Mold molding material with excellent resistance to sand sintering

Abstract

Provided is a mold material that can advantageously be used to shape a mold in which casting defects associated with sand sintering, mechanical sand sticking, and the like are effectively suppressed or prevented. A mold-shaping material is prepared from a mixture that contains a refractory aggregate and contains either a modified linear phenol resin alone or a combination of a modified linear phenol resin and a resol resin, and such that the volatile rate, expressed as the weight loss rate after a 1-hour heat exposure treatment at a temperature of 500°C under a nitrogen atmosphere, of the cured product of the aforementioned resin alone or combination is 45 to 60%.

Description

Technical Field

[0001] This invention relates to mold-making materials with excellent resistance to casting sand sintering, and in particular to mold materials that can advantageously shape molds such as shell molds that can effectively suppress or even prevent casting defects. Background Technology

[0002] In the casting process using shell molds obtained by binding refractory aggregates such as silica sand with binders, casting defects such as surface deterioration of castings can occur due to mechanical sand adhesion of molten metal and sintering of casting sand. As a result, a process of coating the mold surface with a molding agent containing graphite, zircon, alumina, etc. has been carried out. However, this coating process is a complex process that complicates the casting process and worsens its workability. In addition, there are problems such as the reduced disintegration of the mold after casting.

[0003] Therefore, Japanese Patent Application Publication No. 2002-316237 discloses a shell-type resin-coated sand, which is prepared by forming a coating layer containing thermosetting resin and carbonaceous material on the surface of refractory aggregate, and the gas production rate during heating under specified conditions is 1 cm³ / s. 3 The amount in the mold is above 20 mL, which indicates that the shell (mold) can be protected from the high temperature of the molten metal and the surface of the casting can be improved without the use of a molding compound.

[0004] However, for shell molds obtained by molding with such resin-coated sand, even when pouring high-temperature molten liquid during casting, the final gas production of the mold is high, resulting in gas defects. Furthermore, the surface improvement of the castings has not been sufficient to date, especially in terms of casting defects such as sand sintering and mechanical sand adhesion.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-316237 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Here, the present invention has been made against the background described above, and its solution lies in providing a mold material that can advantageously mold molds for castings that effectively suppress or even prevent casting defects related to sand sintering, mechanical sand adhesion, etc. Furthermore, another solution of the present invention lies in providing a mold material that can advantageously mold molds, such as shell molds, that can effectively improve casting operations without the need for applying a molding compound.

[0010] Solution for solving the problem

[0011] Furthermore, the present invention can be suitably implemented in various ways as listed below to solve the aforementioned problems; however, the various methods described below can also be used in any combination. It should be understood that the methods and technical features of the present invention are not arbitrarily limited by the following description, but can be understood based on the inventive concept grasped from the entire description and the accompanying drawings.

[0012] Therefore, the present invention aims to solve the aforementioned problems by providing a molding material with excellent resistance to casting sand sintering, characterized in that it is formed from a mixture comprising refractory aggregate and a single modified linear phenolic resin, or a combination of modified linear phenolic resin and methyl phenolic resin, wherein the volatilization rate of the cured product of the above-mentioned single resin or combination after heat exposure treatment at 500°C for 1 hour under a nitrogen atmosphere is 45-60%.

[0013] It should be noted that, according to one of the preferred embodiments of the molding material of the present invention, the aforementioned modified linear phenolic resin has been modified with at least one of polyphenols, polycyclic phenols and alkylphenols.

[0014] Furthermore, regarding the molding material according to the present invention, the aforementioned first-order phenolic resin is characterized by having a weight-average molecular weight of 3000 or less.

[0015] Furthermore, according to another preferred embodiment of the material for molding according to the present invention, the mixing ratio of the aforementioned modified linear phenolic resin to the aforementioned methyl phenolic resin is 10:90 to 95:5 by mass.

[0016] Furthermore, according to another ideal aspect of the invention, it is characterized by further containing a volatilization accelerator capable of promoting the volatilization of the aforementioned cured material, and the aforementioned volatilization rate is determined in the presence of the volatilization accelerator.

[0017] Moreover, as such a volatility promoter, it is advantageously selected from the group consisting of organophosphates and / or organohalides.

[0018] In addition, according to another ideal embodiment of the invention, it also contains carbon materials.

[0019] Moreover, for the purposes of this invention, it is advantageous to form a covering layer comprising the aforementioned individual resin or combination thereof in such a manner as to cover the surface of the aforementioned refractory aggregate.

