KR910001768B1 - Mold material for forming sandmold without requiring mold wash - Google Patents

Abstract

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Description

Molding material used to form sand molds that do not require figures

The present invention relates to a molding material used for the production of a sprayed mold used in the manufacture of metal castings, in particular, the strength after being left under ambient temperature and the strength after pouring the molten metal are both excellent, and the figure is absolutely necessary. The present invention relates to a molding material capable of producing a sand mold for casting, which requires only a simple figure without a spray or the like.

In general, casting sand molds (hereinafter simply referred to as sand molds) used to manufacture various metal castings are roughly divided into two methods, namely, sand casting sand granules having a particle size of 325 mesh or more. It is produced by the method of solidifying with an organic binder and the method of solidifying with an organic binder and what consists of a zircon sand and a chromite sand (henceforth simply a sand).

Among them, as the method of using the former organic binder, for example, a phenol resin or furan resin as a binder mixed with sand is cured with a hard acid hardener such as sulfuric acid, phosphoric acid, toluene sulfonic acid or chiselene sulfonic acid, and the sand A method of oxidizing the phenol resin, a polyisocyanate, and a basic catalyst by mixing the sand with sand, thereby causing a urethanation reaction between the phenol resin and the polyisocyanate to cure the sand (pepset method), and There is a method (linocure method) in which sand is cured by using a urethaneization reaction caused by a mixture of a modified alkyd resin, a naphthenate metal salt and a polyisocyanate. In addition, as a method of using the latter inorganic binder, a method of preparing sand molds by mixing cement and sand to harden (OJ process) and a method of hardening sand by injecting CO ₂ gas into sand containing sodium silicate are known. .

However, in the conventional sand molds produced by the above-described organic binders, in general, the strength after pouring the molten metal (hereinafter, referred to as high temperature strength) drops, and when the molten metal is injected into the sand molds, the organic binder is burned to form a particulate ( 결합) The coupling between them is relaxed, and a borrowing accident in which the molten metal penetrates between the sands occurs. Therefore, in order to prevent the molten metal from penetrating into the sand mold, it is necessary to apply a painting agent on the surface of the sand mold in contact with the molten metal, mica powder, charcoal powder, talc, etc. with a brush or a spray. On the other hand, in the sand mold solidified with an inorganic binder, there is no borrowing of the molten metal into the sand mold, but the strength (hereinafter referred to as the standing strength) after being left for a certain period of time at room temperature is generally lowered. In order to prevent this, it is necessary to shape the history sand wall after adding wood flour, coke flour or the like to the sand. Therefore, in any case, a figure is required, and this figure work occupies up to 30-50% of the execution cost of the death penalty, and has a problem that is a major cause of the cost increase of the death penalty.

The present invention aims to provide a molding material capable of producing sand molds for castings which are excellent in high-temperature strength and require no figures at all, or require only very simple figures. It provides a casting material used to produce a sand mold composed of the following.

(a) an organic binder composed of a synthetic resin: 0.4-3.0%, (b) a curing agent for curing the resin: 0.2-2.0%, (c) an ester of silicate, its hydrolyzate, a water-dispersible silica sol, and an alcohol Ceramic binder composed of at least one member selected from the group consisting of disperse silica sol: 0.05-2.0% as SiO ₂ min, (d) curing agent for curing the ceramic binder: 0.05-2.0% and (e) Foundry sand: the rest.

In addition, if necessary, the molding material of the present invention (f) is preferably a refractory fine powder for preventing borrowing having a particle size of 10-30 µ: 0.1-3.0%, a high temperature strengthening agent: 0.1-3.0%, a molding improving agent: 0.1-2.0% and graphite spheroidizing stabilizer: 0.03-0.5%, at least 1 sort (s) can be contained.

MEANS TO SOLVE THE PROBLEM The present inventors discovered the following as a result of research to obtain the casting material which can manufacture the sand mold for casting which is excellent in the standing strength and high temperature strength, and does not need a figure at all, or only an extremely simple figure.

(1) When the sand molds made of the mold material mixed with the binder are left standing for a certain time, that is, the leaving strength is large, since the sand molds are not easily destroyed during casting, productivity is improved and handling of the sand molds is easy. Although the high standing strength is originally required, at least 1 selected from the group consisting of silicate esters such as ethyl silicate, hydrolyzate products thereof, water dispersible silica sol, and alcohol dispersed silica sol, in addition to organic binders such as conventional furan resins. When molding with a ceramic binder composed of more than one kind (hereinafter, collectively referred to as the ceramic binder of the present invention) and a casting material to which isocyanate is added as its curing agent, Improved by 1.5-3 times.

