Disintegrant for resin-coated sand and resin-coated sand

Abstract

To provide a disintegrant for resin-coated sand that can impart excellent peel-back resistance and disintegration properties to resin-coated sand while ensuring strength and fusion point. [Solution] A disintegrant for resin-coated sand, comprising a specific phosphonic acid ester compound A and a specific phosphonic acid ester compound B, wherein the mass ratio of phosphonic acid ester compound A to phosphonic acid ester compound B (phosphonic acid ester compound A:phosphonic acid ester compound B) is 99.0:1.0 to 90.0:10.0.

Description

[Technical Field]

[0001] The present invention relates to a disintegrant for resin-coated sand and resin-coated sand containing the same. More specifically, the present invention relates to a disintegrant for resin-coated sand that, when incorporated into resin-coated sand, ensures strength and fusion point, and enables the formation of a shell mold with excellent peel-back resistance and disintegration properties, and to resin-coated sand. [Background technology]

[0002] In the shell molding method, one of the casting methods, resin-coated sand (RCS) has traditionally been used, which is obtained by melting refractory aggregates for molds, such as silica sand, and binders, such as phenolic resin, and then adding and mixing an aqueous solution of hexamethylenetetramine, which is a hardening agent. The RCS is then heated and hardened in a mold to form the mold. Molten metal is then poured into the mold to form a casting. This mold needs to be removed after the molten metal has cooled and solidified, and is generally removed by vibrating to break down the mold. If it does not easily break down with vibration alone, a method of heating and thermal decomposition is used before applying vibration.

[0003] On the other hand, in recent years, aluminum parts have come to be used in automotive components and other products for the purpose of weight reduction. Because aluminum alloys have a lower melting point compared to metals such as iron, it has been difficult to apply sufficient heat during the thermal decomposition process mentioned above, resulting in problems such as the mold remaining in the casting without collapsing. To solve this problem, additives (hereinafter referred to as disintegrants) to improve the disintegration properties of the mold are blended into RCS. For example, Patent Document 1 discloses a resin-coated sand for molds that uses a binder prepared by blending phosphate esters and an oxidizing agent as disintegrants with a phenolic resin. On the other hand, blending a disintegrant into RCS tends to reduce the fusion point of the RCS and the strength of the formed mold. If the fusion point of the RCS is low, blocking of the RCS is more likely to occur, and if the strength of the mold is low, the risk of mold breakage during the casting process increases. Therefore, a disintegrant that does not reduce the fusion point and strength is desirable. As such a disintegrant, for example, Patent Document 2 discloses a resin composition for shell molds containing a phenolic resin and an aromatic condensed phosphate ester. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-244990 [Patent Document 2] Japanese Patent Publication No. 2007-275988 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When casting parts with complex shapes, hollow molds are used. These hollow molds are formed by heating and hardening RCS (Roller Coated Steel) in the mold, and then inverting the mold when the mold reaches a predetermined thickness to discharge the unhardened RCS. During this process, peel-back can occur, where a portion of the mold detaches, resulting in insufficient mold thickness. Since peel-back increases the risk of hollow mold damage during casting, it is desirable to suppress peel-back. However, the aforementioned prior art did not adequately address peel-back, and there was a need for an additive that could suppress peel-back while improving the mold's collapse properties. As described above, the object of the present invention is to solve the above problems, and more specifically, to provide a resin-coated sand disintegrant that, when incorporated into RCS, ensures strength and fusion point, and forms a shell mold with excellent peel-back resistance and disintegration properties, and resin-coated sand containing the same. [Means for solving the problem]

[0006] The inventors of the present invention conducted diligent research to solve the above problems and found that the above problems can be solved by including an additive in RCS that combines the compounds shown in formulas (1) and (2) in specific ratios. In other words, the present invention is as follows [1] to [2].