[0020] Furthermore, the molding material according to the invention is advantageously used for molding molds for casting molten iron.

[0021] It should be noted that the main purpose of this invention is to provide a casting mold with excellent resistance to casting sand sintering, characterized in that it is formed by molding a casting mold material containing the above-described structure and then heating and curing it.

[0022] The effects of the invention

[0023] As described above, in the mold-making material with excellent anti-sintering properties of casting sand according to the present invention, the volatilization rate of the cured product of the modified linear phenolic resin used as the binder resin, or the combination of the modified linear phenolic resin and the methyl phenolic resin, based on heat exposure treatment under a nitrogen atmosphere, is 45% to 60%. Therefore, even in the reducing atmosphere formed around the mold during casting, the binder resin can effectively generate volatile components. The gas moves from the inside of the mold towards the surface of the molten metal, increasing the gas pressure and forming an effective barrier layer between the molten metal and the mold. This effectively protects the mold from the effects of the high-temperature molten metal, and the volatile components effectively form a carbide film near the molten metal. As a result, the occurrence of casting sand sintering can be effectively suppressed or even prevented, and problems such as mechanical sand adhesion to the molten metal can be prevented, effectively improving the surface of the resulting casting. Moreover, such features are particularly advantageous in molds used in the casting of ferrous molten metals. Attached Figure Description

[0024] Figure 1 This is an illustration of a longitudinal section of a sand mold used in the casting test for evaluating the properties of the casting mold in the manufacturing examples.

[0025] Figure 2 For use Figure 1 The diagram shows the longitudinal section of the cast iron casting obtained from the sand mold used in the casting test.

[0026] Figure 3 A graph showing the relationship between the modification rate and the volatility of the shell molding material obtained in the examples and comparative examples. Detailed Implementation

[0027] First, the molding material for casting according to the present invention, which has excellent anti-sintering properties of casting sand, is prepared as follows: for a specified refractory aggregate, a single modified linear phenolic resin, or a combination of modified linear phenolic resin and methyl phenolic resin, is mixed as a binder, a volatilization accelerator is used advantageously to ensure the aforementioned volatilization rate, and other additives are used as needed. The molding material for casting is generally a resin-coated sand (RCS) formed by forming a coating layer mainly composed of a specified phenolic resin on the particle surface of the refractory aggregate, and such coating layer advantageously contains a volatilization accelerator and other additives added as needed.

[0028] Furthermore, for such mold-forming materials (RCS), it is necessary to adjust the curing rate of the modified linear phenolic resin used as its binder alone, or the cured product of the combination of modified linear phenolic resin and methyl phenolic resin (in the case of using a volatilization accelerator, it is assumed to contain it), to be within a specific range of 45-60% when subjected to heat exposure treatment at 500°C for 1 hour in a nitrogen atmosphere. Thus, even in the reducing atmosphere during casting, the binder resin can effectively generate volatile components at a relatively low temperature below 500°C. This can effectively suppress or even prevent the occurrence of defects in the castings obtained by casting, specifically the occurrence of casting sand sintering, mechanical sand adhesion, etc., and can advantageously improve the surface of the casting.

[0029] Here, the volatile content of the cured resin is an essential technical feature for solving the problems of the present invention. If such a volatile content becomes less than 45%, it becomes difficult to solve the problems of the present invention, namely, the prevention of casting sand sintering and the prevention of mechanical sand adhesion, and it becomes difficult to eliminate casting defects. Furthermore, if the volatile content becomes as high as 60%, the surface strength will decrease due to heat resistance issues, and there is a concern that problems such as casting sand sintering may occur more easily or that the mold may be deformed.

[0030] Therefore, the refractory aggregate constituting the molding material according to the present invention is a refractory material that functions as the base material of the mold, and can be any of the various refractory granular or powdered materials that have been used for mold making. Specifically, it can be represented by silica sand and artificial silica sand, and can include special sands such as alumina sand, olivine sand, zircon sand, and chromite sand; slag-based particles such as ferrochrome slag, ferronickel slag, and converter slag; artificial particles such as alumina particles and alumina-rich andalusite particles, and their recycled particles; alumina spheres, magnesiaclinker, etc. It should be noted that these refractory aggregates can be new sand, or they can be recycled sand or reclaimed sand that has been used as casting sand once or multiple times in the molding of the mold, and furthermore, they can be mixed sand formed by adding new sand to such recycled sand or reclaimed sand. Moreover, such refractory aggregates are typically formed into a particle size of about 40 to 200 based on the AFS index, and preferably into a particle size of about 60 to 150.

