 50 to 150. The refractory aggregate is preferably a spherical aggregate, and more preferably has a coefficient of angularity (coefficient of angularity) of 1.2 or less, and still more preferably 1.0 to 1.1. By using the refractory aggregate having an angle coefficient of 1.2 or less, the fluidity and filling property are improved, and the number of joints between aggregates is increased, so that the amount of the binder and the amount of the additive required for expressing the same strength can be reduced. The angular coefficient of the aggregate used herein is generally used as one of the dimensions showing the outer shape of the particle, and is also referred to as angular index, and the closer the value is to 1, the closer the value is to a sphere (sphere). The angular coefficient is a value calculated using a sand surface area measured by a known method, and is, for example, a value obtained by measuring the surface area of each 1g of actual sand grains using a sand surface area measuring instrument (manufactured by Georg Fischer Ltd) and dividing the surface area by the theoretical surface area. The theoretical surface area is a surface area when all the sand grains are assumed to be spherical.
In the mold material composition of the present invention, as the binder to be blended with the refractory aggregate, a material containing water glass as an essential component can be used. The 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 ammonium silicate, and among these, sodium silicate (sodium silicate) can be used favorably in the present invention. The binder may be any of various water-soluble binders, for example, thermosetting resins, saccharides, proteins, synthetic polymers, salts, inorganic polymers, and the like, as long as water glass is used as an essential component. When another water-soluble binder is used in combination with water glass, the proportion of water glass in the entire binder is preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more, based on the solid content. The water glass may be used in the form of a hydrate.
Further, sodium silicate is usually according to SiO2/Na2The molar ratio of O is used in the range of 1 to 5. Specifically, sodium silicate No. 1 is SiO2/Na2Sodium silicate with a molar ratio of O of 2.0-2.3, and sodium silicate No. 2 being SiO2/Na2Sodium silicate having a molar ratio of O of 2.4 to 2.6, and further sodium silicate No. 3 is SiO2/Na2Sodium silicate having a molar ratio of O of 2.8 to 3.3. In addition, sodium silicate No. 4 is SiO2/Na2Sodium silicate with the molar ratio of O being 3.3-3.5, and the sodium silicate No. 5 is SiO2/Na2Sodium silicate having a molar ratio of O of 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. In the present invention, these various sodium silicates may be used alone or in combination, or SiO may be adjusted by mixing2/Na2Molar ratio of O. In addition, SiO2/Na2The molar ratio of O is not limited to the range defined in sodium silicate nos. 1 to 5, and may be, for example, in the range of 0.8 to 4.0.
Further, in the present invention, in order to favorably obtain the intended mold composition, SiO, which is a sodium silicate constituting water glass used as a binder, is used2/Na2The molar ratio of O is preferably 1.9 or more, preferably 2.0 or more, more preferably 2.1 or more, and the classification of sodium silicate is described aboveOf these, sodium silicates corresponding to nos. 1 and 2 are particularly advantageously used. The sodium silicate 1 and 2 each stably obtained a mold composition having good properties even when the concentration of sodium silicate in water glass was in a wide range. In addition, SiO of the sodium silicate2/Na2The upper limit of the molar ratio of O is appropriately selected depending on the characteristics of the water glass in the form of an aqueous solution, and is usually 3.5 or less, preferably 3.2 or less, and more preferably 2.7 or less. Here, if SiO2/Na2The molar ratio of O is less than 1.9, and particularly in the dry state, the viscosity of water glass is low, and if the water content is not reduced to a large extent, the mold material composition may be difficult to be in the dry state, while if it is more than 3.5, the solubility to water is reduced, and the bonding area is not obtained, and the strength of the finally obtained mold may be reduced.
The water glass used in the present invention is a solution of a silicic acid compound dissolved in water, and may be used in a state of being diluted by adding water to a stock solution, in addition to the stock solution as it is, which is commercially available. The nonvolatile component (water glass component) obtained by removing volatile substances such as water and solvents from such water glass is referred to as a solid component, and corresponds to a soluble silicate compound such as sodium silicate. Further, the higher the ratio of such solid components (nonvolatile components), the higher the silicate compound concentration in the water glass becomes. Therefore, when the solid content of the water glass used in the present invention is constituted only by the stock solution, the amount obtained by subtracting the amount of water in the stock solution corresponds to the solid content of the water glass used, and when a diluted solution obtained by diluting the stock solution with water is used, the amount obtained by subtracting the amount of water in the stock solution and the amount of water used for dilution corresponds to the solid content of the water glass used.
The solid content in the water glass is preferably contained in an appropriate ratio depending on the type of the water glass component (soluble silicic acid compound), and is preferably 20 to 50 mass%. By appropriately making the water glass component corresponding to the solid component exist in the aqueous solution, the refractory aggregate can be uniformly and uniformly covered with the water glass component in a dry state and the aggregate and the water glass can be uniformly and uniformly mixed in a wet state at the time of mixing (kneading) with the refractory aggregate, whereby the target mold can be favorably molded. When the concentration of the water glass component in the water glass is too low and the total amount of the solid content is less than 20% by mass, the heating temperature needs to be increased or the heating time needs to be prolonged for drying the mold material composition in a dry state, which causes problems such as energy loss. In the wet state, the time for heating in the mold becomes long, which causes a problem of extending the molding cycle of the mold. Further, when the ratio of the solid component in the water glass becomes too high, it becomes difficult to uniformly cover the surface of the refractory aggregate with the water glass component in a dry state, and when the viscosity of the water glass becomes too high in a wet state, it becomes difficult to uniformly and uniformly mix the aggregate and the water glass, which causes a problem in improving the characteristics of the intended mold, and therefore, it is desirable to prepare the water glass in the form of an aqueous solution so that the solid component becomes 50 mass% or less and the moisture content becomes a ratio of 50 mass% or more.
The water glass is preferably used in a ratio of 0.1 to 5.0 parts by mass in terms of solid content in consideration of only nonvolatile components with respect to 100 parts by mass of the refractory aggregate, and particularly preferably 0.3 to 4.0 parts by mass. Here, the measurement of the solid content in the water glass is performed as follows. That is, 10g of a sample was placed in a sample dish made of aluminum foil (vertical: 9cm, horizontal: 9cm, height: 1.5cm) and weighed, and placed on a hot plate maintained at 180. + -. 1 ℃ for 20 minutes, then the sample dish was inverted, and further placed on the hot plate for 20 minutes. Thereafter, the sample dish was taken out from the hot plate, cooled in a desiccator, weighed, and the solid content (% by mass) was calculated by 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) ] } × 100
In the present invention, when the amount of water glass used is too small, it is difficult to form a coating layer on the surface of the refractory aggregate in the dry mold composition, while it is impossible to cover the aggregate with water glass in an aqueous solution in the wet mold composition, and there is a fear that curing or hardening of the mold composition during mold molding is difficult to sufficiently proceed. Further, when the amount of the water glass is too large, an excessive amount of the water glass adheres to the surface of the refractory aggregate even in a dry state, and thus it is difficult to form a uniform coating layer, and the molding material compositions are fixed to each other and agglomerated (composite granulation) is generated, and an excessive amount of the water glass is not uniform at the time of molding of the mold even in a wet state, and thus uniform physical properties of the mold are hindered, which may adversely affect physical properties of the finally obtained mold and further cause a problem of difficulty in shakeout of the core after metal pouring.
In the mold composition of the present invention, the following features are important: the predetermined neutralizing agent is used as an essential component together with the refractory aggregate and a binder containing water glass as an essential component.
That is, when casting is carried out using a mold formed of the mold material composition of the present invention by adding a predetermined neutralizing agent (neutralizing agent that causes a neutralization reaction between a decomposition product generated by heating and an alkali component of water glass), the mold is heated (usually to a temperature exceeding 300 ℃) by a molten metal, and a part or all of the alkali component of water glass is neutralized by the decomposition product generated by the neutralizing agent by heating at the time of casting. Since the water glass becomes physically brittle by neutralizing a part or the whole of the alkali component of the water glass, the mold material composition of the present invention, which is used to form a mold, has good disintegration properties after casting. Further, the alkali component of the water glass is neutralized by heating (heating at the time of casting) accompanied by pouring of the molten metal, and therefore the mold material composition containing the refractory aggregate (precoated sand) covered with the coating layer can effectively prevent the dissolution of the coating layer on the surface of the precoated sand caused by the alkali component becoming high temperature, and favorably suppress the re-welding (sintering) between the precoated sand particles caused by heating at the time of pouring. Furthermore, in the refractory aggregate (sand) which is cast using the mold made of the mold material composition of the present invention and then recovered, a part or the entire amount of the alkali component of the water glass is neutralized to be in a deactivated state, and therefore, in regenerating the recovered sand, a firing treatment at a high temperature for removing the alkali component, a neutralization treatment using an acid, and the like are not necessary. Further, the alkali component of the water glass is neutralized, and the coating on the surface of the coated sand becomes brittle, so that the collected refractory aggregate grains become brittle, and the advantage of easy regeneration by grinding can be enjoyed. The alkali component of the water glass is contained in the solid component of the water glass, and is dissolved in the water contained in the water glass, and the alkali metal ion generated in the water glass is neutralized with the decomposition product of the neutralizing agent. Further, as is clear from the "mold composition in a dry state" described above, the mold composition in a dry state also contains water remaining in the water glass contained therein.
Here, the neutralizing agent used in the present invention is a neutralizing reaction between a decomposition product generated by heating at the time of casting and an alkali component of the water glass. More specifically, a compound which is not decomposed by heating (heating at a temperature of usually 300 ℃ or less) during preparation (production) of the mold material composition or molding of the mold but is decomposed by heating (heating at a temperature exceeding 300 ℃) by the molten metal during casting, and the generated decomposition product converts an alkali component of the water glass (for example, Na in the case of sodium silicate) into a neutralizing agent in the present invention2O) neutralization. The decomposition here means complete decomposition, and even if the compound starts to be decomposed partially by heating at 300 ℃ or lower, the compound can be used as the neutralizing agent of the present invention as long as the complete decomposition temperature exceeds 300 ℃ and the decomposition product is neutralized with the alkali component of the water glass. The compound having such a property is not particularly limited, and in the present invention, an organic halogen compound or a phosphate ester is preferably used as the neutralizing agent, and an organic halogen compound is particularly preferably used. Organic halogenThe compound is decomposed by heating (heating at a temperature exceeding 300 ℃) by molten metal at the time of casting to release halogen, and the released halogen reacts with sodium of water glass, whereby the alkali component of the water glass is neutralized. In the present invention, it is most preferable to use an organic chlorine compound or an organic bromine compound as the neutralizing agent from the viewpoint of the neutralizing effect and the cost. In the present invention, the neutralizing agent is present in a uniformly dispersed state in the coating layer when produced by a production method described later, and therefore, in the present invention, the neutralizing agent does not become uneven, which is a problem when, for example, an acid is added as the neutralizing agent.
