Binder composition for forming mold

Abstract

The present invention is a binder composition for forming a mold for carbon dioxide curing, the binder composition containing an alkali phenol resin, an oxyanion compound, and a tertiary amine compound, and the tertiary amine compound being at least one selected from N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine. According to the present invention, it is possible to provide a binder composition for forming a mold that suppresses dents on the mold surface caused by extrusion pins during removal of the mold from a die, a composition for forming a mold, and a method for producing a mold.

Description

Binder composition for mold making

[0001] The present invention relates to a binder composition for mold making.

[0002] A known mold-making method uses a phenolic resin as a binder and cures the phenolic resin with an organic ester, carbon dioxide gas, or amine gas. For example, Japanese Patent Application Laid-Open No. 2000-15389 describes a carbon dioxide gas-curing binder composition that contains a water-soluble phenolic resin and a cyclic urea compound, and that can improve the surface stability of the mold while maintaining high mold strength and suppress thickening of the binder.

[0003] The present invention provides a carbon dioxide-curing binder composition for forming foundries, which comprises an alkaline phenolic resin, an oxyanion compound, and a tertiary amine compound, wherein the tertiary amine compound is one or more selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

[0004] The present invention also provides a composition for mold making, which contains the binder composition for mold making and refractory particles.

[0005] The present invention also provides a method for producing a mold, comprising: a mixing step of mixing refractory particles, an alkali phenolic resin, an oxyanion compound, and a tertiary amine compound to obtain a composition for mold formation; and a curing step of filling a mold with the composition for mold formation and curing the composition with carbon dioxide gas, wherein the tertiary amine compound includes one or more compounds selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

[0006] Photographs showing an example of a test mold and a metal mold immediately after demolding. Photographs showing an example of a test mold with a depression removed from the metal mold. Photographs showing a state in which a linear gauge is placed along the apex of the corner of the test mold. Detailed Description of the Invention

[0007] In the manufacture of a casting mold using a carbon dioxide gas-hardening binder composition, a mold-making composition containing refractory particles and a carbon dioxide gas-hardening binder composition is blown into the mold, the carbon dioxide gas-hardening binder composition is hardened by passing carbon dioxide gas through the mold, and the mold is then removed from the mold with an ejector pin. During this removal process, there is a problem in that the part of the mold that comes into contact with the ejector pin becomes indented. When a casting is produced using a mold with an indentation on its surface, the surface of the casting develops a protruding defect, which may render the casting unusable as a product.

[0008] The technique described in the above-mentioned Japanese Patent Application Laid-Open No. 2000-15389 was insufficient in its effect of improving the depressions on the mold surface caused by the ejector pin.

[0009] The present invention provides a binder composition for mold-making that suppresses indentations on the mold surface caused by an ejector pin when the mold is removed from a metal mold, a composition for mold-making, and a method for producing a mold.

[0010] The present invention provides a carbon dioxide-curing binder composition for forming foundries, which comprises an alkaline phenolic resin, an oxyanion compound, and a tertiary amine compound, wherein the tertiary amine compound is one or more selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

[0011] The present invention also provides a composition for mold making, which contains the binder composition for mold making and refractory particles.

[0012] The present invention also provides a method for producing a mold, comprising: a mixing step of mixing refractory particles, an alkali phenolic resin, an oxyanion compound, and a tertiary amine compound to obtain a composition for mold formation; and a curing step of filling a mold with the composition for mold formation and curing the composition with carbon dioxide gas, wherein the tertiary amine compound includes one or more compounds selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

[0013] According to the present invention, it is possible to provide a binder composition for foundry molding, a composition for foundry molding, and a method for manufacturing a mold, which suppress indentations on the mold surface caused by an ejector pin when the mold is removed from a metal mold.

[0014] An embodiment of the present invention will be described below.

[0015] <Carbon dioxide gas-hardening binder composition for mold making> The carbon dioxide gas-hardening binder composition for mold making of this embodiment (hereinafter also referred to simply as the binder composition) contains an alkali phenol resin, an oxyanion compound, and a tertiary amine compound, and the tertiary amine compound includes one or more compounds selected from N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine. The binder composition of this embodiment can prevent dents on the mold surface caused by an ejector pin when the mold is removed from the mold.

