JP2022152231A - Mold production method - Google Patents

Abstract

To provide a mold production method capable of producing a mold having excellent heat resistance.SOLUTION: A mold production method comprises: an impregnation step in which a mold precursor as a hardened material comprising a refractory granular material and an organic binder is separately impregnated with colloidal silica and water glass; and a hardening step in which the water glass impregnated into the mold precursor is hardened.SELECTED DRAWING: None

Description

The present invention relates to a mold manufacturing method.

Conventionally, casting molds (hereinafter also referred to simply as "molds") include normal molds and special molds, and normal molds include green molds and dry molds. On the other hand, special molds include thermosetting molds, self-hardening molds, and gas-hardening molds.
Refractory granular material such as silica sand is used as the material for the mold, but because the refractory granular material alone tends to crumble when dried, a binder is added to prevent crumbling.
Clays such as bentonite are commonly used as binders in molds. On the other hand, for special molds, organic binders such as phenol resin, furan resin, and urethane resin, and inorganic binders such as water glass are used.

For example, Patent Documents 1 and 2 disclose a mold that is baked after being impregnated with water glass having a specific molar ratio (molar ratio of SiO ₂ and Na ₂ O) as an inorganic binder in a mold molded with an organic binder. is disclosed.
Patent Document 3 discloses a method for manufacturing a mold, in which a mold molded with an organic binder is impregnated with a water-soluble inorganic salt such as sodium chloride, and then baked.
Patent Document 4 discloses a method of manufacturing a mold by three-dimensional additive manufacturing, in which the steps of forming a thin layer of a refractory molding substrate and printing water glass and a binder on predetermined locations of the thin layer are repeated. It is

JP-A-3-248740 JP 2018-158377 A Japanese Patent Application Laid-Open No. 2020-22981 Japanese Patent Publication No. 2017-538585

However, in the case of the methods described in Patent Documents 1 to 4, the heat resistance of the mold may be insufficient. The mold is exposed to high temperature by pouring a liquid (molten metal) that melts metals such as iron, copper, and aluminum at high temperature. It may be deformed. Therefore, the mold is required to have heat resistance so that it can exhibit sufficient strength even when exposed to high temperatures.
An object of the present invention is to provide a method for manufacturing a mold that can manufacture a mold having excellent heat resistance.

The present invention has the following aspects.
[1] an impregnation step of separately impregnating colloidal silica and water glass into a template precursor, which is a cured mixture of a refractory granular material and an organic binder;
a curing step of curing the water glass impregnated in the mold precursor;
A method of manufacturing a mold, comprising:
[2] The mold manufacturing method according to [1], further comprising a baking step after the curing step.
[3] The mold manufacturing method according to [1] or [2], wherein the mold precursor is manufactured by three-dimensional additive manufacturing.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the casting_mold|template which can manufacture the casting_mold|template which is excellent in heat resistance can be provided.

It is a figure which shows typically the casting_mold|template precursor manufactured in Example 17, (a) is a perspective view, (b) is a side view. 4 is a photograph of a test piece (fired body) obtained in Example 17. FIG. 4 is a photograph of a test piece (fired body) obtained in Comparative Example 11. FIG.

[Mold manufacturing method]
An embodiment of the mold manufacturing method of the present invention will be described below.
In the mold manufacturing method of the present embodiment, a mold is obtained by impregnating a mold precursor with colloidal silica and water glass separately (impregnation step) and then curing the water glass (hardening step).
The mold manufacturing method of the present embodiment may further include the following baking step after the curing step.
In this specification, in order to distinguish between the mold obtained by the curing process and the mold obtained by the baking process, the mold obtained by the curing process is also referred to as a "cured body", and the mold obtained by the baking process is referred to as " Also called "fired body".

<Template precursor>
A mold precursor is a cured mixture comprising a refractory particulate material and an organic binder.
When producing the mold precursor, it is preferable to use a curing agent together with the refractory granular material and the organic binder.
The mold precursor may optionally contain components (optional components) other than the refractory particulate material, organic binder and curing agent.

(refractory granular material)
As the refractory granular material, conventionally known materials such as natural sand such as silica sand, chromite sand, zircon sand, olivine sand, amorphous silica, alumina sand and mullite sand; artificial sand and the like can be used. In addition, used refractory granular material recovered (recovered sand) or reclaimed (reclaimed sand) can also be used. These refractory granular materials may be used singly or in combination of two or more.

The average particle size of the refractory granular material is preferably 50-600 μm, more preferably 60-550 μm, even more preferably 75-500 μm. If the average particle size of the refractory granular material is at least the above lower limit, a mold with high strength can be obtained. If the average particle size of the refractory granular material is equal to or less than the above upper limit, the surface properties of castings cast using the mold will be excellent. In particular, if the average particle size of the refractory granular material is 300 μm or less, it is suitable for producing a mold precursor by three-dimensional layered manufacturing, and a mold having excellent surface compatibility can be obtained.
The average particle diameter of the refractory granular material is the median diameter of 50% of the cumulative volume of the refractory granular material measured by the dynamic light scattering method.

(organic binder)
Examples of organic binders include binders used when manufacturing molds by the shell mold method, binders used when manufacturing molds by the amine cold box method, alkali phenol resins, and acid-curable binders. etc. These organic binders may be used individually by 1 type, and may use 2 or more types together.
Among these, acid-curable binders are preferred.

Examples of binders used in producing molds by the shell molding method include novolac-type phenolic resins and resol-type phenolic resins.
Novolak-type phenolic resins are obtained by reacting phenols and aldehydes in the presence of an acidic catalyst, and are usually solid.
Examples of phenols include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 3,5-xylenol, m-ethylphenol, m-propylphenol, m-butylphenol, p-butylphenol, o-butylphenol, resorcinol, hydroquinone, catechol, 3-methoxyphenol, 4-methoxyphenol, 3-methylcatechol, 4-methylcatechol, methylhydroquinone, 2-methylresorcinol, 2,3-dimethylhydroquinone, 2,5-dimethyl resorcinol, 2-ethoxyphenol, 4-ethoxyphenol, 4-ethylresorcinol, 3-ethoxy-4-methoxyphenol, 2-propenylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 3,4, 5-trimethylphenol, 2-isopropoxyphenol, 4-pyropoxyphenol, 2-allylphenol, 3,4,5-trimethoxyphenol, 4-isopropyl-3-methylphenol, pyrogallol, phloroglicinol, 1,2 , 4-benzenetriol, 5-isopropyl-3-methylphenol, 4-butoxyphenol, 4-t-butylcatechol, t-butylhydroquinone, 4-t-pentylphenol, 2-t-butyl-5-methylphenol, 2-phenylphenol, 3-phenylphenol, 4-phenylphenol, 3-phenoxyphenol, 4-phenoxyphenol, 4-hexyloxyphenol, 4-hexanoylresorcinol, 3,5-diisopropylcatechol, 4-hexylresorcinol, 4-heptyloxyphenol, 3,5-di-t-butylphenol, 3,5-di-t-butylcatechol, 2,5-di-t-butylhydroquinone, di-sec-butylphenol, 4-cumylphenol, nonylphenol, 2-cyclopentylphenol, 4-cyclopentylphenol, bisphenol A, bisphenol F and the like. These phenols may be used individually by 1 type, and may use 2 or more types together.