In the present invention, examples of the organic halogen compound used as the neutralizing agent include organic chlorine compounds such as chlorinated paraffin, chlorinated biphenyl (chlorodiphenyl), chlorinated ethane, chlorinated polyethylene, chlorinated polyphenyl (chloropolyphenyl), chlorinated biphenyl, vinyl chloride, perchlorocyclopentadecanone, tetrachlorobisphenol a, trichloroethyl phosphate, tris (dichloropropyl) phosphate, and tris-. beta. -chloropropyl phosphate; organic bromine compounds such as brominated paraffin, brominated polyphenylene, tetrabromoethane, tetrabromobenzene, decabromodiphenyl ether, octabromodiphenyl ether, hexabromocyclododecane, bis (tribromophenoxy) ethane, ethylenebistetrabromophthalimide, hexabromobenzene, polydibromophenyl ether, tetrabromobisphenol a, tris (2, 3-dibromopropyl-1) isocyanurate, tribromophenol allyl ether, brominated polystyrene, tribromoneopentanol, dibromodichloropropane, dibromotetrafluoroethane, tris (tribromophenyl) phosphate, and tris (tribromoneopentyl) phosphate; organic fluorine compounds such as polytetrafluoroethylene, perfluoroalkoxyalkane, perfluoroethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and the like. In the present invention, examples of the phosphate ester used as the neutralizing agent include triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), cresyldiphenyl phosphate (CDP), xylyldiphenyl phosphate (XDP), resorcinol-bis- (diphenyl phosphate), 2-ethylhexyl diphenyl phosphate, dimethyl methyl phosphate, triallyl phosphate (Reofos), and alkyl phosphate.
In the mold composition of the present invention, if the amount of the neutralizing agent (amount of the neutralizing agent to be added) is too small as described above, the amount of the alkali component in the water glass neutralized by heating at the time of casting is inevitably small, and there is a fear that the effect of the present invention cannot be favorably enjoyed. Therefore, in the present invention, the predetermined neutralizing agent is preferably contained in the mold material composition in the following ratio: the alkali component of the water glass is neutralized by a decomposition product generated by heating at the time of casting, so that the proportion of the alkali component of the water glass after casting becomes 15 mass% or less. Particularly, in the case of using sodium silicate (soda silicate) as the water glass, the neutralizing agent is used in the above amount ratio to make the solid content (SiO) in the water glass of the refractory aggregate (sand) recovered after casting2+Na2O) alkali component (Na)2O) of 15% by mass or less, the water glass is solidified, and the alkali component (Na) is formed2O) is not eluted from the solidified water glass, and therefore the effects of the present invention can be more advantageously enjoyed. In addition, for the solidification of water glass (sodium silicate), the technique in the art is only referred to by the conventionally known Na2O-SiO2State diagrams are understood in the art. With respect to Na2O-SiO2The state diagram can be confirmed in The homepage (URL: http:// www.toso-singyo. com/products/keisansoda 2-2. html) of Tosoh corporation, and various papers (e.g., "KracekF. C.," The System Sodium Oxide-Silica ", J.Phys. chem.,34, p.1583-1598 (1930)). In the present invention, it is preferable that the neutralizing agent is not added in an excessive amount relative to the amount at which the alkali content in the water glass becomes 0 mass% by heating at the time of casting.
In the mold composition of the present invention, various known additives may be appropriately contained in the mold composition, as needed, in addition to the predetermined neutralizing agent. Examples of such additives include surfactants, lubricants, inorganic oxide particles, carbonates and/or borates, and moisture resistance improvers.
By adding a surfactant to the mold material composition of the present invention, the permeability of water, in other words, the wettability of the mold material composition to water can be improved. In particular, when water is supplied to a mold material composition in a dry state during mold formation, the surfactant intervenes between the supplied water and the water glass, and the entire mold material composition is effectively humidified even with a small amount of water, and therefore, 1) the time for supplying water to the mold material composition (for example, in the case of supplying water by steam, the time for ventilating water vapor) can be suppressed to a required minimum limit, and 2) the amount of water supplied to a molding die (molding cavity) can be suppressed to a small amount, and as a result, the mold obtained by molding can advantageously enjoy the following effects: the mold has excellent releasability from a mold and exhibits excellent strength.
In the present invention, the amount of the surfactant contained in the mold composition is preferably 0.1 to 20.0 parts by mass, more preferably 0.5 to 15.0 parts by mass, particularly preferably 0.75 to 12.5 parts by mass, based on 100 parts by mass of the solid content of the water glass. If the amount of the surfactant contained is too small, the above-mentioned effects may not be favorably enjoyed, while if the amount of the surfactant is too large, improvement of the effects corresponding to the amount of the surfactant cannot be confirmed, and further, it is not a good measure from the viewpoint of cost efficiency.
As such a surfactant, any of a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a silicone surfactant, and a fluorine surfactant can be used. Specifically, the cationic surfactant includes aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, and the like. Examples of the anionic surfactant include fatty acid soaps, N-acyl-N-methylglycinate, N-acyl-N-methyl- β -alaninate, N-acyl glutamate, alkyl ether carboxylate, acylated peptide, alkyl sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, dialkyl sulfosuccinate salt, alkyl sulfoacetate, α -olefin sulfonate, N-acyl methyl taurine, sulfated oil, higher alcohol sulfate salt, higher secondary alcohol sulfate salt, alkyl ether sulfate, higher secondary alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglyceride sulfate, fatty acid alkylolamide sulfate salt, alkyl ether phosphate salt, and alkyl phosphate salt. Further, as the amphoteric surfactant, a carboxybetaine type, a sulfobetaine type, an aminocarboxylate, an imidazolinium betaine, and the like can be cited. Further, examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, polyoxyethylene alkylphenyl ethers (e.g., Emulgen911), polyoxyethylene sterol ethers, polyoxyethylene lanolin derivatives, polyoxyethylene polyoxypropylene alkyl ethers (e.g., NEWPOLPE-62), polyoxyethylene glycerin fatty acid esters, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyethylene glycol fatty acid esters, fatty acid monoglycerides, polyglycerol fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkylamines, alkylamine oxides, acetylene glycols, acetylene alcohols, and the like.
Among various surfactants, a surfactant having a siloxane structure as a nonpolar portion is particularly called a silicone surfactant, and a surfactant having a perfluoroalkyl group is called a fluorine surfactant, and examples of the silicone surfactant include polyester-modified silicone, acrylic-terminal polyester-modified silicone, polyether-modified silicone, acrylic-terminal polyether-modified silicone, polyglycerol-modified silicone, and aminopropyl-modified silicone. Examples of the fluorine-based surfactant include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl trimethylammonium salt, perfluoroalkyl ethylene oxide adduct, and perfluoroalkyl group-containing oligomer.
In the present invention, as described above, various surfactants can be used alone or in combination of 2 or more. Naturally, since the surfactant may react with water glass and the surface-active ability may be reduced or lost with the passage of time, an anionic surfactant, a nonionic surfactant, and a silicone surfactant that do not react with water glass are particularly advantageously used in the mold material composition of the present invention.
In the present invention, it is preferable to add a lubricant as an additive to the surface of the refractory aggregate of the mold material composition. Due to the presence of the lubricant, the fluidity of the mold material composition can be advantageously improved.
The amount of the lubricant contained in the mold composition of the present invention is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 8 parts by mass, particularly preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the solid content of the water glass. If the amount of the lubricant contained is too small, the above-described effects may not be favorably enjoyed, while if the amount of the lubricant is too large, the mold strength may be lowered, and further, it is not a good measure from the viewpoint of cost efficiency.
Examples of the lubricant used in the present invention include waxes such as paraffin wax, synthetic polyethylene wax, and montan wax; fatty acid amides such as stearic acid amide, oleic acid amide and erucic acid amide; alkylene fatty acid amides such as methylene bis stearamide and ethylene bis stearamide; stearic acid, stearyl alcohol; metal stearates such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate; stearic acid monoglyceride, stearic acid stearyl ester, hydrogenated oil, etc. Of these, calcium stearate and the like are particularly advantageously used.
The mold composition of the present invention may contain inorganic oxide particles. By containing the inorganic oxide particles in the mold material composition, the fluidity, filling property, moisture resistance of the finally obtained mold, and the like of the mold material composition can be improved. The inorganic oxide particles used in the present invention are preferably smaller in size than the refractory aggregate that together constitutes the mold material composition, and specifically, inorganic oxide particles having an average particle diameter of 0.01 μm or more and 300 μm or less, more preferably 0.3 μm or more and 200 μm or less, and particularly preferably 0.5 μm or more and 100 μm or less are used. The average particle diameter can be determined from a particle size distribution measured by a laser diffraction particle size distribution measuring apparatus or the like. The content of the inorganic oxide particles in the mold composition is usually 5 to 200 parts by mass, preferably 10 to 100 parts by mass, based on 100 parts by mass of the solid content of the binder containing water glass as an essential component.
The inorganic oxide particles used in the present invention may be spherical particles or non-spherical particles, and the use of spherical particles is preferable in that the effect of mixing the inorganic oxide particles can be more favorably enjoyed, and a cast product having a more favorable cast surface can be obtained. Such spherical particles do not necessarily have a regular spherical shape as long as they have a spherical shape of a degree generally recognized, and those having a sphericity of usually 0.5 or more, preferably 0.7 or more, and more preferably 0.9 or more can be used favorably. Here, the sphericity is an average value of aspect ratios (ratio of short diameter/long diameter) obtained by randomly selecting 10 single particles and projecting the particles on a scanning electron microscope. In the case of using inorganic oxide particles that are not spherical, since projections and depressions are present on the surface of such inorganic oxide particles, when the inorganic oxide particles are caused to flow between the refractory aggregates together with a binder containing water glass as an essential component, which is in the form of a solution due to supplied moisture, for example, the projections and the like on the surface of the inorganic oxide particles collide with the refractory aggregates and other inorganic oxide particles, thereby causing a sliding prevention effect, and the flow of the binder and the inorganic oxide particles between the refractory aggregates is inhibited, and as a result, there is a fear that the filling property of the finally obtained mold and the strength thereof are lowered.