[0031] Furthermore, in order to achieve the volatility specified in this invention, as described above as a binder resin mixed in refractory aggregates, a single modified linear phenolic resin, or a combination of the above modified linear phenolic resin and a methyl phenolic resin, is used. By using such specific phenolic resins or combinations thereof, the volatility of the cured resins can be advantageously adjusted to the range of 45% to 60%.

[0032] Phenolic resins, as is well known, are solid or liquid (including varnish and emulsion forms) condensation products obtained by reacting phenols with aldehydes in the presence of an acidic or alkaline catalyst. Depending on the type of catalyst used, they are called linear phenolic resins (novalak type) or methyl phenolic resins. They exhibit thermosetting properties by heating in the presence or absence of a specified curing agent and curing catalyst. Furthermore, the phenols reacting with aldehydes include not only phenol but also those obtained by replacing at least a portion of the phenol with other modifying raw materials (phenol + modifying raw material). By reacting with aldehydes under an acidic catalyst, the modified linear phenolic resin of this invention can be obtained.

[0033] It should be noted that, as a modifying raw material to replace phenol in order to obtain such a modified linear phenolic resin, various known phenolic derivatives can be used, advantageously including polyphenols such as resorcinol, bisphenol F, bisphenol A, and the purification residues of these bisphenols; polycyclic phenols such as 1-naphthol, 2-naphthol, 1-hydroxyanthracene, and 2-hydroxyanthracene; and at least one of alkylphenols such as cresol, xylenol, p-tert-butylphenol, and nonylphenol. It is believed that by modifying the phenolic resin using such a modifying raw material, interstitial spaces are formed in the phenolic resin skeleton, promoting its decomposition and thereby increasing the volatility.

[0034] Furthermore, the modification rate of the modified linear phenolic resin, in other words, the substitution ratio of phenol in the modifying raw material, is generally advantageously 20-100% by mass, preferably 25-95% by mass, and more preferably 30-90% by mass. If such a modification rate of the linear phenolic resin is excessively low, the resin decomposition cannot be sufficiently promoted, thus making it difficult to effectively increase the volatility. Furthermore, with a high modification rate, the resin's heat resistance is easily reduced, and there is concern that the generation of gases, etc., may cease before the solidification of the cast iron or other molten metal being cast. It should be noted that, as described above, without hindering the objectives of the present invention, unmodified conventional linear phenolic resin may also be used together with the modified linear phenolic resin as a binder resin.

[0035] Furthermore, the methyl phenolic resin used in combination with the aforementioned modified linear phenolic resin can be manufactured in the same manner as before, using an alkaline catalyst. This methyl phenolic resin functions as a curing aid, replacing hexamethylenetetramine. Moreover, the cured product containing this methyl phenolic resin and the modified linear phenolic resin tends to have a lower crosslinking density and a higher volatile content compared to the hexamethylenetetramine-based cured product of the modified linear phenolic resin. Therefore, it is effective in achieving the volatility according to the present invention. It should be noted that, generally, a methyl phenolic resin with a weight-average molecular weight of 3000 or less is suitable. If the weight-average molecular weight of this methyl phenolic resin is excessively high, it becomes difficult to fully realize its performance. Furthermore, there is concern about reduced mold strength, increased resin viscosity, and difficulty in covering the surface of refractory aggregates during RCS manufacturing, potentially leading to reduced mold strength.

[0036] Furthermore, when using modified linear phenolic resin and methyl phenolic resin in the above combination, it is advantageous to adopt a mixing ratio of modified linear phenolic resin to methyl phenolic resin of 10:90 to 95:5, preferably 20:80 to 90:10, based on mass. It should be noted that if the proportion of modified linear phenolic resin increases (and the proportion of methyl phenolic resin decreases), the curing speed tends to slow down. Furthermore, a lower proportion of modified linear phenolic resin and a higher proportion of methyl phenolic resin can lead to problems such as reduced mold strength.

[0037] It should be noted that the ratio of the binder resin containing the above-mentioned individual modified linear phenolic resin, or a combination thereof with methyl phenolic resin, in the molding material is appropriately determined considering the type of resin used, the required strength of the mold, etc. Therefore, it cannot be limited in general, but it is generally in the range of about 0.2 to 10 parts by weight relative to 100 parts by weight of refractory aggregate, preferably 0.5 to 8 parts by weight, and more preferably 0.5 to 5 parts by weight.