Examples of aldehydes include formaldehyde, trioxane, furfural, paraformaldehyde, benzaldehyde, methylhemiformal, ethylhemiformal, propylhemiformal, salicylaldehyde, glyoxal, butylhemiformal, phenylhemiformal, acetaldehyde, propylaldehyde, phenylacetaldehyde, α-phenylpropylaldehyde, β-phenylpropylaldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-chlorobenzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-methyl benzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, p-ethylbenzaldehyde, pn-butylbenzaldehyde and the like. These aldehydes may be used individually by 1 type, and may use 2 or more types together.
Examples of acidic catalysts include hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, butyric acid, lactic acid, benzenesulfonic acid, p-toluenesulfonic acid and boric acid. These acidic catalysts may be used singly or in combination of two or more. Metal salts such as zinc chloride or zinc acetate may also be used, or used in combination with an acidic catalyst.

A silane coupling agent may be added to the novolak-type phenol resin during the manufacturing process for the purpose of improving mold strength. If the silane coupling agent is not blended in the manufacturing process, the novolac phenolic resin and the silane coupling agent may be used together.
Examples of the silane coupling agent include silane coupling agents exemplified in the explanation of the acid-curable resin below.

A resol-type phenolic resin is obtained by reacting phenols and aldehydes in the presence of a basic catalyst.
Examples of phenols and aldehydes include the phenols and aldehydes exemplified above in the description of the novolak-type phenolic resin.
Examples of basic catalysts include sodium hydroxide, potassium hydroxide, ammonia, hexamine, and amines. These basic catalysts may be used singly or in combination of two or more.

A resol-type phenolic resin is usually obtained in a state of being dispersed in a solvent such as water (hereinafter, a resol-type phenolic resin in this state is referred to as a "liquid resol-type phenolic resin").
The resol-type phenolic resin may be used in a liquid state, or the liquid resol-type phenolic resin may be subjected to a dehydration treatment or the like to remove the solvent, and dried at room temperature to be used in a solid state.
In some cases, a resol type phenolic resin is also mixed with a silane coupling agent during the manufacturing process for the purpose of improving mold strength. If the silane coupling agent is not blended in the manufacturing process, the resol-type phenolic resin and the silane coupling agent may be used together.

Examples of the binder used in producing the mold by the amine cold box method include a two-liquid binder composed of a phenol resin solution and a polyisocyanate solution using an organic solvent as a solvent.

The alkali phenol resin is prepared by a conventional method in the presence of an alkali metal hydroxide, with one or more selected from the group consisting of phenols and bisphenols (hereinafter referred to as "phenol compounds") and aldehydes. is obtained by reacting in an aqueous system.
Examples of phenols and aldehydes include the phenols and aldehydes exemplified above in the description of the novolak-type phenolic resin.
Examples of bisphenols include bisphenol A, bisphenol F, bisphenol C, bisphenol S, bisphenol Z and the like.
As the phenolic compound, either one of phenols and bisphenols may be used alone, or a mixture of phenols and bisphenols may be used.

Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Among these, sodium hydroxide and potassium hydroxide are preferred. These alkali metal hydroxides may be used singly or in combination of two or more.

Examples of acid-curable resins include furfuryl alcohol and furan resin. Moreover, you may use the resol type phenol resin illustrated previously as an acid hardening resin.
Among these, furfuryl alcohol and furan resin are preferred, and furfuryl alcohol is more preferred.

Furan resin is a resin containing furfuryl alcohol, urea, formaldehyde, etc. as main raw materials, and is cured by polycondensation while undergoing dehydration reaction with an acid catalyst.
The furan resin is mainly composed of one or more condensates or co-condensates of furfuryl alcohol or furfuryl alcohol and urea with aldehydes, and mixtures with furfuryl alcohol. It is preferable to use one containing at least one of phenols and bisphenols.
Examples of phenols and aldehydes include the phenols and aldehydes exemplified above in the description of the novolak-type phenolic resin.

Two particularly preferred embodiments of the furan resin are listed below. In addition, the (co)condensate below means at least one of a condensate and a cocondensate.
i) A mixture of a (co)condensate (a) obtained by condensing urea, furfuryl alcohol and aldehydes with furfuryl alcohol and optionally at least one of phenols and bisphenols.
ii) mixtures of condensates of urea and aldehydes, furfuryl alcohol and optionally at least one of phenols and bisphenols.

As the furan resin, in addition to those described above, for example, a mixture of one or more selected from the group consisting of 2,5-bis(hydroxymethyl)furan, phenols and bisphenols, and furfuryl alcohol; urea and aldehyde A condensate with a condensate, a mixture of furfuryl alcohol and 2,5-bis(hydroxymethyl)furan, and the like can also be used.

The acid-curable resin may contain a silane coupling agent for the purpose of increasing the strength of the mold.
Silane coupling agents include, for example, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-glycidoxysilane. propyltrimethoxysilane and the like.

When the acid-curable resin contains a silane coupling agent, the content of the silane coupling agent is preferably 0.01 to 3% by mass, preferably 0.1 to 3% by mass, based on the total mass of the solid content of the acid-curable resin. 2% by mass is more preferred. If the content of the silane coupling agent is at least the above lower limit, the effect of improving the strength of the mold can be sufficiently obtained. The effect of improving the strength of the mold tends to be more likely to be obtained as the content of the silane coupling agent increases. Therefore, the content of the silane coupling agent is preferably 3% by mass or less.
The solid content of the acid-curable resin indicates the non-volatile content at 100°C.

The acid-curable resin may contain a curing accelerator for the purpose of increasing the curing speed.
Curing accelerators include resorcinol, formalin, furfural, and the like. Among these, resorcinol is preferable because it also has the effect of reducing formaldehyde generated during mold making.
When the acid-curable resin contains a curing accelerator, the content of the curing accelerator is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, based on the total mass of the solid content of the acid-curable resin. . When the content of the curing accelerator is at least the above lower limit, the curing speed is sufficiently increased. The curing speed tends to be more easily obtained as the content of the curing accelerator increases, but if the content is too high, the effect will only plateau. Therefore, the content of the curing accelerator is preferably 20% by mass or less.
From the viewpoint of reducing formaldehyde, urea, gallic acid, and pyrogallol may be used in addition to resorcinol.

