JPH0523788A - Curing agent composition for curable mold and manufacture of mold - Google Patents

Abstract

PURPOSE:To provide curing agent composition for curable mold and manufacture for sand mold in molding method for self-curable and gas curable mold. CONSTITUTION:To manufacture the curing agent composition for curable mold containing metals of IB-VIII groups in the periodic table or these metal compounds in organic ester and sand mold for molding the refractory granular material by using the above composition. In this manufacture of the sand mold for molding the refractory granular material, by using the above curing agent composition for curable mold, strength of the mold molded from reconditioned sand can be drastically improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hardening agent composition for a curable mold and a sand mold for a casting in a self-hardening and gas-curable molding method. As a curing agent, an organic ester as a curing agent, when used in a method for manufacturing a sand mold for casting for molding a refractory granular material, the reusability of the refractory granular material is significantly improved curable mold curing agent composition and The present invention relates to a method for manufacturing a sand mold for casting using the curing agent composition.

[0002]

2. Description of the Related Art As a molding method for manufacturing a mold such as a main mold or a core using an organic binder, a self-hardening mold method, a cold box mold method, a cloning method (shell Method) is known. In particular, the organic self-hardening mold making method is mainly used in the field of mechanical casting to improve productivity, casting quality,
From the viewpoint of safety and health, it has already become a general-purpose molding method in place of the inorganic type. On the other hand, conventionally, in order to manufacture a mold at medium to high speed, a cloning method in which a so-called Coated Sand in which a phenol resin is coated on a granular refractory is heat-cured to manufacture a mold is widely used. However, in order to save energy at the time of mold production, mold production speed, and further improve the quality of the mold and casting, the cold-box mold method in which the material is cooled at room temperature with a gaseous or aerosol-like substance is used as a mold manufacturing method that replaces the cloning method. The industry is trying to introduce it seriously.

Recently, as a binder composition for improving casting quality and working environment, a water-soluble phenol resin is used as a binder,
A binder composition for molding sand used in an organic self-hardening mold molding method and a gas-curable mold molding method in which it is cured with an organic ester is disclosed in JP-A-50-130627 and JP-A-58-154433.
It has come to be known from Japanese Patent Publication No. 58-154434 and Japanese Patent Publication No. 58-154434. In the mold making method using this binder, unlike the conventional acid-curable binder, since the binder composition does not contain elemental sulfur or nitrogen, the working environment due to the generation of sulfurous acid gas during pouring Contrary to the above, there is no pollution, or there are few casting defects due to elemental sulfur and nitrogen to the casting, but the reproducibility of the binder type foundry sand is extremely poor,
It is well known that its use is limited, and its improvement is strongly desired.

In such a binder composition, since the strength of the obtained mold is low, the amount of the resin added must be increased in order to obtain the mold strength required for molding. As a particularly big drawback of this binder, the more difficult it is to secure the mold strength, the more difficult it is to secure the mold strength with the use of recovered sand for the purpose of reuse after casting and reclaimed sand that has been used repeatedly. There was a drawback that it was easy to fall into a vicious circle, such as the amount used. Further, such an increase in the amount of the binder in the mold leads to an increase in the amount of the pyrolysis gas at the time of pouring, and also has drawbacks such as a gas defect of the casting and a deterioration of working environment. In order to reduce such defects as much as possible, generally, to remove residual organic substances and alkaline components on the sand surface, a strong mechanical polishing regeneration treatment is performed, and at the same time, the supply ratio of new sand is increased, or Or the current situation is to deal with it by throwing away sand. Therefore, when the foundry sand is used for regeneration, the sand regeneration rate is limited to about 85% at most (FOUNDRY TRADE JOURNAL-8 / 22 DECEMBER 198).
9).

The difference in the sand reproducibility becomes even clearer as compared with the case of the acid-curing furan resin which is generally popular. That is, in the case of the acid-curing furan resin, generally, the strength of the mold can be made higher by using the reclaimed sand than by using the new sand, so that the amount of the binder added is somewhat reduced in the reclaimed sand system. Moreover, the recovery rate of the reclaimed sand is about 95% or more because no strong mechanical polishing reclaiming process is required.