(2) The high temperature strength of the sand molds formed using the molding material containing only the organic binder is generally reduced to about one third of the standing strength, but at the time of sand molding, the ceramic binder of the present invention, or the salt or borax When a high temperature strengthening agent that melts at a high temperature such as boric acid is added to the sand, a high temperature strengthening agent such as silica or boric acid supplied from the ceramic binder of the present invention is welded to the sand at a high temperature to firmly bind the particles of the sand. Since the high temperature strength of the sand mold is reduced to about 1/2 of the neglect strength, and the neglect strength itself is raised as described above, the high temperature strength is remarkably improved compared to the conventional sand mold cured only with an organic binder.

(3) When sand molds are formed by using sandblasting material containing inorganic binder, wood powder, coke flour, etc. are conventionally added to sand by sand sanding, and sand sand is pressed again during casting. That is, although the welding at the time of casting was prevented, when the casting material which the organic binder coexisted in addition to the ceramic binder of this invention is used as a binder, this welding does not exist at all and the sand mold excellent in fusion resistance can be obtained.

(4) Although the sand molds formed by using the mold material added with the above-described ceramic binder of the present invention in addition to the organic binder in the sand are not shaped, an accident that the molten metal is borrowed into the sand mold occurs, but the silica alumina and zirconia are previously added to the mold material. When fine powders of inorganic refractory materials such as the like are mixed as anti-charging agents, in the sand molds formed with the casting material, these fine powders form voids between the sands, and at the time of injection, the fine powders and sands are formed by the high temperature at the time of injection. As a result of strong and hard fusion by the ceramic binder, there is no borrowing to the molten metal, so that not only the figure can be omitted in the small casting, but also the injection molding can be sufficiently prevented by simply spraying the mold in the large casting. that.

(5) For molding of sand molds that require high temperature strength, such as casting sand castings of cast steel and special steel, in particular, the above-mentioned high temperature strengthening agents such as the above-mentioned antireflection refractory powder such as silica and boric acid Although it is necessary to use the casting material mixed a lot, when the addition amount of these additives increases, the formation of a sand mold falls, and the need to increase a binder also arises. Therefore, the larger the binder in the mold material, the higher the cost and the deterioration of the sand mold, but the addition of an excipient improving agent such as sugars and dextrins to the mold material improves the molding of the sand mold. The use of a modifier can improve the formability without increasing the binder, that is, while maintaining the disintegration property of the sand mold, and (6) when a sulfur compound is present in the molten metal during casting of ductile cast iron, Since the spheroidization of graphite is inhibited, the presence of this compound is not preferable. However, in the case of making a sand mold using a mold material containing an organic binder, for example, a self-hardening phenol resin, urea modified furan resin, or the like The sulfur content supplied from sulfuric acid or euphonic acid, which is used for curing, is the same as magnesium added to spheroidize. In response, magnesium is consumed and this inhibits the spheroidization of graphite. Therefore, in order to prevent this, conventionally, a mold coating agent has been applied to the sand mold, but when a graphite spheroidizing stabilizer such as iron oxide or magnesium oxide is added to the casting material, Reaction does not hinder the spheroidization of at all.

The present invention has been made in accordance with the above finding, and the casting material used to mold the sand mold of the present invention has the composition as described above. In addition, all the% represents the weight% throughout the specification.

Next, the reason why each structure of the casting material of this invention was limited as mentioned above is demonstrated below.

(a) organic binder

As the organic binder used in the molding material of the present invention, in addition to resins such as furfuryl alcohol, phenol or polyester, resins modified or reacted with these, such as urea-furan resin, phenol-furan resin, polyester-furan Synthetic resins used as conventional sand-type organic binders such as resins, phenols, or polyester-isocyanate-type resins are used. When these synthetic resins are added to the sand and cured, sand rusting strength is improved and sand fusion is prevented. However, if the content is less than 0.4%, the above action is not sufficient. On the other hand, if the content exceeds 3.0%, the decayability of the sand mold is decreased, and the cost generated by the increase of the organic binder is also increased. It was set to 0.4-3.0%. Preferred range is 0.4-2.0%.

