JP5430313B2 - Binder composition for mold making - Google Patents

Description

  The present invention relates to a binder composition for mold making containing an acid curable resin and hydrolyzable tannin, and a method for producing a mold using the same.

  An acid-curable self-hardening mold is obtained by adding a mold-forming binder containing an acid-curable resin and a curing agent containing phosphoric acid, organic sulfonic acid, sulfuric acid, etc. to refractory particles such as silica sand. After kneading these, the obtained kneaded sand is filled into a mold such as a wooden mold and the acid curable resin is cured. Furan resin, phenol resin, etc. are used for acid curable resin. Furan resin is furfuryl alcohol, furfuryl alcohol / urea formaldehyde resin, furfuryl alcohol / formaldehyde resin, furfuryl alcohol / phenol / formaldehyde. Resins and other known modified furan resins are used.

  One of the important conditions for producing a mold is the productivity of the mold. For self-hardening molds, in order to increase mold productivity, it is necessary to increase the mold curing speed after filling the mold with kneaded sand and shorten the time required to remove the mold from the mold (molding time). There is.

  In order to improve the productivity of the mold, for example, Patent Document 1 discloses a binder composition in which the curing rate of the mold is increased by adding a furan compound.

  On the other hand, from the viewpoint of the working environment, it is desired to reduce sulfur components in hardeners that cause bad odors such as formaldehyde during mold casting and sulfur oxides during casting, and various measures have been proposed. ing. For example, Patent Document 2 discloses a binder composition containing an extract mainly composed of condensed tannin extracted from bark such as acacia, quebraco, and radiatapine. Patent Document 3 discloses a furan resin composition in which polynuclear polyphenol glycosides are added as a preventive measure for precipitation of aminoplasts when aminoplasts such as urea formaldehyde resin are dissolved in furfuryl alcohol to form furan resins. Is disclosed. Patent Document 4 discloses a binder composition containing a plant natural product extract composition extracted from a natural product such as a plant-derived leaf, fruit, seed, or worm hump parasitic on a plant. . In order to make the final strength of the mold sufficient, an aminosilane coupling agent is used as a mold strength improver.

JP 2006-70247 A JP 2007-326122 A JP 56-81359 A JP 2009-119505 A

  However, when the hydrolyzable tannin and the aminosilane coupling agent coexist, the binder composition containing the furan resin, the hydrolyzed tannin and the aminosilane coupling agent has poor storage stability, and the binder composition contains There was a problem that precipitation occurred. Usually, the binder composition is stored in a tank, supplied to a mixer by piping, and mixed with foundry sand and a hardener. If such precipitation occurs, the supply stability of the resin will be insufficient due to clogging of the pipe, etc., and the strength of the mold will decrease, and the effective tank capacity will decrease due to accumulation in the tank. Become.

  The present invention provides a binder composition for mold making that improves the mold curing rate, has excellent mold strength, and does not cause resin precipitation, and a mold manufacturing method using the same. provide.

  The binder composition for mold making of the present invention comprises an acid curable resin (A), a hydrolyzable tannin (B), and at least one silane coupling agent (C) selected from epoxy silane, mercaptosilane, and ureidosilane. ) Containing a binder composition for mold making.

  The mold production method of the present invention is a mold production method comprising a step of curing a mixture containing refractory particles, a mold forming binder composition and a curing agent, and the mold forming binder composition It is a manufacturing method of the casting_mold | template which uses the binder composition for casting_mold | template shaping | molding of the said this invention as.

  According to the binder composition for mold making of the present invention, the mold curing rate is improved, the mold strength is excellent, the resin is not precipitated, and the storage stability is excellent. It is possible to provide a binder composition for mold making having excellent properties. Further, according to the method for producing a mold of the present invention, since a stable one-pack binder composition for mold making is used, the operation is simple and the mold productivity is good.

