Curing agent composition for cast molding

Abstract

The present invention is a curing agent composition for cast molding, the composition comprising at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylenesulfonic acid, the content of water is 50.0%-99.0% by mass, and the content of dixylyl sulfone is more than 0% by mass and less than 0.43% by mass. According to the present invention, a curing agent composition for cast molding capable of suppressing cracking of a hard vinyl chloride tube of a cast molding facility can be provided.

Description

Hardener composition for casting

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

[0002] The acid-hardening self-hardening mold is produced by supplying a binder composition for foundry molding and a hardener composition for foundry molding to a kneader through pipes using a supply device, kneading them with refractory particles, filling the resulting kneaded sand into a master such as a wooden mold, and hardening the acid-hardening resin (for example, Japanese Patent Laid-Open No. 7-88591).

[0003] The hardener composition for mold making of the present invention contains at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylene sulfonic acid, the water content is 50.0% by mass or more and 99.0% by mass or less, and the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass. Detailed Description of the Invention

[0004] The mold-making equipment, including the supply device and the kneader, uses piping made of rigid polyvinyl chloride (hereinafter also referred to as rigid PVC pipes). However, when the hardener composition for mold-making is delivered within the mold-making equipment, the rigid PVC pipes of the mold-making equipment often crack, causing problems with liquid leakage.

[0005] The present invention provides a hardener composition for mold making that can suppress cracking of rigid PVC pipes in mold making equipment.

[0006] Analysis of the mold-making hardener composition being delivered through the cracked PVC hardener pipe revealed the presence of dixylyl sulfone and diisononyl phthalate, which were not incorporated into the mold-making hardener composition. Dixylyl sulfone is a by-product of the synthesis of xylene sulfonic acid from xylene. Therefore, the dixylyl sulfone in the mold-making hardener composition is likely a by-product of the synthesis of xylene sulfonic acid. Furthermore, the mold-making device uses flexible polyvinyl chloride piping (hereinafter also referred to as flexible PVC pipe) in addition to rigid PVC pipes. Diisononyl phthalate is used as a plasticizer for the flexible PVC pipes. Therefore, the diisononyl phthalate in the mold-making hardener composition is likely derived from the flexible PVC pipes. Based on these findings, it was speculated that dixylyl sulfone or diisononyl phthalate may be the cause of the cracks in the rigid PVC pipes. Therefore, rigid PVC pipes were immersed in a dixylyl sulfone aqueous solution, a diisononyl phthalate aqueous solution, and an aqueous solution of dixylyl sulfone and diisononyl phthalate, respectively. No cracking was observed in the rigid PVC pipes immersed in the dixylyl sulfone aqueous solution or the diisononyl phthalate aqueous solution, but cracking was observed only in the rigid PVC pipes immersed in the dixylyl sulfone and diisononyl phthalate aqueous solution. Because diisononyl phthalate originates from the flexible PVC pipes used in the mold-making device, replacing the flexible PVC pipes with piping made of a different material could be considered to prevent the inclusion of diisononyl phthalate, but this is economically difficult. Therefore, the inventors focused on dixylyl sulfone and conducted further research. They discovered that cracking of rigid PVC pipes can be suppressed by reducing the dixylyl sulfone content below a certain amount in a hardener composition for mold-making containing xylene sulfonic acid as an acid component, thereby completing the present invention.

[0007] The hardener composition for mold making of the present invention contains at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylene sulfonic acid, the water content is 50.0% by mass or more and 99.0% by mass or less, and the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass.

[0008] According to the present invention, it is possible to provide a hardener composition for mold making that can suppress cracking of rigid PVC pipes in mold making equipment.

[0009] An embodiment of the present invention will be described below.

[0010] <Hardening agent composition for mold making> The hardener composition for mold making of this embodiment (hereinafter also referred to as hardener composition) contains at least an acid component, water, and dixylyl sulfone, the acid component contains xylene sulfonic acid, the water content is 50.0 mass% or more and 99.0 mass% or less, and the dixylyl sulfone content is more than 0 mass% and less than 0.43 mass%. The hardener composition of this embodiment can suppress cracking of rigid PVC pipes.

[0011] [Acid Component] The hardener composition contains xylene sulfonic acid as an acid component that hardens the acid-hardening resin contained in the binder composition for mold formation.