Regeneration of sand is an important economic problem when making molds and cores from sand bound by a curable binder. In order to regenerate sand from a mold or core, after removing the casting, the used mold and core are mechanically vibrated or decomposed to break up the sand, destroy the lumps or aggregates, and collect the sand. . Since the unburned component of the binder is present on the recovered sand surface, it is usually regenerated next. There are three generally accepted methods for reclaiming recycled sand (mechanical, wet, and thermal). The wet regeneration method is a relatively unfavorable method because of the waste problems associated with wash water and the energy costs of drying sand. The thermal regeneration method is also a relatively unfavorable method because of the high energy cost of this method. On the other hand, since the mechanical regeneration method is the most economical, it is the most commonly used and popular regeneration method in the foundry industry.

In the reclaimed sand thus obtained, a binder process of using a water-soluble phenolic resin as a binder and curing with an organic ester does not provide sufficient mold strength. This is a phenomenon which is completely different from the case of acid-curing furan resin which has a drawback and is widely used, and improvement is strongly desired. Recently, for the purpose of improving the strength of a mold using reclaimed sand, a method by lowering the resin solid content concentration in the binder is disclosed in JP-A 1-262042, and reclaimed sand is pretreated with a silane solution in advance. The method is disclosed in JP-A 1-262043. However, although some of these methods improve the strength of reclaimed sand to some extent, satisfactory mold strength cannot be obtained.

[0008]

As a result of intensive studies to solve the above problems, the inventors of the present invention mold a fire-resistant granular material using a water-soluble phenol resin as a binder and an organic ester as a curing agent. In the curing agent composition used in the method for manufacturing a sand mold for castings, by using a curing agent composition containing a specific amount of a specific metal element, a refractory granular material regenerated (hereinafter referred to as reclaimed sand) is molded. The inventors have found that the strength of the mold is significantly improved, and have completed the present invention. That is, the present invention is characterized by using a curing agent composition for a curable template and a curing agent composition characterized by containing a metal of Group IB to VIII of the Periodic Table or the metal compound in an organic ester. The present invention provides a method for producing a mold.

Explaining the present invention in more detail, the hardener composition of the present invention comprises Cu, A in the IB group of the IB to VIII groups.
g, Mg, Ca, Sr, Ba, Zn, Cd in Group II, Sc, Y, Al, in Group III
Ga, In, Tl, Ti, Zr, Hf, Sn, Pb in IV group, V, Nb, T in V group
a, Bi, Cr, Mo, W, Po in VI, Mn, Tc, Re, VIII in VII
In the genus, it can be obtained by mixing and / or dissolving a compound containing one or more metal elements selected from Fe, Co and Ni in an organic ester at 5 to 200,000 ppm as a metal element. The metal element-containing compound used in the present invention may have various forms such as metal powder, oxides, hydroxides, inorganic acid salts, organic acid salts, and complex compounds, but any of them can be used. is there. As long as the metal element is contained in the binder composition of the organic ester which is a curing agent,
It is not restricted to the form of the compound containing any metal element. Specific examples of metal elements and compounds containing them will be given below, but the invention is not limited thereto.

As the metal powder, Cu, Ag in Group IB, Mg, Ca, Sr, Ba, Zn, Cd, etc. in Group II, Al, Sc, Ga, etc. in Group III, IV
Ti, Zr, Sn, etc. in genus, Sb, Bi, etc. in genus V, Cr, Mo in genus VI
Etc. In the VII group, Mn, Tc, etc. are mentioned, and in the VIII group, Fe, Co, Ni, etc. are mentioned, but B, Si, As, Te etc. which are usually called semimetals are not preferable. Examples of the alloy powder include duralumin, magnarium, ferromanganese and the like. In addition, typical compounds containing a metal element of Group IB to VIII of the periodic table include salts and double salts, hydroxides, oxides, hydrocarbon groups such as alkyl groups and aryl groups, and metal atoms. Bonded organometallic compounds, nitrides, alkoxides, hydrides,
Carbides, metal imides, peroxides, sulfides, phosphides, nitrates, anilides, phenolates, hexaammonides, ferrocene and its similar compounds, dibenzenechromium and its similar compounds, inorganic heteropolymers, metal carbonyls, metal-containing enzymes , Inclusion compounds, metal complexes, chelate compounds, coordination polymers and the like.

