WO2020196068A1 - Sand composition, method for producing same, and method for producing mold - Google Patents

Abstract

This sand composition contains a fire-resistant granular material, an acid catalyst, and inorganic fine particles having an average primary particle size of 5-500 nm. The content of the inorganic fine particles is preferably 0.1-2.0 parts by mass and the content of the acid catalyst is preferably 0.05-2.0 parts by mass with respect to 100 parts by mass of the fire-resistant granular material.

Description

Sand composition and its manufacturing method, and mold manufacturing method

The present invention relates to a sand composition, a method for producing the same, and a method for producing a mold.
The present application claims priority based on Japanese Patent Application No. 2019-064856 filed in Japan on March 28, 2019, the contents of which are incorporated herein by reference.

Conventionally, a self-hardening mold is known as one of casting molds (hereinafter, also simply referred to as "mold"). The self-hardening mold is a fire-resistant granular material such as silica sand, a binder containing furan resin as a main component (acid-curable binder), and an acid catalyst such as sulfuric acid or xylene sulfonic acid (hardener). Is added and kneaded, and then the obtained kneaded sand is filled in a wooden mold or resin mold (hereinafter, these are collectively referred to as "model"), and the binder is hardened. is there.

By the way, in order to manufacture a mold having a complicated shape, it is inevitably necessary to increase the number of models, but increasing the number of models causes complication of the process. Moreover, even if the number of models can be increased, the mold cannot be manufactured unless the mold can be removed from the model.
In order to solve such a problem, in recent years, a method for manufacturing a mold by three-dimensional laminated molding has been proposed, which enables direct manufacturing of a mold without using a model.

The three-dimensional laminated modeling is a method of manufacturing a mold or the like by directly using a three-dimensional shape input on a CAD (computer aided design) system as a three-dimensional model (three-dimensional model).
As a method for manufacturing a mold by three-dimensional laminated molding, kneaded sand containing a fire-resistant granular material and a liquid acid catalyst is laminated (recoated), and an acid-curable binder is printed on the kneaded sand based on CAD data. There is known a method of removing the kneaded sand in the non-printed portion after the acid-curable binder has hardened by repeating the operation.

As kneaded sand for three-dimensional laminated molding, natural silica sand, natural or artificial sand having a smaller linear thermal expansion than natural silica sand, and casting sand containing an acid catalyst are known (see Patent Document 1). ..

Japanese Patent No. 5249447

Depending on the type of refractory granular material, fluidity may be poor and recoating may be difficult. Therefore, in particular, refractory granular materials and kneaded sand used for three-dimensional laminated modeling are required to have excellent fluidity.
Further, the mold is required to have enough strength not to collapse during the casting operation.

However, the foundry sand described in Patent Document 1 does not necessarily have sufficient fluidity.
An object of the present invention is to provide a sand composition capable of producing a mold having practical strength and excellent fluidity, a method for producing the same, and a method for producing the mold.

The present invention has the following aspects.
[1] A sand composition containing a refractory granular material, an acid catalyst, and inorganic fine particles having an average primary particle diameter of 5 to 500 nm.
[2] The sand composition according to [1], wherein the content of the inorganic fine particles is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material.
[3] The sand composition according to [1] or [2], wherein the content of the acid catalyst is 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material.
[4] The sand composition according to [3], wherein the content of the acid catalyst is 0.15 to 0.3 parts by mass with respect to 100 parts by mass of the refractory granular material.
[5] The sand composition according to any one of [1] to [4], wherein the inorganic fine particles have an average primary particle diameter of 10 to 100 nm.
[6] The sand composition according to [5], wherein the inorganic fine particles have an average primary particle diameter of 30 to 100 nm.
[7] The sand composition according to any one of [1] to [6], wherein the inorganic fine particles are one or more selected from the group consisting of silica, titania and alumina.
[8] The sand composition according to [7], wherein the inorganic fine particles are at least one selected from the group consisting of precipitated silica, fumed silica, fumed titania and fumed alumina.
[9] The inorganic fine particles are hydrophilic silica, and the content of the hydrophilic silica is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the refractory granular material [7]. Alternatively, the sand composition according to [8].
[10] The inorganic fine particles are hydrophobic silica, and the content of the hydrophobic silica is 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the fire-resistant granular material [7]. Alternatively, the sand composition according to [8].
[11] The average primary particle size of the hydrophobic silica is 10 to 100 nm, and the content of the hydrophobic silica is 0.2 to 0.7 parts by mass with respect to 100 parts by mass of the refractory granular material. The sand composition according to [10].
[12] The inorganic fine particles are hydrophilic titania, and the content of the hydrophilic titania is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the fire-resistant granular material [7]. Alternatively, the sand composition according to [8].
[13] The inorganic fine particles are hydrophobic titania, and the content of the hydrophobic titania is 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the refractory granular material [7]. Alternatively, the sand composition according to [8].
[14] The inorganic fine particles are hydrophilic alumina, and the content of the hydrophilic alumina is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the refractory granular material [7]. Alternatively, the sand composition according to [8].
[15] The inorganic fine particles are hydrophobic alumina, and the content of the hydrophobic alumina is 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the refractory granular material [7]. Alternatively, the sand composition according to [8].
[16] The sand composition according to any one of [1] to [15], wherein the refractory granular material has an average particle size of 50 to 600 μm.
[17] The sand composition according to [16], wherein the refractory granular material has an average particle size of 75 to 150 μm.
[18] The sand composition according to any one of [1] to [17], wherein the inorganic fine particles satisfy the following condition (a).
Condition (a): The pH of the dispersion liquid in which the solvent and the inorganic fine particles are mixed so that the concentration of the inorganic fine particles is 4% by mass is 8.5 or less at 25 ° C. However, when the inorganic fine particles are hydrophilic, the solvent is water, and when the inorganic fine particles are hydrophobic, the solvent is a mixed solvent of water and methanol (mass ratio 1: 1).
[19] The sand composition according to any one of [1] to [18], wherein the acid catalyst is at least one selected from the group consisting of sulfuric acid, phosphoric acid, sulfonic acid and carboxylic acid.
[20] The sand composition according to [19], wherein the acid catalyst is one or more sulfonic acids selected from the group consisting of paratoluenesulfonic acid, xylenesulfonic acid, benzenesulfonic acid, and methanesulfonic acid.
[21] The sand composition according to any one of [1] to [20], further comprising a solvent.
[22] The sand composition according to [21], wherein the solvent is water.
[23] The sand composition according to [21] or [22], wherein the content of the solvent is 1.0 part by mass or less with respect to 100 parts by mass of the refractory granular material.
[24] The sand composition according to any one of [1] to [23], wherein the refractory granular material is at least one of natural sand and artificial sand.
[25] The sand composition according to any one of [1] to [24], which is used for three-dimensional laminated mold molding.
[26] The method for producing a sand composition according to any one of [1] to [25], wherein the refractory granular material, the acid catalyst, and the inorganic fine particles are mixed. Manufacturing method of things.
[27] The sand composition according to [26], wherein the mixture (1) is prepared by mixing the fire-resistant granular material and the acid catalyst, and then the obtained mixture (1) and the inorganic fine particles are mixed. Manufacturing method of things.
[28] The sand composition according to [26], wherein the mixture (2) is prepared by mixing the fire-resistant granular material and the inorganic fine particles, and then the obtained mixture (2) and the acid catalyst are mixed. Manufacturing method of things.
[29] The method for producing a sand composition according to any one of [1] to [25], wherein a solution of the acid catalyst is added to a heated refractory granular material, and further, the inorganic fine particles are added. A method for producing a sand composition.
[30] A method for producing a mold, wherein the sand composition according to any one of [1] to [25] is brought into contact with an acid-curable binder and cured.
[31] The method for producing a mold according to [30], wherein a mixture of the sand composition and the acid-curable binder is filled in a mold for molding to cure the acid-curable binder.
[32] The step (A) of laying the sand composition in layers and the sand laid in layers so as to bond the sand composition laid in layers corresponding to the target three-dimensional laminated mold molding. The composition includes a step (B) of selectively injecting the acid-curable binder into the composition to cure the composition, and the steps (A) and (B) are combined to form a target three-dimensional laminated mold molding. The method for producing a mold according to [30], which is repeated until the above.
[33] The method for producing a mold according to any one of [30] to [32], wherein the acid-curable binder contains at least one of furfuryl alcohol and furan resin.
[34] The method for producing a mold according to any one of [30] to [33], wherein the acid-curable binder contains a silane coupling agent.
[35] The template according to any one of [30] to [34], wherein the acid-curable binder contains one or more curing accelerators selected from the group consisting of resorcinol, formalin and furfural. Production method.