(curing agent)
The curing agent may be selected from known curing agents according to the type of organic binder and curing method.
For example, in the case of using a binder that is used in manufacturing a mold by the shell mold method as the organic binder, hexamethylenetetramine is preferred as the curing agent.
When using the binder used when producing a mold by the amine cold box method as the organic binder, the curing agent is preferably an amine gas such as triethylamine or diethylamine. These curing agents may be used singly or in combination of two or more.
When an alkali phenol resin is used as an organic binder, curing agents include methyl formate, ethyl formate, triacetin, diacetin, monoacetin, ethylene glycol diacetate, ethylene glycol monoacetate, γ-butyrolactone, Propiolactone, ε-caprolactone and the like are preferred. In the gas curing mold making method, highly volatile esters are preferred, and methyl formate and the like are more preferred.
When an acid-curable resin is used as the organic binder, inorganic acids such as sulfuric acid, phosphoric acid, and hydrochloric acid are used as the curing agent; etc.), carboxylic acids (eg, formic acid, acetic acid, oxalic acid, lactic acid, maleic acid, malic acid, citric acid, tartaric acid, malonic acid, succinic acid, benzoic acid, etc.).
These curing agents may be used singly or in combination of two or more.

The curing agent can be used in the form of an aqueous solution, that is, as an aqueous curing agent solution.
The content of the curing agent with respect to the total mass of the aqueous curing agent solution is preferably 20 to 75% by mass, more preferably 30 to 70% by mass.
The water content is preferably 25 to 80% by mass, more preferably 30 to 70% by mass, relative to the total mass of the aqueous curing agent solution.
The aqueous curing agent solution may contain a solvent (another solvent) other than water, and examples of other solvents include alcohols such as methanol, ethanol, and butanol.

(Optional component)
Optional components include, for example, silane coupling agents, lubricants, disintegrants, and curing accelerators.
Examples of the silane coupling agent include the silane coupling agents exemplified above in the explanation of the acid-curable resin.
Examples of lubricants include fatty acid amides and calcium stearate.
Disintegrants include, for example, nitrates.
Examples of hardening accelerators include benzoic acid and salicylic acid.

(Method for producing template precursor)
A template precursor is obtained, for example, by the following method (I) or method (II).
Method (I): A mixture (hereinafter also referred to as “mixture (A)”) containing a refractory granular material, an organic binder, and optionally optional ingredients is filled into a mold for molding, and the organic A method for producing a mold precursor by curing a binder.
Method (II): A method of manufacturing a template precursor by three-dimensional additive manufacturing.

<<Method (I)>>
In method (I), the mixture (A) can be prepared, for example, by mixing the refractory particulate material, the organic binder and optional ingredients. The mixture (A) thus obtained is also called "kneaded sand".
The content of the organic binder in the mixture (A) is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3.5 parts by mass, based on 100 parts by mass of the refractory granular material. If the content of the organic binder is at least the above lower limit, sufficient strength can be maintained until the curing step described later. If the content of the organic binder is equal to or less than the above upper limit, the mold can be easily dismantled after pouring. In addition, the amount of gas generated due to thermal decomposition of the acid-curable binder during pouring can be reduced.

Methods for curing the organic binder include heat curing, normal temperature curing, gas curing and the like. Here, "normal temperature curing" means curing at normal temperature without external heating or gas ventilation.
When the organic binder is cured by thermosetting or normal temperature curing, that is, when a mold is produced by a thermosetting mold making method or a self-hardening mold making method, the mixture (A) preferably contains a curing agent. Hereinafter, the mixture (A) containing the curing agent is also particularly referred to as "mixture (A1)".
The content of the curing agent in the mixture (A1) is preferably 0.1 to 0.5 parts by mass, more preferably 0.2 to 0.4 parts by mass, per 100 parts by mass of the refractory granular material. If the content of the curing agent is within the above range, a mold with higher strength can be easily obtained.

The mixture (A1) can be produced, for example, by mixing a refractory granular material, an organic binder, an aqueous curing agent solution, and optionally optional ingredients.
Alternatively, for example, a refractory granular material is heated to a predetermined temperature, and an aqueous hardening agent solution is added to the heated refractory granular material to produce coated sand, and the resulting coated sand, an organic binder, Optionally, optional ingredients may be mixed to produce a mixture (A1). The heating temperature of the refractory granular material is preferably a temperature higher than the boiling point of the solvent contained in the aqueous curing agent solution, usually 100 to 150°C.

When the organic binder is cured by gas curing, that is, when the mold is produced by the gas curing mold making method, the mixture (A) is filled in the mold for making the mold, and the gaseous curing agent is passed through to form the organic binder. Allow the binder to harden.
The aeration flow rate and aeration time of the gaseous curing agent are not particularly limited as long as they are within the range of the aeration flow rate and aeration time in a normal gas curing mold making method.

By curing the organic binder by a method such as heat curing, normal temperature curing, gas curing, etc., a mold precursor composed of a cured product of the mixture (A) can be obtained.
The template precursor thus obtained is removed from the template-making mold. Since the mold precursor can maintain its shape due to the cured organic binder, it does not easily collapse even when it is taken out from the mold for molding.

<<Method (II)>>
In the case of method (II), a step of spreading a mixture (hereinafter also referred to as "mixture (B)") containing a refractory granular material, a curing agent, and optional components as necessary (hereinafter referred to as "step (a)”), and an organic binder is added to the coated sand spread in layers so as to bond the mixture (B) spread in layers to correspond to the target three-dimensional laminate model. A mold precursor is manufactured by repeating the step of selectively injecting and curing (hereinafter also referred to as “step (b)”) until the desired three-dimensional laminate-molded article is formed.
Acid-curable resins are preferred as the organic binder used in method (II).

Mixture (B) can be produced, for example, by mixing the refractory particulate material, the curing agent and optionally optional ingredients.
Alternatively, for example, a refractory granular material may be heated to a predetermined temperature, and an aqueous hardening agent solution may be added to the heated refractory granular material to produce coated sand, which may be used as the mixture (B), A mixture of coated sand and optional components may be used as the mixture (B), if desired.

Process (a) and process (b) are performed as follows, for example, using a three-dimensional lamination apparatus using a printing modeling method.
The three-dimensional stacking device preferably includes a blade mechanism, a print nozzle head mechanism, and a modeling table mechanism. Furthermore, it is preferable to include a control unit that controls the operation of each mechanism using the three-dimensional data of the object to be formed.
The blade mechanism includes a recoater, and coats sand with a predetermined thickness on the bottom surface of the metal case or on the upper layer of the shaped part that has already been bonded with an organic binder.
The printing nozzle head mechanism prints with an organic binding agent on the layered coated sand, and forms each layer by binding the coated sand.
When the modeling of one layer is completed, the modeling table mechanism descends by a distance corresponding to one layer to realize layered modeling with a predetermined thickness.