The material constituting the inorganic oxide particles is not particularly limited, and is preferably an inorganic metal oxide. As the particles containing the inorganic metal oxide, particles containing silica, alumina, titania, etc., which are favorably usedAmong them, silica particles are particularly preferable in that a binder containing strongly basic water glass can react with silanol groups formed on the surface of silica, and in that strong bonds are formed between silica and a solid binder at the time of evaporation of water, thereby improving the mold strength. The silica preferably has a crystalline state and an amorphous state, and the amorphous silica includes precipitated silica, calcined silica produced in an arc or by flame hydrolysis, and ZrSiO4Silica produced by thermal decomposition of (a), silica produced by oxidizing metal silicon with an oxygen-containing gas, silica glass powder of spherical particles produced from crystalline quartz by melting and then rapidly cooling, and the like. These may be used alone or in combination of 2 or more. In the present invention, silica is treated as an inorganic metal oxide. In addition, silicone resin particles may be added instead of the inorganic oxide particles, or in combination.
In the mold composition of the present invention, at least one of carbonate and borate is preferably used. The carbonate releases carbon dioxide by heat generated by molding and casting, cracks are generated in the adhesive film of the water glass, and the adhesive film of the water glass is broken, whereby the mold is easily disintegrated, and the generated carbon dioxide is changed into weak-acid carbonated water by water in the water glass, thereby promoting neutralization of the alkali component of the water glass. On the other hand, in the case of borate, hydroxyl groups (-OH) in the water glass react with tetraboric acid ions or metaboric acid ions generated from borate due to heat generated by molding and casting, and the hydroxyl groups (-OH) in the water glass are blocked, so that the water glass is not easily redissolved, and the adhesive film of the water glass can be prevented from softening. Thus, the disintegration of a mold formed by molding using the mold material composition can be further improved, and the moisture resistance of the mold can be improved, and the strength deterioration due to moisture absorption can be suppressed.
In the present invention, the amount of the carbonate and/or borate contained in the mold composition is preferably 0.5 to 50 parts by mass, more preferably 1 to 20 parts by mass, particularly preferably 2 to 15 parts by mass, based on 100 parts by mass of the solid content of the water glass. If the amount of carbonate and/or borate contained is too small, the above-mentioned effects may not be favorably obtained, while if the amount of carbonate and/or borate is too large, the effect corresponding to the amount of carbonate and/or borate cannot be improved, and further, it is not a good measure from the viewpoint of cost efficiency. It is to be noted that the carbonate and the 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, and sodium carbonate. Examples of such borate salts 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. Of these, basic zinc carbonate, sodium tetraborate, potassium metaborate may be advantageously used.
In the present invention, a moisture resistance improver may be further contained as another additive. By adding the moisture resistance improver to the water glass, the moisture resistance of the finally obtained casting mold can be improved. The moisture resistance improver used in the present invention may be any conventionally used moisture resistance improver for a molding composition such as coated sand, and may be used without impairing the effects of the present invention. Specifically, examples thereof include sulfates such as sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, titanium sulfate, aluminum sulfate, zinc sulfate, and copper sulfate, phosphates such as sodium phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, lithium hydrogen phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, aluminum phosphate, and zinc phosphate, hydroxides such as lithium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide, and zinc hydroxide, and oxides such as silicon, zinc, magnesium, aluminum, calcium, lithium, copper, iron, boron, and zirconium. Among these, lithium sulfate and lithium hydroxide are particularly advantageous in improving moisture resistance. The moisture resistance improving agents represented by the above-mentioned substances may be used alone or in combination of 2 or more.
The amount of the moisture resistance improver to be used is generally preferably about 0.5 to 50 parts by mass, more preferably 1 to 20 parts by mass, particularly preferably 2 to 15 parts by mass, based on 100 parts by mass of the solid content of the water glass. In order to favorably enjoy the effect of adding the moisture resistance improver, the amount of the moisture resistance improver is preferably 0.5 parts by mass or more, and on the other hand, if the amount is too large, the binding of aggregate by water glass is inhibited, and there is a concern that the strength of the finally obtained mold may be reduced, and therefore, 50 parts by mass or less is desirable.
In addition, it is also effective to contain, as another additive, a coupling agent for reinforcing the bond between the refractory aggregate and the water glass, and for example, a silane coupling agent, a zirconium coupling agent, a titanium coupling agent, or the like can be used. Further, as the release agent, paraffin wax, light oil, engine 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, and the like can be used. These other additives are contained in an amount of usually 5% by mass or less, preferably 3% by mass or less, based on the solid content of the water glass.
In addition, when the mold composition of the present invention is produced, it can be produced, for example, by the following method: 1) a mold composition (hereinafter, referred to as "1-layer structured CS (mold composition)") in which a coating layer containing a binder containing water glass as an essential component and a predetermined neutralizing agent is composed of Coated Sand (CS) formed on the surface of a refractory aggregate (sand). ) And 2) a mold composition (hereinafter, referred to as "2-layer structured CS (mold composition)" comprising a solid first coat layer containing a predetermined neutralizing agent formed on the surface of a refractory aggregate (sand) and a Coated Sand (CS) having a second coat layer containing a binder containing water glass as an essential component formed on the first coat layer. ).
(1) Production of "1-layer CS (mold composition)"
a) In "CS (mold composition) having a 1-layer structure", when a mold composition having no room-temperature fluidity and being in a wet state is produced, the following method is generally employed: water glass as a binder and a predetermined neutralizing agent are kneaded or mixed together with an additive used as needed at normal temperature to form a coating layer of a water glass composition having a high moisture content (a coating layer containing a binder containing water glass as an essential component and a predetermined neutralizing agent) on the surface of the refractory aggregate, thereby uniformly mixing the materials.
b) On the other hand, when producing a dry CS (mold composition) having a 1-layer structure with room-temperature fluidity, the following method is generally employed: a coating layer of a water glass composition (a coating layer containing a binder containing water glass as an essential component and a predetermined neutralizing agent) is formed on the surface of a refractory aggregate by kneading or mixing water glass as a binder and a predetermined neutralizing agent together with an additive used as needed to uniformly mix them, covering the surface of the refractory aggregate with a water glass composition containing a neutralizing agent or the like, and evaporating water in the water glass composition. In such a method, since it is necessary to quickly evaporate the water in the coating layer before the water glass is cured or hardened, it is desirable that the water glass in the form of an aqueous solution is charged (mixed) into the refractory aggregate, and the water content is dispersed to form a dry powder mold material composition, usually within 5 minutes, more preferably within 3 minutes. This is because, when the time for the above-mentioned evaporation becomes longer, the mixing (kneading) cycle becomes longer, the productivity of the mold material composition is lowered, and water glass and CO in the air are generated2The contact time becomes long and there is a high possibility that problems such as deactivation occur.
c) In the production process of the above-described 1-layer CS (mold composition) in a dry state, as one of effective means for rapidly evaporating water in the water glass, the following method is suitably employed: the refractory aggregate is heated in advance, and water glass in the form of an aqueous solution, a predetermined neutralizing agent, and the like are kneaded or mixed and mixed. By kneading or mixing water glass with the preheated refractory aggregate, the water in the water glass can be evaporated extremely rapidly by the heat of the refractory aggregate, and therefore, the water content of the obtained mold material composition can be effectively reduced, and a dry powder having room-temperature fluidity can be advantageously obtained. The preheating temperature of the refractory aggregate can be suitably selected depending on the water content of the water glass, the amount of the water glass to be blended, and the like, and a temperature of about 100 to 160 ℃ is usually employed, and a temperature of about 100 to 140 ℃ is preferred. If the preheating temperature is too low, the water cannot be effectively evaporated, and it takes time to dry, so that it is preferable to use a temperature of 100 ℃ or higher, and if the preheating temperature is too high, the water glass component is solidified or hardened during cooling of the obtained molding material composition, and composite granulation proceeds, so that problems occur in the function as the molding material composition, particularly in the physical properties such as strength of the finally obtained mold.
d) In the above-described method for producing a mold material composition, the neutralizer contained in the coating layer together with the water glass, and other additives used as needed, for example, a surfactant, a lubricant, and the like, may be added to the refractory aggregate in a state of being previously mixed in the water glass and kneaded, or may be added separately from the water glass and kneaded at the time of kneading, or may be charged and kneaded with a time difference between the charging of the water glass and the charging of the water glass at the time of kneading. Therefore, the coating layer in the dry mold composition of the present invention is formed in a state in which, for example, water glass and a neutralizing agent are mixed, or in a state in which the concentration of the solid content (nonvolatile content) of water glass gradually decreases or increases and the concentration of the neutralizing agent or the like gradually increases or decreases from the surface of the refractory aggregate to the outside. Furthermore, the water glass as the binder may be diluted with water in order to adjust the viscosity thereof. In addition, water glass and water may be added separately during kneading or mixing.