According to the present invention, it is possible to provide a sand composition having practical strength and excellent fluidity, a method for producing the same, and a method for producing the mold.

It is a graph which took the bending strength of the test piece in Examples 1-1 to 1-3 and Comparative Example 1-1 on the vertical axis. It is a graph which took the bending strength of the test piece in Example 2-1, 2-3, 2-5, and Comparative Example 2-1 on the vertical axis. 3 is a graph showing the bending strength of the test pieces in Examples 3-1 to 3-6 and Comparative Example 3-1 on the vertical axis. It is a photograph which shows the result of the slump test in the evaluation 1 of fluidity, (a) is comparative example 1-1, (b) is Example 1-1, (c) is Example 1-2, (d) is Examples 2-1 and (e) are Examples 2-2, (f) is Example 2-3, (g) is Example 2-4, (h) is Example 3-1 and (i) is. Examples 3-2 and (j) are Examples 3-3. It is a photograph showing the result of the slump test in the evaluation 2 of fluidity, (a) is Comparative Example 1-1, (b) is Example 1-3, and (c) is Example 2-3. It is a graph which took the bending strength of the test piece in Examples 4-1 to 4-6 and Comparative Example 4-1 on the vertical axis. It is a photograph showing the result of the slump test in the evaluation 1 of fluidity, (a) is Example 4-1, (b) is Example 4-2, (c) is Example 4-3, (d) is. Examples 4-4, (e) is Example 4-5, and (f) is Example 4-6. 6 is a graph showing the bending strength of the test pieces in Examples 5-1 to 5-5 and Comparative Example 5-1 on the vertical axis. It is a photograph which shows the result of the slump test in the evaluation 1 of fluidity, (a) is Example 5-1, (b) is Example 5-2, (c) is Example 5-3, (d) is Examples 5-4 and (e) are Examples 5-5. 6 is a graph showing the bending strength of the test pieces in Examples 6-1 to 6-6 and Comparative Example 6-1 on the vertical axis. It is a photograph showing the result of the slump test in the evaluation 1 of fluidity, (a) is Example 6-1, (b) is Example 6-2, (c) is Example 6-3, (d) is. Examples 6-4 and (e) are Examples 6-5, and (f) is Example 6-6. 6 is a graph showing the bending strength of the test pieces in Examples 7-1 to 7-6 and Comparative Example 7-1 on the vertical axis. It is a photograph which shows the result of the slump test in the evaluation 1 of fluidity, (a) is Example 7-1, (b) is Example 7-2, (c) is Example 7-3, (d) is. Examples 7-4 and (e) are Examples 7-5, and (f) is Example 7-6.

In the following specification, the "mold" is formed by using the sand composition of the present invention. Further, the case where a mold is manufactured by three-dimensional laminated molding is particularly referred to as "three-dimensional laminated mold molding", and the mold obtained by three-dimensional laminated mold molding is also referred to as "three-dimensional laminated molding mold".

[Sand composition]
The sand composition of the present invention contains a refractory granular material, an acid catalyst, and inorganic fine particles. The sand composition may contain a solvent.

<Fire resistant granular material>
As the fire-resistant granular material, conventionally known materials such as silica sand, chromate sand, zircon sand, olivine sand, amorphous silica, alumina sand, mullite sand and other natural sands can be used. Further, a material obtained by recovering a used refractory granular material (recovered sand) or a material regenerated (recycled sand) can also be used.
These refractory granular materials may be used alone or in combination of two or more.
Natural sand is preferable from the viewpoint of production cost, and silica sand is more preferable among them. Artificial sand is preferable from the viewpoint of being less likely to expand due to heat. In consideration of the balance between production cost and heat resistance, natural sand and artificial sand may be mixed and used.

The average particle size of the refractory granular material is preferably 50 to 600 μm, more preferably 60 to 500 μm, further preferably 70 to 300 μm, and particularly preferably 75 to 150 μm. When the average particle size of the refractory granular material is at least the above lower limit, the handling is excellent and the workability can be maintained well. When the average particle size of the refractory granular material is not more than the above upper limit, a mold having higher strength can be obtained. In addition, the surface properties of the casting cast using this mold are also excellent. In addition, the smaller the average particle size of the refractory granular material, the more suitable for the production of a three-dimensional laminated molding mold capable of directly producing the mold without using a mold, and the three-dimensional having excellent facetability. A laminated molding mold can be obtained. In particular, when the average particle size of the refractory granular material is 300 μm or less, a suitable sand composition can be obtained by producing a three-dimensional laminated molding mold.
The average particle size of the refractory granular material is a median diameter of 50% of the cumulative volume of the refractory granular material measured by the laser diffraction method.

<Acid catalyst>
The acid catalyst is a catalyst that cures an acid-curable binder that acts as a binder in the production of a mold.
Examples of the acid catalyst include sulfuric acid, phosphoric acid, sulfonic acid and carboxylic acid.
Examples of the sulfonic acid include paratoluenesulfonic acid, xylenesulfonic acid, benzenesulfonic acid, methanesulfonic acid and the like.
Examples of the carboxylic acid include lactic acid, citric acid, malic acid, tartaric acid, malonic acid, succinic acid, maleic acid, oxalic acid, acetic acid, and benzoic acid.
These acid catalysts may be used alone or in combination of two or more.
Xylene sulfonic acid is preferable because it has excellent performance as a curing agent.