[0038] Furthermore, in the molding material according to the present invention, in addition to the special binder resin comprising the aforementioned modified linear phenolic resin alone, or a combination thereof with a methyl phenolic resin, it advantageously also contains a volatilization accelerator that promotes the volatilization of the cured binder resin. Thus, the volatilization rate of the cured binder resin can be advantageously adjusted to the range of 45% to 60%. By using such a volatilization accelerator to achieve the volatilization rate, the gas pressure can be increased even at relatively low temperatures below 500°C. The volatile components generated by the cured binder resin can effectively form a carbon film on the molten surface, thereby suppressing or even preventing sand sintering and mechanical sand adhesion, and advantageously improving the surface of the casting. As such a volatilization accelerator, organophosphates and / or organohalides are preferably selected and used. It should be noted that the amount of such a volatilization accelerator used is typically about 1 to 50 parts by weight relative to 100 parts by weight of the binder resin, preferably in the range of 5 to 30 parts by weight.

[0039] Specifically, examples of organophosphate esters used as volatilization promoters include aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, methyl diethyl phosphate, methyl dibutyl phosphate, ethyl dibutyl phosphate, and tri(β-chloropropyl) phosphate; triphenyl phosphate; tricresyl phosphate; tri(xylyl) phosphate; tri(xylyl) phosphate; toluene diphenyl phosphate; 2-ethylhexyl diphenyl phosphate; tert-butylphenyl diphenyl phosphate; bis(tert-butylphenyl) phosphate; tri(tert-butylphenyl) phosphate; isopropylphenyl diphenyl phosphate; and bis(isopropyl) phosphate. Aromatic phosphate esters such as phenyl(diphenyl) phosphate and tri-(isopropylphenyl) phosphate, and further, oligomeric ethyl ethylene phosphate, modified oligomeric ethyl ethylene phosphate, phenylene bis(phenylcresol) phosphate, 2,2-bis{4-[bis((mono or di)methylphenoxy)phosphoryloxy]phenyl}propane, 1,3-phenylene bis(xylyl) phosphate, α-diphenoxyphosphoryl-ω-phenoxy poly(n=1~3)[oxy-1,4-phenyleneisopropylidene-1,4-phenyleneoxy(phenoxyphosphoryl)] and other aliphatic condensed phosphate esters and aromatic condensed phosphate esters.

[0040] In addition, as organohalides, examples include chlorinated paraffin, chlorinated diphenyl, chlorinated ethane, chlorinated polyethylene, chlorinated polyphenyl, chlorinated biphenyl, vinyl chloride, perchlorocyclopentadecanone, tetrachlorobisphenol A, trichloroethyl phosphate, tris(1,3-dichloroisopropyl) phosphate, tri-β-chloropropyl phosphate, and other organochlorine compounds; brominated paraffin, brominated polyphenyl, tetrabromoethane, tetrabromobenzene, decabromodiphenyl ether, octabromodiphenyl ether, hexabromocyclododecane, bis(tribromophenoxy)ethane, ethylene bis(tetrabromophthalimide), hexabromobenzene, polydibromophenyl ether, tetrabromobisphenol A, tris(2,3-dibromopropyl-1) isocyanurate, and tribromophenol allyl ether. Organic bromine compounds such as ether, brominated polystyrene, tribromoneopentol, dibromodichloropropane, dibromotetrafluoroethane, tri(tribromophenyl) phosphate, tri(tribromoneopentyl) phosphate, etc.; organic fluorine compounds such as polytetrafluoroethylene, perfluoroalkoxyalkylene, perfluoroethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, etc.

[0041] Furthermore, regarding the molding material according to the present invention, a carbon material is advantageously included as a melt-repellent agent, which imparts a property of repelling the poured molten metal to the mold surface in contact with the molten metal. As this carbon material, known substances can be suitably selected, such as graphite, carbon powder, resin carbon, smokeless carbon, charcoal, mesophase carbon, petroleum pitch coke, fossil pitch coke, precursors, organic matter carbonized, and carbides such as silicon carbide. Moreover, such a carbon material is typically used with a particle size of about 1 to 500 μm, preferably about 3 to 350 μm, and more preferably about 5 to 200 μm. It should be noted that, as the amount added, it is typically contained in a ratio of about 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass relative to 100 parts by mass of refractory aggregate. If the carbon material content is too low, it will be difficult to achieve sufficient results; and if it is too high, there are concerns that it may cause problems such as reduced mold strength.