(2) Production of "CS (mold composition) of 2-layer Structure
a-1) in producing "a 2-layer CS (mold composition)", a solid first coating layer containing a predetermined neutralizing agent is first formed on the surface of a refractory aggregate. The first coating layer may be composed of only a predetermined neutralizing agent, or may be composed of a predetermined neutralizing agent and an organic compound from the viewpoint of dispersion of the neutralizing agent and isolation from the water glass. When the first coating layer located directly above the refractory aggregate contains an organic compound, when a molten metal is poured into a mold using a mold material composition having such a configuration, the organic compound contained in the first coating layer is thermally decomposed and gasified, and the generated gas favorably destroys the cured product or hardened product of the water glass at the joint portion between the refractory aggregate particles, resulting in excellent disintegration properties of the mold. Further, when the organic compound contained in the first coat layer is thermally decomposed and gasified, the hardened or cured product of the water glass present on the refractory aggregate particles is broken from the inside (from the refractory aggregate side) by the internal pressure of the gas, and therefore, for example, in the grinding step when the refractory aggregate (sand) recovered from the cast after casting is recycled, the water glass hardened or cured is easily peeled from the surface of the cast sand particles, and the recycling of the sand is easy. Further has the following advantages: in casting using a mold, gas is generated by thermal decomposition of the organic compound contained in the first coating layer, so that a gas layer that suppresses intrusion of molten metal into the refractory aggregate particles constituting the mold is advantageously formed between the mold surface and the cast product, and the cast surface of the finally obtained cast product is good. When a neutralizer that reacts with water glass to accelerate curing, such as phosphate, is used, it is preferable that a first coating layer containing such a neutralizer and an organic compound is formed, and excessive curing due to reaction of the neutralizer with water glass can be prevented with respect to a CS (mold composition) having a 2-layer structure in which the neutralizer and water glass are present in different layers.
a-2) in the present invention, the solid first coating layer formed on the surface of the refractory aggregate has a film thickness of 0.1 to 6 μm, preferably 0.2 to 5 μm, more preferably 0.3 to 3 μm, and still more preferably 0.5 to 2 μm. If the film thickness is less than 0.1 μm, the coating layer is not easily formed and vaporization is not easily generated inside the second coating layer formed of the binder composition containing water glass, while if it is more than 6 μm, odor is generated from the organic compound. As a method for measuring the film thickness of the first coat layer, the following methods can be mentioned: the refractory aggregate particles on which the first coating layer is formed are embedded in an epoxy resin or the like, the cross section of the foundry sand particles cut by a cutting device such as an ion cutter is observed by an optical device such as an optical microscope or an electron microscope, 10 points are randomly selected for the cross-sectional particles, and the film thickness of the coating layer is measured. In addition, when the refractory aggregate particles are spherical with respect to the film thickness, the film thickness can be calculated from the average particle diameter of the refractory aggregate particles and the addition amounts of the refractory aggregate particles and the organic compound.
a-3) the organic compound used in the present invention is not particularly limited as long as it can form a solid coating layer on the surface of the refractory aggregate particles, and is preferably at least one selected from the group consisting of a crosslinked curable resin and a cured product thereof, a thermoplastic resin, and a carbohydrate. Among these organic compounds, a cross-linked curable resin and a cured product thereof can be advantageously used from the viewpoint of maintaining the strength of the Coated Sand (CS).
a-4) the crosslinking curable resin means a resin which exhibits crosslinking curability in the presence or absence of a curing agent such as hexamethylenetetramine, an organic ester, an organic acid, carbon dioxide, a peroxide, a metal ion, or an amine, or a curing catalyst, and is formed into a mold by bonding refractory aggregate particles to each other with heating or non-heating (room temperature). Specific examples of such a crosslinking curable resin include a phenol resin, a phenol urethane resin, an epoxy resin, a melamine resin, an unsaturated polyester resin, a polyfunctional acrylamide resin (see japanese unexamined patent publication No. 7-106421), an unsaturated alkoxide resin, an unsaturated fatty acid-modified alkoxide resin, a diallyl phthalate resin, and a resin obtained by combining these resins as needed. Among these, particularly preferred are novolak-type and resol-type phenolic resins and phenolic urethane resins used in combination with a polyisocyanate compound, from the viewpoint of more favorably enjoying the effects of the present invention.
a-5) curing the curable resin to increase the molecular weight of the polymer compound by curing the curable resin having a low molecular weight. The coating composition is prepared by applying a low-molecular-weight material having a low melt viscosity to the surface of foundry sand particles, and then heating the coating composition to cure the coating composition by adding a curing agent thereto, whereby alkali deterioration can be prevented, a high-molecular-weight coating layer having good surface stability can be formed, and both coverage and surface stability can be achieved. Further, the cured product of the crosslinked curable resin has the following advantages as compared with the uncured crosslinked curable resin: 1) the softening of the coating layer by heat can be suppressed to improve the mold strength, 2) the heat required for hardening is consumed in advance, and therefore the heat is effectively used for thermal decomposition, and the thermal decomposition becomes faster, and therefore the mold disintegratability is further improved, and 3) the gas accompanying hardening is released in advance, and therefore the amount of gas generated during casting can be suppressed.
a-6) and more specifically, examples of the thermoplastic resin include resins formed from polyvinyl alcohol, polyvinyl acetate, polystyrene, styrene acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, ethylene vinyl acetate copolymer, polymethyl methacrylate, methacrylic acid-styrene copolymer, cellulose acetate, polycarbonate, polyvinyl chloride, and the like. Among these, polyvinyl alcohol, polyvinyl acetate, polystyrene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, cellulose acetate, and polycarbonate are particularly preferable from the viewpoint of solvent solubility (film-forming property).
a-7), specific examples of the carbohydrate include carbohydrates containing glucose, fructose, galactose, lactose, sucrose, maltose, trehalose, starch, glycogen, and cellulose. Among these, trehalose, starch, and glycogen are particularly preferable from the viewpoint of film formability. Examples of the other organic compounds include acrylamide, N-methylolacrylamide, bisacrylamide dimethyl ether, methylenebisacrylamide, ethylenebisacrylamide, and ethyleneglycol bisacrylamide.
a-8) in the present invention, the organic compound contained in the first coating layer on the surface of the refractory aggregate particles is preferably a polymer compound (polymer, multimer) from the viewpoint of the covering property with respect to the refractory aggregate particles. Specifically, a high molecular compound (polymer, multimer) having a weight average molecular weight of 300 or more, preferably 300 to 100000000, more preferably 500 to 50000000, and further preferably 800 to 20000000 can be favorably used. Even if the organic compound is not included in the category of the polymer compound (polymer, multimer), the molecular weight is preferably 300 or more from the viewpoint of surface stability of the solid coating layer, and is preferably 100000000 or less from the viewpoint of covering property with the refractory aggregate particles.
a-9) in addition, in the present invention, an organic compound which is hardly soluble or insoluble with water is favorably used, and particularly, an organic compound which is insoluble with water is suitable as an organic compound contained in the solid-state first coating layer. This is because: when an organic compound that is easily water-soluble is used, the organic compound is eluted into the water contained in the second coating layer made of a liquid binder composition containing water glass, which covers the surface of the first coating layer, and the first coating layer does not remain in a solid state. Specifically, in the present invention, an organic compound having a solubility of 1 mass% or less, preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and still more preferably 0.1 mass% or less with respect to 100g of water at 25 ℃ is used as the organic compound contained in the solid coating layer. The solubility is the amount of the organic compound dissolved in the solvent (water) when 10g of the organic compound is put into 100g of water at 25 ℃, stirred for 1 hour, and left to stand for 1 hour. The water-insoluble organic compound means an organic compound that is insoluble in water.
b) In the present invention, when a solid layer made of only a predetermined neutralizing agent is formed on the surface of the refractory aggregate as the first coat layer, various conventionally known methods are appropriately selected and used according to the form, characteristics, and the like of the neutralizing agent. For example, when the neutralizing agent is a neutralizing agent having a property of melting without decomposing at a temperature lower than the temperature at which the agent is heated at the time of casting (hereinafter, referred to as the temperature in this paragraph), the refractory aggregate and the neutralizing agent are mixed in a state of being heated to the temperature, and a layer of the melted neutralizing agent is formed on the surface of the refractory aggregate, followed by cooling, whereby a solid first coating layer made of the neutralizing agent can be formed on the surface of the refractory aggregate.
c-1) on the other hand, when a solid layer containing a predetermined neutralizing agent and an organic compound is formed as the first coat layer on the surface of the refractory aggregate, a method suitable for the form, characteristics, and the like of the neutralizing agent and the organic compound is also appropriately selected and adopted from various conventionally known methods. Specifically, a dry-hot coating method, a cold coating method, and the like can be exemplified, and the method is not particularly limited as long as a solid coating layer can be formed.
c-2) the dry heat coating method is as follows: the method for producing a solid coating layer on the surface of a refractory aggregate includes adding a solid organic compound and a predetermined neutralizing agent to a refractory aggregate heated to 130 to 180 ℃, mixing the mixture, melting the solid organic compound by the heat of the refractory aggregate, covering the surface of the refractory aggregate with the melted organic compound, and then cooling the mixture while maintaining the mixed state, thereby forming a solid coating layer including the organic compound and the predetermined neutralizing agent on the surface of the refractory aggregate. In addition, the cold coating method is a method of: the organic compound is added to the refractory aggregate as it is or dissolved in a solvent such as methanol to form a liquid, and the liquid is mixed with a predetermined neutralizing agent, and the solvent is volatilized to form a solid coating layer containing the organic compound and the predetermined neutralizing agent on the surface of the refractory aggregate.
c-3) when a crosslinkable curable resin is used as the organic compound, for example, the molecular weight of the crosslinkable curable resin contained in the first coating layer can be increased by forming a solid first coating layer by the above-mentioned coating method and then curing the crosslinkable curable resin by further heating and/or by adding a curing agent or a curing catalyst. When the crosslinking curable resin is cured by heating, there are, for example, a method of placing the resin in a thermostatic bath at 120 to 300 ℃ and performing reaction curing for about 5 to 60 minutes, or a method of heating foundry sand to 150 to 300 ℃ and kneading the sand in a kneader heated to 120 to 300 ℃ for about 5 to 60 minutes to perform reaction curing. The casting composition in which the cross-linked curable resin contained in the coating layer is cured can be integrated into a block or can be made into composite particles by providing strong connecting sites (rock) between the refractory aggregate particles (sand grains), and therefore, in order to improve the surface state of the refractory aggregate covered with the first coating layer, it is preferable to perform reaction curing by using a fast kneader (speed muller) having a kneading action and a high rotational speed. Further, since the kneading for a long time causes exfoliation and may generate fine powder, it is preferable to carry out the reaction at a high temperature for a short time. On the other hand, when the cross-linking curable resin is cured by using a curing agent or a curing catalyst, for example, hexamethylenetetramine, an organic ester, an organic acid, carbon dioxide, a peroxide, a metal ion, an amine, or the like can be used as the curing agent or the curing catalyst. In the case where the crosslinkable hardening resin is a phenol urethane resin, the resin can be hardened by mixing a phenol resin and a polyisocyanate resin. Even when a curing agent is used to cure a crosslinked curable resin, it is preferable to react and cure the resin while kneading the resin with a kneader.