The content of the acid catalyst is preferably 0.05 to 2.0 parts by mass, more preferably 0.05 to 1.0 parts by mass, and 0.1 to 0.7 parts by mass with respect to 100 parts by mass of the fire-resistant granular material. The parts by mass are more preferable, and 0.15 to 0.3 parts by mass are particularly preferable. When the content of the acid catalyst is at least the above lower limit value, the acid-curable binder can be sufficiently cured. When the content of the acid catalyst is not more than the above upper limit value, the generation of gas at the time of pouring can be reduced.

<Inorganic fine particles>
Examples of the inorganic fine particles include silica, titania, alumina, zeolite, silicate minerals such as kaolin, talc and mica, and diatomaceous earth.
These inorganic fine particles may be used alone or in combination of two or more.
Silica, titania, and alumina are preferable, silica is more preferable, and hydrophobic silica is further preferable, because dust is less likely to fly during the production of the sand composition and the production of the mold.

Silica may be amorphous or crystalline. Further, the silica may be natural silica or synthetic silica.
Examples of synthetic silica include wet silica such as precipitation silica and silica gel; dry silica such as fumed silica (flame hydrolysis silica), arc silica, plasma silica, and quartz glass (flame fused silica).
Among these, synthetic silica is preferable because it can be easily hydrophobized.

When titania is used as the inorganic fine particles, fumed titania is preferable.
When alumina is used as the inorganic fine particles, fumed alumina is preferable.

The inorganic fine particles may be hydrophilic or hydrophobic. The hydrophilic inorganic fine particles are those whose particle surface is not treated with a surface treatment agent. Hydrophobic inorganic fine particles have a particle surface treated with a surface treatment agent.
Examples of the surface treatment agent include hexamethyldisilazane, methyltrimethoxysilane, ethyltrimethoxysilane, dimethyldichlorosilane, and polydimethylsiloxane.

If the inorganic fine particles are hydrophilic silica, the fluidity of the sand composition can be improved with a smaller amount than that of hydrophobic silica while maintaining the strength of the mold.
If the inorganic fine particles are hydrophobic silica, the fluidity of the sand composition is improved. In addition, the interfacial strength (adhesive strength) between the refractory granular material and the acid-curable binder described later can be increased, and as a result, the strength of the mold is increased.

If the inorganic fine particles are hydrophilic titania, the fluidity of the sand composition is improved. In addition, the strength of the mold is increased.
If the inorganic fine particles are hydrophobic titania, the fluidity of the sand composition can be improved with a smaller amount than that of hydrophilic titania while maintaining the strength of the mold.

If the inorganic fine particles are hydrophilic alumina, the fluidity of the sand composition can be improved with a smaller amount than that of hydrophobic alumina. In addition, the strength of the mold is increased.
If the inorganic fine particles are hydrophobic alumina, the fluidity of the sand composition can be improved while maintaining the strength of the mold.

The average primary particle diameter of the inorganic fine particles is 5 to 500 nm, preferably 5 to 300 nm, more preferably 5 to 200 nm, further preferably 5 to 150 nm, further preferably 5 to 100 nm, particularly preferably 10 to 100 nm, and 30 to 100 nm. Most preferably 100 nm. When the average primary particle size of the inorganic fine particles is at least the above lower limit value, the fluidity of the sand composition can be improved while maintaining the strength of the mold. When the average primary particle size of the inorganic fine particles is not more than the above upper limit value, the fluidity of the sand composition can be maintained well. In particular, when the average primary particle diameter of the inorganic fine particles is 30 to 100 nm, the strength of the mold is increased.
The average primary particle size of the inorganic fine particles is a value obtained by measuring the particle size from an image observed on a transmission electron microscope and averaging the number of particles. Further, when the specific surface area and specific gravity of the inorganic fine particles are known, it is possible to substitute the values obtained by the following formula for convenience.

Generally, assuming that the radius of the sphere is r [m], the specific surface area is A [m ² / g], and the specific gravity is B, the specific surface area of the sphere can be obtained from the following equation (1). However, since the unit is converted here, the specific gravity is regarded as the density for convenience.
A [m ² / g] = surface area of sphere / weight of sphere ... (1)
Since the surface area of the sphere is 4πr ² [m ² ] and the weight of the sphere is the value obtained by multiplying the volume of the sphere (4 / 3πr ³ [m ³ ]) by the density, these are substituted into the above equation (1). Then, the following equation (2) holds.
A [m ² / g] = 4πr ² / (4 / 3πr ³ × B × 10 ³ ) = 3 / (r × B × 10 ³ ) ・ ・ ・ (2)
The equation (2) can be converted into the following equation (3).
r [m] = 3 / (B × 10 ³ × A) ・ ・ ・ (3)
Assuming that the primary particle diameter of the inorganic fine particles is regarded as the diameter of the sphere and the diameter of the sphere is D [nm], the following formula (4) is established from the above formula (3).
D [nm] = 2 x r x 10 ⁶ = 6 x 10 ⁶ / (B x 10 ³ x A) = 6 x 10 ³ / (B x A) ... (4)
Substituting the specific surface area of the inorganic fine particles into A of the above formula (4) and substituting the specific gravity of the inorganic fine particles into B of the above formula (4), the diameter D [nm] obtained is substituted as the average primary particle diameter of the inorganic fine particles. To do.

The inorganic fine particles preferably satisfy the following condition (a).
Condition (a): The pH of the dispersion liquid in which the solvent and the inorganic fine particles are mixed so that the concentration of the inorganic fine particles is 4% by mass is 8.5 or less at 25 ° C. However, when the inorganic fine particles are hydrophilic, the solvent is water, and when the inorganic fine particles are hydrophobic, the solvent is a mixed solvent of water and methanol (mass ratio 1: 1).
The higher the pH of the dispersion, the more the acid catalyst is consumed, the effect of the acid catalyst is not sufficiently exhibited, and the strength of the template tends to decrease. Even if the pH of the dispersion is high, the consumption of the acid catalyst can be reduced by increasing the amount of the acid catalyst, but if the amount of the acid catalyst is increased, gas is generated at the time of pouring and the working environment is deteriorated. When the pH of the dispersion is 8.5 or less, the consumption of the acid catalyst can be suppressed and a high-strength template can be obtained.
The pH of the dispersion is more preferably 7.5 or less, further preferably 7.0 or less, and particularly preferably 6.0 or less.
The pH of the dispersion is measured by mixing the solvent and the inorganic fine particles so that the concentration of the inorganic fine particles is 4% by mass, stirring at 25 ° C. and stabilizing the pH, and then using a pH meter.

The content of the inorganic fine particles is preferably 0.1 to 2.0 parts by mass, and more preferably 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the refractory granular material. When the content of the inorganic fine particles is at least the above lower limit value, the fluidity of the sand composition is improved. When the content of the inorganic fine particles is not more than the above upper limit value, the strength of the mold can be maintained.