[0042] Furthermore, it is also effective to include coolant particles that can exert a cooling effect in the molding material of the present invention. Examples of such coolant particles include those that reduce the fluidity of the molten metal in contact with the mold by accelerating its cooling, thereby inhibiting or even preventing its intrusion into the mold. Examples of coolant particles include metal powders such as iron, aluminum, and copper, as well as powders of iron oxide, ferric oxide, aluminum oxide, copper oxide, ferric hydroxide (iron oxide yellow), aluminum hydroxide, zircon, magnesium oxide, and silicon oxide. The amount of these coolant particles added is approximately 0.5 to 20 parts by weight, preferably 1 to 15 parts by weight, and more preferably 2 to 10 parts by weight, relative to 100 parts by weight of the refractory aggregate. This is because if the amount of coolant particles added is too small, its additive effect cannot be fully achieved, and if the amount is too large, there are concerns about problems such as reduced mold strength.

[0043] Furthermore, in order to achieve curing, the molding material according to the present invention, in addition to adding or containing a curing agent such as hexamethylenetetramine, which has been known to date, can also be further added as needed, such as various known curing accelerators, for example, organic carboxylic acids, alkaline materials, etc. In addition, when using a combination of modified linear phenolic resin and methyl phenolic resin as the binder resin, as explained in Japanese Patent Application Publication No. 2003-158810, WO2013 / 118572, etc., at least one of Arrhenius base, Brønsted base, and Lewis base can be advantageously used as a curing accelerator.

[0044] Furthermore, in the molding material of the present invention, various additives commonly used to date can be appropriately blended as needed for the purpose of improving the physical properties of the molding material itself and the physical properties of the molding mold. For example, as a lubricant that helps improve the flowability of the molding material (RCS), waxes such as paraffin wax, synthetic polyethylene wax, and lignite wax can be added; stearic acid, stearyl alcohol, glyceryl monostearate, and stearyl stearate; stearate metal salts such as calcium stearate, zinc stearate, magnesium stearate, and lead stearate; and hydrogenated oils. In addition, coupling agents containing additives such as reinforcing refractory aggregates and binder resins are also effective; for example, silane coupling agents, zircon coupling agents, and titanium coupling agents can be used. Furthermore, as a release agent, paraffin wax, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid esters, organic acids, mica, vermiculite, fluorinated release agents, and organosilicon release agents can also be used. Furthermore, these additives are used at a ratio of approximately 0.001 to 10 parts by weight, preferably approximately 0.01 to 7 parts by weight, and more preferably approximately 0.1 to 5 parts by weight relative to 100 parts by weight of the binder resin.

[0045] Furthermore, as described above, when manufacturing the molding material (RCS) according to the present invention using the additives, various known mixing / coating methods can be used without particular limitation, such as any of the conventionally known methods, including dry hot coating, semi-hot coating, cold coating, and powder solvent methods. Advantageously, the so-called dry hot coating method is employed as follows: In a mixing mill such as a vortex mixer or high-speed mixer, refractory aggregate (granules) preheated to a temperature of approximately 110–170°C, preferably 120–150°C, is mixed with a binder resin (a specified phenolic resin), and further with other additives such as a volatility accelerator and carbon materials selected as needed. Then, a specified curing agent and curing accelerator, such as hexamethylenetetramine, are added in the form of an aqueous solution if water-soluble, and water is added simultaneously as cooling water if not water-soluble. The blocky contents are then broken down into granules by air cooling. Finally, calcium stearate (a lubricant) is added.

[0046] It should be noted that the timing of mixing the binder resin, volatilization accelerator, carbon materials, further additives, and curing agents / curing accelerators with the refractory aggregates can be appropriately selected based on the common knowledge of those skilled in the art. Besides mixing them individually and sequentially, they can also be mixed in combination. Furthermore, additives such as volatilization accelerators and carbon materials can be mixed with the binder resin, or all components can be mixed simultaneously, as long as the additives do not lose their effectiveness due to changes caused by heat or chemical reactions. They can be mixed during the synthesis of the binder resin, while the newly synthesized binder resin is still in a molten state, or added and mixed during or after the mixing of the refractory aggregates and binder resins. Moreover, when the amount of these additives is large, they can be added in batches after the binder resin is mixed with the refractory aggregates and the binder resin.

[0047] Furthermore, when using the molding material obtained above to mold a mold such as a target shell mold, in order to achieve heat curing of the molding material (RCS), the target mold is molded under heat. There are no particular limitations on such heat molding method, and any of the methods known in the art can be used advantageously. For example, by gravity dropping or blowing, the molding material described above can be filled into a mold having the desired molding space for providing the target mold and heated to approximately 150–300°C, then cured. The cured mold is then demolded from the mold to obtain the target casting mold. It should be noted that such a casting mold is advantageously molded with a filling rate of 50% or more. By achieving such a filling rate, the internal structure of the mold easily becomes a stone wall structure, which can prevent the intrusion of molten metal or advantageously increase the gas pressure from the mold. Furthermore, the filling rate of such a mold can be determined by known methods, such as the method described in paragraph

[0060] of Japanese Patent Application Publication No. 2019-177402.