[0007] [1] A disintegrant for resin-coated sand, comprising a phosphonic acid ester compound A represented by formula (1) and a phosphonic acid ester compound B represented by formula (2), wherein the mass ratio of phosphonic acid ester compound A to phosphonic acid ester compound B (phosphonic acid ester compound A:phosphonic acid ester compound B) is 99.0:1.0 to 90.0:10.0. [ka] (In equation (1), R 1 and R 2 Each of these independently represents a hydrocarbon group with 1 to 22 carbon atoms. [Chemical formula] (In formula (2), R 3 represents a hydrocarbon group having 1 to 22 carbon atoms.) [2] A resin-coated sand comprising a resin composition containing 0.1 to 25 parts by mass of the disintegrant for resin-coated sand described in [1] above with respect to 100 parts by mass of the phenolic resin, and a refractory aggregate. [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide a disintegrant for resin-coated sand that can impart excellent peel-back resistance and disintegration properties while ensuring strength and fusion point to the resin-coated sand, and a resin-coated sand containing the same. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, the disintegrant for resin-coated sand of the present invention (hereinafter also referred to as "the additive of the present invention") and embodiments of the resin-coated sand will be described in detail. In this specification, a numerical range defined using the symbol "~" includes the numerical values at both ends (upper limit and lower limit) of "~". For example, "2~5" represents 2 or more and 5 or less.

[0010] [Disintegrant for Resin-Coated Sand] The additive of the present invention is composed of a phosphonate ester compound A represented by the following formula (1) and a phosphonate ester compound B represented by the formula (2), and the mass ratio of the phosphonate ester compound A to the phosphonate ester compound B (phosphonate ester compound A: phosphonate ester compound B) is 99.0:1.0 to 90.0:10.0. It is a disintegrant for resin-coated sand. Each phosphonate ester compound will be described.

[0011] [Phosphonate Ester Compound A] The phosphonate ester compound A is represented by the following formula. [Chemical formula] In formula (1), R 1 and R 2 each independently represents a hydrocarbon group having 1 to 22 carbon atoms. Also, R 1 and R 2 may be the same or different.

[0012] The hydrocarbon group in formula (1) may be saturated or unsaturated, aliphatic or aromatic, and in the case of an aliphatic group, it may be linear, branched or cyclic. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an aryl group and an aralkyl group. R 1 and R 2 From the perspective of the disintegration property of RCS, a hydrocarbon group having 2 to 18 carbon atoms is preferable, and a hydrocarbon group having 8 to 12 carbon atoms is more preferable. Also, the hydrocarbon group is preferably saturated and preferably aliphatic. In the case of an aliphatic group, it is preferably linear or branched, and more preferably branched.

[0013] Examples of the alkyl group include linear alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, heptyl group, octyl group, decyl group, lauryl group, myristyl group, palmityl group, stearyl group, behenyl group, etc., branched alkyl groups such as isopropyl group, isobutyl group, t-butyl group, isopentyl group, isooctyl group, 2-ethylhexyl group, isononyl group, 3,5,5-trimethylhexyl group, isodecyl group, isostearyl group, 2-octyldecyl group, 2-octyldodecyl group, 2-hexyldecyl group, etc., and cyclic alkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, etc.

[0014] Examples of alkenyl groups include palmitrail (also known as cis-9-hexadecenyl), oleyl (also known as cis-9-octadecenyl), and linoleyl (also known as cis, cis-9, 12-octadecadienyl). When the number of carbon atoms in an aliphatic hydrocarbon group such as an alkyl group or alkenyl group is 23 or more, it may be difficult to obtain. Examples of aryl groups include phenyl, naphthyl, tolyl, xylyl, cumenyl, mesityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, and nonylphenyl groups.

[0015] Examples of aralkyl groups include benzyl group, phenethyl group, naphthylmethyl group, benzhydryl group, trityl group, methylbenzyl group, and methylphenethyl group. R 1 and R 2 From the viewpoint of the disintegration properties of the RCS, a 2-ethylhexyl group and a lauryl group are preferred, and a 2-ethylhexyl group is particularly preferred.

[0016] The method for producing the phosphonic acid ester compound A represented by formula (1) above is not particularly limited, but one example is to carry out an esterification reaction between a phosphonic acid and an alcohol at, for example, 80 to 180°C. In the esterification reaction for producing this ester compound, it is preferable to use an amount of alcohol that is at least twice the molar ratio of the acid.