d) In the above method, when a "2-layer structure CS (mold composition)" having no room temperature fluidity is produced in a wet state using any of the refractory aggregate formed on the surface on which the solid first coating layer composed only of the predetermined neutralizing agent is formed or the refractory aggregate formed on the surface on which the solid first coating layer composed of the predetermined neutralizing agent and the organic compound is formed, the casting composition is produced, for example, by the following steps. That is, a mold material composition in which a mixture of a refractory aggregate provided with a solid first coating layer containing a predetermined neutralizing agent and a liquid binder composition containing water glass, in other words, a mold material composition in which a second coating layer formed of a binder composition containing water glass is formed so as to cover the first coating layer on the surface of the refractory aggregate is obtained by kneading or mixing water glass as a binder with an additive as needed to the refractory aggregate provided with the first coating layer and uniformly mixing the mixture. The various conditions for mixing are appropriately determined depending on the kind and water content of the aqueous inorganic binder, and the temperature for mixing is usually about room temperature to 40 ℃. In the production of the wet mold composition of the present invention, the moisture content is adjusted so that the obtained mold composition is in a suitable wet state. Specifically, the amount of the solid content of the water glass is adjusted to be more than 55 mass%, preferably 70 to 900 mass%, and more preferably 95 to 500 mass%. The wet-state mold composition of the present invention, in which the moisture content is adjusted in this manner, prevents the wet-state mold composition from drying and clogging by blowing gas during filling into a mold during molding of the mold, and can maintain the wettability of the mold composition, and a mold molded using such a mold composition also has excellent characteristics. The water content of the mold material composition can be measured by the karl fischer method based on the change in weight when heated in a dryer or the like.
e) On the other hand, when "a mold composition (2-layer structure)" having room-temperature fluidity and being in a dry state is produced using a refractory aggregate on which a solid first coating layer is formed, it can be produced by the same method as that described in detail in section "b)" in section "production of" a mold composition (1) "a CS (1-layer structure)". Specifically, the following method may be employed: phase (C)The refractory aggregate on which the first coating layer is formed is uniformly mixed by kneading or mixing water glass as a binder together with additives used as needed, and the surface of the first coating layer of the refractory aggregate is covered with a water glass composition, and the water of such a water glass composition is evaporated, thereby forming a covering layer of the water glass composition (a second coating layer containing a binder containing water glass as an essential component) as the outermost layer of the surface of the refractory aggregate. In the above method, since the evaporation of the water in the second coating layer must be performed quickly before the water glass is cured or hardened, it is desirable that the water glass in the form of an aqueous solution is charged (mixed) into the refractory aggregate, and then the contained water is scattered within 5 minutes, and more preferably within 3 minutes, to prepare a dry powder mold material composition. This is because: when the time for the above-mentioned evapotranspiration is long, the mixing (kneading) cycle becomes long, the productivity of the mold material composition is lowered, and water glass and CO in the air are generated2The contact time becomes long, and there is a high possibility of problems such as deactivation.
f) In the above "production of 2-layer CS (mold composition)", (2) "various additives such as a surfactant used as needed may be contained in the first coat layer or the second coat layer depending on the purpose of use of each additive, or may be contained in both the first coat layer and the second coat layer depending on the type of additive.
Further, as a method for producing a mold by using the mold material composition in a wet state of the present invention, for example, there is a method comprising: first, the mold material composition is filled into a molding cavity of a mold for providing a target mold, the mold is heated to a temperature of 80 to 300 ℃, preferably 100 to 200 ℃ and held in the mold until the filled mold material composition is dried. By such heat holding in the mold, curing or hardening of the filled mold material composition in a wet state proceeds, and a target mold can be obtained.
That is, the aggregate (bonded material) of the refractory aggregate in the shape of an integral mold is formed by filling and holding the wet mold material composition in the cavity of the mold heated to the above temperature, whereby the refractory aggregate particles constituting the mold material composition are bonded to each other and linked by the water glass contained in the binder composition existing around. In this case, as an additive for promoting the hardening of the water glass, a predetermined hardening agent may be introduced into the chamber in a liquid state or a gas state. In general, water glass is solidified by evaporation and drying of water without adding any additive, and is hardened by adding a hardening agent. In the present invention, the mold formed of an aggregate (connected body) of the coated sand includes any of those obtained by curing (solidified material) alone and those obtained by curing (solidified material) with a curing agent.
In addition, when the casting mold material composition in a wet state is heated in the cavity of the molding die, it is advantageously preferable that: after a mold is prepared which is heated (preheated) to a predetermined temperature in advance and is kept at the temperature, a cavity of the mold is filled with a mold material composition, and the mold material composition is heated. By heating the mold in advance in this manner, drying of the mold material composition can be accelerated, and molding time can be shortened. The holding temperature for the preheating is 80 to 300 ℃, preferably 100 to 200 ℃, and more preferably 120 to 180 ℃. The holding temperature is preferably 80 ℃ or higher from the viewpoint of accelerating drying, shortening the molding time, and improving the wet strength by the additive, and is preferably 300 ℃ or lower from the viewpoint of preventing the problem that moisture evaporates before the bond between the refractory aggregate particles is sufficiently formed and the mold strength is not expressed. By heating the molding die at a temperature within such a temperature range, the wet strength of the finally obtained mold can be improved, and the drying of the mold material composition can be favorably performed.
Further, in order to promote the evaporation of water during the holding of the mold material composition in the mold, a method of blowing hot air or superheated steam into the mold to ventilate the filling phase (mold material composition) in the mold may be suitably employed. By such ventilation with hot air or superheated water vapor, the filler phase containing the mold material composition can be dried rapidly to the inside, so that the curing or hardening of the filler phase can be promoted more favorably, the curing (hardening) rate can be increased favorably, the properties such as the breaking strength of the resulting mold can also be improved favorably, and the molding time of the mold can also be facilitated favorably to be shortened. In order to more favorably accelerate the solidification or hardening of the mold material composition while holding the mold material composition in the mold, a method of blowing a carrier gas containing at least 1 gas of carbon dioxide, argon, nitrogen, and helium into the mold and ventilating the filling phase may be suitably employed. At this time, carbon dioxide acts as a curing agent, and argon, nitrogen, and helium act as curing accelerators. By allowing such a carrier gas to act on the water-soluble inorganic binder, curing or hardening of the mold material composition can be further promoted. In this case, a method of performing the ventilation of the hot air or the superheated water vapor and the ventilation of the carrier gas, or performing the ventilation of the carrier gas after the ventilation of the hot air or the superheated water vapor, or performing the ventilation of the hot air or the superheated water vapor after the ventilation of the carrier gas, or the like may be employed. In short, the ventilation with hot air or the like and/or carrier gas may be carried out at any timing as long as the mold material composition in a wet state is filled into the cavity of the mold and then held in the mold.
In addition, in the molding of a mold using the wet mold composition of the present invention, in addition to the above-described method of heating in the mold, it is possible to adopt: a method of introducing the aforementioned hardening agent into a mold to cure or harden the mold material composition, and a method of reducing the pressure in a mold filled with the mold material composition to cure or harden the mold material composition.
Here, the introduction of the hardening agent into the mold is carried out by a reaction between another binder (for example, a water-soluble inorganic binder) used in combination with the water glass and the hardening agent. As a method for introducing the curing agent, any of the following methods may be employed: a method of adding a curing agent to a mold material composition before filling a mold, and filling the mold material composition to which the curing agent is added into the mold; and a method of introducing a hardening agent into a mold material composition filled in a mold by introducing the hardening agent into the mold in the form of a carrier gas. In addition, while the curing agent is cured during the holding in the mold, it is also effective to blow hot air or superheated steam into the mold in order to promote the evaporation of water. Further, in order to more favorably accelerate the curing or hardening of the mold material composition, a carrier gas containing at least 1 gas of carbon dioxide, argon, nitrogen, and helium may be blown into the mold. When the curing agent is added, the mold is not necessarily heated, but the mold is preferably heated in order to more favorably accelerate curing or curing.
Examples of the hardening agent used in the present invention include carbon dioxide (carbonated water), sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, carboxylic acids, organic acids such as p-toluenesulfonic acid, esters such as methyl formate, ethyl formate, propyl formate, γ -butyrolactone, β -propionate, ethylene glycol diacetate, diethylene glycol diacetate, glycerol triacetate, and propylene carbonate, and monohydric alcohols such as methanol, ethanol, butanol, hexanol, and octanol. These hardeners may be used alone or in combination of 2 or more.
In the method of reducing the pressure in the mold, the precoated sand filled in the cavity of the mold is dried and cured by the reduced pressure. Examples of the method of reducing the pressure include a method of reducing the pressure in the mold by a known suction means. When the pressure of the mold is reduced, the mold does not necessarily need to be heated, but the mold is preferably heated in order to more favorably accelerate curing or hardening.
On the other hand, when the mold material composition in a dry state is used to mold a target mold, for example, the following two methods can be employed. Namely, the method 1 is the following water addition method: the dry casting material composition is wet-kneaded with water at a casting site, and the wet casting material composition is filled into a molding cavity of a mold for providing a target casting mold, and the mold is heated to a temperature of 80 to 300 ℃ and held in the mold until the filled casting material composition is dried. The method 2 is a method of filling a dry mold material composition into a molding cavity of a mold for providing a target mold, and then blowing water vapor into the molding cavity to ventilate the filling phase containing the mold material composition, and the method is characterized in that the dry mold material composition is supplied with water by the ventilation of the water vapor to be in a wet state (wet state), and then the mold material composition is heated to 80 to 200 ℃ until the wet mold material composition is dried.
In such molding, it is preferable that a mold to be filled with the molding material composition having fluidity at room temperature and in a dry state, such as a metal mold or a wooden mold, is heated in advance, and thereby kneading with water and drying of the molding material composition in a wet state by steam can be advantageously performed. The preheating temperature is preferably 80 to 300 ℃, preferably 90 to 250 ℃, and more preferably about 100 to 200 ℃ in the method 1, and preferably 80 to 200 ℃, preferably 90 to 150 ℃, and more preferably about 100 to 140 ℃ in the method 2. If the holding temperature is too high, it is difficult for steam to pass through to the surface of the mold, while if the temperature is too low, it takes time to dry the molded mold.