  The binder composition for mold making of the present invention (hereinafter, also simply referred to as “binder composition”) is used as a binder when producing a mold, and is an acid-curable resin ( A), hydrolyzable tannin (B), and one or more silane coupling agents (C) selected from epoxy silane, mercaptosilane and ureidosilane. Hereinafter, the components contained in the binder composition of the present invention will be described.

<Acid curable resin (A)>
As the acid curable resin, conventionally known resins can be used, for example, furfuryl alcohol, condensate of furfuryl alcohol and aldehydes, condensate of phenols and aldehydes, condensate of melamine and aldehydes, and urea. And those consisting of one kind selected from the group consisting of condensates of aldehydes and those consisting of a mixture of two or more kinds selected from these groups can be used. Moreover, what consists of 2 or more types of cocondensates chosen from these groups can also be used. Among these, from the viewpoint of resin viscosity, it is preferable to use one or more selected from furfuryl alcohol, a condensate of furfuryl alcohol and aldehydes, and a condensate of urea and aldehydes, and co-condensates thereof. . Since furfuryl alcohol can be produced from a plant whose raw material is a non-petroleum resource, it is preferable to use furfuryl alcohol, furfuryl alcohol and aldehyde condensates, and co-condensates thereof from the viewpoint of the environment. . From the viewpoint of adjusting the nitrogen content in the binder composition to a suitable range described later, and from the viewpoint of cost, the condensate of urea and aldehydes, and the condensate of urea and aldehydes and furfuryl alcohol It is preferable to use a cocondensate, and it is more preferable to use formaldehyde as the aldehydes. From the viewpoint of adjusting the nitrogen content in the binder composition to a suitable range described later, and from the viewpoint of the curing rate of the mold, the condensate of melamine and aldehydes, and the condensate of melamine and aldehydes and furfuryl It is preferable to use a co-condensate with alcohol, and it is more preferable to use a condensate of melamine and formaldehyde.

  Examples of the aldehydes include formaldehyde, acetaldehyde, glyoxal, furfural, terephthalaldehyde, and the like, and one or more of these can be used as appropriate. From the viewpoint of 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 or terephthalaldehyde.

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

  In the case of producing a condensate of furfuryl alcohol and aldehydes, it is preferable to use 0.01 to 1 mol of aldehyde with respect to 1 mol of furfuryl alcohol from the viewpoint of improving the curing speed and improving the mold strength. . Moreover, when manufacturing the condensate of phenols and aldehydes, it is preferable to use 1-3 mol of aldehydes with respect to 1 mol of phenols from a viewpoint of mold intensity | strength improvement. Moreover, when manufacturing the condensate of a melamine and aldehydes, it is preferable to use 1-3 mol of aldehydes with respect to 1 mol of melamine from a viewpoint of mold intensity | strength improvement. Moreover, when manufacturing the condensate of urea and aldehydes, it is preferable to use 1-2 mol of aldehydes with respect to 1 mol of urea from a viewpoint of a mold | die strength improvement, and 1.5-1.8. It is more preferable to use molar.

  The content of the acid curable resin in the binder composition is preferably 55 to 95% by weight, more preferably 60 to 90% by weight, and still more preferably from the viewpoint of sufficiently expressing the mold strength. 65 to 85% by weight.

  In the binder composition of the present invention, the nitrogen content in the binder composition is preferably 0.5% by weight or more, and 1.0% by weight or more from the viewpoint of increasing the strength of the obtained mold. More preferred is 2.0% by weight or more. Further, from the viewpoint of reducing nitrogen gas defects in the casting, the nitrogen content in the binder composition is preferably 6.0% by weight or less, more preferably 5.0% by weight or less, and 4.0% by weight. % Or less is more preferable. Taking the above viewpoints together, the nitrogen content in the binder composition is preferably 0.5 to 6.0% by weight, more preferably 1.0 to 5.0% by weight, and 2.0 to 4.0% by weight is more preferable. In order to adjust the nitrogen content in the binder composition within the above range, the content of the nitrogen-containing compound in the binder composition may be adjusted. As the nitrogen-containing compound, urea, melamine, a condensate of urea and aldehydes, a condensate of melamine and aldehydes, a urea resin, a urea-modified resin, and the like are preferable. The nitrogen content in the binder composition can be quantified by the Kjeldahl method. Furthermore, the amount of nitrogen derived from urea, urea resin, furfuryl alcohol / urea resin (urea-modified resin), and furfuryl alcohol / urea formaldehyde resin was determined by 13C-NMR for the carbonyl group (C = O group) derived from urea. It can also be obtained by quantification.