[0012] From the viewpoint of curing the acid-curable resin, the content of xylene sulfonic acid in the curing agent composition is preferably 10.0% by mass or more, more preferably 15.0% by mass or more. From the viewpoint of curing the acid-curable resin, the content of xylene sulfonic acid in the curing agent composition is preferably 40.0% by mass or less, more preferably 35.0% by mass or less.

[0013] The curing agent composition may contain one or more conventionally known acid components other than xylenesulfonic acid as the acid component that cures the acid-curing resin, such as carboxylic acids such as 2,6-dihydroxybenzoic acid, oxalic acid, maleic acid, pyruvic acid, malonic acid, 2-furancarboxylic acid, phthalic acid, fumaric acid, lactic acid, citric acid, and malic acid, sulfonic acid compounds other than xylenesulfonic acid such as toluenesulfonic acid (particularly p-toluenesulfonic acid) and methanesulfonic acid, phosphoric acid, sulfuric acid, etc. Among these, sulfuric acid is preferred from the viewpoint of improving the strength of the mold.

[0014] When the curing agent composition contains sulfuric acid, the content of sulfuric acid in the curing agent composition is preferably more than 0% by mass, and more preferably 3.0% by mass or more, from the viewpoint of improving the strength of the mold. The content of sulfuric acid in the curing agent composition is preferably 30% by mass or less, more preferably 20.0% by mass or less, and even more preferably 10.0% by mass or less, from the viewpoint of improving the strength of the mold. Furthermore, when the curing agent composition contains sulfuric acid, the content of sulfuric acid in the curing agent composition is preferably more than 0% by mass and 30% by mass or less, more preferably 3.0% by mass or more and 20.0% by mass or less, and even more preferably 3.0% by mass or more and 10.0% by mass or less, from the viewpoint of improving the strength of the mold.

[0015] [Water] The hardener composition contains water from the viewpoint of uniformly mixing the hardener composition, the refractory particles, and the binder composition for mold formation.

[0016] The water content in the hardener composition is 50.0% by mass or more, preferably 60.0% by mass or more, from the viewpoint of uniformly mixing the hardener composition, the refractory particles, and the binder composition for mold making. The water content in the hardener composition is 99.0% by mass or less, preferably 80.0% by mass or less, from the viewpoint of improving mold strength. The water content in the hardener composition is 50.0% by mass or more and 99.0% by mass or less, preferably 60.0% by mass or more and 80.0% by mass or less, from the viewpoint of uniformly mixing the hardener composition, the refractory particles, and the binder composition for mold making.

[0017] [Dixylyl sulfone] The curing agent composition contains dixylyl sulfone, which is produced as a by-product during the synthesis of xylene sulfonic acid.

[0018] The content of dixylyl sulfone in the curing agent composition is less than 0.43% by mass, and preferably 0.35% by mass or less, from the viewpoint of suppressing cracking of the rigid PVC pipe of the mold-making device. The content of dixylyl sulfone in the curing agent composition is more than 0% by mass, and preferably 0.05% by mass or more, from the viewpoint of production costs. The content of dixylyl sulfone in the curing agent composition is more than 0% by mass and less than 0.43% by mass, and preferably 0.05% by mass or more and 0.35% by mass or less, from the viewpoint of suppressing cracking of the rigid PVC pipe of the mold-making device and from the viewpoint of production costs.

[0019] The ratio of the dixylyl sulfone content to the xylene sulfonic acid content in the curing agent composition (dixylyl sulfone content / xylene sulfonic acid content) is preferably 0.001 or more, more preferably 0.005 or more, from the viewpoint of production costs. The ratio of the dixylyl sulfone content to the xylene sulfonic acid content in the curing agent composition (dixylyl sulfone content / xylene sulfonic acid content) is preferably 0.012 or less, more preferably 0.011 or less, from the viewpoint of suppressing cracking of the rigid PVC pipe of the mold-making device. The ratio of the dixylyl sulfone content to the xylene sulfonic acid content in the curing agent composition (dixylyl sulfone content / xylene sulfonic acid content) is preferably 0.001 or more and 0.012 or less, more preferably 0.005 or more and 0.011 or less, from the viewpoint of production costs and suppressing cracking of the rigid PVC pipe of the mold-making device.

[0020] The formation of dixylyl sulfone during the synthesis of xylene sulfonic acid from xylene can be suppressed by adjusting the reaction temperature and reaction time, changing the sulfonium ion source, and the like.