First, using a three-dimensional lamination apparatus using a printing molding method, the mixture (B) is laminated on the bottom surface of a metal case installed in the three-dimensional lamination apparatus by means of a blade mechanism having a recoater (step (a)). Then, on the layered mixture (B), the print nozzle head is scanned by the print nozzle head mechanism based on the data obtained by 3D CAD designing the shape of the desired three-dimensional laminate model (three-dimensional laminate model) to print (inject) the organic binder (step (b)). The bottom of the metal case is a modeling table that can be moved up and down. After printing the organic binding agent, the bottom surface of the metal case (modeling table) is lowered by one layer, and the mixture (B) is laminated in the same manner as before (step (a)), and the organic binding agent is placed thereon. is printed (step (b)). These stacking and printing operations are repeated until a desired three-dimensional laminate-molded article is manufactured. The thickness of one layer is preferably 100-500 μm, more preferably 200-300 μm.

The coating amount of the organic binder when printing is preferably 0.4 parts by mass or more in terms of solid content, with respect to 100 parts by mass of the refractory granular material in the mixture (B) for one layer in the printing area. , more preferably 0.4 to 4.6 parts by mass, more preferably 0.5 to 4 parts by mass, particularly preferably 0.6 to 3 parts by mass, and most preferably 0.7 to 2 parts by mass.

The template precursor obtained by the method (II) is shaped while being buried in the powder of the mixture (B). Therefore, the mixture (B) in the area where the organic binder is not printed (non-printed area) is removed with a brush, a vacuum cleaner, or the like, and the mold precursor is taken out. Since the mold precursor can maintain its shape due to the cured organic binder, it does not easily collapse even when the mold precursor is taken out.
In addition, in this specification, the template precursor obtained by the method (II) is also referred to as a "three-dimensional laminate-molded article".

<Impregnation process>
The impregnation step is a step of separately impregnating the template precursor with colloidal silica and water glass.
Colloidal silica is a dispersion of silica particles (SiO ₂ ) dispersed in water or an organic solvent.
Colloidal silica is not particularly limited, and conventionally known colloidal silica can be used. Examples of colloidal silica include aqueous colloidal silica exhibiting acidity, aqueous colloidal silica exhibiting alkalinity, and cationic colloidal silica.

As aqueous colloidal silica exhibiting acidity, for example, the product names manufactured by Nissan Chemical Co., Ltd.: Snowtex OXS ( _SiO2 solid content 10% by mass), Snowtex OS ( _SiO2 solid content 20% by mass), Snowtex O (SiO ₂ solids content 20% by weight), Snowtex O-40 ( _SiO2 solids content 40% by weight), Snowtex OL ( _SiO2 solids content 20% by weight), Snowtex OYL ( _SiO2 solids content 20% by weight), Snowtex Tex OUP ( _SiO2 solid content 15% by weight) and the like.
Examples of water-based colloidal silica exhibiting alkalinity include product names manufactured by Nissan Chemical Industries, Ltd.: Snowtex XS ( _SiO2 solid content: 20% by mass), Snowtex30 ( _SiO2 solid content: 30% by mass), Snowtex50-T. ( _SiO2 solids 48% by weight), Snowtex 30L ( _SiO2 solids 30% by weight), Snowtex UP ( _SiO2 solids 20% by weight), Snowtex NXS ( _SiO2 solids 15% by weight), Snow Tex NS (SiO ₂ solid content 20% by weight), Snowtex N (SiO ₂ solid content 20% by weight), Snowtex N-40 (SiO ₂ solid content 40% by weight) and the like.
Examples of cationic colloidal silica include product names manufactured by Nissan Chemical Industries, Ltd.: Snowtex AK ( _SiO2 solid content: 20% by mass), Snowtex AK-L ( _SiO2 solid content: 20% by mass), and Snowtex AK-YL. (SiO ₂ solid content 30% by mass).
As colloidal silica dispersed in an organic solvent, for example, the product name manufactured by Nissan Chemical Co., Ltd.: Organosilica sol IPA-ST (SiO ₂ solid content 30% by mass, solvent isopropyl alcohol), Methanol silica sol (SiO ₂ solid content 30% by mass, solvent methyl alcohol) and the like.
These colloidal silica may be used individually by 1 type, and may use 2 or more types together.

The method for impregnating colloidal silica is not particularly limited, but for example, a method of immersing a template precursor in colloidal silica (dipping method); Examples include a method of applying to the body.

The impregnated amount of colloidal silica is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and even more preferably 3 to 7% by mass. If the impregnated amount of colloidal silica is at least the above lower limit, the molar ratio (SiO ₂ /M) of SiO ₂ and M (M=K ₂ O or Na ₂ O) as the entire mold is sufficiently increased, and the heat resistance of the mold is increased. more improved. If the impregnated amount of colloidal silica is equal to or less than the above upper limit, the strength of the mold can be maintained without excessively increasing the molar ratio.
Hereinafter, the molar ratio (SiO ₂ /M) of SiO ₂ and M (M=K ₂ O or Na ₂ O) in the template as a whole is also referred to as the "molar ratio of the template".
The details of how to determine the impregnated amount of colloidal silica will be described in Examples described later.

The water glass is not particularly limited, and conventionally known ones can be used. For example, sodium silicate (specifically, Nos. 1, 2, and 3 described in JIS K 1408: 1966 and sodium metasilicate (types 1 and 2)), potassium silicate, and mixtures thereof can be used. can.
In addition, the molar ratio (SiO ₂ /M) of SiO ₂ and M (M=K ₂ O or Na ₂ O) in water glass is preferably 1.9 to 4.0, more preferably 2.0 to 3.5. It is preferably from 2.0 to 3.2, more preferably from 2.0 to less than 3.1, and most preferably from 2.1 to 3.0. If the molar ratio of water glass is at least the above lower limit, a sufficient curing speed can be obtained. If the molar ratio of water glass is equal to or less than the above upper limit, water glass is less likely to precipitate and the mold precursor is sufficiently impregnated with water glass.

The method of impregnating water glass is not particularly limited, but the same method as the impregnating method of colloidal silica can be used.
The impregnated amount of water glass is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and even more preferably 3 to 7% by mass. When the impregnated amount of water glass is at least the above lower limit, the molar ratio of the mold is sufficiently increased, and the heat resistance of the mold is further improved. If the impregnated amount of water glass is equal to or less than the above upper limit, it is possible to suppress the amount of alkali metal in the mold and prevent a decrease in the molar ratio of the mold.
The details of how to determine the impregnation amount of water glass will be described in Examples described later.

The order of impregnating the template precursor with colloidal silica and water glass is not particularly limited.
When the step of impregnating the template precursor with colloidal silica is referred to as “step (α)” and the step of impregnating the template precursor with water glass is referred to as “step (β)”, step (β ) may be performed, or step (α) may be performed after step (β). Also, the step (α) and the step (β) may be repeated.
From the viewpoint of further increasing the molar ratio of the template and further improving the heat resistance of the template, it is preferable to perform the step (β) after the step (α).

