Kit for mold formation

Abstract

To provide a kit for mold formation, a composition for a mold and a method for producing a mold, that enable adequate mold strength to be ensured in low-temperature environments even when a binder composition for mold formation containing a small amount of monomeric furfuryl alcohol is used.SOLUTION: A kit for mold formation comprising a binder composition for mold formation and a curing agent composition for mold formation is provided. The binder composition for mold formation contains furfuryl alcohol and polyhydric phenol, and the curing agent composition for mold formation contains a sulfonic acid, the kit for mold formation satisfying the following conditions: the content of furfuryl alcohol in the binder composition for mold formation is 30.0 mass% or less; the content of the polyhydric phenol in the binder composition for mold formation is 2.0 mass% or more and 24.0 mass% or less; the content of the sulfonic acid in the curing agent composition for mold formation is 46.0 mass% or more and 75.0 mass% or less; and the mass ratio of the curing agent composition for mold formation (A) to the binder composition for mold formation (B), (A) / (B), is 0.32 or more and 0.69 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a kit for making a mold. [Background technology]

[0002] Acid-hardening molds are generally produced by adding a binder composition for mold making containing an acid-hardening resin and a hardener composition containing sulfonic acid, sulfuric acid, phosphoric acid, or the like to refractory particles such as silica sand, kneading the mixture, filling a master such as a wooden pattern with the resulting mixed sand, and curing the acid-hardening resin. Examples of acid-hardening resins include furan resins and phenolic resins. Furan resins include furfuryl alcohol-urea-formaldehyde resins, furfuryl alcohol-formaldehyde resins, furfuryl alcohol-phenol-formaldehyde resins, and other known modified furan resins. Such mold manufacturing methods allow for a high degree of freedom in molding operations and, due to the excellent thermal properties of the molds, can produce high-quality castings, and are therefore widely used in the casting of machine parts, construction machinery parts, automotive parts, and other castings.

[0003] One of the important conditions for producing a mold is to improve the working environment during mold production (resin curing). In particular, it is desirable to reduce the amount of monomeric furfuryl alcohol in the furan resin in order to reduce the amount of furfuryl alcohol that volatilizes during mold production.

[0004] For example, Patent Document 1 below discloses that the use of a binder composition with a low content of monomeric furfuryl alcohol can reduce the release of furfuryl alcohol and formaldehyde during kneading and molding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2014-501175 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally proposed binder compositions for mold making that contain a low content of monomeric furfuryl alcohol are in a hydrophobic state, which is thought to result in poor compatibility with sulfuric acid-based hardeners used particularly at low temperatures (e.g., below 5°C), resulting in insufficient mold strength, particularly in low-temperature environments, and leaving room for improvement.

[0007] Patent Document 1 describes that the use of sulfonic acid as a curing agent improves the compatibility between the binder and the curing agent. However, because sulfonic acid has a lower acid strength than sulfuric acid and the like, the curing reaction does not proceed sufficiently in a low-temperature environment, resulting in insufficient mold strength.

[0008] An object of the present invention is to provide a foundry molding kit, a foundry mold composition, and a method for producing a foundry mold, which are capable of obtaining sufficient mold strength in a low-temperature environment even when using a binder composition for foundry molding that contains a small amount of monomeric furfuryl alcohol. [Means for solving the problem]

[0009] The present invention provides A foundry molding kit comprising a foundry molding binder composition and a foundry molding hardener composition, The binder composition for mold formation contains furfuryl alcohol (component A) and a polyhydric phenol (component B), The hardener composition for mold making contains a sulfonic acid (component C), The following conditions (1) to (4) are met. Condition (1): The content of furfuryl alcohol (component A) in the binder composition for mold formation is 30.0 mass % or less. Condition (2): The content of polyhydric phenol (component B) in the binder composition for mold formation is 2.0% by mass or more and 24.0% by mass or less. Condition (3): The content of sulfonic acid (component C) in the hardener composition for mold making is 46.0% by mass or more and 75.0% by mass or less. Condition (4): The mass ratio of the hardener composition for foundry molding to the binder composition for foundry molding (mass of the hardener composition for foundry molding / mass of the binder composition for foundry molding) is 0.32 or more and 0.69 or less.

[0010] The present invention also provides a foundry composition obtained by mixing the foundry binder composition and the foundry hardener composition constituting the foundry mold-making kit with refractory particles.