[0048] Moreover, the mold obtained in this way can be advantageously endowed with excellent characteristics such as anti-sintering properties of casting sand, as mentioned above, and is particularly advantageous for casting molten iron such as cast iron, cast steel, and FCD, so that its characteristics can be further effectively utilized.

[0049] Example

[0050] The following describes some embodiments of the present invention in further detail, but the present invention is not limited to any of the embodiments described herein. Furthermore, it should be understood that, in addition to the embodiments described below and the specific descriptions above, various changes, modifications, and improvements can be made based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. It should be noted that the parts and percentages in the following embodiments and comparative examples are expressed on a mass basis, and the determination of volatile matter rate and the evaluation of cast sand sintering / casting surface are performed as follows.

[0051] -Determination of volatility-

[0052] The adhesive resin (phenolic resin or a mixture thereof) used in the examples or comparative examples was mixed with the curing agent (hexamethylenetetramine) at the usage ratio in the examples or comparative examples, and then pulverized. The mixture was then heated / cured at 150°C for 30 minutes to obtain a cured product. Next, approximately 100g of the pulverized and homogenized cured product was accurately weighed and its weight (W1) was determined. The product was then subjected to a heat exposure treatment at 500°C for 1 hour in an electric furnace under a nitrogen atmosphere. The residue after this heat exposure treatment was accurately weighed and its weight (W2) was determined.

[0053] Then, using the weights obtained above: W1 and W2, calculate the volatilization rate of the solidified material: C1 (%) according to the following formula (1).

[0054] C1=(1-W2 / W1)×100···(1)

[0055] In addition, for cases where a volatilization accelerator is used in the examples and comparative examples, the volatilization accelerator is mixed with the cured product obtained as described above at the same ratio as in the examples or comparative examples, and the mixture is then weighed accurately as described above to determine its weight (W3). Next, for the mixture described above, it is subjected to heat exposure treatment at 500°C for 1 hour under a nitrogen atmosphere as described above, and the residue after the heat exposure treatment is weighed accurately to determine its weight (W4). Then, based on the values ​​of W3 and W4 obtained above, the volatilization rate of the cured product in the presence of the volatilization accelerator is calculated according to the following formula (2): C2 (%).

[0056] C2=(1-W4 / W3)×100···(2)

[0057] It should be noted that, in determining the volatility, in addition to the method described above of separately preparing a cured product of the binder resin, different from the molding material (RCS), and subjecting it to heat exposure treatment, a method can also be used to cure the molding material (RCS) itself and determine the volatility from the cured product. In this case, for the molding material (RCS) as the test object, after heating / curing at 150°C for 30 minutes, the resulting cured product is subjected to heat exposure treatment at 500°C for 1 hour in a nitrogen atmosphere, and its weight loss rate (W5) is determined. Next, the cured product after the above heat exposure treatment is burned at 900°C for 1 hour in the presence of oxygen (e.g., in air) to burn off the organic components in the cured product, and its weight loss rate (W6) is determined. Then, using these obtained W5 and W6 values, the volatility rate: C (%) is calculated according to the following formula (3).

[0058] C=[W5 / (W5+W6)]×100···(3)

[0059] -Evaluation of Sand Sintering / Casting Surface-

[0060] First, such as Figure 1As shown, in a split-type hollow main mold 6 (mold cavity diameter: 6cm, height: 6cm) pre-made from room temperature self-hardening sand, with a molten metal inlet 2 at the top and a core head fixing part 4 at the bottom, a circular solid core 10 (diameter: 5cm, height: 5cm), obtained by filling the mold with molding materials blown into a mold heated to 250°C and then heating for 120 seconds, is bonded and fixed to the core head fixing part 4. Then, the split-type hollow main molds 6 are bonded and fixed together to create a sand mold 12 for casting tests. It should be noted that to prevent leakage of molten metal during casting, the bonded main molds are clamped with pliers or secured firmly with coiled steel wire. Then, molten cast iron FC200 (temperature: 1380°C±40°C) is poured into the molten metal inlet 2 of the sand mold 12 for casting tests and solidified. After solidification, the main mold 6 and the core 10 are destroyed, as shown. Figure 2 As shown, the cylindrical casting 16 is removed. Then, the resulting casting 16 is cut in half, and the condition of the sand sintering and the surface of the casting (the surface of the casting) is confirmed by visual inspection and touch. Evaluation is carried out in 3 stages and 4 stages respectively according to the criteria shown below.