When the inorganic fine particles are hydrophilic silica, the content of the hydrophilic silica is preferably 0.1 to 0.6 parts by mass and 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the refractory granular material. Parts by mass are more preferred.
When the inorganic fine particles are hydrophobic silica, the content of the hydrophobic silica is preferably 0.1 to 1.0 parts by mass and 0.3 to 0.9 parts by mass with respect to 100 parts by mass of the refractory granular material. Parts by mass are more preferred. In particular, the content of hydrophobic silica having an average primary particle diameter of 10 to 100 nm is preferably 0.2 to 0.7 parts by mass with respect to 100 parts by mass of the refractory granular material.

When the inorganic fine particles are hydrophilic titania, the content of hydrophilic titania is preferably 0.1 to 0.6 parts by mass and 0.3 to 0.5 parts by mass with respect to 100 parts by mass of the fire-resistant granular material. Parts by mass are more preferred.
When the inorganic fine particles are hydrophobic titania, the content of hydrophobic titania is preferably 0.1 to 0.5 parts by mass and 0.2 to 0.4 parts by mass with respect to 100 parts by mass of the refractory granular material. Parts by mass are more preferred.

When the inorganic fine particles are hydrophilic alumina, the content of hydrophilic alumina is preferably 0.1 to 0.6 parts by mass and 0.3 to 0.5 parts by mass with respect to 100 parts by mass of the refractory granular material. Parts by mass are more preferred.
When the inorganic fine particles are hydrophobic alumina, the content of hydrophobic alumina is preferably 0.1 to 0.5 parts by mass, and 0.2 to 0.4 parts by mass with respect to 100 parts by mass of the refractory granular material. Parts by mass are more preferred.

<Solvent>
Examples of the solvent include water, alcohol, and a mixture thereof. Examples of the alcohol include methanol, ethanol, 1-propanol, 2 propanol and the like.
Among these, water is preferable as the solvent.
In the present specification, the solvent contained in the sand composition generally refers to a solvent derived from an acid catalyst solution.

The content of the solvent is preferably 1.0 part by mass or less, more preferably 0.5 part by mass or less, further preferably 0.3 part by mass or less, and 0.1 part by mass with respect to 100 parts by mass of the refractory granular material. Part or less is particularly preferable. When the content of the solvent is 1.0 part by mass or less, the fluidity of the sand composition is further improved.
The content of the solvent is preferably more than 0 parts by mass, more preferably 0.01 parts by mass or more, based on 100 parts by mass of the refractory granular material.

<Manufacturing method>
The sand composition can be produced, for example, by mixing a refractory granular material, an acid catalyst, and inorganic fine particles. In the mixing step, the refractory granular material, the acid catalyst, and the inorganic fine particles may be mixed at the same time. Further, the mixture (1) may be prepared by mixing the fire-resistant granular material and the acid catalyst, and then the obtained mixture (1) and the inorganic fine particles may be mixed, or the fire-resistant granular material and the inorganic fine particles may be mixed. May be mixed to prepare a mixture (2), and then the obtained mixture (2) and an acid catalyst may be mixed. Further, the acid catalyst and the inorganic fine particles may be mixed in advance to prepare a mixture (3), and then the obtained mixture (3) and the refractory granular material may be mixed.
The acid catalyst is preferably dissolved in a solvent in advance and used, or when the acid catalyst is liquid at room temperature (25 ° C.), the acid catalyst is preferably diluted with a solvent before use.

In addition to the above-mentioned method, the sand composition can also be produced, for example, as follows.
A solution of the acid catalyst is prepared in advance. Examples of the solvent include the solvents exemplified above. When the acid catalyst is liquid at room temperature (25 ° C.), it is preferably diluted with the solvent.
The refractory granular material is then heated. The heating temperature is preferably higher than the boiling point of the solvent, and is usually 100 to 150 ° C.
The acid catalyst solution is then added to the heated refractory granular material. When a solution of the acid catalyst is added to the heated refractory granular material, the solvent volatilizes and the acid catalyst remains in the refractory granular material, and the acid catalyst is supported on the refractory granular material.
Next, inorganic fine particles are added to the refractory granular material on which the acid catalyst is supported to obtain a sand composition.
The sand composition produced by volatilizing the solvent is also referred to as "Catalyst Coated Sand (CCS)".

<Action effect>
As described above, the kneaded sand containing the refractory granular material and the liquid acid catalyst used in the conventional three-dimensional laminated mold molding and the like has a wet state, so that the fluidity tends to decrease.
However, since the sand composition of the present invention contains a specific amount of specific inorganic fine particles in addition to the refractory granular material and the acid catalyst, the agglomeration of the refractory granular material and the acid catalyst due to moisture absorption of the specific inorganic fine particles is present. Suppressed by presence.
Therefore, the sand composition of the present invention is excellent in fluidity. Moreover, the mold obtained from the sand composition of the present invention has practical strength.

By the way, when a mold is manufactured by three-dimensional laminated molding, it takes one hour or more, and in some cases, about 24 hours, depending on the size of the mold. Normally, the kneaded sand is stored in the hopper, and the hopper recoats the three-dimensional laminated molding apparatus while supplying a certain amount of the kneaded sand. Since the hopper is open, the kneaded sand will be exposed to air until the mold is completed.
However, the sand composition of the present invention can maintain fluidity for a long time due to the presence of specific inorganic fine particles even when exposed to air during mold production in addition to storage and transportation of the sand composition.

The sand composition of the present invention is suitable for producing a self-hardening mold, and is suitable not only for producing a mold using a mold but also for forming a three-dimensional laminated mold.

[Mold manufacturing method]
As a mold manufacturing method, a self-hardening mold molding method can be adopted. Specifically, the sand composition of the present invention is brought into contact with an acid-curable binder and cured to produce a mold.
Examples of the method for producing the mold include the following aspects.

<First Embodiment>
In the method for producing a mold of the present embodiment, a mixture of the sand composition of the present invention and an acid-curable binder is filled in a mold for molding, and the acid-curable binder is cured to produce a mold. The method.

(Acid-curing binder)
The acid-curable binder acts as a binder for refractory granular materials.
Examples of the acid-curable binder include furfuryl alcohol, furan resin, and resole-type phenol resin. These acid-curable binders may be used alone or in combination of two or more.
Of these, furfuryl alcohol and furan resin are preferable.

Furan resin is a resin whose main raw material is furfuryl alcohol, urea, formaldehyde, etc., and is polycondensed and cured while undergoing a dehydration reaction with an acid catalyst.
The furan resin contains one or more condensates or cocondensates of furfuryl alcohol or furfuryl alcohol and urea and aldehydes, and a mixture of furfuryl alcohol as a main component, if necessary. It is preferable to use one containing at least one of phenols and bisphenols.

Examples of phenols include phenol, cresol, resorcin, nonylphenol, cashew nut shell liquid (CNSL) and the like. These phenols may be used alone or in combination of two or more.
Examples of bisphenols include bisphenol A, bisphenol F, bisphenol C, bisphenol S, bisphenol E, and bisphenol Z. These bisphenols may be used alone or in combination of two or more.

Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, furfural, glyoxal, glutaraldehyde, dialdehyde phthalate and the like. These aldehydes may be used alone or in combination of two or more. However, depending on the type of condensate, acid curing may not proceed when glyoxal or furfural is used alone as aldehydes. In such a case, at least formaldehyde may be used as the aldehydes.

When producing a condensate or copolymer of furfuryl alcohol and aldehydes, it is preferable to use 0.1 to 1 mol of aldehydes with respect to 1 mol of furfuryl alcohol. When the amount of aldehydes used is not less than the above lower limit, the condensate has a low degree of polymerization, so that the pot life can be set more easily. On the other hand, when the amount of aldehydes used is not more than the above upper limit value, the condensate has a high degree of polymerization, so that the final template strength expression becomes better.

When producing a condensate or cocondensate of urea and aldehydes, it is preferable to use 1 to 3 mol of aldehydes with respect to 1 mol of urea, more preferably 1.3 to 2.5 mol. Yes, more preferably 1.5 to 2 mol.

The nitrogen atom content derived from urea or the like is preferably in the range of 0.1 to 6% by mass, preferably 0.1 to 4.5% by mass, based on the total mass of the furan resin. Is more preferable.
The nitrogen atom content affects the initial strength and final strength of the template. When the nitrogen atom content is low, the initial strength of the template tends to be high, and when the nitrogen atom content is high, the template tends to be high. The final strength tends to be high.
Therefore, it is preferable to appropriately adjust the nitrogen atom content as necessary, and if the nitrogen atom content is within the above range, it is possible to obtain a template in which both the initial strength and the final strength are preferable.

The following two are particularly preferable embodiments of the furan resin. In the following, the (co) condensate means at least one of the condensate and the cocondensate.
i) A (co) condensate (a) obtained by condensing urea, furfuryl alcohol and aldehydes, and a mixture of furfuryl alcohol and, if necessary, at least one of phenols and bisphenols.
ii) A mixture of a condensate of urea and aldehydes, furfuryl alcohol and, if necessary, at least one of phenols and bisphenols.

When the furan resin has such aspects i) to ii), the pot life can be set more easily and the mold strength can be further improved.
In the aspect of i), the ratio of the (co) condensate (a) to the furan resin is preferably 5 to 90% by mass, more preferably 10 to 80% by mass. The ratio of furfuryl alcohol is preferably 10 to 95% by mass, more preferably 20 to 90% by mass.
In the aspect of ii), the ratio of the condensate of urea and aldehydes to the furan resin is preferably 3 to 30% by mass, and more preferably 5 to 20% by mass. The ratio of furfuryl alcohol is preferably 70 to 97% by mass, more preferably 80 to 95% by mass.
In the embodiments i) to ii), the ratio of at least one of the phenols and the bisphenols to the furan resin is preferably 40% by mass or less, and more preferably 1 to 30% by mass.

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

The furan resin can be obtained by a general production method. An example is shown below.
First, a part of the raw material of the furan resin (furfuryl alcohol, aldehydes, urea, etc.) is mixed with an aqueous solution of sodium hydroxide or the like to make it alkaline, and the temperature is raised to generate an adduct with the aldehydes. Next, the reaction solution is acidified with hydrochloric acid or the like to allow the reaction such as condensation of furfuryl alcohol, urea and aldehydes to proceed, and then the reaction solution is made alkaline again, and the remaining furan resin raw material and necessary The silane coupling agent is mixed accordingly to obtain a mixture containing the furan resin, water and optionally the silane coupling agent. The obtained mixture may be used as it is as an acid-curable binder.
Since the amount of hydrochloric acid added here is small, it does not proceed to the curing reaction. Further, the unreacted furfuryl alcohol plays a role of a diluent for lowering the viscosity of the entire furan resin, and in the curing reaction, it is resinified as a component constituting the cured product to become a cured product.

The acid-curable binder may contain a silane coupling agent for the purpose of increasing the strength of the mold.
Examples of the silane coupling agent include N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ-glycidoxy. Examples thereof include propyltrimethoxysilane.
When the acid-curable binder contains a silane coupling agent, the content of the silane coupling agent is preferably 0.01 to 3% by mass with respect to the total mass of the solid content of the acid-curable binder. More preferably 0.1 to 2% by mass. When the content of the silane coupling agent is at least the above lower limit value, 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 easily obtained as the content of the silane coupling agent increases, but even if the amount is increased too much, the effect only reaches a plateau. Therefore, the content of the silane coupling agent is preferably 3% by mass or less.
The solid content of the acid-curable binder indicates a non-volatile content at 100 ° C.

The acid-curable binder may contain a curing accelerator for the purpose of increasing the curing rate.
Examples of the curing accelerator include resorcinol, formalin, furfural and the like. Among these, resorcinol is preferable because it also has the effect of reducing formaldehyde generated during molding.
When the acid-curable binder contains a curing accelerator, the content of the curing accelerator is preferably 1 to 20% by mass, preferably 5 to 15% by mass, based on the total mass of the solid content of the acid-curable binder. % Is more preferable. When the content of the curing accelerator is at least the above lower limit value, the curing rate is sufficiently increased. The curing rate tends to be more easily obtained as the content of the curing accelerator increases, but if it is increased too much, the effect will only reach a 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.

The acid-curable binder may contain water.
When the acid-curable binder contains water, the content of water is preferably 1 to 35% by mass, more preferably 5 to 30% by mass, based on the total mass of the acid-curable binder.

The mixing ratio of the acid-curable binder is preferably 0.3 to 2.0 parts by mass, preferably 0.5 to 1.8 parts by mass, based on 100 parts by mass of the refractory granular material in the sand composition in terms of solid content. More preferred. When the blending ratio of the acid-curable binder is equal to or higher than the above lower limit, a template having high strength can be easily obtained. When the compounding ratio of the acid-curable binder is not more than the above upper limit, the mold after pouring can be easily disassembled. In addition, the amount of gas generated due to thermal decomposition of the acid-curable binder at the time of pouring can be reduced.

<Second embodiment>
The method for producing a mold of the present embodiment includes a step of laying the sand composition of the present invention in layers (hereinafter, also referred to as "step (A)") and a three-dimensional lamination of the sand composition laid in layers for the purpose. A step (hereinafter, also referred to as “step (B)”) of selectively injecting an acid-curable binder onto the sand composition spread in layers so as to bond to the molded product. ), And the steps (A) and (B) are repeated until the target three-dimensional laminated mold model is formed to manufacture the mold.
Examples of the acid-curable binder include the acid-curable binder exemplified above in the description of the first embodiment.

The step (A) and the step (B) are carried out as follows, for example, by using a three-dimensional laminating apparatus using a printing modeling method.
The three-dimensional stacking device preferably includes a blade mechanism, a printing nozzle head mechanism, and a modeling table mechanism. Further, it is preferable to include a control unit that controls the operation of each mechanism by using the three-dimensional data of the modeling object.
The blade mechanism includes a recoater and is a structure in which a sand composition is laminated to a predetermined thickness on the bottom surface of a metal case or an upper layer of a shaped portion already bonded with an acid-curable binder.
The printing nozzle head mechanism prints the laminated sand composition with an acid-curable binder and binds the sand composition to form each layer.
When the modeling of one layer is completed, the modeling table mechanism is lowered by the distance of one layer to realize laminated modeling with a predetermined thickness.