[0017] <Phosphonic acid ester compound B> The phosphonic acid ester compound B is represented by the following formula. [ka] In formula (2), R 3 This indicates a hydrocarbon group with 1 to 22 carbon atoms.

[0018] The hydrocarbon group in formula (2) may be saturated or unsaturated, aliphatic or aromatic, and in the case of aliphatic, it may be linear, branched or cyclic. Examples of hydrocarbon groups include alkyl groups, alkenyl groups, aryl groups, and aralkyl groups. R 3 From the viewpoint of the disintegration properties and peel-back resistance of the RCS, hydrocarbon groups having 2 to 18 carbon atoms are preferred, and hydrocarbon groups having 8 to 12 carbon atoms are more preferred. Furthermore, the hydrocarbon groups are preferably saturated and preferably aliphatic. If they are aliphatic, they are preferably linear or branched, and more preferably linear.

[0019] Examples of alkyl groups include linear alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, decyl, lauryl, myristyl, palmityl, stearyl, and behenyl groups; branched alkyl groups such as isopropyl, isobutyl, t-butyl, isopentyl, isooctyl, 2-ethylhexyl, isononyl, 3,5,5-trimethylhexyl, isodecyl, isostearyl, 2-octyldecyl, 2-octyldodecyl, and 2-hexyldecyl groups; and cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl groups.

[0020] Examples of alkenyl groups include palmitrail (also known as cis-9-hexadecenyl), oleyl (also known as cis-9-octadecenyl), and linoleyl (also known as cis, cis-9, 12-octadecadienyl). When the number of carbon atoms in an aliphatic hydrocarbon group such as an alkyl group or alkenyl group is 23 or more, it may be difficult to obtain. Examples of aryl groups include phenyl, naphthyl, tolyl, xylyl, cumenyl, mesityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, and nonylphenyl groups.

[0021] Examples of aralkyl groups include benzyl group, phenethyl group, naphthylmethyl group, benzhydryl group, trityl group, methylbenzyl group, and methylphenethyl group. R 3 From the viewpoint of the RCS's disintegration properties and peel-back resistance, a 2-ethylhexyl group and a lauryl group are preferred, with a lauryl group being particularly preferred.

[0022] The method for producing the phosphonic acid ester compound B represented by formula (2) above is not particularly limited, but one example is to carry out an esterification reaction between phosphonic acid and an alcohol at, for example, 80 to 180°C.

[0023] In the resin-coated sand disintegrant of the present invention, the mass ratio of phosphonate compound A to phosphonate compound B (phosphonate compound A:phosphonate compound B) is 99.0:1.0 to 90.0:10.0. If the content of phosphonate compound A in the resin-coated sand disintegrant exceeds 99.0% by mass, the peel-back resistance deteriorates, and if it is less than 90.0% by mass, sufficient disintegration may not be obtained, or the fusion point may decrease. From this viewpoint, the mass ratio of phosphonate compound A to phosphonate compound B (phosphonate compound A:phosphonate compound B) is preferably 99.0:1.0 to 92.0:8.0, more preferably 98.5:1.5 to 93.0:7.0, and particularly preferably 98.5:1.5 to 95.0:5.0.

[0024] [Resin-coated sand] The resin-coated sand of the present invention contains a resin composition containing the additives of the present invention and a phenolic resin, and a refractory aggregate.

[0025] (Resin composition) The resin composition contains the additive of the present invention and a phenolic resin. The phenolic resin used in the present invention is a solid or liquid condensation product obtained by reacting phenols and aldehydes in the presence of an acidic or basic catalyst, and is referred to as a novolac-type phenolic resin or a resol-type phenolic resin depending on the type of catalyst used.