[0021] [Other Components] The curing agent composition may contain other components within the range that does not impair the effects of the mold of this embodiment. Examples of such other components include the following components.

[0022] The curing agent composition may contain one or more organic solvents selected from the group consisting of alcohols and ether alcohols, with alcohols being more preferred.

[0023] From the viewpoint of improving mold strength, the alcohols are preferably methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, or benzyl alcohol, and the ether alcohols are preferably ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, or ethylene glycol monophenyl ether.

[0024] The content of the organic solvent in the curing agent composition is adjusted appropriately depending on the temperature of the working environment and the temperature of the refractory particles to obtain a desired reaction rate and mold strength, but generally, from the viewpoint of improving mold strength and 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 same viewpoints, the content of the solvent in the curing agent composition is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0025] <Foundry Composition> The foundry composition of the present embodiment contains a binder composition for foundry molding (hereinafter also referred to as a binder composition) containing refractory particles and an acid-curing resin, and the hardener composition.

[0026] [Refractory 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. Among these, silica sand is preferred.

[0027] [Binder Composition for Foundry Forming] The binder composition contains an acid-curing resin as a binder component.

[0028] The acid-hardening resin may be at least one selected from the group consisting of a furan resin, a condensate of melamine and an aldehyde, a condensate of urea and an aldehyde, and a condensate of ethylene urea and an aldehyde. From the viewpoint of improving mold strength, the acid-hardening resin preferably contains a furan resin.

[0029] 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 under low-temperature environments while reducing the content of monomeric furfuryl alcohol, the furan resin may be 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, It is preferable that the resin contains one or more selected from the group consisting of condensates of furfuryl alcohol and aldehydes, and condensates of furfuryl alcohol, phenols, and aldehydes, and one or more co-condensates of two or more selected from the group, and it is more preferable that the resin contains one or more selected from the group consisting of urea-modified furan resin, furfuryl alcohol condensates, and condensates of furfuryl alcohol and aldehydes, and one or more co-condensates of two or more selected from the group.

[0030] 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, formaldehyde is preferably used, and from the viewpoint of reducing the amount of formaldehyde generated during molding, furfural, terephthalaldehyde, or hydroxymethylfurfural is preferably used.

[0031] 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.

[0032] 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.

[0033] From the viewpoint of improving mold strength, the content of the furan resin in the acid-hardening resin 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, even more preferably substantially 100% by mass, and even more preferably 100% by mass.

[0034] The content of the acid-hardening resin in the binder composition is preferably 5.0% by mass or more, more preferably 6.0% by mass or more, and even more preferably 7.0% by mass or more from the viewpoint of improving mold strength, and is preferably 45.0% by mass or less, more preferably 43.0% by mass or less, and even more preferably 42.0% by mass or less from the viewpoint of maintaining good kneadability with the refractory aggregate and suppressing a decrease in mold strength.

[0035] In the foundry composition, the mass ratio of the refractory particles, the binder composition, and the hardener composition can be appropriately set. From the viewpoint of improving mold strength, however, it is preferable that the binder composition be in a range of 0.5 to 1.5 parts by mass and the hardener be in a range of 0.07 to 1 part by mass relative to 100 parts by mass of the refractory particles.

[0036] <Method for Manufacturing a Mold> The hardener composition for foundry molding can be used to manufacture a mold. The method for manufacturing a mold 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 curing step of curing the foundry composition.

[0037] 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 mold-making composition, and then the mold-making 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 mold-making 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.

[0038] The contents of the components in the binder composition and the hardener composition, and the contents of the components in the foundry composition, can be considered to be the blending amounts of the components in the binder composition and the hardener composition, and the blending amounts of the components in the foundry composition.

[0039] 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.

[0040] In the mold manufacturing method of this embodiment, the mold can be manufactured by utilizing the conventional mold manufacturing process as is, except for the mixing step.

[0041] In relation to the above-described embodiments, the present specification further discloses the following compositions, etc.