Moreover, a drying step may be performed between the step (α) and the step (β) or between the step (β) and the step (α). In particular, when the step (β) is performed after the step (α), the colloidal silica can sufficiently adhere to the refractory granular material, and the precipitation of the water glass on the mold surface can be suppressed. ) and step (β), a drying step is preferably carried out.
When the drying step is performed between the step (α) and the step (β), the drying temperature is preferably 100 to 200°C, more preferably 110 to 150°C, even more preferably 120 to 130°C. If the drying temperature is at least the above lower limit, removal of the solvent contained in the colloidal silica and hardening of the binder in the mold can be further enhanced. If the drying temperature is equal to or lower than the above upper limit, decomposition of the binder in the mold can be suppressed. The drying time is not particularly limited, and may be appropriately determined according to the shape and size of the mold.
When the drying step is performed between the step (β) and the step (α), the drying temperature is preferably 100 to 200°C, more preferably 110 to 150°C, even more preferably 120 to 130°C. If the drying temperature is at least the above lower limit, removal of the solvent contained in the water glass and hardening of the binder in the mold can be further enhanced. If the drying temperature is equal to or lower than the above upper limit, decomposition of the binder in the mold can be suppressed. The drying time is not particularly limited, and may be appropriately determined according to the shape and size of the mold.
When the drying step is performed, it is preferable to perform step (α) or step (β) after cooling the template precursor to room temperature (25° C.) after the drying step.

<Curing process>
The curing step is a step of curing the water glass impregnated with the mold precursor.
The curing temperature is preferably 100 to 300°C, more preferably 100 to 250°C, even more preferably 100 to 200°C. If the curing temperature is at least the above lower limit, the water glass will be sufficiently cured in a short time. If the drying temperature is equal to or lower than the above upper limit, the decomposition of the binder in the mold can be suppressed, and the strength at room temperature is excellent. In addition, when performing the drying process mentioned above, it is preferable that the curing temperature is higher than the drying temperature.
The curing time is not particularly limited, and may be appropriately determined according to the shape and size of the mold.

The molar ratio of the mold after the curing step is preferably 4-10, more preferably 5-9, even more preferably 6-8. When the molar ratio of the template is at least the above lower limit, the heat resistance of the template is further improved. As a result, the shape of the mold can be favorably maintained while maintaining strength to the extent that the mold can withstand exposure to high temperatures. In particular, even if the mold has a complicated shape, the shape can be maintained well. The higher the molar ratio of the mold, the higher the heat resistance tends to be, but if the molar ratio is too high, the adhesive strength as an inorganic binder may be lowered and the strength may be lowered. When the molar ratio of the mold is within the above range, the mold has an excellent balance between heat resistance and strength.
In particular, when the precursor template is produced by method (ii), the molar ratio of the template after the curing step is preferably 5-9, more preferably 5.5-7.
The details of how to determine the molar ratio of the template will be described in Examples described later.

After hardening the water glass, it is cooled to room temperature (25° C.) (cooling step) to obtain a mold (hardened body).
As a cooling method, a known method can be employed, and examples thereof include a method of natural cooling at room temperature, a method of forced cooling using air blowing, and the like.

The template (cured body) obtained in the curing step contains the cured organic binder and the cured inorganic binder (mainly the cured water glass). And its cured product may be thermally decomposed during pouring. Thermal decomposition of the organic binder and its cured product generates gas (pyrolysis gas), which may cause defects in castings and worsen the working environment due to odor.
Therefore, when it is desired to eliminate the organic binder and its cured product from the mold, it is preferable to carry out the baking step described later.
In addition, when performing a baking process after a hardening process, it is not necessary to provide a cooling process between a hardening process and a baking process.

<Baking process>
The baking step is a step of baking the mold (cured body) obtained in the curing step.
By performing the baking step, the organic binder contained in the cured body and its cured product are thermally decomposed and gasified, and are removed from the mold as thermal decomposition gas.
The mold (fired body) obtained in the firing step contains a hardened inorganic binder (mainly a hardened water glass).

The firing temperature may be determined according to the type of the organic binder contained in the cured body, but is preferably at least the decomposition temperature of the organic binder and preferably below the decomposition temperature of colloidal silica and water glass.
Specifically, the firing temperature is preferably 350 to 1000°C, more preferably 400 to 800°C. When the baking temperature is at least the above lower limit, the organic binder and its cured product are sufficiently thermally decomposed. If the firing temperature is equal to or lower than the above upper limit, colloidal silica and water glass, and hardened materials such as water glass, are less likely to be thermally decomposed.
The baking time is not particularly limited as long as the organic binder contained in the cured product and the cured product thereof are sufficiently thermally decomposed, and may be appropriately determined according to the shape and size of the mold.
As a method for baking the cured product, a known method can be employed, and examples thereof include a method using an electric furnace and an oven.

After baking the cured body, it is cooled to room temperature (25° C.) (cooling step) to obtain a mold (fired body).
As a cooling method, a known method can be employed, and examples thereof include a method of natural cooling at room temperature, a method of forced cooling using air blowing, and the like.

<Effect>
As described above, conventionally, a mold is produced by impregnating a mold (mold precursor) molded with an organic binder with water glass, or a mold is produced by three-dimensional additive manufacturing using water glass. It has been known. When the molar ratio of water glass is high, precipitation occurs, and the impregnability of water glass tends to decrease. Therefore, it is common to use water glass with a low molar ratio.
However, since water glass with a low molar ratio has a low melting point, a mold manufactured using water glass with a low molar ratio has low heat resistance and is not suitable for casting castings that require high pouring temperatures. be. If the heat resistance of the mold is low, casting defects and deformation such as seizure and glare may occur.

According to the mold manufacturing method of the present embodiment, colloidal silica and water glass are separately impregnated into a mold precursor made of an organic binder, so that the molar ratio of the mold is increased and a mold having excellent heat resistance can be produced. , the shape of the mold can be favorably maintained while maintaining strength to the extent that the mold can withstand exposure to high temperatures. Moreover, since it is not necessary to use water glass with a high molar ratio, the mold precursor can be sufficiently impregnated with water glass.

In the case of a method of manufacturing a casting mold by mixing a refractory granular material and a binding agent and filling the kneaded sand into a casting mold, it is also possible to use water glass with a high molar ratio as the binding agent. can. However, this method is unsuitable for manufacturing molds with complex shapes.
However, with the mold manufacturing method of the present embodiment, it is also possible to manufacture a mold precursor by three-dimensional layered manufacturing, and even a mold with a complicated shape can be easily manufactured.