[0016] [Alkaline Phenol Resin] The alkaline phenolic resin is generally obtained by polycondensation of a phenolic compound and an aldehyde compound under alkaline conditions. Among these, the phenolic compounds include phenols such as phenol, bisphenol A, bisphenol F, cresol, 3,5-xylenol, resorcinol, catechol, nonylphenol, p-tert-butylphenol, isopropenylphenol, phenylphenol, and other substituted phenols, as well as mixtures of various phenolic compounds such as cashew nut shell liquid. Furthermore, the aldehyde compounds include formaldehyde, acetaldehyde, furfural, glyoxal, and the like, and these compounds can be used alone or in combination. These compounds can be used as aqueous solutions, if necessary. Furthermore, these may be mixed with monomers capable of condensing with aldehyde compounds such as urea, melamine, and cyclohexanone, monohydric aliphatic alcohol compounds such as methanol, ethanol, isopropyl alcohol, normal propyl alcohol, and butyl alcohol, water-soluble polymer polyacrylates, cellulose derivative polymers, polyvinyl alcohol, and lignin derivatives.

[0017] The alkali catalyst used in synthesizing the alkali phenolic resin includes alkali metal hydroxides such as LiOH, NaOH, and KOH, with NaOH and / or KOH being particularly preferred. These alkali catalysts may also be mixed with the binder composition. The alkali metal hydroxide is preferably used in an amount of 0.01 to 6 moles, more preferably 0.5 to 2.5 moles, per mole of phenol.

[0018] Generally, the alkaline phenolic resin is used in the form of an aqueous solution. The content of the alkaline phenolic resin in the alkaline phenolic resin aqueous solution (solid mass after drying the alkaline phenolic resin aqueous solution at 105°C for 3 hours) is preferably 30% by mass or more, more preferably 50% by mass or more, from the viewpoint of improving mold strength. The content of the alkaline phenolic resin in the alkaline phenolic resin aqueous solution is preferably 85% by mass or less, more preferably 75% by mass or less, from the viewpoint of improving mold strength and workability. Furthermore, the content of the alkaline phenolic resin in the alkaline phenolic resin aqueous solution is preferably 30 to 85% by mass, more preferably 50 to 75% by mass, from the viewpoint of improving mold strength and workability.

[0019] The weight average molecular weight (Mw) of the alkaline phenol resin is preferably 500 or more, more preferably 800 or more, and even more preferably 1200 or more, from the viewpoint of improving mold strength. The weight average molecular weight (Mw) of the alkaline phenol resin is preferably 8000 or less, more preferably 5000 or less, and even more preferably 3000 or less, from the viewpoint of improving mold strength and workability. Furthermore, the weight average molecular weight (Mw) of the alkaline phenol resin is preferably 500 to 8000, more preferably 800 to 5000, and even more preferably 1200 to 3000, from the viewpoint of improving mold strength and workability. The weight average molecular weight of the alkaline phenol resin is measured by the method described in the examples.

[0020] The content of the alkali phenol resin in the binder composition is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 43% by mass or more, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the alkali phenol resin in the binder composition is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less, and even more preferably 53% by mass or less, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding and improving workability. Furthermore, the content of the alkali phenol resin in the binder composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, even more preferably 30 to 55% by mass, even more preferably 40 to 53% by mass, and even more preferably 43 to 53% by mass, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding and improving workability.

[0021] [Tertiary Amine Compound] The tertiary amine compound includes one or more selected from N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

[0022] The content of the tertiary amine compound in the binder composition is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the tertiary amine compound in the binder composition is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 17% by mass or less, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the tertiary amine compound in the binder composition is preferably 0.2 to 25% by mass, more preferably 0.3 to 20% by mass, and even more preferably 0.4 to 17% by mass, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding.

[0023] The content of the tertiary amine compound in the binder composition relative to 100 parts by mass of the alkali phenol resin is preferably 0.4 parts by mass or more, more preferably 0.6 parts by mass or more, and even more preferably 0.8 parts by mass or more, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the tertiary amine compound in the binder composition relative to 100 parts by mass of the alkali phenol resin is preferably 55 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, still more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, from the viewpoint of suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the tertiary amine compound in the binder composition relative to 100 parts by mass of the alkaline phenol resin is preferably 0.4 to 55 parts by mass, more preferably 0.6 to 50 parts by mass, even more preferably 0.8 to 45 parts by mass, still more preferably 0.8 to 40 parts by mass, and still more preferably 0.8 to 35 parts by mass, from the viewpoint of suppressing indentations on the mold surface due to an ejection pin during demolding.