[0011] The present invention is a method for producing a mold, which includes a curing step of filling a mold with the above-described foundry composition and curing the foundry composition. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a foundry molding kit, a foundry mold composition, and a method for producing a mold, which are capable of obtaining sufficient mold strength in a low-temperature environment even when using a binder composition for foundry molding with a low content of monomeric furfuryl alcohol. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Mold making kit> The mold-making kit of this embodiment is a mold-making kit having a mold-making binder composition and a mold-making hardener composition, wherein the mold-making binder composition contains furfuryl alcohol (component A) and a polyhydric phenol (component B), and the mold-making hardener composition contains a sulfonic acid (component C), and satisfies the following conditions (1) to (4): Condition (1): The content of furfuryl alcohol (component A) in the binder composition for mold formation is 30.0 mass % or less. Condition (2): The content of polyhydric phenol (component B) in the binder composition for mold formation is 2.0% by mass or more and 24.0% by mass or less. Condition (3): The content of sulfonic acid (component C) in the hardener composition for mold making is 46.0% by mass or more and 75.0% by mass or less. Condition (4): The mass ratio of the hardener composition for foundry molding to the binder composition for foundry molding (mass of the hardener composition for foundry molding / mass of the binder composition for foundry molding) is 0.32 or more and 0.69 or less.

[0014] According to the mold-making kit of the present embodiment, sufficient mold strength can be obtained even in a low-temperature environment, even when the binder composition for mold-making has a low content of monomeric furfuryl alcohol. The reason why the mold-making kit of the present embodiment exhibits such an effect is not clear, but is thought to be as follows.

[0015] Polyhydric phenols are known as curing accelerators that improve the curing rate of acid-curing resins such as furan resins, but they tend to reduce mold strength. This is thought to be because the high reactivity of polyhydric phenols causes the curing reaction of binder compositions containing polyhydric phenols to occur locally, resulting in the formation of a non-uniform crosslinked structure. On the other hand, as mentioned above, sulfonic acids improve the compatibility between binder compositions for foundry molding and hardener compositions for foundry molding, but their acid strength is lower than that of sulfuric acid and the like, resulting in insufficient mold strength in low-temperature environments (e.g., below 5°C). The mold-making kit of this embodiment uses a polyhydric phenol having the above-described characteristics in combination with a sulfonic acid, thereby improving the compatibility between the binder composition for mold-making and the hardener composition for mold-making, while compensating for the lack of hardening speed due to the sulfonic acid with the high reactivity of the polyhydric phenol and suppressing the high reactivity of the polyhydric phenol with the low reactivity of the sulfonic acid, thereby suppressing the formation of a non-uniform crosslinked structure.As a result, it is believed that sufficient mold strength can be obtained even in a low-temperature environment, even with a binder composition for mold-making that contains a low content of monomeric furfuryl alcohol.

[0016] [Binder composition for mold making] [Furfuryl alcohol (ingredient A)] The content of Component A in the binder composition for mold formation (hereinafter also simply referred to as the binder composition) is 30.0% by mass or less, preferably 25.0% by mass or less, and more preferably 20.0% by mass or less, from the viewpoint of suppressing release of furfuryl alcohol into the working environment. The content of Component A in the binder composition is preferably more than 0% by mass, more preferably 5.0% by mass or more, even more preferably 10.0% by mass or more, even more preferably 15.0% by mass or more, and even more preferably 20.0% by mass or more, from the viewpoint of improving mold strength in a low-temperature environment. The content of Component A can be measured by the method described in the Examples.

[0017] [Polyphenol (ingredient B)] Examples of Component B include resorcinol, pyrogallol, phloroglucinol, catechol, hydroquinone, methylene bisphenol, bisphenol A, bisphenol F, tannins, etc. From the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol, Component B preferably contains one or more selected from the group consisting of resorcinol, bisphenol A, bisphenol F, and tannins, more preferably contains one or more selected from the group consisting of resorcinol and bisphenols, and even more preferably contains resorcinol.

[0018] Examples of the tannins include condensed tannins and hydrolyzable tannins. Examples of these condensed tannins and hydrolyzable tannins include tannins having a pyrogallol skeleton or a resorcinol skeleton. Furthermore, extracts from natural products such as bark extracts, plant-derived leaves, fruits, seeds, and galls parasitizing plants, which contain these tannins, may also be added.

[0019] The content of Component B in the binder composition is 2.0% by mass or more, preferably 3.0% by mass or more, more preferably 4.0% by mass or more, even more preferably 5.0% by mass or more, and even more preferably 7.0% by mass or more, from the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol. The content of Component B in the binder composition is 24.0% by mass or less, preferably 22.0% by mass or less, and more preferably 20.0% by mass or less, from the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol.