In the above method 1, when the mold material composition in a dry state is kneaded (mixed) with water, after the mold material composition in a dry state is carried to a molding site as a manufacturing site of a mold, at the molding site, water is added to wet the composition, and the obtained wet mold material composition is filled into a mold, the molding of the target mold is carried out in the same manner as in the molding of the aforementioned mold material composition in a wet state, wherein the step of adding water to the dry mold material composition to wet the composition is sufficient to wet the mold material composition only by charging the dry mold material composition and a predetermined amount of water into an appropriate mixer and mixing them, therefore, the operation can be performed by a very simple operation, and the operation can be performed very simply and easily even in a modeling site having a poor operation environment. The mold composition may be preheated to 40 to 100 ℃ before adding water. When water is added, 1 or more selected from other additives, hardening accelerators, and water-soluble inorganic binders for readjustment of mold strength may be added together. When the other additives are liquid, those containing water in the liquid can be used.
In the method 2, when steam is blown into the mold material composition (filling phase) filled in the molding cavity of the mold, the temperature of the steam is usually about 80 to 150 ℃, and preferably about 95 to 120 ℃. When high-temperature steam is used, a large amount of energy is required for its production, and therefore a steam temperature in the vicinity of 100 ℃ is particularly advantageously used. The pressure of the steam to be ventilated is preferably about 0.01 to 0.3MPa, more preferably about 0.02 to 0.1MPa in terms of gauge pressure. Further, as the aeration time, aeration time of about 2 seconds to about 60 seconds is generally employed. The reason is that: if the aeration time of the water vapor is too short, it is difficult to sufficiently wet the surface of the mold composition in a dry state, and if the aeration time is too long, there is a possibility that problems such as dissolution and outflow of water glass constituting a coating layer (a coating layer on the surface of the refractory aggregate) on the surface of the mold composition occur.
In the above-mentioned methods 1 and 2, in order to actively dry the filling phase containing the wet mold material composition, a method of blowing hot air or superheated steam into the mold to ventilate the filling phase may be suitably employed. By such ventilation with hot air or superheated water vapor (hot air or the like), the filling phase of the mold material composition can be dried rapidly to the inside, whereby the solidification or hardening of the filling phase can be further promoted more favorably, the hardening speed can be increased favorably, the properties such as the breaking strength of the resulting mold can also be improved favorably, and further, the molding time of the mold can be facilitated favorably. In the method 1, for example, before the aeration with hot air or the like, the method 2 may be carried out by aerating the curing agent in a gaseous or mist state between the aeration with steam and the aeration with hot air or the like, for the purpose of more favorably accelerating the curing or curing of the filler phase, and the curing or curing can be further accelerated by neutralizing the water glass (and other water-soluble inorganic binder) with the curing agent. The aeration of the curing agent may be performed simultaneously with the aeration with hot air or the like in the above-described method 1, or may be performed simultaneously with the aeration with water vapor or the aeration with hot air or the like in the above-described method 2. As another method for positively drying the filling phase, the pressure inside the mold may be reduced. The molding material composition filled in the cavity of the molding die is dried and solidified by the decompression. Examples of the method of reducing the pressure include a method of reducing the pressure in the mold by a known suction means. When the pressure in the mold is reduced, hot air or superheated steam may be blown into the mold to promote the evaporation of water.
The mold of the present invention obtained by the above-described production method using the mold material composition in a wet state or a dry state, and the mold obtained by another production method can advantageously enjoy the following excellent effects. That is, when the mold is used for casting, the mold is heated by molten metal (usually heated to a temperature exceeding 300 ℃), and the decomposition product generated by the neutralizing agent and the alkali component of the water glass are neutralized by the heating, whereby the water glass becomes physically fragile, and the mold after casting has good disintegratability. In addition, in the refractory aggregate (sand) recovered after casting, since the whole amount of the alkali component of the water glass or a part thereof is neutralized and deactivated, a firing treatment at a high temperature for removing the alkali component, a neutralization treatment using an acid, or the like is not necessary when the recovered sand is regenerated.
Examples
The present invention will be described more specifically with reference to examples of the present invention, but it should be understood that the present invention is not to be construed as being limited by the description of such examples. In the following examples and comparative examples, "%" and "part(s)" are expressed on a mass basis unless otherwise specified. Further, a disintegration test of a mold obtained using each of the mold material compositions (precoated sand: CS) of examples and comparative examples, an evaluation of a recovered refractory aggregate (recovered sand), a calculation of an alkali reduction rate, a measurement of pH, and a grinding and peeling test were performed as follows.
Disintegration test of the casting mold
First, as shown in FIG. 1, a circular blank core 10 (diameter: 5cm, height: 5cm) having a core base 8, which is manufactured using each CS, is bonded and fixed to a core base fixing part 4 in a half-split hollow master mold 6 (cavity diameter: 6cm, height: 6cm) which is manufactured in advance from normal temperature self-hardening sand and has a melt inlet 2 at the upper part and a core base fixing part 4 (this part is a discharge port for discharging a waste core from a casting) at the lower part, and then the half-split hollow master molds 6 are bonded and fixed to each other to manufacture a sand mold 12 for a casting test. Next, after an aluminum alloy melt (temperature: 710. + -.5 ℃ C.) was injected from the melt inlet 2 of the sand mold 12 for casting test and solidified, the master mold 6 was broken, and a casting 16 having a circular waste core discharge port 14 (diameter: 1.6cm) as shown in FIG. 2 was taken out. Then, when the temperature is changed to a predetermined temperature, the obtained cast product 16 is subjected to a press of: 0.2MPa, 1 time and 3 seconds of impact (blow) was applied by an air hammer, and the mixture was discharged from the discharge port 14. The number of hits until the core was subjected to 100% sand discharge was counted and evaluated according to the following criteria.
O: the sand discharge rate is 100% through 1-5 times of striking.
And (delta): the sand discharge rate is 100% through 6-10 times of striking.
X: even through 10 times of striking, the sand discharge rate cannot reach 100 percent.
Evaluation of recycled refractory aggregates (recycled sand) -
In the above disintegration test, 100g of the recovered refractory aggregate (recovered sand) was heated in a thermostatic bath at 500 ℃ for 1 hour. The state of the heated recovered sand (exposed sand) was visually observed, and evaluated according to the following criteria.
O: no lumps were observed in the exposed sand.
And (delta): tiny lumps were observed in the hot sand.
X: the exposed sand became lumpy and re-fusion was clearly observed.
Calculation of the alkali reduction Rate
The above-mentioned hot sand was put into water, and the amount of alkali eluted into the water (the amount of alkali remaining in the hot sand) was measured. The alkali reduction rate (%) obtained by subtracting the measured alkali residual amount was calculated assuming that the amount of alkali in the mold material composition was 100%.
Determination of the pH-
50g of the above-mentioned heat-exposed sand was put in distilled water and stirred for 30 minutes, followed by filtration through a filter paper and measurement of the pH of the filtrate.
Polish strip test
100g of the refractory aggregate (reclaimed sand) taken out in the disintegration test and constituting the round hollow-free core was put into a ball mill and ground for 1 hour. Thereafter, the resultant was sieved at 200 mesh for 1 minute to separate a refractory aggregate and peeled fine powder, and the amount of the obtained fine powder was measured to evaluate the easiness of peeling in the recovered sand by 3 grades according to the following criteria.
O: the amount of the fine powder is 0.3% by mass or more based on the mass of the refractory aggregate.
And (delta): the amount of the fine powder is 0.1 mass% or more and less than 0.3 mass% based on the mass of the refractory aggregate.
X: the amount of the fine powder is less than 0.1% by mass based on the mass of the refractory aggregate.
The raw materials used for producing each Coated Sand (CS) were as follows.
Refractory aggregate: alumina-based spherical aggregate
(product name: ESPEARL #60, manufactured by Shanchuan Industrial Co., Ltd.)
Refractory aggregate: flattery silica sand (Flattery No. 6)
Water glass: no. 1 sodium silicate
(product name, manufactured by Fuji chemical Co., Ltd., SiO)2/Na2Molar ratio of O: 2.1, solid content: 45% by mass)
Water glass: no. 2 sodium silicate
(product name, manufactured by Fuji chemical Co., Ltd., SiO)2/Na2Molar ratio of O: 2.5, solid content: 41% by mass)
Water glass: no. 3 sodium silicate
(product name, manufactured by Fuji chemical Co., Ltd., SiO)2/Na2Molar ratio of O: 3.0, solid content: 35% by mass)
Neutralizing agent: chlorinated paraffin
(product names: EMPARA 70, Ajinomoto Fine-Techno Co., manufactured by Inc.)
Neutralizing agent: chlorinated paraffin
(product name: Toyoparax 40S, manufactured by Tosoh corporation)
Neutralizing agent: vinyl chloride
(product name:
Figure BDA0003282137280000361
paste, manufactured by Tosoh corporation)
Neutralizing agent: tetrabromobisphenol A
(product name: FLAMECUT 120G, manufactured by Tosoh corporation)
Neutralizing agent: brominated aliphatic and aromatic compounds
(product name: Pyroguard SR130, product of the first Industrial pharmaceutical Co., Ltd.)
Neutralizing agent: brominated aliphatic and aromatic compounds
(product name: SR720N, first Industrial pharmaceutical Co., Ltd.)
Neutralizing agent: polytetrafluoroethylene
(product name: Fluon L169J, manufactured by AGC K.K.)
Neutralizing agent: phosphoric acid esters
[ triphenyl phosphate (TPP), manufactured by Daba chemical industries Co., Ltd ]
Production example 1 of wet CS
Using water glass (sodium silicate No. 2), an aqueous water glass solution having a solid content (concentration) of 41% was prepared. A foundry material composition (wet CS: CS1a) in a wet state, in which a coating layer containing water glass and a neutralizing agent (chlorinated paraffin) was provided on the surface of a refractory aggregate, was obtained by charging the refractory aggregate (ESPEARL #60) into a Kawakawa universal mixer (5DM-r type, manufactured by DALTON CORPORATION) at room temperature, adding the above water glass aqueous solution at a ratio of 1.0 part to 100 parts of the refractory aggregate, adding chlorinated paraffin (EMPARA 70) as a neutralizing agent at a ratio of 0.10 part to 100 parts of the refractory aggregate, kneading for 3 minutes, stirring and mixing until uniform.