[0024] [Oxyanion Compound] The oxyanion compound is thought to absorb carbon dioxide gas to form an ionomer, thereby polymerizing the alkali phenol resin. Examples of the oxyanion compound include boric acid compounds such as boric acid and borate salts. Examples of borates include sodium tetraborate decahydrate (borax), potassium tetraborate decahydrate, sodium metaborate, sodium pentaborate, and potassium pentaborate. From the viewpoint of improving mold strength and improving the mold hardening speed, sodium tetraborate decahydrate (borax) is preferred.

[0025] The content of the oxyanion compound in the binder composition is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and even more preferably 6% by mass or more, from the viewpoints of improving mold strength, improving the hardening rate of the mold, and suppressing dents on the mold surface caused by an ejector pin during demolding. The content of the oxyanion compound in the binder composition is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoints of improving mold strength, improving the fluidity of the foundry molding composition, and suppressing dents on the mold surface caused by an ejector pin during demolding. The content of the oxyanion compound in the binder composition is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, even more preferably 5 to 15% by mass, and even more preferably 6 to 10% by mass, from the viewpoints of improving mold strength, increasing the hardening rate of the mold, improving the fluidity of the mold-forming composition, and suppressing dents on the mold surface caused by an ejector pin during demolding.

[0026] The total content of the boric acid compound in the oxyanion compound is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 98% by mass or more, and even more preferably 100% by mass, from the viewpoints of improving mold strength, improving the hardening rate of the mold, and suppressing dents on the mold surface caused by the ejection pin during demolding.

[0027] The total content of boric acid and borate in the oxyanion compound is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 98% by mass or more, and even more preferably 100% by mass, from the viewpoints of improving mold strength, improving the mold hardening rate, and suppressing dents on the mold surface caused by the ejector pin during demolding.

[0028] The content of borax in the oxyanion compound is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass, from the viewpoints of improving mold strength, improving the hardening speed of the mold, and suppressing dents on the mold surface caused by the ejection pin during demolding.

[0029] The ratio of the mass of the oxyanion compound contained in the binder composition to the mass of the tertiary amine compound contained in the binder composition (mass of oxyanion compound / mass of tertiary amine compound) is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.4 or more, from the viewpoints of improving mold strength, improving mold hardening speed, and preventing dents on the mold surface caused by an ejector pin during demolding. The ratio of the mass of the oxyanion compound contained in the binder composition to the mass of the tertiary amine compound contained in the binder composition is preferably 35 or less, more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, even more preferably 10 or less, and even more preferably 5 or less, from the viewpoints of improving mold strength, improving mold hardening speed, and preventing dents on the mold surface caused by an ejector pin during demolding. Furthermore, the ratio of the mass of the oxyanion compound contained in the binder composition to the mass of the tertiary amine compound contained in the binder composition is preferably 0.1 to 35, more preferably 0.2 to 30, even more preferably 0.4 to 25, still more preferably 0.4 to 20, and even more preferably 0.4 to 5, from the viewpoints of improving mold strength, improving the hardening rate of the mold, and suppressing dents on the mold surface caused by an ejector pin during demolding.

[0030] From the viewpoint of suppressing dents on the mold surface caused by an ejector pin during demolding, the binder composition preferably contains 10 to 70% by mass of the alkali phenol resin, 1 to 30% by mass of the oxyanion compound, and 0.2 to 25% by mass of the tertiary amine compound.

[0031] [Other Components] The binder composition may further contain additives such as water, a silane coupling agent, and an aluminate to the extent that the effects of this embodiment are not impaired.

[0032] [Water] The water content in the binder composition is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, from the viewpoint of improving the fluidity of the foundry molding composition. The water content in the binder composition is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of improving the mold strength and the fluidity of the foundry molding composition. Furthermore, the water content in the binder composition is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, even more preferably 25 to 45% by mass, and even more preferably 25 to 40% by mass, from the viewpoint of improving the fluidity of the foundry molding composition and the mold strength.

[0033] [Silane Coupling Agent] The binder composition preferably contains a silane coupling agent from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by ejector pins during demolding. Examples of the silane coupling agent include γ-(2-amino)propylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and N-β-(aminoethyl)γ-aminopropylmethyldimethoxysilane. The content of the silane coupling agent in the binder composition is preferably 0.1 to 5% by mass, more preferably 0.3 to 1% by mass, from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by ejector pins during demolding.