<Hydrolyzed tannin (B)>
The binder composition of the present invention contains hydrolyzable tannin from the viewpoint of increasing the curing rate of the mold. Hydrolyzed tannin is a kind of polyphenol also called tannic acid, and has the property of hydrolyzing into a water-soluble substance when added to dilute hydrochloric acid and boiled. For example, it is an ester of a polyhydric phenolic acid and a polyhydric alcohol extracted from leaves, seeds, fruits, insect worms and the like of dicotyledonous plants. Preferred hydrolyzable tannins are hydrolyzed tannins extracted from gallic and / or pentaploids (Nurdeaceae or insects of the same genus) from the viewpoint of availability, component stability, and high extraction efficiency. Yes, it is an ester of sugar and gallic acid. Hydrolyzed tannin belongs to a different structural group from condensed tannin condensed with flavonoid polyphenols in that it has a large number of ester bonds that can be hydrolyzed and is likely to interact with moisture. is there.

  From the viewpoint of solubility in the binder composition, the molecular weight of the hydrolyzable tannin is preferably 500 to 3000, more preferably 1000 to 2000, and further preferably 1500 to 2000. Further, the content of the hydrolyzable tannin in the binder composition is preferably 0.1 to 40% by weight from the viewpoint of solubility in the binder composition and from the viewpoint of enhancing the deep curability of the mold. More preferably, it is 1-20 weight%, More preferably, it is 1-15 weight%, More preferably, it is 5-10 weight%.

  Although the details of the relationship between the deep curability of the mold and the hydrolyzable tannin are unknown, when the binder composition containing hydrolyzable tannin and the curing agent are mixed, the hydrolyzable type Acid curable resin that is a dehydration condensation reaction occurs in the deep part of the mold that is not exposed to the outside air due to the hydrolysis reaction of the ester in tannin and the consumption of water from the curing reaction system by the amount of the reaction water ( This is presumably because the reaction of furan resin) is promoted.

  In addition, since the hydrolyzable tannin described above can be obtained from natural materials as described above, an excellent binder composition can be stably provided even if petroleum resources are tight. In addition, hydrolyzable tannin has good solubility in an acid curable resin such as furan resin, and therefore can suppress the occurrence of precipitation and turbidity when the binder composition is stored for a long period of time. This makes it possible to stably supply the binder composition in an automatic supply facility for the binder composition during mold production.

<One or more silane coupling agents (C) selected from epoxy silane, mercaptosilane, and ureidosilane>
The binder composition of the present invention contains one or more silane coupling agents (C) selected from epoxy silane, mercaptosilane, and ureidosilane. The specific silane coupling agent (C) of the present invention is blended from the viewpoint of improving the mold strength and from the viewpoint of not causing precipitation in the binder composition. When a conventionally known aminosilane is used in combination with hydrolyzable tannin, both cause gelation, the solubility in the binder composition decreases, and precipitation occurs.

  Epoxy silane is a silane coupling agent containing an epoxy group. Furthermore, it is preferable that no amino group is contained. Specific examples include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltri An ethoxysilane is mentioned. From the viewpoint of the reactivity of the silane coupling agent, 3-glycidoxypropyltrimethoxysilane is more preferable.