(b) Curing agent for organic binder

As a curing agent for curing the organic binder, sulfuric acid, phosphoric acid, benzenesulfonic acid, toluene sulfonic acid, xylene sulfonic acid, isocyanate, preferably diisocyanate, and diphenylmethane -4.4 'diisocyanate (MDI) are used. ), Hexamethylene diisocyanate (HDI) and toluene-2,4- or 2,6-diisocyanate (2,4TDl) or (2,6TDl) or mixtures thereof can be used.

That is, the curing agent for an organic binder of the present invention may include all materials conventionally used to cure an organic binder including such a catalyst.

In general, when the amount of the curing agent added is less than 0.2%, the curing of the organic binder is not sufficient, and when it exceeds 2%, the curing rate is too fast and the molding operation cannot be performed smoothly, so the amount of the curing agent is set to 0.2-2%. . Preferred range is 0.3-1.5%.

(c) ceramic binder

In the casting material of the present invention, one or two or more kinds of silicate esters, hydrolyzates thereof, water-dispersible silica sols and alcohol-dispersed silica sols are used as ceramic binders, and among them, as ethyl silicate, especially ethyl Preference is given to polymers such as silicates (ethyl silicate), methyl silicates, propyl silicates, butyl silicates or tetramers to tetramers thereof, or mixtures thereof. This ester of silicate is easily hydrolyzed by water or an aqueous acid solution, and a product obtained by hydrolyzing the ester of silicate with an aqueous hydrochloric acid solution containing an alcohol, for example, is also used as the ester of silicate.

As the water or alcohol-dispersed silica sol, a silica sol obtained by dispersing fine powder silica having a particle diameter of 20 mu or less in water, an alcohol such as ethanol or an aqueous solution of alcohol is used, for example, from Aerosil Japan Co., Ltd. It is marketed under the name of (AEROSIL) (the trademark). Average particle size: The silica sol prepared from highly disperse amorphous silica of about 12μ can be conveniently used.

Any of the particulate silicas supplied by these ceramic binders has the property of sintering sand and sand at 800-850 ° C and melting at 1000-1200 ° C to further fuse the sand and sand more firmly. Therefore, it is extremely excellent as a binder in the high temperature region, and thus not only has an effect of remarkably improving the high temperature strength of the sand mold, but also prevents the injection of the molten metal together with the refractory fine powder for preventing borrowing described later, thus eliminating or simplifying the figure work. Although the silica powder in these ceramic binders is less than 0.05%, the desired effect cannot be obtained in the above-described action. On the other hand, when the silica content exceeds 2.0%, the decay property of the sand mold is deteriorated. The mixing ratio was set to 0.1-2.0% as silica powder (SiO ₂ minutes). Preferred range is 0.1-1.0%.

(d) Curing Agent for Ceramic Binder

The alcohol component in the silicate ester used as the ceramic binder, the alcohol and water contained in the hydrolysis product of the silicate ester, and the water or alcohol contained in the silica sol lower the curing rate of the organic binder and leave the mold dead. Since the hardness is also lowered, isocyanate is used to remove the alcohol content and water in the ceramic binder to maintain the curing rate of the organic binder and the standing hardness of the sand mold at a sufficient height. As such isocyanate, any isocyanate may be used as long as it reacts with various alcohols or water, and preferred is diisocyanate, and diphenylmethane 4,4 'diisocyanate (MDI), hexaethylene di Preference is given to using isocyanates (HDI) and toluene-2,4- or 2,6-diisocyanates (2,4 TDI or 2,6 TDI) or mixtures thereof.

If the amount of isocyanate added is less than 0.05%, the above-mentioned action is insufficient, while even if it exceeds 2.0%, only the cost increases without any effect on the action, so that it is set at 0.05-2.0%. Preferred range is 0.1-1.5%.

(e) Borrowing Refractory Fine Powder

As described above, the refractory fine powder prevents the gap between the sand and the sand, thereby suppressing the borrowing of the molten metal in accordance with the above-described action of the ceramic binder of the present invention, thereby omitting or simplifying the figure work. As an effective additive aiming at this, generally, silica, alumina, and zirconium having a particle size of 10-30 µm are preferably used, and the above anti-charging effect is sufficient when the addition amount of such refractory fine powder is less than 0.1%. In addition, when it exceeds 3%, the standing strength is lowered, so the range is set to 0.1-3.0%. The suitable range is 0.5-2.0%.