[0020] [Acid-curable resin (component D)] The binder composition may contain an acid-curing resin (component D) used as a binder for mold formation. Examples of the acid-curing resin include one or more selected from the group consisting of furan resin, condensates of melamine and aldehydes, condensates of urea and aldehydes, and condensates of ethylene urea and aldehydes. The acid-curing resin preferably contains a furan resin, from the viewpoint of improving mold strength in low-temperature environments while reducing the content of monomeric furfuryl alcohol. The acid-curing resin does not contain furfuryl alcohol.

[0021] The furan resin is obtained by polymerizing a monomer composition containing furfuryl alcohol, and can be used without any particular limitation as long as it can be used as a binder for mold making. From the viewpoint of significantly improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol, the furan resin is preferably one selected from the group consisting of a condensate of furfuryl alcohol and urea, a condensate of furfuryl alcohol and melamine, a condensate of furfuryl alcohol and ethyleneurea, a condensate of furfuryl alcohol, urea, and aldehydes (urea-modified furan resin), a condensate of furfuryl alcohol, melamine, and aldehydes, a condensate of furfuryl alcohol, ethyleneurea, and aldehydes, a furfuryl alcohol condensate, a condensate of furfuryl alcohol and aldehydes, and a condensate of furfuryl alcohol, a phenol, and aldehydes, and a co-condensate of two or more condensates selected from the group. The resin preferably contains one or more of the above, more preferably one or more selected from the group consisting of a condensate of furfuryl alcohol and urea, a condensate of furfuryl alcohol and melamine, a condensate of furfuryl alcohol and ethylene urea, a condensate of furfuryl alcohol, urea and aldehydes (urea-modified furan resin), a condensate of furfuryl alcohol, melamine and aldehydes, and a condensate of furfuryl alcohol, ethylene urea and aldehydes, as well as a co-condensate of two or more condensates selected from the above group, and even more preferably one or more selected from the group consisting of a urea-modified furan resin, a furfuryl alcohol condensate, and a condensate of furfuryl alcohol and aldehydes, as well as a co-condensate of two or more condensates selected from the above group.

[0022] Examples of the aldehydes include formaldehyde, acetaldehyde, glyoxal, furfural, terephthalaldehyde, hydroxymethylfurfural, etc., and one or more of these can be used as appropriate. From the viewpoint of improving mold strength, it is preferable to use formaldehyde, and from the viewpoint of reducing the amount of formaldehyde generated during molding, it is preferable to use furfural, terephthalaldehyde, or hydroxymethylfurfural.

[0023] Examples of the phenols include phenol, cresol, resorcinol, bisphenol A, bisphenol C, bisphenol E, and bisphenol F, and one or more of these can be used.

[0024] The furan resin can be produced by a known method. For example, when the furan resin is a urea-modified furan resin, the urea-modified furan resin can be obtained by reacting 100.0 parts by mass of furfuryl alcohol with 0.6 to 30.0 parts by mass of urea and 0.4 to 50.0 parts by mass of paraformaldehyde.

[0025] The content of Component D in the binder composition is preferably 10.0% by mass or more, more preferably 20.0% by mass or more, and even more preferably 30.0% by mass or more, from the viewpoints of improving the crosslink density of the resin and improving mold strength in a low-temperature environment. The content of Component D in the binder composition is preferably 70.0% by mass or less, more preferably 60.0% by mass or less, even more preferably 55.0% by mass or less, even more preferably 51.0% by mass or less, even more preferably 50.0% by mass or less, and even more preferably 45.0% by mass or less, from the viewpoints of maintaining good kneadability with the refractory aggregate and suppressing a decrease in mold strength.

[0026] [water] The binder composition may further contain water. For example, when synthesizing various condensates, such as a condensate of furfuryl alcohol and aldehydes, the raw materials are used in aqueous solution form or condensation water is generated, so the condensate is usually obtained in the form of a mixture with water. When using such a condensate in a binder composition, the water may be removed by topping or other methods as needed, but it is not necessary to remove it during production as long as the curing reaction rate can be maintained. Furthermore, water may be further added to adjust the viscosity of the binder composition to an easy-to-handle state. When water is further added to adjust the viscosity of the binder composition to an easy-to-handle state, the water content of the binder composition is preferably 5.0% by mass or more, more preferably 8.0% by mass or more, even more preferably 10.0% by mass or more, and even more preferably 12.0% by mass or more. However, from the viewpoint of suppressing a decrease in mold strength, the water content of the binder composition is preferably 30% by mass or less, more preferably 27% by mass or less, and even more preferably 24% by mass or less.