[0026] Here, the above-mentioned phenols refer to phenols and phenol derivatives, and in addition to phenols, examples include alkylphenols such as cresol, xylenol, p-tert-butylphenol, and nonylphenol, polyhydric phenols such as resorcinol, bisphenol F, and bisphenol A, and naphthols. These phenols may be used individually or in combination of two or more. Furthermore, examples of the above-mentioned formaldehyde compounds include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, paraaldehyde, and propionaldehyde, and other known aldehyde compounds can also be used as appropriate. In addition, aqueous solutions of formaldehyde compounds, such as formalin (aqueous solution of formaldehyde), can also be used. These aldehyde compounds may be used individually or in combination of two or more. The novolac-type phenolic resin and resol-type phenolic resin described above may be used individually, or they may be mixed in any proportion as needed.

[0027] Furthermore, as reaction catalysts, when preparing novolac-type phenolic resins, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, or organic acids such as oxalic acid, p-toluenesulfonic acid, benzenesulfonic acid, and xylenesulfonic acid, as well as zinc acetate, zinc oxide, zinc chloride, magnesium oxide, and zinc acetate can be used. When preparing resol-type phenolic resins, oxides or hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide and calcium hydroxide can be used, as well as aliphatic primary, secondary, and tertiary amines such as dimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, diethylenetriamine, and dicyandiamide, aliphatic amines with aromatic rings such as N,N-dimethylbenzylamine, aromatic amines such as aniline and 1,5-naphthalenediamine, ammonia, hexamethylenetetramine, and other divalent metal naphthenic acids and divalent metal hydroxides can also be used.

[0028] The content of the additive of the present invention in the resin composition of the present invention is 0.1 to 25 parts by mass, preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass, and particularly preferably 7.5 to 12.5 parts by mass, per 100 parts by mass of phenolic resin. If the content of the additive of the present invention is too low, sufficient peel-back resistance and disintegration resistance may not be obtained. If the content of the additive of the present invention is too high, the strength and fusion point may deteriorate.

[0029] The resin composition of the present invention may contain lubricants, silane coupling agents, and the like, to the extent that they do not impair the essential effects of the present invention. Examples of lubricants include ethylenebisstearate, ethylenebisoleate, methylenebisstearate, oxystearate, stearate, palmitate, oleate, methylolamide, calcium stearate, polyethylene wax, paraffin wax, montan wax, and carnauba wax. The amount of lubricant added is preferably 0.3 to 5 parts by mass per 100 parts by mass of phenolic resin. Adding 0.3 parts by mass or more significantly improves strength and blocking resistance, while adding 5% by mass or less is preferable as it increases the curing speed and enhances the adhesive strength between sand grains.

[0030] While there are no particular limitations on the silane coupling agent, aminosilane coupling agents are preferred. Examples of aminosilane coupling agents include N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxysilane. The amount of silane coupling agent is not particularly limited, but it is desirable to use 0.05 to 5 parts by mass per 100 parts by mass of phenol resin. Using 0.05 parts by mass or more significantly improves the strength due to the coupling agent, while using 5 parts by mass or less reduces the risk of blocking in the phenol resin, which is preferable.

[0031] The method of adding (mixing) each additive to the phenolic resin is not particularly limited, but it is desirable to add them at a temperature of 130°C or higher, and more preferably at 150°C or higher. Furthermore, the mixing time after addition is not particularly limited, but it is desirable to mix for at least one hour. Additionally, each additive can be added after the resin composition is manufactured, when the resin composition (binder) and refractory aggregate are kneaded together to produce the RCS.

[0032] (Fire-resistant aggregate) The refractory aggregate used in the present invention is a mold aggregate and is typically a refractory granular material. Examples of such refractory granular materials include silica sand mainly composed of quartz, chromite sand, zircon sand, olivine sand, mullite sand, synthetic mullite sand, magnesia, special sands, and recovered or recycled sands thereof. In the present invention, various refractory granular materials can be used without particular limitation, such as new sand, recovered sand, recycled sand, or mixtures thereof. Furthermore, the particle size distribution and particle shape of the refractory granular material can be selected without particular limitation, as long as it has sufficient refractory resistance to withstand casting and is suitable for mold formation. The content of refractory aggregate in the resin-coated sand is not particularly limited, but is preferably 500 to 15,000 parts by mass, and more preferably 2,000 to 8,000 parts by mass, per 100 parts by mass of the resin composition. [Examples]

[0033] The present invention will be described in further detail below with reference to examples and comparative examples. Examples 1 and 2 below show the synthesis of phosphonic acid ester compound A represented by formula (1), examples 3 and 4 below show the synthesis of phosphonic acid ester compound B represented by formula (2), and examples 1 and 2 below show the production of additives consisting of phosphonic acid ester compound A and phosphonic acid ester compound B.