[0034] [Aluminate] The binder composition preferably contains an aluminate from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by the ejector pin during demolding. Examples of the aluminate include alkali metal salts of aluminic acid. The aluminate is preferably sodium aluminate from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the aluminate in the binder composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the aluminate in the binder composition is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by the ejector pin during demolding. The content of the aluminate in the binder composition is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 3% by mass, from the viewpoint of improving mold strength and suppressing dents on the mold surface caused by an ejection pin during mold removal.

[0035] <Method for Manufacturing a Mold> In the method for manufacturing a mold of this embodiment, a mold can be manufactured by utilizing a conventional mold manufacturing process as is. A preferred method for manufacturing a mold includes a mixing step of mixing at least refractory particles, the alkali phenolic resin, the oxyanion compound, and the tertiary amine compound to obtain a composition for mold formation, and a curing step of filling the composition for mold formation into a mold and curing it with carbon dioxide gas.

[0036] [Mixing Step] [Refractory Particles] Examples of refractory particles that can be used in the mold manufacturing method of this embodiment include conventionally known refractory particles such as silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, synthetic mullite sand, and alumina ball sand. Also usable are recycled sands obtained by recovering and recycling used refractory particles. The refractory particles can be used alone or in combination of two or more types.

[0037] The average particle size of the refractory particles is preferably more than 50 μm, more preferably 70 μm or more, even more preferably 120 μm or more, and still more preferably 150 μm or more, from the viewpoints of improving mold strength and economy, and from the same viewpoints, is preferably 600 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and still more preferably 250 μm or less. In this specification, the average particle size is measured by the method described in the examples.

[0038] In the mixing step, when obtaining the composition for mold making, the refractory particles, the alkali phenolic resin, the oxyanion compound, the tertiary amine compound, and other components may be added separately and mixed, or the refractory particles, the binder composition, and other components may be mixed together. In this case, the content of the tertiary amine compound in the composition for mold making is preferably within the range of the content of the tertiary amine compound relative to 100 parts by mass of the alkali phenolic resin.

[0039] The content of the alkali phenol resin in the composition for mold making is preferably 3 parts by mass or more and 80 parts by mass or less per 1000 parts by mass of the refractory particles. The amounts of the tertiary amine compound and other components used in the binder composition are the same as those described for the binder composition.

[0040] 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.

[0041] [Curing Step] In the curing step, the foundry molding composition is filled into a mold and cured with carbon dioxide gas.

[0042] From the viewpoint of improving mold strength, the flow rate of carbon dioxide gas is set to 100 cm ３Preferably, the flow rate is 0.2 L / min or more, more preferably 1 L / min or more, even more preferably 5 L / min or more, still more preferably 10 L / min or more, and even more preferably 15 L / min or more, per 100 cm of mold. ３ The flow rate is preferably 40 L / min or less, more preferably 35 L / min or less. From the viewpoint of improving mold strength, the carbon dioxide gas flow time is preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 25 seconds or more, and from the viewpoint of economy, it is preferably 90 seconds or less, more preferably 70 seconds or less, even more preferably 50 seconds or less, and still more preferably 40 seconds or less. From the viewpoint of improving mold strength, the temperature during curing is preferably -5°C or more, more preferably 5°C or more, and even more preferably 10°C or more, and from the viewpoint of economy, it is preferably 45°C or less, more preferably 40°C or less, and even more preferably 35°C or less.

[0043] <Mold-making composition> The mold-making composition of this embodiment contains the refractory particles and the binder composition. That is, the mold-making composition of this embodiment contains the refractory particles, the alkali phenol resin, the oxyanion compound, and the tertiary amine compound.

[0044] The content of the binder composition relative to the refractory particles is as described in the mixing step of the mold manufacturing method.

[0045] The content of the alkaline phenolic resin relative to the refractory particles is as described in the mixing step of the mold manufacturing method, and the content of the oxyanion compound and the tertiary amine compound relative to the alkaline phenolic resin is as described in the binder composition.

[0046] Examples that specifically illustrate the present invention will be described below.