[0027] The binder composition may further contain additives such as a silane coupling agent. For example, the binder composition preferably contains a silane coupling agent, since this can further improve the final strength of the resulting mold. Examples of silane coupling agents include aminosilanes such as N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane; epoxysilanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; ureidosilanes, mercaptosilanes, sulfidosilanes, methacryloxysilanes, and acryloxysilanes. Aminosilanes, epoxysilanes, and ureidosilanes are preferred. More preferred are aminosilanes and epoxysilanes. Among aminosilanes, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane is preferred. Among epoxysilanes, 3-glycidoxypropylmethyldimethoxysilane is preferred.

[0028] From the viewpoint of improving mold strength, the content of the silane coupling agent in the binder composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and from the same viewpoint, the content of the silane coupling agent in the binder composition is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

[0029] From the viewpoint of improving mold strength in a low-temperature environment, the pH of the binder composition is preferably 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less at 25° C. From the viewpoint of improving storage stability, the pH of the binder composition is preferably 3.0 or more, more preferably 5.0 or more, and even more preferably 7.0 or more at 25° C. The pH of the binder composition can be adjusted with an acid such as hydrochloric acid or an alkali such as sodium hydroxide or potassium hydroxide.

[0030] The binder composition for foundry molding of this embodiment is suitable for use in molding a self-hardening mold. Here, a self-hardening mold is a mold in which, when the binder composition and a hardener are mixed with sand, a polymerization reaction progresses over time, resulting in hardening of the mold. The temperature of the sand used in this process is in the range of -20°C to 50°C, and preferably 0°C to 40°C. For sand at such a temperature, the mold can be properly hardened by selecting and adding an appropriate amount of hardener to the sand.

[0031] [Hardening agent composition for casting] The hardener composition for mold making (hereinafter also simply referred to as the hardener composition) contains a hardener that hardens the binder composition, and from the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol, it contains sulfonic acid (component C) as the hardener.

[0032] From the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol, the component C preferably contains one or more selected from the group consisting of xylene sulfonic acid (particularly, m-xylene sulfonic acid), toluene sulfonic acid (particularly, p-toluene sulfonic acid), and methane sulfonic acid.

[0033] The content of component C in the curing agent composition is 46.0% by mass or more, preferably 48.0% by mass or more, more preferably 50.0% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of improving the curing rate and mold strength in a low-temperature environment. The content of component C in the curing agent composition is 75.0% by mass or less, more preferably 70.0% by mass or less, from the viewpoint of the solubility of component C.

[0034] The curing agent composition may contain a curing agent other than Component C. As the curing agent other than Component C, one or more conventionally known curing agents can be used, such as phosphoric acid, phosphoric acid compounds such as acidic phosphate esters, and sulfuric acid. From the viewpoint of improving mold strength in a low-temperature environment, the curing agent composition preferably contains sulfuric acid.

[0035] The content of sulfuric acid in the curing agent composition is preferably more than 0% by mass from the viewpoint of improving mold strength in a low-temperature environment, and is preferably 24.0% by mass or less, more preferably 20.0% by mass or less, even more preferably 15.0% by mass or less, and even more preferably 10.0% by mass or less from the viewpoint of improving mold strength in a low-temperature environment.

[0036] The curing agent composition may contain one or more solvents selected from the group consisting of water, alcohols, ether alcohols, and esters.

[0037] The content of the solvent in the curing agent composition is adjusted appropriately to obtain the desired reaction rate and mold strength depending on the temperature of the working environment and the temperature of the refractory particles, but generally, from the viewpoint of dissolving the curing agent composition, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of improving mold strength, the content of the solvent in the curing agent composition is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0038] In the mold-making kit, the mass ratio of the hardener composition to the binder composition (mass of the hardener composition / mass of the binder composition) is 0.32 or more, preferably 0.35 or more, and more preferably 0.40 or more, from the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol; and from the same viewpoint, it is 0.69 or less, preferably 0.65 or less, and more preferably 0.60 or less.

[0039] <Mold composition> The foundry composition of this embodiment is obtained by mixing the binder composition and the hardener composition constituting the foundry mold-making kit with refractory particles, and has the same effects as the foundry mold-making kit.