Production examples 2 to 4 of wet CS
Except that the amounts of the neutralizer (EMPARA 70) used in production example 1 of wet CS were 0.20 parts, 0.30 parts and 0.05 parts, respectively, casting composition (CS2a to CS4a) in a wet state were obtained by the same procedure as in production example 1.
Production example 5 of wet CS
A wet casting composition (CS5a) was obtained in the same manner as in production example 1, except that the amount of the aqueous water glass solution used was 2.0 parts and the amount of the neutralizing agent (EMPARA 70) used was 0.20 parts in production example 1 of wet CS.
Production example 6 of wet CS
A wet casting composition (CS6a) was obtained in the same manner as in production example 1, except that in production example 1, a water glass aqueous solution having a solid content (concentration) of 45% obtained using water glass (sodium silicate No. 1) was used as the water glass aqueous solution, and the amount of the neutralizer (EMPARA 70) used was 0.14 part.
Production example 7 of wet CS
A wet molding composition (CS7a) was obtained in the same manner as in production example 1, except that an aqueous sodium silicate solution having a solid content (concentration) of 35% obtained from sodium silicate (sodium silicate No. 3) was used as the aqueous sodium silicate solution, and the amount of the neutralizer (chlorinated paraffin: EMPARA 70) was 0.07 part.
Production example 8 of wet CS
A casting composition (CS8a) in a wet state was obtained by the same procedure as in production example 1, except that flatery 6 was used as a refractory aggregate, the amount of the water glass aqueous solution was 3.0 parts, and the amount of the neutralizer (EMPARA 70) was 0.30 parts.
Production example 9 of wet CS
A wet casting mold composition (CS9a) was obtained in the same manner as in production example 1, except that 0.18 parts of chlorinated paraffin (Toyoparax 40S) was used as a neutralizer in production example 1 of wet CS.
Production example 10 of wet CS
In production example 1 of wet CS, vinyl chloride (C) (I)
Figure BDA0003282137280000381
paste)0.13 parts, and a wet mold composition (CS10a) was obtained by the same procedure as in production example 1.
Production example 11 of wet CS
A wet molding composition (CS11a) was obtained in the same manner as in production example 1, except that 0.27 part of tetrabromobisphenol A (FLAMECUT 120G) was used as the neutralizer in production example 1 of wet CS.
Production example 12 of wet CS
A wet casting mold composition (CS12a) was obtained in the same manner as in production example 1, except that 0.25 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in production example 1 of wet CS.
Production example 13 of wet CS
A wet casting mold composition (CS13a) was obtained in the same manner as in production example 1, except that 0.46 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in production example 1 of wet CS.
Preparation example 14 of wet CS
A wet casting mold composition (CS14a) was obtained in the same manner as in production example 1, except that 0.24 parts of brominated aliphatic/aromatic compound (SR720N) was used as the neutralizer in production example 1 of wet CS.
Production example 15 of wet CS
A wet casting mold composition (CS15a) was obtained in the same manner as in production example 1, except that 0.05 parts of polytetrafluoroethylene (Fluon L169J) was used as the neutralizer in production example 1 of wet CS.
Production example 16 of wet CS
The refractory aggregate (ESPEARL #60) was heated to a temperature of about 130 ℃, and then charged into a vortex mixer (manufactured by yokoku corporation), and further, a neutralizing agent (chlorinated paraffin: EMPARA 70) was added in an amount of 0.10 part per 100 parts of the refractory aggregate, and kneaded for 3 minutes, stirred and mixed until the sand grains were disintegrated, and then taken out, thereby forming a solid first coating layer (lower layer) composed of the neutralizing agent (EMPARA 70) on the surface of the refractory aggregate.
Next, using water glass (sodium silicate No. 2), an aqueous water glass solution having a solid content (concentration) of 41% was prepared. Then, the refractory aggregate prepared in the foregoing manner and having the solid first coating layer provided on the surface thereof was charged into a martian universal mixer (5DM-r, manufactured by DALTON CORPORATION) at normal temperature, the above water glass aqueous solution was added at a ratio of 1.0 part to 100 parts of the refractory aggregate, and kneaded for 3 minutes, stirred and mixed until uniform, and then taken out, thereby obtaining a wet molding composition (CS16a) in which a second coating layer (upper layer) made of water glass was provided on the solid first coating layer (lower layer).
Production example 17 of wet CS
A refractory aggregate (ESPEARL #60) was heated to a temperature of about 60 ℃, and then charged into a vortex mixer (manufactured by seiko corporation), and further, 0.20 parts of a neutralizing agent (EMPARA 70) and 0.15 parts of an aromatic polyester polyol (manufactured by kawasaki Chemical & SKC Polyurethanes inc., trade name: polyisocyanate M-200) were added to 100 parts of the refractory aggregate in an amount of 0.10 parts, and the aromatic polyester polyol was reacted with a polyisocyanate to prepare a phenolic urethane resin, and the mixture was taken out until the phenolic urethane resin was hardened, thereby forming a solid first coating layer (lower layer) composed of the neutralizing agent (EMPARA 70) and the phenolic urethane resin on the surface of the refractory aggregate.
Next, using water glass (sodium silicate No. 2), an aqueous water glass solution having a solid content (concentration) of 41% was prepared. Then, the refractory aggregate prepared in the foregoing manner, on the surface of which the solid first coat layer was provided, was charged into a pinkish universal mixer (5DM-r, manufactured by DALTON CORPORATION) at normal temperature, the above water glass aqueous solution was added at a ratio of 1.0 part to 100 parts of the refractory aggregate, and kneaded for 3 minutes, stirred and mixed until uniform, and then taken out, thereby obtaining a wet mold composition (CS17a) in which a second coat layer (upper layer) made of water glass was provided on the solid first coat layer (lower layer).
Preparation example 18 of wet CS
A wet casting mold composition (CS18a) was obtained in the same manner as in production example 16, except that 0.25 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in place of 0.10 parts of chlorinated paraffin (EMPARA 70) in production example 16 of wet CS.
Production example 19 of wet CS
A wet casting mold composition (CS19a) was obtained in the same manner as in production example 17, except that 0.25 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in place of 0.10 parts of chlorinated paraffin (EMPARA 70) in production example 17 of wet CS.
Preparation example 20 of wet CS
A wet casting mold composition (CS19a) was obtained in the same manner as in production example 17, except that 0.22 parts of phosphate ester (TPP) was used as the neutralizer instead of 0.10 parts of chlorinated paraffin (EMPARA 70) in production example 17 of wet CS.
Preparation example 21 of wet CS
A wet casting mold composition (CS21a) was obtained in the same manner as in production example 1, except that the neutralizer (EMPARA 70) was not used in production example 1 of wet CS.
Preparation example 22 of wet CS
A wet casting mold composition (CS22a) was obtained in the same manner as in production example 6, except that the neutralizer (EMPARA 70) was not used in production example 6 of wet CS.
Production example 23 of wet CS
A wet casting mold composition (CS23a) was obtained in the same manner as in production example 7, except that the neutralizer (EMPARA 70) was not used in production example 7 of wet CS.
Preparation example 24 of wet CS
A wet casting mold composition (CS24a) was obtained in the same manner as in production example 8, except that the neutralizer (EMPARA 70) was not used in production example 8 of wet CS.
Production example 25 of wet CS
A wet casting composition (CS25a) was obtained in the same manner as in production example 1, except that 0.21 part of 35% hydrochloric acid was used as a neutralizer in place of 0.10 part of chlorinated paraffin (EMPARA 70) in production example 1 of wet CS.
Mold examples I (examples 1 to 20, comparative examples 1 to 5) of casting mold
The molds used as test bodies (diameter: 5cm, height: 5cm) of round, hollow cores were prepared by filling CS1 a-CS 25a (temperature: 20 ℃) prepared in the above steps into a molding die heated to 150 ℃, holding the molding die, and curing (hardening) the CS filled in the molding die. The CS used for producing each of the casting molds (test bodies) of examples 1 to 20 and comparative examples 1 to 5 is shown in tables 1 to 4 below.
[ Table 1]
Figure BDA0003282137280000421
[ Table 2]
Figure BDA0003282137280000431
[ Table 3]
Figure BDA0003282137280000441
[ Table 4]
Figure BDA0003282137280000451
As is clear from the results of said tables 1 to 3: the mold material compositions in a wet state of the present invention (wet CS: CS1a to CS20a) contain a predetermined neutralizing agent, and thus the molds obtained using them are excellent in disintegration property, and the amount of alkali remaining in the refractory aggregate (recovered sand) recovered after casting is sufficiently low. Further, the evaluation in the polishing and peeling test was also good, and the polishing treatment of the recovered sand was also easy.
On the other hand, as is clear from table 4 above, it was confirmed that the wet CS (CS21a to CS25a) containing no predetermined neutralizing agent was contained in the wet mold composition: 1) in the cases of CS21a to CS24a, the molds obtained using these materials were observed to have poor disintegration properties, and the amount of alkali remaining in the recovered sand was also large; in addition, 2) CS25a, the mold cannot be formed at all.
Production example 1 of dry CS
Using water glass (sodium silicate No. 2), an aqueous water glass solution having a solid content (concentration) of 41% was prepared. A foundry material composition (dry CS: CS1b) in which a coating layer containing water glass and a neutralizer (chlorinated paraffin) was provided on the surface of a refractory aggregate was obtained by heating the refractory aggregate (ESPEARL #60) to a temperature of about 130 ℃, feeding the mixture into a vortex mixer (manufactured by yokoku corporation), adding the above water glass aqueous solution in a proportion of 1.0 part to 100 parts of the refractory aggregate, adding chlorinated paraffin (EMPARA 70) as a neutralizer in a proportion of 0.10 part to 100 parts of the refractory aggregate, kneading the mixture for 3 minutes, stirring and mixing until the mixture became uniform.
Production example 2 of dry CS
A mold composition (CS2b) in a dry state was obtained by following the same procedure as in production example 1, except that the amount of the aqueous water glass solution was 2.0 parts and the amount of the neutralizer (EMPARA 70) was 0.20 parts in production example 1 of dry CS.
Production example 3 of dry CS
A dry casting composition (CS3b) was obtained in the same manner as in production example 1, except that in production example 1, a water glass aqueous solution having a solid content (concentration) of 45% obtained using water glass (sodium silicate No. 1) was used as the water glass aqueous solution, and the amount of the neutralizer (EMPARA 70) used was 0.14 part.