[0042] <1> A hardener composition for foundry molding containing at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylene sulfonic acid, the water content is 50.0% by mass or more and 99.0% by mass or less, and the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass. <2> The hardener composition for foundry molding according to <1>, wherein the xylene sulfonic acid content is preferably 10.0% by mass or more, more preferably 15.0% by mass or more, and preferably 40.0% by mass or less, and more preferably 35.0% by mass or less. <3> The hardener composition for foundry molding according to <1> or <2>, wherein the acid component contains at least one selected from the group consisting of carboxylic acids such as 2,6-dihydroxybenzoic acid, oxalic acid, maleic acid, pyruvic acid, malonic acid, 2-furancarboxylic acid, phthalic acid, fumaric acid, lactic acid, citric acid, and malic acid; sulfonic acid compounds other than xylenesulfonic acid such as toluenesulfonic acid (particularly p-toluenesulfonic acid) and methanesulfonic acid; phosphoric acid; and sulfuric acid. <4> The hardener composition for foundry molding according to any one of <1> to <3>, wherein the content of sulfuric acid in the hardener composition for foundry molding is preferably more than 0% by mass and not more than 30% by mass, more preferably 3.0% by mass or more and not more than 20.0% by mass, and even more preferably 3.0% by mass or more and not more than 10.0% by mass. <5> The hardener composition for foundry molding according to any one of <1> to <4>, further comprising water. <6> The hardener composition for foundry molding according to any one of <1> to <5>, wherein the water content is 50.0% by mass or more and 99.0% by mass or less, and preferably 60.0% by mass or more and 80.0% by mass or less. <7> The hardener composition for foundry molding according to any one of <1> to <6>, wherein the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass, and preferably 0.05% by mass or more and 0.35% by mass or less. <8> The hardener composition for foundry molding according to any one of <1> to <7>, wherein the ratio of the dixylyl sulfone content to the xylene sulfonic acid content (dixylyl sulfone content / xylene sulfonic acid content) is preferably 0.001 or more and 0.012 or less, and more preferably 0.005 or more and 0.011 or less.<9> The hardener composition for foundry molding according to any one of <1> to <8>, which contains one or more organic solvents selected from the group consisting of alcohols and ether alcohols. <10> The hardener composition for foundry molding according to any one of <1> to <9>, in which the content of the organic solvent is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. <11> A foundry composition, which contains the refractory particles, the binder composition for foundry molding containing the acid-curing resin, and the hardener composition for foundry molding according to any one of <1> to <10>. <12> The foundry composition according to <11>, in which the refractory particles are at least one or two or more of silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, and synthetic mullite sand. <13> The foundry composition according to <11> or <12>, wherein the acid-curable resin is at least one selected from the group consisting of a furan resin, a condensate of melamine and an aldehyde, a condensate of urea and an aldehyde, and a condensate of ethylene urea and an aldehyde. <14> The foundry composition according to any one of <11> to <13>, wherein the furan resin contains at least 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 ethylene urea, a condensate of furfuryl alcohol, urea, and an aldehyde (urea-modified furan resin), a condensate of furfuryl alcohol, melamine, and an aldehyde, a condensate of furfuryl alcohol, ethylene urea, and an aldehyde, a furfuryl alcohol condensate, a condensate of furfuryl alcohol and aldehydes, and a condensate of furfuryl alcohol, a phenol, and an aldehyde, and at least one selected from the group consisting of co-condensates of two or more selected from the above group. <15> The foundry composition according to any one of <11> to <14>, wherein the aldehyde is at least one selected from the group consisting of formaldehyde, acetaldehyde, glyoxal, furfural, terephthalaldehyde, and hydroxymethylfurfural.<16> The foundry composition according to any one of <11> to <15>, wherein the phenol is at least one selected from the group consisting of phenol, cresol, resorcinol, bisphenol A, bisphenol C, bisphenol E, and bisphenol F. <17> The foundry composition according to any one of <11> to <16>, wherein the content of the furan resin in the acid-curable resin 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, even more preferably substantially 100% by mass, and even more preferably 100% by mass. <18> The foundry composition according to any one of <11> to <17>, wherein the content of the acid-curing resin in the binder composition for foundry production is preferably 5.0% by mass or more, more preferably 6.0% by mass or more, even more preferably 7.0% by mass or more, and is preferably 45.0% by mass or less, more preferably 43.0% by mass or less, and even more preferably 42.0% by mass or less. <19> The foundry composition according to any one of <11> to <18>, wherein the mass ratio of the refractory particles, the binder composition for foundry production, and the hardener composition for foundry production is 0.5 to 1.5 parts by mass and 0.07 to 1 part by mass, per 100 parts by mass of the refractory particles. <20> A method for producing a mold, comprising: a mixing step of mixing the refractory particles, the acid-curing resin-containing foundry-making binder composition, and the hardener composition for foundry-making according to any one of <1> to <10> to obtain the foundry-making composition; and a curing step of curing the foundry-making composition. <21> The method for producing a mold according to <20>, wherein in the mixing step, the foundry-making binder composition, the hardener composition for foundry-making, and the refractory particles are added and mixed in any order, and the foundry-making binder composition and the hardener composition for foundry-making may be mixed together to produce the foundry-making composition, and then the foundry-making composition and the refractory particles may be mixed together, or the foundry-making binder composition, the hardener composition for foundry-making, and the refractory particles may be added and mixed together, respectively. <22> The method for manufacturing a mold according to <20> or <21>, wherein the method for mixing the raw materials in the mixing step is a method for adding and kneading the raw materials using a batch mixer, or a method for supplying and kneading the raw materials to a continuous mixer.<23> Use of the hardener composition for foundry molding according to any one of <1> to <10> for producing a mold.