[0040] [Fire-resistant particles] The refractory particles may be one or more of conventionally known refractory particles such as silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, synthetic mullite sand, etc., or may be recovered or recycled used refractory particles. Of these, silica sand is preferred.

[0041] In the mold composition, the mass ratio of the refractory particles, the binder composition, and the hardener composition can be set as appropriate. From the viewpoint of improving the hardening rate and mold strength, however, it is preferable that the binder composition be in the range of 0.50 to 1.50 parts by mass and the hardener composition be in the range of 0.15 to 1.05 parts by mass per 100 parts by mass of the refractory particles.

[0042] <Mold manufacturing method> The mold manufacturing method of this embodiment includes a step of filling a mold with the foundry composition and curing the foundry composition. That is, the mold manufacturing method of this embodiment includes a mixing step of mixing the refractory particles, the binder composition, and the hardener composition to obtain the foundry composition, and a hardening step of filling a mold with the foundry composition and curing the foundry composition. The mold manufacturing method has the same effects as the binder composition.

[0043] In the mixing step, the order in which the binder composition, the hardener composition, and the refractory particles are added and mixed is not particularly limited. The binder composition and the hardener composition may be mixed to produce a foundry molding composition, and then the foundry molding composition and the refractory particles may be mixed. Alternatively, the binder composition, the hardener composition, and the refractory particles may be added and mixed separately. However, from the viewpoints of storage stability and mold productivity, it is preferable to mix the binder composition, the hardener composition, and the refractory particles to obtain a foundry molding composition. Furthermore, from the viewpoint of improving mold strength, it is preferable to add the hardener composition to the refractory particles and mix them, and then add the binder composition and mix them. Furthermore, when two or more hardener compositions are used, the individual hardener compositions may be mixed and then added, or each hardener composition may be added separately. The content of each component in each composition described herein can be considered to be the amount of each component in each composition described herein.

[0044] In the mixing step, the mixing ratio of the hardener composition to the binder composition (mass of the hardener composition for mold making / mass of the binder composition for mold making) is preferably 0.32 or more, more preferably 0.35 or more, and even more preferably 0.40 or more, from the viewpoint of improving mold strength in a low-temperature environment while reducing the content of monomeric furfuryl alcohol; and from the same viewpoint, it is preferably 0.69 or less, more preferably 0.65 or less, and even more preferably 0.60 or less.

[0045] In the mixing step, the raw materials can be mixed using a known general method, for example, a method in which the raw materials are added and kneaded using a batch mixer, or a method in which the raw materials are supplied to a continuous mixer and kneaded.

[0046] In the mold manufacturing method of this embodiment, the mold can be manufactured by utilizing the conventional mold manufacturing process as it is, except for the mixing step. [Example]

[0047] <Methods for measuring physical properties> [Water content] Measurement was carried out using an automatic moisture measuring device (Hiranuma Sangyo Co., Ltd., AQV-2200A) based on the Karl Fischer method specified in JIS K 0068.

[0048] [Furfuryl alcohol content] Measurement was carried out by gas chromatography analysis under the following conditions using a gas chromatograph (Shimadzu Corporation, GC-2014S). Measurement sample dilution solvent: Methanol Calibration curves: Calibration curves for furfuryl alcohol and bishydroxymethylfuran were prepared using 1,6-hexanediol as an internal standard. Column: PEG-20M Chromosorb WAW DMCS 60 / 80 mesh (GL Sciences) Column temperature: 80-200°C (8°C / min) Injection temperature: 210℃ Detector type: FID Detector temperature: 250°C Carrier gas: 50 mL / min (He)

[0049] [pH of binder composition] The pH of the binder composition was measured by mixing the binder composition with ion-exchanged water of an equal mass to that of the binder composition at 25°C using a pH meter (personal pH meter PH71 manufactured by Yokogawa Electric Corporation).