Typical structures of salts, hydroxides and oxides containing the metal element of Group IB to VIII of the periodic table are represented by the following general formula.

MaXb (in the formula, M is the metal element of IB to VIII group, X is an oxygen atom or a hydroxyl group, or an anion atomic group of an inorganic acid or an anionic atomic group of an organic acid or an acid exhibiting a sequestering property). Anionic atomic group, and a and b represent an integer of 1 or more.) As M, Cu, Ag,
Mg, Ca, Sr, Ba, Zn, Cd, etc. in Group II, Al, S in Group III
c, Ga, etc., IV, Ti, Zr, Sn, etc., V group, Sb, Bi, etc., V
Cr, Mo, etc. in Group I, Mn, Tc, etc. in Group VII, Fe,
Co, Ni, etc. can be mentioned, but B, S usually called semimetals
i, As, Te, etc. are not preferable.

Specific examples of X include oxygen atom, hydroxyl group,
Halogens (F, Cl, Br
Etc.), SO ₄ , SO ₃ , S ₂ O ₃ , S ₂ O ₆ , SiF ₆ , MoO ₄ , MnO ₄ , NO
₃ , NO ₂ , ClO ₃ , ClO, CO ₃ , HCO ₃ , CrO ₄ , IO ₃ , PO ₃ ,
PO ₄ , HPO ₃ , HPO ₄ , H ₂ PO ₄ , P ₂ O ₇ , H ₂ PO ₂ , SiO ₃ , B
O ₂ , BO ₃ , B ₄ O ₇ , Fe (CN) _{6 and the} like can be mentioned. Examples of the anionic atomic group of organic acid include formic acid, acetic acid, oxalic acid, tartaric acid, anionic atomic groups of carboxylic acid such as benzoic acid, sulfamic acid, xylenesulfonic acid, toluenesulfonic acid, phenolsulfonic acid, Examples thereof include anionic atomic groups of organic sulfonic acids such as benzenesulfonic acid and alkylbenzenesulfonic acid. Further, examples include anionic atomic groups of organic phosphoric acid such as methyl phosphoric acid and ethyl phosphoric acid. As the double salt, M ₂ ³⁺ (SO ₄ ) ₃・ M ₂ ¹⁺ SO ₄・ 24H ₂
Alum, which can be represented by the general formula O, is mentioned, and the trivalent metal corresponding to M ³⁺ is Al, V, Mn, Fe, or the like.
^Examples of ¹⁺ include Na and K.

Typical compounds used in the present invention as such salts, double salts and hydroxides are as follows.

As salts, calcium chloride, magnesium chloride, barium chloride, copper chloride, zinc chloride, calcium bromide, aluminum fluoride, vanadium chloride, molybdenum chloride, manganese chloride, iron chloride, nickel chloride, calcium sulfate, calcium carbonate, There are magnesium phosphate, calcium phosphate, aluminum chloride, tin chloride, calcium formate, magnesium oxalate, calcium toluene sulfonate, magnesium acetate, zinc acetate, aluminum acetate and the like. Examples of double salts include potassium alum and ammonium alum. Examples of hydroxides include aluminum hydroxide, calcium hydroxide, magnesium hydroxide and zinc hydroxide. Examples of the oxide include magnesium oxide, calcium oxide, barium oxide, zinc oxide, aluminum oxide, and the like. Further, a complex compound composed of a combination of two or more kinds of these oxides and the oxidation of the above oxides and other elements A compound compound composed of a substance or a salt is preferably used.

Typical examples of such a compound used in the present invention include the following.