[0047] <Method for Evaluating Raw Materials> [Weight-average molecular weight (Mw) of alkaline phenol resin] The weight-average molecular weight (Mw) of the alkaline phenol resin was measured by gel permeation chromatography (GPC) under the following conditions: (a) Sample preparation: The same weight of ion-exchanged water was added to a sample, and 0.1% by mass of H２ SO ４ The resulting precipitate was neutralized by adding the compound. The resulting precipitate was separated by filtration, washed with water, and dried. This was dissolved in tetrahydrofuran (THF) to prepare a sample for GPC. (b) Column: One guard column TSX (manufactured by Toyo Soda Kogyo Co., Ltd.) HXL (6.5 mmφ×4 cm), one TSK3000HXL (7.8 mmφ×30 cm), and one TSK2500HXL (7.8 mmφ×30 cm) were used. The guard columns were connected in this order from the injection port side: 3000HXL, 2500HXL. (c) Standard substance: Monodisperse polystyrene (manufactured by Toyo Soda Kogyo Co., Ltd.) with a known weight-average molecular weight. (d) Eluent: THF (flow rate: 1 cm ３ / min) (e) Column temperature: 25°C (f) Detector: ultraviolet spectrophotometer (quantitative determination at the wavelength of the maximum peak of ultraviolet absorption of phenol) (g) Resolution method for molecular weight calculation: time resolution (2 sec)

[0048] <Method for measuring average particle size of refractory particles> Based on the method specified in Appendix 2 of JIS Z2601 (1993) "Test methods for molding sand", measurements were carried out using sieves of 850, 600, 425, 300, 212, 150, 106, 75 and 53 μm, and the particle size at 50% cumulative mass was taken as the average particle size.

[0049] <Production of Raw Materials> [Preparation of Alkaline Phenolic Resin Aqueous Solution] 380.0 g of phenol, 666.3 g of 48% by mass potassium hydroxide aqueous solution, 297.3 g of water, and 263.7 g of 92% paraformaldehyde were mixed in a 2-liter glass vessel equipped with a thermometer and a stirrer, and the mixture was reacted at 85°C to obtain an alkaline phenolic resin aqueous solution. The solids concentration of the alkaline phenolic resin aqueous solution was 58.6% by mass. The weight-average molecular weight (Mw) of the alkaline phenolic resin was 1,820.

[0050] <Preparation of Binder Composition> [Example 1] 80.7 mass% of the alkaline phenol resin aqueous solution (47.3 mass% alkaline phenol resin), 1.5 mass% sodium aluminate, 6.5 mass% sodium tetraborate decahydrate (borax), 0.8 mass% γ-glycidoxypropyltrimethoxysilane (KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent, and 10.5 mass% 1,4-diazabicyclo[2.2.2]octane were mixed to obtain a binder composition of Example 1. The composition of the obtained binder composition is shown in Table 1.

[0051] Examples 2 to 13 and Comparative Examples 1 and 2 Binder compositions of Examples 2 to 13 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that predetermined amounts of the alkaline phenolic resin aqueous solution, sodium aluminate, sodium tetraborate decahydrate, and γ-glycidoxypropyltrimethoxysilane, and a tertiary amine compound shown in Table 1 were used so as to obtain the compositions shown in Table 1. The compositions of the resulting binder compositions are shown in Table 1.

[0052] Comparative Example 3 A binder composition of Comparative Example 3 was obtained in the same manner as in Example 1, except that predetermined amounts of an aqueous phenolic resin solution, sodium aluminate, 3-glycidoxypropyltrimethoxysilane, and N,N,N',N",N"-pentamethyldiethylenetriamine were used so as to obtain the composition shown in Table 1.

[0053] Evaluation of Mold Dent Caused by Ejector Pin (Examples 1 to 13 and Comparative Examples 1 and 2) 2,000 parts by mass of refractory particles (Mikawa silica sand R grade No. 6 [average particle size 181 μm], manufactured by Mikawa Silica Co., Ltd.) and 60 parts by mass of the binder composition were added to a kitchen mixer "Kenmix Aiko Chef" (manufactured by Aikosha Seisakusho Co., Ltd.) equipped with an aluminum beater mixing blade, and mixed at a rotation speed of 300 rpm for 2 minutes to obtain a foundry molding composition. The obtained foundry molding composition was filled into a 22.3 × 22.3 × 180 mm test piece mold at a blow pressure of 0.25 MPa using a CSR-43 blow molding machine (manufactured by Shinto Kogyo Co., Ltd.). Carbon dioxide gas was then passed through the mold at 25°C at a flow rate of 30 L / min for 30 seconds to harden the foundry molding composition and obtain a test mold. Immediately thereafter, the test mold was demolded from the die using an ejector pin (diameter 10 mm, extrusion speed 0.2 m / s). Figure 1 is a photograph showing an example of the test mold 2 and die 1 immediately after demolding. During demolding, an ejector pin with a valley-shaped tip corresponding to the mountain-shaped shape of the corner of the test mold 2 was pushed out from two ejector pin holes 11 provided in the die 1, and the ejector pin created a depression 21 at the corner of the test mold 2. Figure 2 is a photograph showing an example of the test mold 2 with the depression 21 removed from the die 1. A linear gauge 3 was placed along the apex of the corner of the test mold 2, and a photograph of the depression 21 was taken from a direct lateral direction using a digital microscope (VHX-5000, manufactured by Keyence Corporation) ( Figure 3 ). The distance between the linear gauge 3 and the depression 21 (the depth of the depression 21) was measured using communication software (VHX-900F, manufactured by Keyence Corporation). Twenty-five test molds for each example were measured, and the number of molds with dents of 540 μm or more (approximately the size of three refractory particles) that required repair was counted to evaluate the dents in the molds. The evaluation results are shown in Table 1.