[0050] <Production Example of Binder Composition> A three-neck flask was charged with 726 g of furfuryl alcohol (Tokyo Chemical Industry Co., Ltd.), 1 g of 25% by weight aqueous sodium hydroxide solution (Fujifilm Wako Pure Chemical Industries, Ltd.), 197 g of 92% by weight paraformaldehyde (Mitsubishi Gas Chemical Company, Inc.), and 36 g of benzoic acid (Fujifilm Wako Pure Chemical Industries, Ltd.), and the mixture was allowed to react at 125°C under atmospheric pressure for 2 hours. The mixture was then cooled to 90°C, and 34 g of urea (Fujifilm Wako Pure Chemical Industries, Ltd.) was added. The mixture was then heated to 105°C and allowed to react at the same temperature for 2 hours. After the reaction, the mixture was cooled to 75°C, and 7 g of urea was added. The mixture was allowed to react at the same temperature for 20 minutes, yielding resin composition A. The resulting resin composition A had a composition of 69.4% by weight of furan resin, 25.0% by weight of furfuryl alcohol, and 5.6% by weight of water. Each component was added to the resin composition A so as to obtain the composition shown in Table 1, thereby obtaining binder compositions according to Examples 1 to 15 and Comparative Examples 1 to 6. The silane coupling agent in Table 1 was N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.).

[0051] <Production Example of Curing Agent Composition> Each component was added to obtain the composition shown in Table 1, and curing agent compositions according to Examples 1 to 15 and Comparative Examples 1 to 6 were obtained.

[0052] <Production Example of Foundry Composition> Under conditions of 5°C and 55% RH, the hardener composition was added to the furan reclaimed silica sand, followed by the binder composition, and they were mixed to obtain a foundry composition. The amount of binder composition added per 100 parts by mass of furan reclaimed silica sand was 0.8 parts by mass, and the hardener composition was added in an amount that achieved the "hardener composition / binder composition (mass ratio)" value shown in Table 1.

[0053] <Evaluation of mold compressive strength> The mold composition immediately after mixing was filled into a cylindrical test piece frame with a diameter of 50 mm and a height of 50 mm, and the frame was demolded after 2 hours. 24 hours after filling, the compressive strength (MPa) was measured using the method described in JIS Z 2604-1976 and recorded as the "mold compressive strength after 24 hours." A higher value indicates a higher mold compressive strength. Furthermore, the relative ratio (%) of the "mold compressive strength after 24 hours" of each Example to the evaluation result of Comparative Example 1, where the "mold compressive strength after 24 hours" of Comparative Example 1 was set to 100%, was also calculated. The evaluation results are shown in Table 1.

[0054] [Table 1]

Claims

1. A foundry molding kit comprising a foundry molding binder composition and a foundry molding hardener composition, The binder composition for mold formation contains furfuryl alcohol (component A) and a polyhydric phenol (component B), The hardener composition for mold making contains a sulfonic acid (component C), A mold making kit that satisfies the following conditions (1) to (4): Condition (1): The content of furfuryl alcohol (component A) in the binder composition for mold formation is 30.0 mass % or less. Condition (2): The content of polyhydric phenol (component B) in the binder composition for mold formation is 2.0% by mass or more and 24.0% by mass or less. Condition (3): The content of sulfonic acid (component C) in the hardener composition for mold making is 46.0% by mass or more and 75.0% by mass or less. Condition (4): The mass ratio of the hardener composition for foundry molding to the binder composition for foundry molding (mass of the hardener composition for foundry molding / mass of the binder composition for foundry molding) is 0.32 or more and 0.69 or less.

2. 2. The mold-making kit according to claim 1, wherein the polyhydric phenol (component B) comprises at least one member selected from the group consisting of resorcinol, bisphenol A, bisphenol F, and tannins.

3. 2. The mold-making kit according to claim 1, wherein the binder composition for mold-making contains an acid-curing resin (component D).

4. 4. The mold-making kit according to claim 3, wherein the acid-hardening resin (component D) contains a furan resin.

5. 5. The mold-making kit according to claim 4, wherein the furan resin contains at least one resin selected from the group consisting of a condensate of furfuryl alcohol and urea, a condensate of furfuryl alcohol and melamine, a condensate of furfuryl alcohol and ethylene urea, a urea-modified furan resin, a condensate of furfuryl alcohol, melamine and an aldehyde, and a condensate of furfuryl alcohol, ethylene urea and an aldehyde, and a co-condensate of two or more condensates selected from the group consisting of the above-mentioned condensates.

6. A foundry composition obtained by mixing the foundry binder composition and the foundry hardener composition constituting the foundry mold making kit according to any one of claims 1 to 5 with refractory particles.

7. A method for producing a mold, comprising the steps of filling a mold with the foundry composition according to claim 6 and hardening the foundry composition.

8. 8. The method for manufacturing a mold according to claim 7, wherein a mixing ratio of the hardener composition for foundry molding to the binder composition for foundry molding (mass of the hardener composition for foundry molding / mass of the binder composition for foundry molding) is 0.32 or more and 0.69 or less.

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