Cements include hydraulic lime, roman cement, natural cement, Portland cement, alumina cement, blast furnace cement, silica cement, fly ash cement, masonry cement, expansive cement, special cement and blast furnace slag. Blast furnace residue,
There are magne refining dregs, ferrochrome dregs, bentonite, etc., whose main chemical structure is mCaO.nSiO ₂ ,
mCaO · nAl ₂ O ₃ , mBaO · nAl ₂ O ₃ , CaO · mAl ₂ O ₃
・ NSiO ₂ , CaO ・ mMgO ・ nSiO ₂ , mCaCO ₃・ nMgC
O ₃ , mCaO ・ nFe ₂ O ₃・ lCaO ・ mAl ₂ O ₃・ nFe ₂ O
₃ (l, m, and n are represented by a combination of 0 or an integer of 1 or more). Examples of oxides or complex compounds include other clay-like raw materials, iron oxide raw materials, and other mineral raw materials. When the oxide is used, its particle size is preferably as small as possible, and the average particle size is usually 200 μm or less, preferably 50 μm or less.

Examples of the organometallic compound in which a hydrocarbon group such as an alkyl group or an aryl group containing the metal element of Group IB to VIII of the Periodic Table is bound to a metal atom are as follows. _{Al (CH 3) 3, Al} (C 2 H 5) 3, Al (C 6 H 5) 3, (C 2 H 5) 2 A
lI, (C ₂ H ₅ ) ₂ AlH, (C ₂ H ₅ ) ₂ AlCN, Al (iC ₄ H ₉ ) ₃ , (CH ₂ = CH)
₃ Al, Zn (C ₆ H ₅ ) ₂ , (CH ₂ = CH) ₂ Zn, Ca (C ₂ H ₅ ) ₂ and R-Mg
-X (R; alkyl group or aryl group, X; halogen)
Grignard reagent. Examples of the metal alkoxide containing the metal element of Group IB to VIII of the periodic table include Al [OCH
(CH ₃ ) ₂ ] ₃ , Zn (OCH ₃ ) _{2 and the} like. Periodic table IB
~ As a hydride containing the metal element of Group VIII, AlH ₃ ,
Examples include CaH ₂ and BaH ₂ . Examples of the carbide containing the metal element of Group IB to VIII of the periodic table include Al ₄ C ₃ and CaC ₂ . Examples of the metal imide containing the metal element of Group IB to VIII of the Periodic Table include Ca (NH ₂ ) _{2 and the} like. Periodic table I
As the peroxide containing the metal element of Group B to VIII, Ca is
O ₂ , BaO ₂ , BaO _{4 and the} like can be mentioned. Examples of sulfides containing the metal element of Group IB to VIII of the periodic table include ZnS, Cu ₂ S, and CuS.
Etc. Examples of the phosphide containing the metal element of Group IB to VIII of the periodic table include AlP and the like. The nitrate containing the metal element of Group IB to VIII of the periodic table,
CuNO _{2 and the} like can be mentioned. Examples of the anilide containing the metal element of Group IB to VIII of the periodic table include Al (NHPh) _{3 and the} like. Examples of the phenolate containing the metal element of Group IB to VIII of the periodic table include Al-phenolate, Zn-phenolate,
Ca-phenolate and the like can be mentioned.

Examples of the hexaammonium compound containing the metal element of Group IB to VIII of the periodic table include Ca (NH ₃ ) _{6 and the} like.
Ferrocene (Fe (C ₅ H ₅ ) ₂ ) which is a ferrocene containing the metal element of Group IB to VIII of the Periodic Table
, Zn (C ₅ H ₅ ) ₂ , Ni (C ₅ H ₅ ) ₂ , Mn (C ₅ H ₅ ) ₂ , V (C ₅ H ₅ ) _{2 and the} like. As dibenzene chromium and its similar compounds containing the metal element of Group IB to VIII of the periodic table, Cr (C
_{6 H 6) 2, Mo (} C 6 H 6) 2, V (C 6 H 6) 2 and the like.