(f) high temperature strengthening agents

In the case of casting metals having a relatively high melt temperature, for example, cast iron or special steel, a particularly high high temperature strength is required for sand dies. For this purpose, the sand mold needs to be reinforced by a material that melts at the mold temperature of the molten metal and firmly welds sand, binder, and other additives, so that a high temperature reinforcing agent is applied to the mold material as needed. Salt, boric acid, and borax are used preferably. When the addition amount of this high temperature strengthening agent is less than 0.1%, the said effect is not enough, and when it exceeds 3.0%, since the collapse | disruption property of a sand mold falls, the range was set to 0.1-3.0%. Suitable range is 0.3-2.0%

(h) molding improvers

In sand molds such as cast steel and special steel sand molds, which must maintain a particularly high high temperature strength, the amount of added refractory fine powder or a high temperature strengthening agent is increased as described above, resulting in a decrease in the molding, but in order to improve the molding, If it is increased, the decayability of the sand mold is decreased, and since such sand mold requires high high temperature strength, if the amount of the hot solvent is increased to improve the high temperature strength, the formation of sand mold is reduced. In particular, when it is desired to improve the molding without causing disintegration and high temperature strength in the sand mold, it is necessary to add a saccharide such as molasses or dextrin as a molding improving agent if necessary. It is good, but if the added amount is less than 0.1%, it is not possible to obtain a sufficient effect on the original action of the molding improver which can improve the molding even without increasing the amount of the binder. It was set at 0.1-2.0%. A suitable range is 0.3-1.5%.

(i) Graphite Spheroid Stabilizer

Since iron oxide and magnesium oxide react with sulfur compounds supplied to a curing agent for an organic binder and the like to promote these compounds, when fine powders of iron oxide and magnesium oxide are previously contained in the sand mold, the compound is prevented from being mixed into the cast product. As a result, nodular spheroidization in ductile iron is not inhibited. Therefore, for example, it is preferable to add a graphite spheroidizing stabilizer which reacts with sulfur compounds and promotes them to sand molds used in casting of ductile cast iron, if necessary, which include one or two kinds of fine powders of iron oxide and magnesium oxide. Is conveniently used. If the addition amount of this nodular spheroidizing stabilizer is less than 0.03%, the above-mentioned nodular spheroidizing stabilization effect cannot be obtained. On the other hand, even if it exceeds 0.5%, the effect is not improved very much and the cost is high. It was set at 0.5%. Preferred range is 0.1-0.4%.

Next, the casting material of the present invention will be described more clearly with reference to Examples.

(Example)

The Example of this invention is described, comparing with a comparative example. First, the following materials were prepared in order to manufacture sand-shaped Nos, 1-13 and Nos, 1 "-13" using the casting material according to the present invention, and comparative sand Nos, 1 and 2 using conventional casting materials. In Tables 1 and II, the names of the materials used for the death penalty are indicated using the alphabetic symbols shown in parentheses below, and the numbers indicate the types.

(a) Organic binder (R):

Furfuryl alcohol (R-1), phenol resin (R-2), urea-furan resin (R-3), polyester-furan resin (R-4), phenol-furan resin (R-5), alkyd resin (R-6), phenol (urethane type) resin (R-7) and polyester resin (R-8).

(b) Curing agent for organic binder (RC):

Toluenesulfonic acid (RC-1), xylenesulfonic acid (RC-2), benzenesulfonic acid (RC-3), diphenylmethane 4,4 diisocyanate (RC-4), toluene-2,4 diisocyanate (RC- 5), toluene-2,6 diisocyanate (RC-6) and hexamethylene diisocyanate (RC-7)

(c) Ceramic binder (CB):

Methyl silicate hydrolyzate (CB-1), ethyl silicate hydrolyzate (CB-2), propyl silicate hydrolyzate (CB-3), butyl silicate hydrolyzate (CB-4), alcohol dispersion silica sol ( CB-5), and water dispersion silica sol (CB-6)

(d) Curing Agent for Ceramic Binder (CC):

Diphenylmethane-4,4 'diisocyanate (CC-1), toluene-2,4-diisocyanate (CC-2), toluene-2,6 diisocyanate (CC-3), and hexaethylene diisocyanate (CC -4)