First, using a three-dimensional laminating device using a printing modeling method, the sand composition is laminated on the bottom surface of a metal case installed in the three-dimensional laminating device by a blade mechanism having a recorder (step (A)). Then, the print nozzle head is scanned by the print nozzle head mechanism based on the data obtained by 3DCAD designing the shape of the target three-dimensional laminated model (three-dimensional laminated molding mold) on the laminated sand composition. Then, the acid-curable binder is printed (injected) (step (B)). The bottom of the metal case is a modeling table that can be moved up and down. After printing the acid-curable binder, the bottom surface (modeling table) of the metal case is lowered by one layer, and the sand composition is laminated in the same manner as before (step (A)), and the acid-curable viscosity is formed therein. The binder is printed (step (B)). These laminating and printing operations are repeated until the desired three-dimensional laminated mold model is formed. The thickness of the layer is preferably 100 to 500 μm, more preferably 200 to 300 μm.

The coating amount when printing the acid-curable binder is 0.4 to 10 parts by mass when the mass of the sand composition for one layer in the printing area is 100 parts by mass in terms of solid content. The amount is preferable, and the coating amount of 0.8 to 5 parts by mass is more preferable.

<Action effect>
According to the method for producing a mold of the present invention described above, since the sand composition of the present invention is used, a mold having practical strength can be produced.
Moreover, since the sand composition of the present invention has excellent fluidity, it is easy to recoat when manufacturing a mold by three-dimensional laminated mold molding. Moreover, the sand composition in the portion where the acid-curable binder is not printed is in an unbonded state and maintains fluidity, so that it can be easily removed with a brush, a vacuum cleaner, or the like.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. The refractory granular material, acid catalyst, inorganic binder and acid curable binder used in each example are shown below. In addition, various measurement methods and evaluation methods are as follows.

<Fire resistant granular material>
As the refractory granular material, artificial sand (manufactured by Ito Kiko Co., Ltd., "Alsand S # 1000", average particle size 120 μm, free moisture 0%) obtained by the melting method was used.

<Acid catalyst>
As the acid catalyst, a mixture of 60 parts by mass of xylene sulfonic acid and 40 parts by mass of water (a solution of an acid catalyst having a concentration of 60% by mass) was used.

<Inorganic fine particles>
As the inorganic fine particles, those shown below were used. The average primary particle diameter of each inorganic fine particle other than hydrophilic silica (vi) and hydrophobic silica (vii) was substituted from the catalog value. The average primary particle size of the hydrophilic silica (vi) and the hydrophobic silica (vii) was determined from the above formula (4) using the specific surface area and specific gravity indicated by the manufacturer.
Hydrophilic silica (i): fumed silica (trade name "AEROSIL 200" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 12 nm, pH of the dispersion liquid = 4.0 to 4.5).
Hydrophilic silica (ii): fumed silica (trade name "AEROSIL VP SG40" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 80 to 100 nm, pH of the dispersion liquid = 4.51).
Hydrophobic silica (iii): fumed silica (trade name "AEROSIL RX200" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 12 nm, pH of the dispersion liquid = 5.5 to 8.5).
Hydrophobic silica (iv): fumed silica (trade name "AEROSIL RX50" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 40 nm, pH of the dispersion liquid = 6.0 to 8.0).
Hydrophobic silica (v): fumed silica (trade name "AEROSIL VP RX40 S" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 80 to 100 nm, pH of the dispersion liquid = 6.06).
-Hydrophilic silica (vi): Precipitated silica (trade name "Nipsil E-150J" manufactured by Toso Silica Co., Ltd., specific surface area = 100 m ² / g, specific gravity = 2, average primary particle size = 30 nm, the dispersion Liquid pH = 7.0).
Hydrophobic silica (vii): Precipitation silica (trade name "Nipsil SS-30P" manufactured by Toso Silica Co., Ltd., specific surface area = 110 m ² / g, specific gravity = 2, average primary particle size = 27 nm, the dispersion Liquid pH = 7.5).
Hydrophilic titania (viii): Fume de titania (trade name "AEROXIDE TiO ₂ P90" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 14 nm, pH of the dispersion liquid = 3.2 to 4.5).
Hydrophobic titania (ix): Fume de titania (trade name "AEROXIDE TiO ₂ NKT90" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 14 nm, pH of the dispersion liquid = 3.0 to 4.0).
Hydrophilic alumina (x): fumed alumina (trade name "AEROXIDE Alu C" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 13 nm, pH of the dispersion liquid = 4.5 to 5.5).
Hydrophobic alumina (xi): fumed alumina (trade name "AEROXIDE Alu C805" manufactured by Nippon Aerosil Co., Ltd., average primary particle size = 13 nm, pH of the dispersion liquid = 3.0 to 4.5).

<Acid-curable binder>
As the acid-curable binder, a mixture of 89.9 parts by mass of furfuryl alcohol, 10 parts by mass of resorcinol, and 0.2 parts by mass of N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane was used.

<Measurement / evaluation>
(Measurement of pH of dispersion)
For the hydrophobic silica (v), the pH of the dispersion was measured as follows. The pH of the dispersion in the remaining inorganic fine particles was substituted from the catalog value.
A mixed solvent of water and methanol (mass ratio 1: 1) and hydrophobic silica (v) are mixed and stirred at 25 ° C. so that the concentration of hydrophobic silica (v) is 4% by mass. After stabilization, the pH of the dispersion was measured at 25 ° C. using a pH meter.

(Measurement of flexural strength)
The flexural strength of the test pieces obtained in each Example and Comparative Example was measured by using the measuring method described in the JACT test method SM-1.

(Evaluation of liquidity 1)
The fluidity of the sand composition was evaluated based on the slump test.
For the slump test, a slump cone having an upper bottom diameter of 58 mm, a lower bottom diameter of 85 mm, and a height of 140 mm was used.
After filling the slump cone with the sand composition obtained in each Example and Comparative Example, the state (collapse condition) of the sand composition when the slump cone was gently pulled up vertically was visually confirmed, and the following The fluidity of the sand composition was evaluated according to the evaluation criteria.
⊚: The sand composition is smooth.
〇: The sand composition is slightly agglomerated.
Δ: The sand composition is slightly agglomerated.
X: The sand composition is agglomerated.

(Evaluation of liquidity 2)
After filling the slump cone with the sand composition, it was stored for 24 hours in an atmosphere of a temperature of 25 ° C. and a humidity of 50%. After that, the state (collapse condition) of the sand composition when the slump cone was gently pulled up vertically was visually confirmed, and the fluidity of the sand composition was evaluated according to the same evaluation criteria as in the evaluation 1 of fluidity. ..