Examples of the inorganic heteropolymer containing the metal element of Group IB to VIII of the Periodic Table include the following. Hydrogenated inorganic heteropolymers such as beryllium hydride polymer, magnesium hydride polymer, aluminum hydride polymer. Inorganic polymers such as aluminum nitride containing Al-N bonds. Alumino-silicates such as zeolite, fluorite and fluorite. Layered silicates such as mica. Other examples include aluminum phosphate and hydrotalcite.

Inclusion compounds containing the metal element of Group IB to VIII of the periodic table include cyclic polyether (crown ether), cyclic polyamine (azacrown compound), cyclic polythiaether (thiacrown compound), and complex donor. Complexes with crown compounds, bicyclic crown compounds (cryptands), polymeric crown compounds, cyclic phenols (caxarene), cyclodextrin derivatives, etc. For example, it is a complex of dibenzo-18-crown-6 and Ca ²⁺ , a complex of cryptad [2 · 2 · 2] with Ca ^2+, and the like. As the metal complex containing the metal element of Group IB to VIII of the periodic table,
^{Cl -, CN -, NCS -} , SO 4 2-, NO 2-, ONO - NO 3-, CH 3 C
_{^{OO -, C 2 O 4 2-}} , CO 3 2-, OH -, H 2 N · CH 2 · COO -, F
^{-, Br -, ONO -,} I -, NH 2-, SCN - like anionic and /
Alternatively, neutral ligands such as H ₂ N ・ CH ₂ CH ₂ NH ₂ , C ₆ H ₅ N, NH ₃ , H ₂ O and / or H ₂ N ・ NH ³⁺ , H ₂ N ・ CH ₂ CH ₂
It has a cationic ligand such as NH ³⁺ and is selected from coordination numbers 2 to 8, and one example is [Al (C
₂ O ₄ ) ₃ ] Cl ₃ , [Zn (NH ₃ ) ₆ ] Cl _{2 and the} like. In addition, examples of the compound containing the metal element of Group IB to VIII of the periodic table include metal carbonyls such as Ni (CO) ₄ and Mn ₂ (CO) ₁₀ , metal-containing enzymes such as carboxypeptidase A and thermolysin, Examples thereof include zirco aluminum compounds.

Further, a sequestering compound containing the metal element of Group IB to VIII of the periodic table may be used. Examples of such sequestering compounds include the following. Typical examples of acetic acid type aminocarboxylic acid type are ethylenediaminetetraacetic acid (EDTA) or salts thereof, nitrilotriacetic acid (NTA) or salts thereof, trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA).
Or its salts, diethylenetriaminepentaacetic acid (DTP
A) or salts thereof, triethylenetetramine hexaacetic acid (T
THA) or salts thereof, glycol ether diamine tetraacetic acid (GEDTA) or salts thereof, iminodiacetic acid (ID
A) or a salt thereof, polyalkylenediaminetetraacetic acid or a salt thereof, and N-hydroxyalkyleneiminodiacetic acid or a salt thereof are typical of the phenyl-based aminocarboxylic acid type are 2-oxyphenyliminodiacetic acid or a salt thereof. Salts, phenyliminodiacetic acid or salts thereof, 2-oxybenzyliminodiacetic acid or salts thereof, benzyliminodiacetic acid or salts thereof, and N, N′-ethylenebis-
[2- (O-hydroxyphenyl)] glycine or a salt thereof is a typical aminocarboxylic acid type having a mercaptan group, and β-mercaptoethyliminodiacetic acid or a salt thereof is an aminocarboxylic acid having an ether bond. A typical type is ethyl ether diamine tetraacetic acid or a salt thereof and an aminocarboxylic acid having a thioether bond. A typical type is an ethyl thioether diamine tetraacetic acid or a salt thereof is an aminocarboxylic acid having a sulfonic acid group. A typical acid type is β-aminoethylsulfonic acid-N, N-diacetic acid or a salt thereof, and a typical aminocarboxylic acid type having a phosphonic acid group is nitrilodiacetic acid-methylenephosphonic acid. Or a salt thereof, a typical aminocarboxylic acid type having a peptide bond is N,
N'-diglycylethylenediamine-N ', N'',N''', N ''''
-Tetraacetic acid or a salt thereof or the like is a typical one of oxycarboxylic acid type, gluconic acid or a salt thereof, citric acid or a salt thereof, and tartaric acid or a salt thereof or the like, and a typical phosphoric acid type is , Tripolyphosphoric acid or salts thereof, hydroxyethanediphosphonic acid (HEDP) or salts thereof,
And nitrilotristyrenephosphonic acid (NTP) or salts thereof, and acetylacetone.