  Mercaptosilane is a silane coupling agent containing a mercapto group. Furthermore, it is preferable that no amino group is contained. Specific examples include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane. From the viewpoint of the reactivity of the silane coupling agent, 3-mercaptopropyltrimethoxysilane is more preferable.

  Ureidosilane is a silane coupling agent containing a ureido group. Furthermore, it is preferable that no amino group is contained. Specific examples include 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropylmethyldimethoxysilane and 3-ureidopropylmethyldiethoxysilane. From the viewpoint of the reactivity of the silane coupling agent, 3-ureidopropyltriethoxysilane is more preferable.

  The content of the specific silane coupling agent (C) of the present invention in the binder composition is preferably 0.01 to 0.7% by weight from the viewpoint of improvement in mold strength and cost. More preferably, it is 05-0.5 weight%, and it is still more preferable that it is 0.08-0.3 weight%.

  Among the specific silane coupling agents (C) of the present invention, mercaptosilane and ureidosilane are preferable from the viewpoint of mold strength, and ureidosilane is more preferable. Moreover, 2 types or 3 types or more may be selected from epoxy silane, mercapto silane, and ureido silane, and you may use together in the range of the said content.

<Hardening accelerator (D) selected from the group consisting of aromatic dialdehyde and phenol derivative>
The binder composition of the present invention is a curing accelerator from the viewpoint of increasing the pot life and shortening the mold release time, that is, from the viewpoint of shortening the mold release time in the case of the same pot life. It preferably contains a curing accelerator (D) selected from the group consisting of aromatic dialdehydes and phenol derivatives (hereinafter simply referred to as “curing accelerator (D)”). The content of the curing accelerator (D) in the binder composition is a viewpoint that extends the pot life and shortens the mold release time, that is, the viewpoint that the mold release time can be shortened in the case of the same pot life. Therefore, it is preferably 0.1 to 25% by weight, more preferably 0.5 to 15% by weight, and still more preferably 1 to 10% by weight. The curing accelerator (D) may be added to the kneaded sand as a third component as a curing accelerator in addition to those contained in the binder composition.

  When the acid curable resin (A), the hydrolyzable tannin (B) and the curing accelerator (D) coexist, the pot life can be increased and the mold release time can be shortened, that is, the same pot life. Can shorten the die-cutting time, further improve the deep curability of the mold, and prevent the mold from cracking. Although the clear mechanism is unknown, it is speculated that the aldehyde group of the aromatic dialdehyde or the hydroxyl group of the phenol derivative acts on the hydrolyzable tannin as a crosslinking agent.

  Aromatic dialdehydes include terephthalaldehyde, phthalaldehyde, isophthalaldehyde, and the like, and derivatives thereof. These derivatives mean compounds having a substituent such as an alkyl group on the aromatic ring of an aromatic compound having two formyl groups as the basic skeleton. From the viewpoint of extending the pot life and shortening the mold release time, that is, from the viewpoint of shortening the mold release time for the same pot life, and from the viewpoint of preventing cracking of the mold, terephthalaldehyde and terephthalaldehyde derivatives are used. Preferably, terephthalaldehyde is more preferable. The content of the aromatic dialdehyde in the binder composition is a viewpoint that lengthens the pot life and shortens the mold release time, that is, the viewpoint that the mold release time can be shortened when the same pot life is used. From the viewpoint of sufficiently dissolving the aromatic dialdehyde in the acid curable resin and suppressing the odor of the aromatic dialdehyde itself, it is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight. Yes, more preferably 1 to 5% by weight.

  Examples of the phenol derivative include resorcin, cresol, hydroquinone, phloroglucinol, methylene bisphenol, and the like. Among these, from the viewpoint of improving the mold strength, resorcin and phloroglucinol are preferable, and resorcin is more preferable. The content of the phenol derivative in the binder composition is preferably 1.5 to 25% by weight from the viewpoint of the solubility of the phenol derivative in the acid-curable resin and the mold strength. It is more preferably from 0 to 15% by weight, still more preferably from 3.0 to 10% by weight.