[0034] [Synthesis Example 1, Compound A-1 of Formula (1)] A thermometer and nitrogen inlet tube were inserted into a 1 L four-necked flask, and 651 g (5 mol) of 2-ethylhexanol and 164 g (2 mol) of phosphorous acid were charged. The reaction was carried out at 120°C under reduced pressure of 200 Torr or less. The reaction was terminated when the decrease in acid value per hour was 0.5 mg KOH / g or less. After the reaction was complete, the unreacted starting materials were removed by distillation at 150°C under reduced pressure of 30 Torr or less to obtain compound A-1 of formula (1).

[0035] [Synthesis Example 2, Compound A-2 of Formula (1)] Compound A-2 of formula (1) shown in Table 1 was synthesized by replacing 2-ethylhexanol in Synthesis Example 1 with lauryl alcohol, following the same procedure as in Synthesis Example 1.

[0036] [Table 1]

[0037] [Synthesis Example 3, Compound B-1 of Formula (2)] A thermometer and nitrogen inlet tube were inserted into a 1 L four-necked flask, and 260 g (2 mol) of 2-ethylhexanol and 180 g (2.2 mol) of phosphorous acid were charged. The reaction was carried out at 120°C under reduced pressure of 200 Torr or less. The reaction was stopped when the decrease in acid value per hour was 0.5 mg KOH / g or less. Then, an amount of deionized water equivalent to 20% by mass of the reaction mixture was added, and the mixture was stirred at 60°C for 10 minutes, then allowed to stand for 10 minutes, and the separated aqueous layer was removed. Subsequently, the mixture was dehydrated by stirring at 100°C and 30 Torr for 1 hour to obtain compound B-1 of formula (2).

[0038] [Synthesis Example 4, Compound B-2 of Formula (2)] In Synthesis Example 3, 2-ethylhexanol was replaced with lauryl alcohol, and compound B-2 of formula (2) shown in Table 2 was synthesized according to Synthesis Example 3.

[0039] [Table 2]

[0040] [Manufacturing Example 1, Additive 1] A thermometer and nitrogen inlet tube were inserted into a 1L four-necked flask, and 485g of compound A-1 synthesized in Synthesis Example 1 and 15g of compound B-2 synthesized in Synthesis Example 4 were mixed and stirred at 25°C for 0.5 hours to obtain additive 1.

[0041] [Manufacturing Examples 2-6, Additives 2-6] By appropriately changing the mixing ratio of the compound of formula (1) and the compound of formula (2) in Production Example 1 and performing the procedure in accordance with Production Example 1, additives 2 to 5 shown in Table 3 were obtained. Furthermore, for the phosphate ester compound shown in additive 6, di-2-ethylhexyl phosphate was used.

[0042] [Table 3]

[0043] [Example 1] A thermometer and nitrogen inlet tube were inserted into a 1 L four-necked flask, and 500 g of phenol, 345 g of 37% formalin, and 5 g of oxalic acid were charged. The reaction was carried out under reflux temperature until the reaction mixture emulsified. After that, the mixture was concentrated under reduced pressure of 30 Torr or less, and the reaction was terminated when the softening point reached 90°C to produce a phenolic resin. To 100 parts by mass of the phenolic resin, 10 parts by mass of additive 1 was added to obtain a resin composition.

[0044] [Examples 2-5 and Comparative Examples 1-4] By appropriately changing the type and blending ratio of additives in Example 1 and performing the procedure in accordance with Example 1, the resin compositions shown in Table 4 were obtained.