As the coordination polymer having the sequestering ability, an amine group, and / or a nitrogen heterocycle, and / or a Schiff base, and / or an alcohol, a carboxylic acid, and / or a ketone are included in the molecule. , Ester, amide, and / or aminocarboxylic acid, and / or phosphonic acid, and / or phosphine, and / or a polymer having thiol. Among the metal-containing compounds of Group IB to VIII described in these specific examples, the preferred metal element is the metal element of Group II to VIII, and more preferably
The metal element of Group II, III and IV, among which Z is
N, Ca, Mg, Al and Zr are preferable.

As the organic ester used in the present invention, lactones or organic esters derived from monohydric or polyhydric alcohols having 1 to 10 carbon atoms and organic carboxylic acids having 1 to 10 carbon atoms are used alone or in a mixture. , It is preferable to use γ-butyrolactone, propionlactone, ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin and the like in the self-hardening template molding method, and methyl formate is used in the gas curable template molding method. However, it may be used in combination with the organic ester used in the self-hardening molding method. By dissolving or mixing the compound containing the metal element with the organic ester which is such a curing agent, the strength of the casting sand mold made of recovered sand or recycled sand that is repeatedly used is significantly restored. The content of the metal compound as a metal element is 5 with respect to the curing agent.
~ 200,000 ppm, more preferably 20-100,000 pp
m. If it is less than 5 ppm, the effect of the present invention is not sufficient, while if it exceeds 200,000 ppm, the effect reaches the saturation region, which is not preferable. It has not been known at all that the strength of reclaimed sand is remarkably recovered by using the curing agent composition of the present invention containing such a metal element.

The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester, for example, phenols including cresol, resorcinol, 3,5-xylenol, bisphenol A and other substituted phenols. It is obtained by reacting with aldehydes such as formaldehyde, acetaldehyde, furyl aldehyde, etc., or a mixture thereof in a large amount of an aqueous solution of an alkaline substance. Further, a formalin-condensable monomer such as urea, melamine, or cyclohexanone may be co-condensed with them to such an extent that they do not become a main constituent unit in a weight ratio. Suitable alkaline catalysts used in the production of these water-soluble phenolic resins are the alkali metal hydroxides sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being Most preferred. The structure of the resin may be a methylene bond type or a benzyl ether type.

Examples of the refractory granular material include silica sand containing silica as a main component, chromite sand, zircon sand, olivine sand, alumina sand and the like. In the present invention, either new sand or reclaimed sand can be used as these refractory granular materials, but the effect of improving the mold strength is particularly remarkable when reclaimed sand is used. When reclaimed sand is used, reclaimed sand obtained by a normal abrasion type or roasting type is used.
The method for obtaining recycled sand is not particularly limited.

In the binder composition, conventionally known silane coupling agents can be used as other additives. Specific examples thereof include γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.
Examples thereof include glycidoxypropyltrimethoxysilane. In the present invention, it is preferable to use this silane coupling agent together with the curing agent composition.

A well-known method is used for producing a sand mold for casting by the self-hardening mold making method using the curing agent composition of the present invention. For example, 100 parts by weight of reclaimed sand and a metal element-containing organic ester which is a curing agent according to the present invention are added.
0.05-9 parts by weight, preferably 0.1-5 parts by weight and 0.4-15 parts by weight of the water-soluble phenolic resin aqueous solution, preferably 0.6
~ 5 parts by weight can be kneaded by a known method, and a conventional self-hardening mold manufacturing process can be used as it is to manufacture a mold.