  The proportion of the curing accelerator (D) in the total curing accelerator is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and still more preferably 90 to 100% by weight, from the viewpoint of improving the mold strength. 100% by weight is even more preferable.

<Curing accelerator other than curing accelerator (D)>
The binder composition of the present invention may contain a curing accelerator other than the curing accelerator (D) selected from the group consisting of the above-mentioned aromatic dialdehydes and phenol derivatives. As a curing accelerator other than the curing accelerator (D) selected from the group consisting of an aromatic dialdehyde and a phenol derivative, from the viewpoint of improving the mold strength, a compound represented by the following general formula (1) (hereinafter, curing) Accelerator (referred to as (1)) is preferred.

[Wherein, X ₁ and X ₂ each represent a hydrogen atom, CH ₃ or C ₂ H ₅ . ]

  As the curing accelerator (1), 2,5-bishydroxymethylfuran, 2,5-bismethoxymethylfuran, 2,5-bisethoxymethylfuran, 2-hydroxymethyl-5-methoxymethylfuran, 2-hydroxy Mention may be made of methyl-5-ethoxymethylfuran and 2-methoxymethyl-5-ethoxymethylfuran. Among these, 2,5-bishydroxymethylfuran is preferably used from the viewpoint of improving the mold strength. 2,5-bishydroxymethylfuran has a higher reactivity than 2,5-bismethoxymethylfuran and 2,5-bisethoxymethylfuran, and is a binder composition containing, for example, furfuryl alcohol as a main component. This is because the curing reaction can be promoted. The content of the curing accelerator (1) in the binder composition is preferably 0.5 to 63% by weight, and 1.8 to 50% by weight from the viewpoints of solubility and mold strength. %, More preferably 2.5 to 50% by weight, and even more preferably 3.0 to 40% by weight.

<Moisture>
The binder composition of the present invention may further contain moisture. For example, when synthesizing various condensates such as a condensate of furfuryl alcohol and aldehydes, an aqueous raw material is used or condensed water is generated. Therefore, the condensate is usually in the form of a mixture with moisture. However, when such a condensate is used in a binder composition, it is not necessary to darely remove these moisture derived from the synthesis process. In addition, moisture may be further added for the purpose of adjusting the binder composition to a viscosity that is easy to handle. However, if the moisture is excessive, the curing reaction of the acid curable resin may be inhibited. Therefore, the moisture content in the binder composition is preferably in the range of 0.5 to 30% by weight, From the viewpoint of making the binder composition easy to handle and maintaining the curing reaction rate, it is more preferably 1 to 10% by weight. Further, from the viewpoint of not causing the precipitation of the resin and not hindering the curing rate, preferably 1 ~ 6% by weight. Further, from the viewpoint of improving deep-part curability, it is preferably 10% by weight or less, and more preferably 5% by weight or less from the viewpoint of preventing resin precipitation and preventing the curing rate.

<PH>
The binder composition of the present invention is a stable binder composition even in the case of a resin containing urea, in which the resin does not precipitate even when the pH of the binder composition is 4-9. Since it can be obtained, there is an advantage that it can be used universally without being restricted by the pH of the resin. Since the furan resin is acid curable, the pH of the binder composition is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more, from the viewpoint of preventing an increase in the viscosity of the resin during long-term storage. On the other hand, from the viewpoint of further increasing the mold curing rate, the pH is preferably 9 or less, more preferably 8 or less, and even more preferably 7 or less. Usually, the pH is appropriately set depending on the storage period / storage temperature of the binder composition and the curing rate of the mold.

  On the other hand, when the monoaminosilane type or diaminosilane type silane coupling agent is interacted with the hydrolyzable tannin (B), precipitation usually occurs in the binder composition when about one day has passed after compounding. In particular, in the region where the pH is high, the amount of precipitation is large. That is, the pH cannot be increased in order to prevent an increase in the viscosity of the resin during a long storage period. This is because both hydrolyzable tannin has high reactivity, and the binder composition containing this has both high viscosity increase rate and long-term storage. Means you can't. The pH is measured with a pH meter at 25 ° C. when the binder composition and an equal weight of ion-exchanged water are mixed.