[0043] Examples that specifically illustrate the present invention will be described below.

[0044] Examples 1 to 6, Comparative Example 1 [Production of Curing Agent Compositions] [Production of Curing Agent Composition A] 576 parts by mass of industrial xylene (manufactured by ENEOS Corporation) was charged into a three-necked flask and stirring was initiated. Next, 424 parts by mass of 25% fuming sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was charged into a dropping funnel and added dropwise to the three-necked flask at a constant rate. After the dropwise addition of fuming sulfuric acid was completed, the mixture was allowed to react at 100°C for 1 hour. After the reaction was completed, the remaining xylene was removed by topping to obtain Curing Agent Composition A. The content of dixylyl sulfone in Curing Agent Composition A was measured by the following method and was found to be 0.22% by mass. The content of xylene sulfonic acid was 47.08% by mass, and the content of sulfuric acid was 9.4% by mass. The contents of xylene sulfonic acid and sulfuric acid were calculated from the blend amounts of the raw materials.

[0045] [Preparation of Curing Agent Composition B] 576 parts by mass of industrial xylene (manufactured by ENEOS Corporation) was charged into a three-neck flask and stirring was initiated. Next, 424 parts by mass of 25% fuming sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was charged into a dropping funnel and added dropwise to the three-neck flask at a constant rate. After the addition of the fuming sulfuric acid was completed, the reaction was allowed to proceed at 125°C for 1 hour. After the reaction was completed, the remaining xylene was removed by topping to obtain Curing Agent Composition B. The content of dixylyl sulfone in Curing Agent Composition B, measured by the following method, was 0.62% by mass. The content of xylene sulfonic acid was 46.68% by mass, and the content of sulfuric acid was 9.4% by mass. The contents of xylene sulfonic acid and sulfuric acid were calculated from the amounts of the raw materials.

[0046] [Quantitative Determination of Dixylyl Sulfone in Curing Agent Composition] 100 cc of water was placed in a 500 cc separatory funnel. Next, 6-10 g of the curing agent composition was weighed out and poured into the separatory funnel. The liquid in the separatory funnel was neutralized with 25% sodium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd.; 25 w / v% sodium hydroxide solution). 200 ml of petroleum ether (Fujifilm Wako Pure Chemical Industries, Ltd.; petroleum ether) was added and the mixture was shaken for approximately 15 minutes. The lower layer (aqueous layer) was then extracted and washed three times with approximately 50 cc of water. The mixture was then dehydrated with approximately 40-50 g of anhydrous sodium sulfate (Fujifilm Wako Pure Chemical Industries, Ltd.; sodium sulfate (anhydrous)) and allowed to stand for approximately 15 minutes. The weight of the 500 cc recovery flask was then accurately weighed. The liquid in the separatory funnel was filtered into a 500 cc recovery flask using filter paper (No. 2 filter paper manufactured by ADVANTEC Corporation). The inside of the separatory funnel was then washed with petroleum ether three to four times and poured into the recovery flask. The liquid in the recovery flask was topped with petroleum ether in an evaporator, and the weight of the recovery flask after drying was precisely weighed. The proportion of dixylyl sulfone in the curing agent composition was calculated by dividing the difference in weight of the recovery flask before and after drying by the amount of curing agent composition charged.