[0061] <Casting Sand Sintering>

[0062] ○: No confirmation found for cast sand sintering

[0063] △: Sintering of casting sand was confirmed in a portion of the casting.

[0064] ×: Confirmed sand sintering on the entire surface of the casting.

[0065] <Casting Surface>

[0066] ◎: The surface of the casting is smooth and there is no hook or snag on the surface.

[0067] 〇: The surface of the casting is generally smooth, but some parts are rough.

[0068] △: The surface of the casting is rough overall, and some parts have hooks.

[0069] ×: Roughness and hooking are present on the overall surface of the casting.

[0070] -Manufacturing of Phenolic Resin A1-

[0071] In a reaction vessel equipped with a thermometer, a stirrer, and a condenser, 200 parts of phenol, 800 parts of bisphenol A (BPA), 234 parts of 47% formalin, and 3 parts of oxalic acid were added. The reaction vessel was then slowly heated to the reflux temperature and refluxed for 90 minutes. After dehydration under normal pressure, the mixture was heated under reduced pressure until it reached 180°C to remove unreacted phenol, thus obtaining resin A1, a modified linear phenolic resin with a BPA modification rate of 80%.

[0072] -Manufacturing of Phenolic Resin A2-

[0073] 700 parts of phenol, 300 parts of bisphenol A, 363 parts of 47% formalin, and 3 parts of oxalic acid were added. Otherwise, following the same steps as in the manufacturing example of phenolic resin A1 above, resin A2 was obtained as a modified linear phenolic resin with a BPA modification rate of 30%.

[0074] -Manufacturing of Phenolic Resin A3-

[0075] Add 700 parts of phenol, 300 parts of 1-naphthol, 395 parts of 47% formalin, and 3 parts of oxalic acid. Otherwise, follow the same steps as in the manufacturing example of phenolic resin A1 above to obtain resin A3, which is a modified linear phenolic resin containing a naphthol modification rate of 30%.

[0076] -Manufacturing of Phenolic Resin A4-

[0077] 700 parts of phenol, 300 parts of o-cresol, 424 parts of 47% formalin, and 3 parts of oxalic acid were added. Otherwise, following the same steps as in the manufacturing example of phenolic resin A1 above, resin A4 was obtained as a modified linear phenolic resin with an o-cresol modification rate of 30%.

[0078] -Manufacturing of Phenolic Resin A5-

[0079] Add 1000 parts of phenol, 441 parts of 47% formalin, and 3 parts of oxalic acid. Otherwise, follow the same steps as in the aforementioned example of manufacturing phenolic resin A1 to obtain resin A5, which is an unmodified, conventional linear phenolic resin (modification rate 0%).

[0080] Preparation of materials for the formation of phenolic polyurethane resins-

[0081] A benzyl ether type phenolic resin (manufactured by Asahi Organics Co., Ltd.: CBP-160EH, MW: 1200) and polymeric MDI (manufactured by Asahi Organics Co., Ltd.: CB-MT3), which is a polyisocyanate compound, are prepared. When forming a coating layer on the surface of refractory aggregate, a mixture of these two components in a 1:1 (mass ratio) ratio is used as a material for forming phenolic polyurethane resin.

[0082] Preparation of Phenolic Resin B1 -

[0083] SP750WM (trade name, weight average molecular weight: 1000), manufactured by Asahi Organic Materials Co., Ltd., which belongs to the aminomethyl phenolic resin category, was selected as the aminomethyl phenolic resin.

[0084] Preparation of Phenolic Resin B2-

[0085] SP400 (trade name, weight average molecular weight: 2100), manufactured by Asahi Organic Materials Co., Ltd., which belongs to the aminomethyl phenolic resin category, was selected as the aminomethyl phenolic resin.

[0086] Preparation of Phenolic Resin B3-

[0087] Asahi Organic Materials Co., Ltd.'s TS-10 (trade name, weight average molecular weight: 3800), which belongs to the alkali-type phenolic resin, was selected as the alkali-type phenolic resin.