(e) refractory fine powder (F):

Silica (F-1) with an average particle diameter of 15μ, Alumina (F-2) with copper 20μ, Zirconia (F-3) with copper 25μ

(f) Ablation Spheroid Stabilizer (CD):

Magnesium oxide (CS-1) with an average particle diameter of 10 µ, copper oxide (CS-2) with 20 µ

(g) High temperature strengthening agent (H):

Boric acid (H-1) with an average particle diameter of 10μ and borax (H-2) with 20μ of copper

(h) Molding Improvement (V):

Molasses (V-1), Dextrin (V-2)

(i) Sand for castings (S):

It has a particle size distribution with a particle size of 28-280 mesh, contains 12.5-13.5% of 150 mesh or less, and has a particle size index (AFS = grain finess number) of 61.2 silica sand (S-1), zircon sand (S-2), And chromide sand (S-3).

Next, among the materials prepared in this way, first, silica sand (S-1) as a sand for casting is put in a high speed sand mixer at room temperature (25 ° C), and while rotating the mixer, toluene sulfonic acid (RC-1) is used as a curing agent for an organic binder. ) 1.9% of the mixture was stirred for 20 seconds, and then furfuryl alcohol (R-1): 2.9% was added as an organic binder, and the mixture was stirred for 20 seconds, followed by silica (F-1): 2.9% as the refractory fine powder. After stirring for 20 seconds in the same manner, after adding 1.9% of silicic acid methyl ester hydrolyzate (CB-1) as a ceramic binder and stirring for 20 seconds in the same manner, diphenylmethane 4 was used as a curing agent for the ceramic binder. 4 'diisocyanate (CC-1): After adding 1.9% and continuing stirring for 30 seconds, the mixer was stopped and the width of 20 kg of sand mixed material thus mixed was placed on the surface plate: 210 mm x length: 290 mm x height: in a metal frame having an inner dimension of 120 mm After filling and filling around the mold quickly, and leaving it for 1 hour, the hardened sand mold is removed from the model and the bottom part is (90 mm x 150 mm) x government: (110 mm x 160 mm) x height: 80 The sand mold No. 1 by the casting material of this invention of the trapezoidal trapezoidal box shape in which the trapezoidal recessed part of the pyramid with the dimension of mm was formed was produced.

The death penalty Nos 2-13 and 1 by the molding material of the present invention which are further shown in Tables I and II by combining materials in the same ratio as shown in Tables I and II in the same order as the above. "-13" was prepared. In addition, when dextrin of a molding improvement agent and iron oxide of a graphite spheroidizing stabilizer were used for sand-deadening, these were added when an anti-charging agent was added.

In order to obtain the conventional sandpaper Nos. 1 and 2 for comparison again, the sand maintained at 25 ° C. was put in the same high-speed sand mixer while rotating the mixer, and 0.5% of toluene sulfonic acid was added to the sand, followed by stirring for 20 seconds. After adding 1.0% of furan resin, stirring for 30 seconds again, the mixer was stopped, and the mixed 20 kg of material was charged into the model in the same manner as described above, and the same as the sand mold by the casting material of the present invention. Comparative sand No. 1 having a shape and dimensions and cured only with an organic binder was produced.

On the other hand, in order to obtain the comparative sand No. 2, the same sand as described above was put in a high-speed sand mixer, and while rotating the mixer, 6% of soda silicate powder was added to the sand, followed by stirring for 30 seconds. Then, the kneaded 20 kg of material was filled into the metal frame, and then the CO ₂ gas generated from the CO ₂ gas generator was sprayed to cure the sand so that the sand mold by the casting material of the present invention had the same shape and dimensions. Furthermore, the non-finished yarn No. 2 cured only with a ceramic-based provider was manufactured.

Hereafter, the sand mold Nos.1-13 and 1 " -13 " and the comparative sand mold Nos. 1 and each of the mold materials of the present invention prepared as described above were measured as follows.

First, any of these executions were measured for 24 hours at room temperature after manufacture, that is, the standing strength was measured by a Penetration Tester manufactured by George and Fisher, and the results are shown in Tables I and II. did.

In order to evaluate the welding resistance and borrowing resistance of these sand molds, no casting was performed on each sand mold, and a casting having a weight of 8.8 kg was prepared by injecting ordinary cast iron molten metal having a temperature of 1250-1300 ° C. After cooling, sand adhered to the casting surface was removed by shot blasting, and then the casting surface and the sand surface were observed to investigate the welding and borrowing conditions of the molten metal. The excellent ones ◎, the good ones ○, and the poor ones were marked with × and shown in Tables I and II.