[0047] [Confirmation of the Presence or Absence of Cracks in Polyvinyl Chloride Test Pieces] The curing agent composition A, the curing agent composition B, and water were mixed to the compositions shown in Examples 1 to 6 and Comparative Example 1 in Table 1, respectively, to obtain curing agent compositions according to each Example and Comparative Example. 110 g of the curing agent composition according to each Example and Comparative Example and 1.1 g of diisononyl phthalate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were charged into a 200 ml glass bottle and mixed. Next, a 100 x 25 x 3 mm polyvinyl chloride (PVC) test piece (manufactured by TP Giken Co., Ltd.) was fixed with bolts to a rounded polyethylene fixture with a radius of 130 mm to prepare an immersion test kit. The prepared kit was placed in a bottle containing the curing agent composition. At this time, the test piece in the bottle was half immersed. The lid of the bottle was closed and the bottle was left to stand in a thermostatic chamber at 35°C for 14 days. After 14 days, the test piece was visually inspected for cracks and evaluated according to the following criteria. The evaluation results are shown in Table 1. A: No cracks B: Fine cracks C: Large cracks D: Completely broken

[0048]

[0049] The curing agent compositions according to Examples 1 to 6 did not cause any cracks or only minute cracks in the polyvinyl chloride test pieces, whereas the curing agent composition according to Comparative Example 1 caused the polyvinyl chloride test pieces to break completely. This shows that the curing agent composition according to Comparative Example 1 corresponds to a conventional curing agent composition.

[0050] Example 7 and Comparative Example 2 Production of Foundry Composition Under conditions of 35°C and 55% RH, 0.32 parts by mass of a hardener composition for foundry molding shown in Table 2 was added to 100 parts by mass of furan reclaimed silica sand and mixed. Next, 0.8 parts by mass of Kao Lightner EF-5402 (manufactured by Kao-Quaker Corporation) was added as a binder composition for foundry molding, and the mixture was mixed to obtain a foundry composition.

[0051] [Evaluation of Mold Compressive Strength] The foundry composition immediately after kneading was filled into a cylindrical test piece frame with a diameter of 50 mm and a height of 50 mm. After 30 minutes, the frame was demolded and the compressive strength (MPa) was measured according to the method described in JIS Z 2604-1976. This strength was designated the "compressive strength after 30 minutes." Separately, a foundry composition was similarly filled into a test piece frame and after 2 hours, the frame was demolded. After 24 hours from filling, the compressive strength (MPa) was measured according to the method described in JIS Z 2604-1976 and designated the "compressive strength after 24 hours." A higher value indicates higher mold strength. The evaluation results are shown in Table 2. The mold (Example 7) produced using the curing agent composition according to the present invention (Example 1) had the same mold strength as the mold (Comparative Example 2) produced using the curing agent composition according to Comparative Example 1, which corresponds to a conventional curing agent composition. This shows that the mold produced using the hardener composition according to the present invention has mold strength that is sufficient for practical use.

[0052]

Claims

1. A hardener composition for foundry molding containing at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylene sulfonic acid, the water content is 50.0% by mass or more and 99.0% by mass or less, and the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass.

2. The hardener composition for mold making according to claim 1, wherein the acid component contains sulfuric acid.

3. The hardener composition for molding a foundry mold according to claim 2, wherein the content of sulfuric acid in the hardener composition for molding a foundry mold is more than 0% by mass and not more than 30% by mass.

4. A foundry composition comprising a binder composition for foundry molding containing refractory particles and an acid-hardening resin, and the hardener composition for foundry molding according to any one of claims 1 to 3.

5. The foundry composition of claim 4, wherein the acid-hardening resin comprises a furan resin.

6. A method for manufacturing a mold, comprising a mixing step of mixing a binder composition for foundry molding containing refractory particles and an acid-hardening resin with a hardener composition for foundry molding according to any one of claims 1 to 3 to obtain a foundry composition, and a hardening step of hardening the foundry composition.

7. The method for producing a mold according to claim 6, wherein the acid-hardening resin contains a furan resin.

8. A hardener composition for foundry molding containing at least an acid component, water, and dixylyl sulfone, wherein the acid component contains xylene sulfonic acid, the water content is 50.0% by mass or more and 99.0% by mass or less, the dixylyl sulfone content is more than 0% by mass and less than 0.43% by mass, and the ratio of the dixylyl sulfone content to the xylene sulfonic acid content in the hardener composition for foundry molding (dixylyl sulfone content / xylene sulfonic acid content) is 0.001 or more and 0.012 or less.

9. Use of the hardener composition for foundry molding according to any one of claims 1 to 3 for producing a mold.

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