[0045] [Examples 1-5 and Comparative Examples 1-4: Production and Evaluation of Resin-Coated Sand] 5 kg of fresh sand heated to 150°C was mixed with 100 g of each resin composition obtained in the above examples and comparative examples in a speed mixer for 45 seconds. Then, 115 g of a 15% hexamethylenetetramine aqueous solution was added and mixed until the sand clumps broke down. When the temperature reached approximately 80°C, 5 g of calcium stearate was added and mixed for 30 seconds, after which the mixture was discharged from the mixer to obtain RCS. The following evaluation tests were performed using the obtained RCS. The evaluation results are shown in Table 4 below.

[0046] (Bending strength) Using each RCS, test specimens were prepared in accordance with JIS-K-6910, and the resulting test specimens were subjected to flexural strength (kgf / cm²) testing according to JACT test method: SM-1. 2 The bending strength was measured. A higher bending strength indicates a stronger mold. The following criteria were used for evaluation. ◎··Bending strength of 55 kgf / cm 2 That's all. 〇...Bending strength of 50 kgf / cm 2 More than 55kgf / cm 2 less than ×...Bending strength is 50 kgf / cm 2 less than

[0047] (fusion point) For each RCS, the fusion point was measured according to the JACT test method: C-1. A higher fusion temperature indicates better blocking resistance of the RCS. The following criteria were used for evaluation. ◎··Fusion point is 100℃ or higher ○··Fusing point is 95℃ or higher but less than 100℃ ×··Fusing point below 95℃

[0048] (Collapse-like) Using each RCS, test specimens were prepared in accordance with JIS-K-6910. The obtained specimens were fired at 600°C for 15 minutes in an air-isolated atmosphere to obtain fired products. The weight of the obtained fired products was then measured. Next, the fired products were placed on a 20-mesh sieve and shaken in a shaker for 2 minutes. The weight of the fired products that passed through the sieve after shaking was then measured. Based on the measured weight, the disintegration rate before and after shaking was calculated using the following formula. A higher disintegration rate indicates better disintegration rate of the RCS. (Formula) Collapse rate = Weight of fired product that passed through the sieve / Weight of fired product before shaking × 100 The following criteria were used for evaluation. ◎··The value of the above formula is 90% or higher ○··The value of the above formula is between 80% and less than 90% × The value of the above formula is less than 80%

[0049] (Peel-back resistance) Each RCS was tested in accordance with the JACT test method: C-4. The percentage of peeled-back sand was calculated using the formula below, and the peel-back resistance was evaluated. A lower percentage of peeled-back sand indicates better peel-back resistance of the RCS. (Formula) Percentage of peeled sand = Weight of peeled sand / Weight of mold × 100 The following criteria were used for evaluation. ◎··The value of the above formula is 10% or less ○··The value of the above formula is greater than 10% and less than or equal to 20% ×...The value of the above formula is over 20%

[0050] [Table 4]

[0051] As is clear from the results shown in Table 4, additives 1 to 3 according to the present invention can provide excellent peel-back resistance and disintegration properties to RCS while ensuring strength and fusion point. On the other hand, in additives 4 and 5, where the mass ratio of the compounds represented by formulas (1) and (2) is outside the range, and in additive 6, which consists of a compound different from those in formulas (1) and (2), a decrease in strength and fusion point occurred, and disintegration and peel-back resistance were inferior.

Claims

1. A disintegrant for resin-coated sand, comprising a phosphonic acid ester compound A represented by formula (1) below and a phosphonic acid ester compound B represented by formula (2), wherein the mass ratio of phosphonic acid ester compound A to phosphonic acid ester compound B (phosphonic acid ester compound A:phosphonic acid ester compound B) is 99.0:1.0 to 90.0:10.

0. 【Chemistry 1】 (In equation (1), R １ and R ２ Each of these independently represents a hydrocarbon group having 1 to 22 carbon atoms. 【Chemistry 2】 (In equation (2), R ３ (This indicates a hydrocarbon group with 1 to 22 carbon atoms.)

2. A resin-coated sand comprising a resin composition containing 0.1 to 25 parts by mass of the resin-coated sand disintegrant described in claim 1 per 100 parts by mass of phenolic resin, and a refractory aggregate.

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