[Example 1-1]
0.1 part by mass of hydrophilic silica (i) was added to 100 parts by mass of the refractory granular material, and the mixture was stirred for 1 minute to obtain a mixture. 0.3 parts by mass of an acid catalyst solution was added to the obtained mixture, and the mixture was stirred for 1 minute to obtain a sand composition. In the obtained sand composition, the content of the acid catalyst is 0.18 parts by mass with respect to 100 parts by mass of the refractory granular material, and the content of the hydrophilic silica (i) is 0.1 parts by mass.
The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (b).

An acid-curable binder was added to the obtained sand composition, and the mixture was stirred for 1 minute to obtain kneaded sand. The amount of the acid-curable binder added was 1.7 parts by mass with respect to 100 parts by mass of the refractory granular material in the sand composition.
The obtained kneaded sand was immediately filled into a wooden mold for making a test piece in which six rectangular parallelepiped molds having a length of 10 mm, a width of 60 mm and a depth of 10 mm were formed under the conditions of a temperature of 25 ° C. and a humidity of 50% and cured. After 180 minutes from the start of curing, 6 test pieces were taken out (molding time 180 minutes).
The six test pieces taken out were left to stand for 24 hours from the start of curing under the conditions of a temperature of 25 ° C. and a humidity of 50%.
The bending strength of 3 test pieces out of the 6 test pieces after being left to stand was measured, and the average value was calculated. The results are shown in Table 1 and FIG.
The remaining three test pieces were dried at a temperature of 100 ° C. for 20 minutes, cooled to 25 ° C., and then the bending strength was measured, and the average value was calculated. The results are shown in Table 1 and FIG.

[Example 1-2]
A sand composition was prepared in the same manner as in Example 1-1 except that the amount of hydrophilic silica (i) added was changed to 0.2 parts by mass. The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (c).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 1 and FIG.

[Example 1-3]
A sand composition was prepared in the same manner as in Example 1-1 except that the amount of hydrophilic silica (i) added was changed to 0.3 parts by mass. The obtained sand composition was subjected to a slump test based on the evaluation 2 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 5 and FIG. 5 (b).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 1 and FIG.

[Comparative Example 1-1]
0.3 parts by mass of an acid catalyst solution was added to 100 parts by mass of a refractory granular material, and the mixture was stirred for 1 minute to obtain a sand composition. In the obtained sand composition, the content of the acid catalyst is 0.18 parts by mass with respect to 100 parts by mass of the refractory granular material, and the content of the inorganic fine particles is 0 parts by mass. The obtained sand composition was subjected to a slump test based on the evaluations 1 and 2 of the fluidity to evaluate the fluidity of the sand composition. The results are shown in Tables 4 and 5, (a) in FIG. 4, and (a) in FIG.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 1 and FIG.

[Example 2-1]
A sand composition was prepared in the same manner as in Example 1-1, except that hydrophobic silica (iii) was used instead of hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (d).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 2 and FIG.

[Example 2-2]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iii) was used instead of hydrophilic silica (i) and the amount added was changed to 0.2 parts by mass. .. The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (e).

[Example 2-3]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iii) was used instead of hydrophilic silica (i) and the amount added was changed to 0.3 parts by mass. .. The obtained sand composition was subjected to a slump test based on the evaluations 1 and 2 of the fluidity to evaluate the fluidity of the sand composition. The results are shown in Tables 4 and 5, (f) in FIG. 4, and (c) in FIG.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 2 and FIG.

[Example 2-4]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iii) was used instead of hydrophilic silica (i) and the amount added was changed to 0.4 parts by mass. .. The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (g).

[Example 2-5]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iii) was used instead of hydrophilic silica (i) and the amount added was changed to 0.5 parts by mass. ..
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 2 and FIG.

[Comparative Example 2-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 2 and FIG.

[Example 3-1]
A sand composition was prepared in the same manner as in Example 1-1, except that hydrophobic silica (iv) was used instead of hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (h).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Example 3-2]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iv) was used instead of hydrophilic silica (i) and the amount added was changed to 0.3 parts by mass. .. The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (i).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Example 3-3]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iv) was used instead of hydrophilic silica (i) and the amount added was changed to 0.5 parts by mass. .. The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Table 4 and FIG. 4 (j).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Example 3-4]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iv) was used instead of hydrophilic silica (i) and the amount added was changed to 0.7 parts by mass. ..
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Example 3-5]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iv) was used instead of hydrophilic silica (i) and the amount added was changed to 0.9 parts by mass. ..
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Example 3-6]
A sand composition was prepared in the same manner as in Example 1-1 except that hydrophobic silica (iv) was used instead of hydrophilic silica (i) and the amount added was changed to 1.1 parts by mass. ..
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

[Comparative Example 3-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 3 and FIG.

From the results of Tables 1 to 3 and FIGS. 1 to 3, a test piece having practical strength could be produced from the sand composition obtained in each example. In particular, when hydrophobic fumed silica is used as the inorganic fine particles (Examples 2-1, 2-3, 2-5, Examples 3-1 to 3-6), the inorganic fine particles are not used (Examples 2-1 and 2-3, 2-5). A test piece having a higher strength than that of Comparative Examples 2-1 and 3-1) was obtained.
In Comparative Examples 1-1, 2-1 and 3-1 the bending strength of the test piece was measured on different days, so the measurement results are different.
In Examples 1-1 to 1-3 and Comparative Example 1-1, the bending strength of the test piece was measured on the same day.
In Examples 2-1, 2-3, 2-5 and Comparative Example 2-1 the bending strength of the test piece was measured on the same day.
In Examples 3-1 to 3-6 and Comparative Example 3-1, the bending strength of the test piece was measured on the same day.

Further, from the results of Table 4 and FIG. 4, the sand composition obtained in each example was superior in fluidity to the sand composition obtained in Comparative Example 1-1. In particular, when hydrophilic fumed silica is used as the inorganic fine particles (Examples 1-1 and 1-2), when hydrophobic fumed silica is used (Examples 2-1 to 2-4, 3). Excellent fluidity could be exhibited with a small amount as compared with -1 to 3-3).
Furthermore, from the results of Table 5 and FIG. 5, the sand composition obtained in each example has excellent fluidity over time, and is not only used during storage and transportation of the sand composition, but also during mold production. It has been shown that fluidity can be maintained even when exposed to air.
In Examples 2-1 to 2-5 and 3-1 to 3-6, it was confirmed that dust was less likely to fly during the production of the sand composition and the production of the mold.

[Examples 4-1 to 4-3]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophilic silica (ii) shown in Table 6 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 6 and 7 (a) to (c).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 6 and FIG.

[Examples 4-4 to 4-6]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophobic silica (v) shown in Table 6 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 6 and 7 (d) to (f).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 6 and FIG.

[Comparative Example 4-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 6 and FIG.