Further, with the mold manufacturing method of the present embodiment, there is no need to increase the curing temperature in the curing step more than necessary, and the water glass is sufficiently cured at a relatively low temperature of, for example, about 100 to 300°C. Therefore, the organic binder and its cured product in the mold precursor are less likely to be thermally decomposed during the curing step, and the water glass, which is an inorganic binder, is hardened before the organic binder and its cured product are thermally decomposed. Cohesive force is sufficiently exerted, even a mold with a complicated shape is difficult to deform, and a mold with good dimensional accuracy can be easily obtained.
Moreover, if the baking process is performed after the curing process, the organic binder and its hardened material are sufficiently removed from the mold, so that the organic binder and its hardened material hardly generate thermal decomposition gas during casting. Therefore, the working environment during casting is favorable, and defects in castings caused by pyrolysis gas can be suppressed.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. The materials used in each example are shown below. Moreover, various measuring methods are as follows.

[Materials used]
As the refractory granular material, artificial sand obtained by a sintering method (containing 95% by mass of Al ₂ O ₃ —SiO ₂ , trade name “CB-X#1450” manufactured by Itochu Ceratec Co., Ltd., particle diameter 53 to 150 μm) was used.

As the organic binder, the following was used.
- Organic binder (i): 87.8 parts by mass of furfuryl alcohol, 10.0 parts by mass of bisphenol A, 2.0 parts by mass of resorcinol, and N-β (aminoethyl) γ-aminopropyl A furan-based binder which is a mixture with 0.2 parts by mass of methyldimethoxysilane.
・Organic binder (ii): 89.8 parts by mass of furfuryl alcohol, 10.0 parts by mass of resorcinol, and 0.2 parts by mass of N-β (aminoethyl)γ-aminopropylmethyldimethoxysilane A furan-based binder that is a mixture of

As the curing agent, the one shown below was used.
Curing agent (iii): an aqueous curing agent solution which is a mixture of 55 parts by mass of xylenesulfonic acid, 10 parts by mass of sulfuric acid, and 35 parts by mass of water.
Curing agent (iv): an aqueous curing agent solution which is a mixture of 60 parts by mass of xylenesulfonic acid and 40 parts by mass of water.

As colloidal silica, a dispersion of silica particles with an average particle size of 9 nm dispersed in water (manufactured by Nissan Chemical Industries, Ltd., trade name “Snowtex OS”, SiO ₂ solid content 20% by mass) was used.

As the water glass, the one shown below was used.
Water glass (v): water is added to an aqueous sodium silicate solution (molar ratio (SiO ₂ /Na ₂ O): 2.1) manufactured by Fuji Chemical Industry Co., Ltd., and the specific gravity at 25 ° C. becomes 1.242. Aqueous solution prepared as follows.
Water glass (vi): water is added to an aqueous sodium silicate solution (molar ratio (SiO ₂ /Na ₂ O): 2.3) manufactured by Fuji Chemical Industry Co., Ltd., and the specific gravity at 25 ° C. becomes 1.214. Aqueous solution prepared as follows.
Water glass (vii): water is added to an aqueous sodium silicate solution (molar ratio (SiO ₂ /Na ₂ O): 2.5) manufactured by Fuji Chemical Industry Co., Ltd., and the specific gravity at 25 ° C. becomes 1.210. Aqueous solution prepared as follows.
Water glass (viii): water is added to an aqueous sodium silicate solution (molar ratio (SiO ₂ /Na ₂ O): 2.7) manufactured by Fuji Chemical Industry Co., Ltd., and the specific gravity at 25 ° C. becomes 1.206. Aqueous solution prepared as follows.
Water glass (ix): water is added to an aqueous sodium silicate solution (molar ratio (SiO ₂ /Na ₂ O): 3.2) manufactured by Fuji Chemical Industry Co., Ltd., and the specific gravity at 25 ° C. becomes 1.174. Aqueous solution prepared as follows.

[Calculation method]
<Calculation of impregnation amount of colloidal silica>
The mass (W _A ) of the template precursor just prior to impregnation with colloidal silica was measured. The mass (W _B ) of the template precursor after being impregnated with colloidal silica and heat-treated was measured. The impregnation amount (S) of colloidal silica was obtained from the following formula (1).
Colloidal silica impregnation amount [% by mass] = (W _B -W _A )/W _A ×100 (1)

<Calculation of water glass impregnation amount>
The mass (W _C ) of the direct mold precursor before impregnation with water glass was measured. The mass (W _D ) of the template precursor after being impregnated with water glass and heat-treated was measured. The impregnation amount (G) of water glass was obtained from the following formula (2).
Water glass impregnation amount [mass%] = (W _D −W _C )/W _C ×100 (2)

<Calculation of total impregnation amount of colloidal silica and water glass>
If the mold is manufactured without a drying step between steps (α) and (β) or between steps (β) and (α), the total amount of colloidal silica and water glass is reduced as follows. It was calculated as an impregnation amount.
The mass (W _E ) of the template precursor just prior to impregnation with colloidal silica and water glass was measured. After one of colloidal silica and water glass was impregnated, the remaining one was impregnated, and the mass (W _F ) of the template precursor after heat treatment was measured. The impregnation amount of colloidal silica was obtained from the following formula (3).
Total impregnation amount [mass%] = ( _WF - _WE ) / _WE x 100 (3)

<Calculation of molar ratio of template>
The molar ratio (SiO ₂ /Na ₂ O) of the template (test piece) was obtained from the following formula (4). M1 in the following formula ( ₄ ) was obtained from the following formula (5), and _M2 in the following formula (4) was obtained from the following formula (6).
_SiO2 / _Na2O = _M2 /M1 ( ₄ )
M ₁ [mol]=(G/100)/(60.1×N+62.0) (5)
M ₂ [mol]=(M ₁ ×N)+{(S/100)/60.1} (6)
In the formulas (5) and (6), "N" is the molar ratio of water glass impregnated in the mold precursor, "G" is the impregnation amount of water glass, and "S" is colloidal silica. is the impregnation amount.

[Measuring method]
<Measurement of bending strength>
The bending strength of the test piece obtained in each example and comparative example was measured using the measuring method described in JACT test method SM-1.

<Measurement of gas generation amount>
The mold was heat-treated in an atmosphere of 1000° C. for 5 minutes, exposing the mold to the same atmosphere as when producing castings. The amount of gas generated during the heat treatment was measured according to JACT test method M-5 "Method for measuring the amount of gas generated".