  The binder composition of the present invention is suitable for a method for producing a mold having a step of curing a mixture containing refractory particles, a binder composition for mold making, and a curing agent. That is, the method for producing a mold of the present invention is a method for producing a mold using the above-mentioned binder composition of the present invention as a binder composition for mold making.

  In the mold manufacturing method of the present invention, the mold can be manufactured using the process of the conventional mold manufacturing method as it is. For example, by adding the binder composition of the present invention and a curing agent for curing the binder composition to the refractory particles and kneading them with a batch mixer or a continuous mixer, the mixture (kneading) Sand).

  As the refractory particles, conventionally known particles such as silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, and synthetic mullite sand can be used. Recycled ones can also be used.

  Curing agents such as sulfonic acid compounds such as xylene sulfonic acid (especially m-xylene sulfonic acid) and toluene sulfonic acid (particularly p-toluene sulfonic acid), acidic aqueous solutions containing phosphoric acid compounds, sulfuric acid and the like are conventionally known. One or more of these can be used. Further, the curing agent may contain one or more solvents selected from the group consisting of alcohols, ether alcohols and esters, and carboxylic acids. Among these, alcohols and ether alcohols are preferable, and ether alcohols are more preferable from the viewpoint of improving the deep curability of the mold and improving the mold strength. Moreover, when the said solvent and carboxylic acid are contained, since the moisture content in a hardening | curing agent is reduced, the deep-part curability of a casting_mold | template will become still more favorable, and casting_mold | template strength will further improve. The content of the solvent or the carboxylic acid in the curing agent is preferably 5 to 50% by weight and more preferably 10 to 40% by weight from the viewpoint of improving the mold strength. Moreover, methanol and ethanol can be contained from a viewpoint of reducing the viscosity of a hardening | curing agent.

  From the viewpoint of improving the deep curability of the mold and improving the mold strength, the alcohol is preferably propanol, butanol, pentanol, hexanol, heptanol, octanol, or benzyl alcohol, and the ether alcohol is 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, ethylene glycol monophenyl ether are preferred, and esters include butyl acetate, Butyl benzoate, ethylene glycol monobutyl ether acetate, diethylene glycol Preferably mono butyl ether acetate, the carboxylic acids, from the viewpoint of improving the strength and odor reduction, preferably a carboxylic acid having a hydroxyl group, lactic acid, citric acid, malic acid are more preferred.

  The ratio of the refractory particles, the binder composition and the curing agent in the kneaded sand can be set as appropriate, but the binder composition is 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the refractory particles. The curing agent is preferably in the range of 0.07 to 1 part by weight. With such a ratio, it is easy to obtain a mold having sufficient strength. Furthermore, the content of the curing agent is such that the amount of water contained in the mold is reduced as much as possible to improve the deep curability of the mold, and from the viewpoint of mixing efficiency in the mixer, the acid curability in the binder composition. The amount is preferably 10 to 40 parts by weight, more preferably 15 to 35 parts by weight, and still more preferably 18 to 25 parts by weight with respect to 100 parts by weight of the resin.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

<Nitrogen content of binder composition and condensate>
Measurement was performed by the Kjeldahl method shown in JIS M 8813.

<Moisture content of binder composition>
Using a Karl Fischer moisture meter (MKS-510N) manufactured by Kyoto Electronics Industry Co., Ltd., the moisture content was measured by the Karl Fischer method. Hydranal composite 5 (manufactured by Riedel De Haan) was used as a titration reagent. In addition, MS (manufactured by Mitsubishi Kasei Co., Ltd.) was used as the dehydrating solvent.