From the results of Table 6 and FIG. 6, from the sand composition obtained in each example, a test piece having higher strength than that of Comparative Example 4-1 in which the inorganic fine particles were not used was obtained. In particular, when hydrophobic fumed silica is used as the inorganic fine particles (Examples 4-4 to 4-6), compared to the case where hydrophilic fumed silica is used (Examples 4-1 to 4-3). However, a stronger test piece was obtained. Further, comparing Examples 1-1 to 1-3 using hydrophilic fumed silica and Examples 4-1 to 4-3, hydrophilic fumed silica having a large average primary particle size is used. The strength of the test piece was higher in Examples 4-1 to 4-3.
In Comparative Examples 1-1 and 4-1 the bending strength of the test piece was measured on different days, so the measurement results are different.
In Examples 4-1 to 4-6 and Comparative Example 4-1, the bending strength of the test piece was measured on the same day.

Further, from the results of Table 6 and FIG. 7, the sand composition obtained in each example was superior in fluidity to the sand composition obtained in Comparative Example 1-1. In particular, when hydrophilic fumed silica is used as the inorganic fine particles (Examples 4-1 to 4-3), when hydrophobic fumed silica is used (Examples 4-4 to 4-6). Excellent fluidity could be exhibited with a smaller amount.

[Examples 5-1 and 5-2]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophilic silica (vi) shown in Table 7 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 7 and 9 (a) and 9 (b).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 7 and FIG.

[Examples 5-3 to 5-5]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophobic silica (vii) shown in Table 7 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 7 and 9 (c) to 9 (e).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 7 and FIG.

[Comparative Example 5-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 7 and FIG.

From the results shown in Table 7 and FIG. 8, a test piece having practical strength could be produced from the sand composition obtained in each example.
In Comparative Examples 1-1 and 5-1 the bending strength of the test piece was measured on different days, so the measurement results are different.
In Examples 5-1 to 5-5 and Comparative Example 5-1, the bending strength of the test piece was measured on the same day.

Further, from the results of Table 7 and FIG. 9, the sand composition obtained in each example was superior in fluidity to the sand composition obtained in Comparative Example 1-1. In particular, when hydrophilic sedimentation silica is used as the inorganic fine particles (Examples 5-1 and 5-2), when hydrophobic precipitation silica is used (Examples 5-3 to 5-5). Excellent fluidity could be exhibited with a smaller amount.

[Examples 6-1 to 6-3]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophilic titania (viii) shown in Table 8 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 8 and 11 (a) to (c).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 8 and FIG.

[Examples 6-4 to 6-6]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophobic titania (ix) shown in Table 8 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 8 and 11 (d) to (f).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 8 and FIG.

[Comparative Example 6-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 8 and FIG.

From the results shown in Table 8 and FIG. 10, a test piece having practical strength could be produced from the sand composition obtained in each example. In particular, when hydrophilic fume dotitania is used as the inorganic fine particles (Examples 6-1 to 6-3), the test piece has higher strength than when the inorganic fine particles are not used (Comparative Example 6-1). was gotten.
Since the flexural strengths of the test pieces were measured on different days in Comparative Examples 1-1 and 6-1, the measurement results were different.
In Examples 6-1 to 6-6 and Comparative Example 6-1, the bending strength of the test piece was measured on the same day.

Further, from the results of Table 8 and FIG. 11, the sand composition obtained in each example was superior in fluidity to the sand composition obtained in Comparative Example 1-1. In particular, when hydrophobic fume de titania is used as the inorganic fine particles (Examples 6-4 to 6-6), when hydrophilic fume de titania is used (Examples 6-1 to 6-3). Excellent fluidity could be exhibited with a smaller amount.

[Examples 7-1 to 7-3]
A sand composition was prepared in the same manner as in Example 1-1, except that the amount of hydrophilic alumina (x) shown in Table 9 was used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 9 and 13 (a) to 13 (c).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 9 and FIG.

[Examples 7-4 to 7-6]
A sand composition was prepared in the same manner as in Example 1-1, except that the amounts of hydrophobic alumina (xi) shown in Table 9 were used instead of the hydrophilic silica (i). The obtained sand composition was subjected to a slump test based on the evaluation 1 of fluidity, and the fluidity of the sand composition was evaluated. The results are shown in Tables 9 and 13 (d) to (f).
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 9 and FIG.

[Comparative Example 7-1]
A sand composition was prepared in the same manner as in Comparative Example 1-1.
Kneaded sand and a test piece were produced in the same manner as in Example 1-1 except that the obtained sand composition was used, and the bending strength was measured. The results are shown in Table 9 and FIG.

From the results shown in Table 9 and FIG. 12, a test piece having practical strength could be produced from the sand composition obtained in each example. In particular, when hydrophilic fumed alumina is used as the inorganic fine particles (Examples 7-1 to 7-3), the test piece has higher strength than when the inorganic fine particles are not used (Comparative Example 7-1). was gotten.
In Comparative Examples 1-1 and 7-1, the bending strength of the test piece was measured on different days, so the measurement results are different.
In Examples 7-1 to 7-6 and Comparative Example 7-1, the bending strength of the test piece was measured on the same day.

Further, from the results of Table 9 and FIG. 13, the sand composition obtained in each example was superior in fluidity to the sand composition obtained in Comparative Example 1-1. In particular, when hydrophilic fume alumina is used as the inorganic fine particles (Examples 7-1 to 7-3), compared with the case where hydrophobic fume de alumina is used (Examples 7-4 to 7-6). Excellent fluidity could be exhibited with a small amount.

According to the sand composition of the present invention, a mold having practical strength can be produced and the fluidity is excellent.

Claims (9)

1. A sand composition containing a refractory granular material, an acid catalyst, and inorganic fine particles having an average primary particle diameter of 5 to 500 nm.
2. The sand composition according to claim 1, wherein the content of the inorganic fine particles is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material.
3. The sand composition according to claim 1 or 2, wherein the content of the acid catalyst is 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the refractory granular material.
4. The sand composition according to any one of claims 1 to 3, wherein the inorganic fine particles are at least one selected from the group consisting of silica, titania and alumina.
5. The sand composition according to any one of claims 1 to 4, wherein the refractory granular material has an average particle size of 50 to 600 μm.
6. The sand composition according to any one of claims 1 to 5, wherein the inorganic fine particles satisfy the following condition (a).
   Condition (a): The pH of the dispersion liquid in which the solvent and the inorganic fine particles are mixed so that the concentration of the inorganic fine particles is 4% by mass is 8.5 or less at 25 ° C. However, when the inorganic fine particles are hydrophilic, the solvent is water, and when the inorganic fine particles are hydrophobic, the solvent is a mixed solvent of water and methanol (mass ratio 1: 1).
7. The sand composition according to any one of claims 1 to 6, wherein the acid catalyst is at least one selected from the group consisting of sulfuric acid, phosphoric acid, sulfonic acid and carboxylic acid.
8. The method for producing a sand composition according to any one of claims 1 to 7.
   A method for producing a sand composition, wherein the refractory granular material, the acid catalyst, and the inorganic fine particles are mixed.
9. A method for producing a mold, wherein the sand composition according to any one of claims 1 to 7 is brought into contact with an acid-curable binder and cured.

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