[0054] Comparative Example 3 2,000 parts by mass of refractory particles (Mikawa silica sand R grade No. 6 [average particle size 181 μm], manufactured by Mikawa Silica Co., Ltd.), 60 parts by mass of the binder composition of Comparative Example 3, and 12 parts by mass of triacetin were added to a kitchen mixer "Kenmix Aiko Chef" (manufactured by Aikosha Seisakusho Co., Ltd.) equipped with an aluminum beater stirring blade, and mixed for 2 minutes at a rotation speed of 300 rpm to obtain a foundry molding composition. The obtained foundry molding composition was filled into a 22.3 × 22.3 × 180 mm test piece mold using a CSR-43 blow molding machine (manufactured by Shinto Kogyo Co., Ltd.) at a blow pressure of 0.25 MPa and allowed to cure for 30 seconds to obtain a test mold according to Comparative Example 3. Immediately thereafter, the mold was removed from the mold using an ejector pin (diameter 10 mm, extrusion speed 0.2 m / s), and the dents in the test mold according to Comparative Example 3 were evaluated in the same manner as in Example 1, etc.

[0055]

[0056] 1 Mold 11 Hole for ejection pin 2 Test mold 21 Recess 3 Linear gauge

Claims

1. Contains an alkaline phenolic resin, an oxyanion compound, and a tertiary amine compound, The carbon dioxide-curing binder composition for mold formation, wherein the tertiary amine compound comprises one or more compounds selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

2. 2. The binder composition for mold formation according to claim 1, wherein the content of the tertiary amine compound in the binder composition for mold formation is 0.2% by mass or more and 25% by mass or less.

3. 2. The binder composition for mold formation according to claim 1, wherein the content of the tertiary amine compound in the binder composition for mold formation is 0.4 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the alkaline phenol resin.

4. 2. The binder composition for mold formation according to claim 1, wherein the content of the alkaline phenol resin in the binder composition for mold formation is 10% by mass or more and 70% by mass or less.

5. 2. The binder composition for mold formation according to claim 1, wherein the content of the oxyanion compound in the binder composition for mold formation is 1% by mass or more and 30% by mass or less.

6. A composition for molding a foundry mold, comprising the binder composition for molding a foundry mold according to claim 1 and refractory particles.

7. The composition contains an alkaline phenolic resin, an oxyanion compound, a tertiary amine compound, water, and refractory particles, The tertiary amine compound is one or more selected from the group consisting of N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.

8. 8. The composition for mold making according to claim 6, wherein the content of the alkaline phenol resin in the composition for mold making is 3 parts by mass or more and 80 parts by mass or less per 1000 parts by mass of the refractory particles.

9. 8. The composition for molding a mold according to claim 6, wherein the content of the tertiary amine compound in the composition for molding a mold is 0.4 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the alkaline phenolic resin.

10. A method for producing a mold, comprising: a mixing step of mixing refractory particles, an alkali phenolic resin, an oxyanion compound, and a tertiary amine compound to obtain a composition for mold-making; and a curing step of filling the composition for mold-making into a mold and curing the composition for mold-making with carbon dioxide gas, The method for producing a mold, wherein the tertiary amine compound comprises one or more compounds selected from N,N,N',N",N"-pentamethyldiethylenetriamine, 3,3-iminobis(N,N-dimethylpropylamine), 6-dimethylamino-1-hexanol, bis(2-morpholinoethyl)ether, 2,2-dimethylaminoethoxyethanol, 1,4-diazabicyclo[2.2.2]octane, and triisopropanolamine.