<PH of binder composition>
The pH in the binder composition was adjusted to the values shown in Table 1 with an aqueous sodium hydroxide solution and an aqueous oxalic acid solution. The measurement method was performed by mixing a binder composition and an equal weight of ion-exchanged water and measuring at 25 ° C. with a pH meter.

<Storage stability (appearance after 1 day of formulation)>
The binder compositions of the following Examples and Comparative Examples prepared by blending each component were placed in a 20 ml transparent glass reagent bottle, sealed, and stored at 25 ° C. and 55% RH. The appearance was visually confirmed after a day and evaluated according to the following criteria (ac).
a: No change at all and transparent.
b: Slight precipitation is observed.
c: Precipitation is observed.

<Mold strength (compressive strength)>
The kneaded sand immediately after kneading was filled into a cylindrical test piece frame having a diameter of 50 mm and a height of 50 mm. When 1 hour passed after filling, the mold was removed, and the compressive strength (MPa) was partially measured by the method described in JIS Z 2604-1976. Further, after removing the remaining mold, the mold was allowed to stand for 24 hours at 25 ° C. and 55% RH, and the compression strength (MPa) was measured in the same manner.

(Examples 1-9 and Comparative Examples 1-8)
Under conditions of 25 ° C. and 55% RH, 0.32 parts by weight of a curing agent (53% by weight aqueous solution of m-xylene sulfonic acid) was added to 100 parts by weight of regenerated furan sand, and then the caking shown in Table 1 0.9 parts by weight of the agent composition was added and mixed to obtain kneaded sand. In addition, as said furan reproduction | regeneration sand, the weight reduction | decrease rate (LOI) when heated at 1000 degreeC for 1 hour in the air was used.

  As shown in Table 1 and Table 2, in Examples 1 to 9, good results were obtained for any of the evaluation items. On the other hand, Comparative Examples 1 to 8 were results that were significantly inferior to Examples 1 to 9 for at least one evaluation item. That is, in the absence of the silane coupling agent, the mold strength was poor, and the phenyl type and vinyl type silane coupling agents could not achieve satisfactory mold strength. On the other hand, monoaminosilane-type and diaminosilane-type silane coupling agents were satisfactory in mold strength, but precipitated, resulting in fatal defects as a binder composition. From this result, it was confirmed that according to the present invention, it is possible to provide a binder composition for mold making that is excellent in mold strength, does not cause resin precipitation, and has excellent storage stability. Furthermore, when the pH is adjusted to 7 (neutral) to prevent an increase in viscosity during long-term storage of the furan resin, in the present invention, as shown in Example 7, no precipitation occurs in the binder composition. On the other hand, when N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane was used as in Comparative Example 7, precipitation occurred at pH 7. That is, the degree of freedom is reduced in the resin composition design. Further, when the amount of water in the binder composition was increased, when aminosilane was used, the degree of occurrence of precipitation was reduced as in Comparative Example 8, but not so much that it was completely eliminated.

Claims (5)

  Binder composition for mold making containing acid curable resin (A), hydrolyzable tannin (B), and at least one silane coupling agent (C) selected from epoxy silane, mercaptosilane and ureidosilane.   The acid curable resin (A) comprises furfuryl alcohol, a condensate of furfuryl alcohol and aldehydes, a condensate of phenols and aldehydes, a condensate of melamine and aldehydes, and a condensate of urea and aldehydes. The binder composition for mold making according to claim 1, comprising one or more selected from the group, or two or more cocondensates selected from the group.   Furthermore, the binder composition for mold making of Claim 1 or 2 containing the hardening accelerator (D) chosen from the group which consists of an aromatic dialdehyde and a phenol derivative.   Moisture content is 1 to 6 weight%, The binder composition for mold making of any one of Claims 1-3. A method for producing a mold comprising a step of curing a mixture comprising refractory particles, a binder composition for mold making, and a curing agent,
The manufacturing method of a casting_mold | template in which the said binder composition for mold making is the binder composition for mold making of any one of Claims 1-4.