Preparation example 4 of dry CS
A dry mold composition (CS4b) was obtained in the same manner as in production example 1, except that an aqueous sodium silicate solution having a solid content (concentration) of 35% obtained from sodium silicate (sodium silicate No. 3) was used as the aqueous sodium silicate solution, and the amount of the neutralizer (chlorinated paraffin: EMPARA 70) was 0.07 part.
Production example 5 of dry CS
In production example 1 of dry CS, vinyl chloride (C) (I)
Figure BDA0003282137280000471
pass) was carried out in the same manner as in production example 1 except that 0.13 parts of pass was used, to obtain a mold material composition (CS5b) in a dry state.
Preparation example 6 of dry CS
A dry mold composition (CS6b) was obtained in the same manner as in production example 1, except that 0.25 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in production example 1 of dry CS.
Preparation example 7 of dry CS
A mold composition (CS7b) was obtained in a dry state by the same procedure as in production example 1, except that 0.24 parts of brominated aliphatic/aromatic compound (SR720N) was used as a neutralizer in production example 1 of dry CS.
Production example 8 of dry CS
A dry mold composition (CS8b) was obtained in the same manner as in production example 1, except that 0.05 part of polytetrafluoroethylene (Fluon L169J) was used as the neutralizer in production example 1 of dry CS.
Preparation example 9 of dry CS
A first solid coating layer (lower layer) composed of a neutralizer (espara 70) and a phenolic urethane resin was formed on the surface of a refractory aggregate by heating the refractory aggregate (ESPEARL #60) to a temperature of about 60 ℃, feeding the heated refractory aggregate into a vortex mixer (manufactured by seiko corporation), further adding 0.20 part of a neutralizer (EMPARA 70) and 0.15 part of an aromatic polyester polyol (manufactured by kawasaki Chemical & SKC Polyurethanes inc., product name: polyisocyanate M-200) to 100 parts of the refractory aggregate, reacting the aromatic polyester polyol with a polyisocyanate to prepare a phenolic urethane resin, and taking out the resulting mixture until the resin is cured.
Next, using water glass (sodium silicate No. 2), an aqueous water glass solution having a solid content (concentration) of 41% was prepared. Then, the refractory aggregate prepared in the past and provided with the solid first coat layer on the surface thereof was heated to a temperature of about 50 ℃, and then charged into a vortex mixer (manufactured by yokoku corporation), the above water glass aqueous solution was added at a ratio of 1.0 part to 100 parts of the refractory aggregate, kneading was performed for 5 minutes while ventilating 120 degrees of hot air into the vortex mixer, and the mixture was stirred and mixed until uniform, and then taken out, thereby obtaining a mold material composition (CS9b) in a dry state in which a second coat layer (upper layer) made of water glass was provided on the solid first coat layer (lower layer).
Preparation example 10 of dry CS
A dry mold material composition (CS10b) was obtained in the same manner as in production example 9, except that 0.25 parts of brominated aliphatic/aromatic compound (Pyroguard SR130) was used as the neutralizer in place of 0.10 parts of chlorinated paraffin (EMPARA 70) in production example 9 of dry CS.
Preparation example 11 of dry CS
A dry casting composition (CS11b) was obtained in the same manner as in production example 17, except that 0.22 part of phosphoric acid ester (TPP) was used as the neutralizing agent in place of 0.10 part of chlorinated paraffin (EMPARA 70) in production example 9 of dry CS.
Preparation example 12 of dry CS
A dry mold composition (CS12b) was obtained by the same procedure as in production example 1, except that the neutralizer (EMPARA 70) was not used in production example 1 of dry CS.
Preparation example 13 of dry CS
A dry mold composition (CS13b) was obtained by the same procedure as in production example 3, except that the neutralizer (EMPARA 70) was not used in production example 3 of dry CS.
Preparation example 14 of dry CS
A dry mold composition (CS14b) was obtained in the same manner as in production example 4 except that the neutralizer (EMPARA 70) was not used in production example 4 of dry CS.
Preparation example 15 of dry CS
A dry casting composition (CS15b) was obtained in the same manner as in production example 1, except that 0.21 part of 35% hydrochloric acid was used as a neutralizer in place of 0.10 part of chlorinated paraffin (EMPARA 70) in production example 1 of dry CS.
Mold examples II (examples 21 to 31, comparative examples 6 to 9) of casting mold
CS1b to CS15b (temperature: 20 ℃) produced in the above steps were charged into a Kawakawa-type universal mixer (5DM-r, manufactured by DALTON CORPORATION) at room temperature, and water was added to the mixer in an amount of 1.0 part per 100 parts of CS to stir the mixture, thereby preparing wet CS (mold material). The wet CS taken out from the stirrer was filled into a molding die heated to 150 ℃, and then held in the molding die, and the CS filled in the molding die was solidified (hardened), thereby producing a mold to be used as a test piece (diameter: 5cm, height: 5cm) of a round hollow-core. The CS used for producing the respective molds (test bodies) of examples 21 to 31 and comparative examples 6 to 9 is shown in tables 5 to 7 below.
[ Table 5]
Figure BDA0003282137280000501
[ Table 6]
Figure BDA0003282137280000511
[ Table 7]
Figure BDA0003282137280000521
As is clear from the results of tables 5 and 6: in the case where the mold material composition of the present invention in a dry state (dry CS: CS1b to CS11b) is wet-formed by adding water thereto, the mold obtained by using the composition is excellent in disintegration property because it contains a predetermined neutralizing agent, and the amount of alkali remaining in the refractory aggregate (recovered sand) recovered after casting is sufficiently low, as in the case of the mold material composition of the present invention in a wet state (wet CS: CS1a to CS20 a). Further, the evaluation in the polishing and peeling test was also good, and the polishing treatment of the recovered sand was also easy.
On the other hand, as is clear from table 7 above, it was confirmed that the dry CS (CS12b to CS15b) containing no predetermined neutralizing agent was contained in the dry mold composition: 1) in the cases of CS12b to CS14b, the molds obtained using these materials were observed to have poor disintegration properties, and the amount of alkali remaining in the recovered sand was also large; in addition, 2) CS15b, the molding of the mold cannot be achieved at all.
Mold example III (examples 32 to 36, comparative examples 10 to 11) of casting mold
CS1b, CS6b, CS9 b-CS 12b, CS15b (temperature: 20 ℃) manufactured according to the above steps are mixed under pressure: blowing the mixture into a molding die heated to 110 ℃ under a gauge pressure of 0.3MPa, and then blowing the mixture at a blowing temperature of 0.05 MPa: steam at 99 ℃ was introduced into the precoated sand (CS) phase filled in the mold for 4 seconds. After the completion of the steam aeration, hot air at 150 ℃ was blown under a gauge pressure of 0.03MPa for 2 minutes to solidify (harden) the CS filled in the molding die, thereby producing a mold to be used as a test piece (diameter: 5cm, height: 5cm) of a round hollow core. The CS used for producing each of the molds (test specimens) of examples 32 to 36 and comparative examples 10 to 11 is shown in tables 8 and 9 below.
[ Table 8]
Figure BDA0003282137280000541
[ Table 9]
Figure BDA0003282137280000551
As is clear from the results of tables 8 and 9: in the case where the dry mold material composition of the present invention (dry CS: CS1b, CS6b, CS9b to CS11b) is aerated with water vapor in a mold, the mold obtained by using them is excellent in disintegration property because it contains a predetermined neutralizing agent, and the amount of alkali remaining in the refractory aggregate (recovered sand) recovered after casting is sufficiently low, as in the case of the wet mold material composition of the present invention (wet CS: CS1a to CS20 a). Further, it was confirmed that: the evaluation in the polishing and peeling test was also good, and the polishing treatment of the recovered sand was also easy.
On the other hand, as is clear from table 9 above, it was confirmed that the dry CS (CS12b, CS15b) containing no predetermined neutralizing agent was contained in the dry mold composition: 1) in the case of CS12b, the mold obtained using these materials had poor disintegration properties, and the amount of alkali remaining in the recovered sand was large; further, 2) in the case of CS15b, the molding of the mold cannot be achieved at all.
Description of the reference numerals
2 molten metal pouring inlet 4 type core seat fixing part
6 main 8 type core seats
10-core 12-sand mold
14 spent core discharge port 16 castings

Claims (12)

1. A casting mold material composition, comprising at least:
(a) a refractory aggregate;
(b) a binder containing water glass as an essential component; and
(c) and a neutralizing agent that neutralizes the alkali component of the water glass with a decomposition product generated by heating during casting.
2. The casting mold material composition of claim 1, wherein the neutralizing agent is an organic halogen compound or a phosphate ester.
3. The mold material composition according to claim 1 or 2, wherein the neutralizing agent is contained in a quantitative ratio of: the alkali component of the water glass is neutralized by the decomposition product generated by heating at the time of casting, so that the proportion of the alkali component of the water glass after casting is 15 mass% or less.
4. The casting mold material composition according to any one of claims 1 to 3, wherein a coating layer containing the binder and the neutralizing agent is formed so as to cover the surface of the refractory aggregate.
5. A casting mold composition according to any one of claims 1 to 3, wherein a solid first coating layer containing the neutralizing agent is formed so as to cover the surface of the refractory aggregate, and a second coating layer containing a binder composition containing the binder is formed so as to cover the first coating layer.
6. The casting mold material composition of claim 5, wherein the first coating layer comprises an organic compound.
7. The casting mold material composition as claimed in any one of claims 1 to 6, wherein the refractory aggregate is spherical.
8. The casting mold material composition as claimed in any one of claims 1 to 7, which has no room-temperature fluidity and is in a wet state.
9. A casting mold composition according to any one of claims 1 to 7, which has room-temperature fluidity and is in a dry state.
10. A method for producing a mold, characterized in that the wet-state mold material composition according to claim 8 is used, and after being filled into a mold, the composition is held in the mold and cured or hardened to obtain a target mold.
11. A method for producing a mold, characterized in that the mold material composition according to claim 9 in a dry state is used, and after filling the composition into a mold, water vapor is introduced and held in the mold, and the composition is cured or hardened to obtain a target mold.
12. A method for producing a mold, characterized in that the dry mold material composition according to claim 9 is used, water is added to the composition to wet the composition, the wet mold material composition is filled into a mold, and then the composition is held in the mold and cured or hardened to obtain a target mold.
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