Moreover, about the casting material 2 ", 4", 8 "-13" of this invention, the sand mold shape | molded on the same conditions from this was inject | poured the molten metal of a normal spherical graphite cast iron, and the casting of weight 8.8 kg was similarly manufactured. Then, the state of the spherical axle of this casting wavefront was observed.

In addition, in order to investigate high-temperature strength, according to the above-mentioned materials and procedures, the sand molds 1-13 and 1 "-13", and the sand molds No. 1 and 2, respectively, were used as the outer diameter: 100 mm x height: 150 The cylindrical sand molds having a dimension of mm were separately molded separately. Put this in the electric furnace. Temperature: The sand mold Nos.1-13 and Nos 1 "-13" by the casting material of the present invention and the comparative sand Nos. The high temperature strength of 1 and 2 was calculated | required, respectively, and the result was also combined with Table 1 and Table II.

From the results shown in Tables I and II, the sand molds made by the casting material of the present invention exhibited higher values in both of the standing strength and the high temperature strength than those of Comparative Sand No. 1 cured only with furan resin. The non-sanding type No. 2 cured with soda silicate is excellent in borrowing resistance, but the neglect strength is remarkably inferior to other sanding type, and the non-sanding type No. 1 is borrowing resistance and the non-sanding type No. 2 is The adhesion is not enough, indicating that a figure is required. On the other hand, it turns out that the sand mold | die by the casting material of this invention is excellent in both fusion resistance and borrowing resistance, and it is the outstanding sand mold which is practical enough without drawing.

In addition, it can be seen that in the sand molds formed of the above-described casting material of the present invention containing graphite spheroidizing stabilizer, castings having excellent graphite spheroidization stability (excellent ◎ table) or good (○ mark) can be produced.

TABLE 1

TABLE 2

Claims (8)

(a) an organic binder composed of a synthetic resin: 0.4-3.0%, (b) a curing agent for curing the resin: 0.2-2.0%, (c) a silicate ester, a hydrolyzate thereof, a water-dispersible silica sol, And a ceramic binder composed of one or more kinds of alcohol-dispersed silica sol: 0.05-2.0% as SiO ₂ powder, (d) a curing agent for curing the ceramic binder: 0.05-2.0%, and (e) molding sand (F) 0.1-3.0% of the refractory fine powder for preventing borrowing, (g) a high temperature strengthening agent selected from the group consisting of salt, borax and kung acid: 0.1-3.0%, and (h) a group consisting of sugars and dextrins. Molding improver selected from: 0.1-2.0% and (i) Graphite spheroidizing stabilizer consisting of at least one member selected from the group consisting of iron oxide and magnesium oxide: Mold for the production of sand molds, characterized in that using 0.03-0.5% material The organic binder of claim 1 is composed of furfuryl alcohol, phenol resin, polyester resin, urea-furan resin, phenol furan resin, polyester-furan resin, phenol-isocyanate resin and polyester-isocyanate resin. Molding material, characterized in that selected from the group The method of claim 1, wherein the curing agent for the organic binder sulfuric acid, phosphoric acid, benzene sulfonic acid, toluene sulfonic acid. Xylenesulfonic acid, isocyanate, diphenylmethane 4,4 'diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene-2, 4-diisocyanate (2,4 TDI), toluene-2,4-di A casting material comprising at least one kind selected from the group consisting of isocyanates (2,6TDI). The casting material according to claim 1, 2 or 3, wherein the curing agent for ceramic binder is made of isocyanate. The method of claim 4, wherein the isocyanate is diphenylmethane 4,4 'diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene-2,4- diisocyanate (2,4TDl) and toluene 2,6-di Molding material characterized by consisting of one or more selected from the group consisting of isocyanates (2,6TDl). The mold material according to claim 1, wherein the refractory fine powder for preventing borrowing is composed of at least one refractory fine powder selected from the group consisting of silica, alumina, and zirconia. The molding material of claim 1, wherein the foundry sand has a particle size of at least 325 mesh or more. The mold material according to claim 1, wherein the refractory fine powder for preventing borrowing has a particle size of 10-30 탆.