[0029]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. Examples 1 to 20 With respect to 100 parts by weight of reclaimed sand in which the type of sand is Fremantle silica sand, 0.375 parts by weight of a hardening agent containing various hardening agents and metal compounds shown in Table 1 and γ-aminopropyltriethoxysilane 0.5. % Of water-soluble phenolic resin (solid content 49%, weight average molecular weight 2300) was added and kneaded, and the mixture was filled into a 50 mmφ × 50 mmh test piece model, and 24 hours of coercive pressure passed after kneading. The change with time was measured.

Comparative Examples 1 to 6 An aqueous solution containing 0.375 parts by weight of various curing agents shown in Table 1 and 0.5% of γ-aminopropyltriethoxysilane per 100 parts by weight of reclaimed sand of which the type of sand is Fremantle silica sand. -Soluble phenolic resin (solid content 49%, weight average molecular weight 2300)
1.5 parts by weight of the mixture was added and kneaded, and the mixture was filled into a test piece model of 50 mmφ × 50 mmh, and the change with time in coercive pressure after kneading was measured for 24 hours.

Method for Preparing Reclaimed Sand A water-soluble phenolic resin containing 0.375 parts by weight of triacetin as a curing agent and 0.5% by weight of γ-aminopropyltriethoxysilane (against phenolic resin) per 100 parts by weight of fresh sand of Fremantle silica sand. (Solid content 49%, weight average molecular weight 2300) 1.5 parts by weight was added and kneaded. FC-25 (S / M = 3.5) was cast using a mold made from a mixture and the recovered sand was crushed by a crusher. Regeneration (A regeneration, 2 passes) was performed using a M type rotary kramer. The reclaimed sand obtained by repeating the above steps 5 times was used for the above-mentioned preparation for the mold strength test.

The quantitative determination of the metal element in the curing agent is generally performed as follows. [Quantification of the metal element in the curing agent] The curing agent is thoroughly mixed and stirred, and 0.5 to 0.8 g is weighed in a 100 ml platinum dish. to this,
After adding 10 ml of concentrated nitric acid and decomposing acid, it decomposes slightly by heat. Add 10 ml of concentrated perchloric acid and treat with white smoke to make the residual amount of concentrated perchloric acid 3 ml. After allowing to cool, 10 ml of HCl (1 + 1) +10 ml of H ₂ O is added and dissolved by heating. This is filtered (No5C filter paper) and washed with diluted hydrochloric acid + warm water. The residue remaining on the filter paper is ashed in a 30 ml platinum crucible at 900 to 1000 ° C and then allowed to cool, 2 g of potassium pyrosulfate is added and the mixture is melted at 800 ° C. The melted product is combined with the above filtrate to make a 100 ml solution in a volumetric flask, and then the metal element is quantified by ICP (inductively coupled plasma emission spectrometry). Examples 1 to 20 and Comparative Example 1
Table 1 shows the measurement results of the coercive pressure after lapse of 24 hours at -6.

[0033]

[Table 1]

[0034]

INDUSTRIAL APPLICABILITY By using the curable mold curing agent composition of the present invention in a method for producing a sand mold for casting for molding a refractory granular material, the strength of a mold molded from recycled sand is significantly improved. You can

Claims (5)

[Claims] 1. A curable mold composition for a curable mold, characterized in that the organic ester contains a metal of Group IB to VIII of the Periodic Table or the metal compound. 2. The curable composition for a curable mold according to claim 1, wherein the metal element is selected from the groups II, III and IV of the periodic table. 3. The curable mold composition for a curable mold according to claim 1, which contains 5 to 200,000 ppm as a metal element. 4. A method for producing a mold, which comprises molding a refractory granular material using the curable composition for a curable mold according to any one of claims 1 to 3. 5. The method for producing a mold according to claim 4, wherein the refractory granular material is recovered sand or reclaimed sand for reuse.