[Example 1]
<Production of template precursor>
100 parts by mass of the refractory granular material and 0.3 parts by mass of the curing agent (iii) were put into a mixer and stirred for 1 minute. Subsequently, 1.5 parts by mass of the organic binder (i) was added, and the mixture was further stirred for 1 minute to obtain a mixture (A1-1).
The resulting mixture (A1-1) was immediately filled into a wooden mold for producing a mold precursor, which had a rectangular parallelepiped shape of 10 mm long, 60 mm wide and 10 mm high under conditions of a temperature of 25° C. and a humidity of 50%. After 3 hours from the start of curing, a rectangular parallelepiped mold precursor having a length of 10 mm, a width of 60 mm, and a height of 10 mm was removed (cutting time: 3 hours), temperature 25 ° C., humidity 50%. At the bottom, it was left for 24 hours from the start of curing.

<Production of test piece>
The mold precursor after standing was impregnated with colloidal silica at room temperature (25° C.) for 60 seconds (step (α)), and then heat-treated at 120° C. for 1 hour (drying step). After the drying step, the template precursor is cooled to room temperature (25°C), impregnated with water glass (v) at room temperature (25°C) for 60 seconds (step (β)), and then heat-treated at 200°C for 1 hour. (curing step). After the curing step, the mold precursor was cooled to room temperature (25° C.) to obtain a test piece (cured body).
The step (α) was performed by immersing the template precursor in colloidal silica, and the step (β) was performed by immersing the template precursor in water glass.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (hardened body) as a mold were calculated. Table 1 shows the results.
The bending strength and gas generation rate of the obtained test piece (cured body) were measured. Table 1 shows the results.
Separately, the test piece (cured body) was heat-treated for 5 minutes in an electric furnace set at 800°C. The bending strength of the test piece immediately after being taken out from the electric furnace was measured. Table 1 shows the results.

[Examples 2 to 5]
A test piece (cured body) was produced in the same manner as in Example 1, except that the types of water glass shown in Table 1 were used, and various measurements and the like were performed. Table 1 shows the results.

[Comparative Example 1]
A template precursor was produced in the same manner as in Example 1.
The mold precursor after standing was heat-treated at 120° C. for 1 hour and used as a test piece for various measurements. Table 2 shows the results.

[Comparative Example 2]
A test piece was produced in the same manner as in Example 1, except that the step (β) and the curing step were not performed, and various measurements and the like were performed. Table 2 shows the results.

[Comparative Examples 3 to 7]
A test piece was produced in the same manner as in Example 1, except that water glass of the type shown in Table 1 was used and the step (α) and the drying step were not performed, and various measurements and the like were performed. Table 2 shows the results.

From the results in Table 1, the test pieces (cured bodies) obtained in Examples 1 to 5 have high bending strength even when heat-treated at a high temperature of 800 ° C., and are heat resistant enough to withstand exposure to high temperatures. had sex. Further, no change in shape was observed even after heat treatment at a high temperature of 800°C.
On the other hand, from the results in Table 2, the test pieces obtained in Comparative Examples 1 and 2 collapsed when taken out from the electric furnace when heat-treated at a high temperature of 800 ° C. Therefore, the bending strength could not be measured, and the heat resistance was inferior to
When the test pieces obtained in Comparative Examples 3 to 7 were heat-treated at a high temperature of 800° C., they were deformed when they were taken out from the electric furnace.

[Examples 6 to 10]
A test piece (cured body) was produced in the same manner as in Example 1, except that the water glass of the type shown in Table 3 was used.
The obtained test piece (cured body) was heat-treated for 1 hour in an electric furnace set at 800° C. (baking step). Allow to cool until the temperature in the electric furnace reaches 32° C. In the meantime, leave the mold precursor after the firing step in the electric furnace, remove it from the electric furnace, further cool it to room temperature (25° C.), A test piece (fired body) was obtained.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (fired body) as a mold were calculated. Table 3 shows the results.
The bending strength and gas generation rate of the obtained test piece (fired body) were measured. Table 3 shows the results.
Separately, the test piece (fired body) was heat-treated for 5 minutes in an electric furnace set at 800°C. The bending strength of the test piece immediately after being taken out from the electric furnace was measured. Table 3 shows the results.

[Comparative Example 8]
A test piece (cured body) was produced in the same manner as in Example 1, except that water glass of the type shown in Table 3 was used and the step (α) and the drying step were not performed.
The obtained test piece (cured body) was heat-treated for 1 hour in an electric furnace set at 800° C. (baking step). Allow to cool until the temperature in the electric furnace reaches 32° C. In the meantime, leave the mold precursor after the firing step in the electric furnace, remove it from the electric furnace, further cool it to room temperature (25° C.), A test piece (fired body) was obtained.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (fired body) as a mold were calculated. Table 3 shows the results.
The bending strength and gas generation rate of the obtained test piece (fired body) were measured. Table 3 shows the results.
Separately, the test piece (fired body) was heat-treated for 5 minutes in an electric furnace set at 800°C. The bending strength of the test piece immediately after being taken out from the electric furnace was measured. Table 3 shows the results.

From the results in Table 3, the test pieces (fired bodies) obtained in Examples 6 to 10 have high bending strength even when heat-treated at a high temperature of 800 ° C., and are heat resistant enough to withstand exposure to high temperatures. had sex. Further, no change in shape was observed even after heat treatment at a high temperature of 800°C. In addition, the test pieces (fired bodies) obtained in Examples 6 to 10 generated less gas.
On the other hand, the test piece obtained in Comparative Example 8 had a lower bending strength after heat treatment at a high temperature of 800° C. than the test pieces obtained in Examples 6 to 10, and was inferior in heat resistance. .

[Example 11]
A test piece (cured body) was produced in the same manner as in Example 1, except that the water glass of the type shown in Table 4 was used, and various measurements and the like were performed. Table 4 shows the results.

[Example 12]
A test piece (cured body) was produced in the same manner as in Example 1, except that water glass of the type shown in Table 4 was used, and the order of step (α) and step (β) was changed, and various measurements were performed. gone. Table 4 shows the results.

[Example 13]
A test piece (cured body) was produced in the same manner as in Example 1, except that the type of water glass shown in Table 4 was used and the drying step between the steps (α) and (β) was not performed. Various measurements were performed. Table 4 shows the results.

[Example 14]
Example except that water glass of the type shown in Table 4 was used, the order of step (α) and step (β) was reversed, and the drying step between step (β) and step (α) was not performed. A test piece (cured body) was produced in the same manner as in 1, and various measurements and the like were performed. Table 4 shows the results.

From the results in Table 4, the test pieces (cured bodies) obtained in Examples 11 to 14 have high bending strength even when heat-treated at a high temperature of 800 ° C., and are heat resistant enough to withstand exposure to high temperatures. had sex.
In particular, the test pieces (cured bodies) obtained in Examples 11 and 13 did not change in shape even after being heat-treated at a high temperature of 800°C.
The test pieces (cured bodies) obtained in Examples 12 and 14 slightly changed in shape when heat-treated at a high temperature of 800° C., but this was of no practical problem.
In addition, the test piece (hardened body) obtained in Example 13 had some precipitates on the surface, but it was practically acceptable.

[Example 15]
<Production of template precursor>
100 parts by weight of the refractory particulate material was heated to 120°C. Next, 0.5 part by mass of the curing agent (iv) was added to the heated refractory granular material and stirred for 3 minutes to obtain a mixture (B-1).
Using a three-dimensional additive manufacturing apparatus using a printing method (product name "sand mold additive manufacturing apparatus SCM-800" manufactured by CMET Co., Ltd.), the mixture (B-1) is processed by a blade mechanism having a recoater. (step (a)). At this time, the shutter aperture of the recoater was set to 49.5°.
Next, on the layered mixture (B-1), the print nozzle head is scanned based on the data obtained by 3D CAD designing the shape of the template precursor, and the mixture (B-1) for one layer is scanned. The organic binder (ii) was printed at a discharge amount of 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material (step (b)). After printing the organic binder (ii), the bottom of the metal case (modeling table) is lowered by one layer (280 μm), and the mixture (B-1) is laminated in the same manner as above (step (a)), The organic binder (ii) was printed thereon at a discharge amount of 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material in the mixture (B-1) for one layer (step (b)). . After repeating these steps (a) and (b), the mixture (B-1) of the non-printed portion of the organic binder (ii) was removed with a brush, and a 10 mm long, 60 mm wide and 10 mm high A rectangular parallelepiped template precursor was obtained.

<Production of test piece>
After the mold precursor was impregnated with colloidal silica at room temperature (25° C.) for 60 seconds (step (α)), it was heat-treated at 120° C. for 1 hour (drying step). After the drying step, the template precursor is cooled to room temperature (25°C), impregnated with water glass (v) at room temperature (25°C) for 60 seconds (step (β)), and then heat-treated at 200°C for 1 hour. (curing step). After the curing step, the mold precursor was cooled to room temperature (25° C.) to obtain a test piece (cured body).
The step (α) was performed by immersing the template precursor in colloidal silica, and the step (β) was performed by immersing the template precursor in water glass.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (hardened body) as a mold were calculated. Table 5 shows the results.
The bending strength and gas generation rate of the obtained test piece (cured body) were measured. Table 5 shows the results.
Separately, the test piece (cured body) was heat-treated for 5 minutes in an electric furnace set at 800°C. The bending strength of the test piece immediately after being taken out from the electric furnace was measured. Table 5 shows the results.

[Example 16]
A test piece (cured body) was produced in the same manner as in Example 15.
The obtained test piece (cured body) was heat-treated for 1 hour in an electric furnace set at 800° C. (baking step). Allow to cool until the temperature in the electric furnace reaches 32° C. In the meantime, leave the mold precursor after the firing step in the electric furnace, remove it from the electric furnace, further cool it to room temperature (25° C.), A test piece (fired body) was obtained.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (fired body) as a mold were calculated. Table 5 shows the results.
The bending strength and gas generation rate of the obtained test piece (fired body) were measured. Table 5 shows the results.
Separately, the test piece (fired body) was heat-treated for 5 minutes in an electric furnace set at 800°C. The bending strength of the test piece immediately after being taken out from the electric furnace was measured. Table 5 shows the results.

[Comparative Example 9]
A template precursor was produced in the same manner as in Example 15.
A mold precursor was heat-treated at 120° C. for 1 hour and used as a test piece for various measurements. Table 5 shows the results.

[Comparative Example 10]
A test piece was produced in the same manner as in Example 15, except that the step (α) and the drying step were not performed, and various measurements and the like were performed. Table 5 shows the results.

From the results in Table 5, the test piece (cured body) obtained in Example 15 and the test piece (fired body) obtained in Example 16 had bending strength even after heat treatment at a high temperature of 800 ° C. It had high heat resistance to the extent that it could withstand exposure to high temperatures. Further, no change in shape was observed even after heat treatment at a high temperature of 800°C. In particular, the test piece (fired body) obtained in Example 16 produced a small amount of gas.
On the other hand, the test piece obtained in Comparative Example 9, when heat-treated at a high temperature of 800° C., collapsed when it was taken out from the electric furnace.
When the test piece obtained in Comparative Example 10 was heat-treated at a high temperature of 800° C., it was deformed when it was taken out from the electric furnace.

[Example 17]
A template precursor was produced in the same manner as in Example 15, except that the shape of the template precursor was 3D CAD designed to have the shape shown in FIG.
Using the obtained mold precursor, the test piece (cured body ) was manufactured.
The obtained test piece (cured body) was heat-treated for 1 hour in an electric furnace set at 800° C. (baking step). Allow to cool until the temperature in the electric furnace reaches 32° C. In the meantime, leave the mold precursor after the firing step in the electric furnace, remove it from the electric furnace, further cool it to room temperature (25° C.), A test piece (fired body) was obtained.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (fired body) as a mold were calculated. Table 6 shows the results.
A photograph of the obtained test piece (fired body) is shown in FIG. When the distance R2 in FIG. 2 was measured, it was 18.39 mm. The difference (R1-R2) between the distance R1 (20 mm) in FIG. 1 and the distance R2 (18.39 mm) in FIG.

[Comparative Example 11]
A template precursor was produced in the same manner as in Example 15, except that the shape of the template precursor was 3D CAD designed to have the shape shown in FIG.
Test piece (cured body) in the same manner as in Example 15 except that the obtained mold precursor was used, the curing time in the curing step was changed to 2.5 hours, and the step (α) and the drying step were not performed. manufactured.
The obtained test piece (cured body) was heat-treated for 1 hour in an electric furnace set at 800° C. (baking step). Allow to cool until the temperature in the electric furnace reaches 32° C. In the meantime, leave the mold precursor after the firing step in the electric furnace, remove it from the electric furnace, further cool it to room temperature (25° C.), A test piece (fired body) was obtained.
The impregnated amounts of colloidal silica and water glass and the molar ratio of a test piece (fired body) as a mold were calculated. Table 6 shows the results.
A photograph of the obtained test piece (fired body) is shown in FIG.

As shown in FIG. 2, although the test piece (cured body) obtained in Example 17 had a complicated shape, even when it was heat-treated at a high temperature of 800.degree. It was 61 mm and was difficult to deform.
On the other hand, as shown in FIG. 3, the test piece (cured body) obtained in Comparative Example 11 was greatly deformed when heat-treated at a high temperature of 800° C., and was inferior in heat resistance.

Claims (3)

an impregnation step of separately impregnating colloidal silica and water glass into a template precursor, which is a cured mixture of a refractory granular material and an organic binder;
a curing step of curing the water glass impregnated in the mold precursor;
A method of manufacturing a mold, comprising: The mold manufacturing method according to claim 1, further comprising a baking step after the curing step. The mold manufacturing method according to claim 1 or 2, wherein the mold precursor is manufactured by three-dimensional layered manufacturing.

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