[0088] -Example 1-

[0089] As a refractory aggregate, a 1:1 mixture of flattery sand and recycled silica sand was preheated to approximately 140°C. Then, 100 parts of this mixture, 2.5 parts of resin A1 (a modified linear phenolic resin), and 3 parts of aliphatic condensed phosphate ester PNX (trade name: Fyrol PNX-LE, manufactured by ICL JAPAN Co., Ltd.) as a volatilization accelerator were sequentially added to a vortex mixer and mixed for 60 seconds. Next, 0.375 parts of hexamethylenetetramine (a curing agent) dissolved in water were added, and the mixture was cooled by air blowing. Subsequently, 0.1 parts of calcium stearate were added to obtain a shell-type molding material (material for molding).

[0090] -Examples 2, 3-

[0091] The aliphatic condensed phosphate ester PNX used as a volatility promoter is 5 or 10 parts. Otherwise, the shell molding material is obtained by the same method as in Example 1.

[0092] -Example 4-

[0093] Five parts of powdered graphite were added as carbon material. Otherwise, the same method as in Example 2 was used to obtain the mold material for the shell.

[0094] -Example 5-

[0095] As a volatility promoter, 5 parts of tetrabromobisphenol A (TBBPA), which belongs to the organic halide, were used instead of the aliphatic condensed phosphate ester: PNX. Otherwise, the same method as in Example 2 was used to obtain the mold material for the shell.

[0096] -Examples 6-8-

[0097] As a modified linear phenolic resin, resin A2, resin A3, or resin A4 were used instead of resin A1. Otherwise, the same method as in Example 2 was used to obtain the molding materials for the shell mold.

[0098] -Example 9-

[0099] As the adhesive resin, resin A1, which belongs to modified linear phenolic resin, and resin B1, which belongs to methyl phenolic resin, are used simultaneously at a ratio of A1:B1 = 75:25 based on the resin solids conversion, and the amount of curing agent is 0.075 parts. Otherwise, the shell mold material is obtained by the same method as in Example 2.

[0100] -Example 10-

[0101] As a first-order phenolic resin, resin B2 was used instead of resin B1, and a mixing ratio of A1:B2 = 50:50 was adopted based on the resin solids conversion. Otherwise, the same method as in Example 9 was used to obtain the mold material for the shell.

[0102] -Comparative Example 1-

[0103] As the binder resin, only resin A5, which is an unmodified linear phenolic resin, was used. On the other hand, PNX, which is a volatilization promoter, was not added. Otherwise, the shell molding material was obtained by the same method as in Example 1.

[0104] -Comparative Example 2-

[0105] Without adding PNX as a volatilization promoter, the same method as in Example 6 was used to obtain the mold material for the shell.

[0106] -Comparative Example 3-

[0107] As a first-order phenolic resin, resin B3 was used instead of resin B2. Otherwise, the same method as in Example 10 was used to obtain the mold material for the shell.

[0108] -Comparative Example 4-

[0109] As a refractory aggregate, the same mixed sand as in Example 1 was used. 1.0 part of the aforementioned phenolic polyurethane resin forming material (benzyl ether type phenolic resin + polyisocyanate compound) was used as a binder resin, and 1.0 part of curing agent was added. These were mixed in a mixer for 60 seconds to obtain the molding material. It should be noted that the molding of the core using the molding material obtained in this comparative example was performed according to the following method. First, the above-mentioned molding material was added to the sand box of the cold box molding machine, and then filled into the core molding mold at a gauge pressure of 0.3 MPa. Next, triethylamine gas was introduced into the mold using a gas generator at a gauge pressure of 0.2 MPa for 1 second, followed by air purging at a gauge pressure of 0.2 MPa for 14 seconds, and then demolding was performed to produce a circular solid core 10 (diameter: 5 cm, height: 5 cm) with a core head 8.

[0110] -Evaluation of casting mold materials-

[0111] For each mold material of Examples 1-10 and Comparative Examples 1-4 obtained above, the volatilization rate of the cured mixture of each binder resin, curing agent, and volatilization accelerator was measured according to the aforementioned test method. Furthermore, in casting operations using molds molded from each mold material, the sintering of the cast sand and the evaluation of the casting surface were performed according to the aforementioned method. These measurement and evaluation results are then shown in Tables 1-3 below. Additionally, Figure 3 In the examples 2, 6, 9 and 1, 2, 3, the relationship between the modification rate and the volatility rate is shown for the shell molding materials obtained.

[0112] [Table 1]

[0113]

[0114] [Table 2]

[0115]

[0116] [Table 3]

[0117]

[0118] For example, by comparing the results in Tables 1 to 3 above, Figure 3 The relationship between the modification rate and the volatility rate shown confirms that, according to the present invention, for the mold materials of Examples 1 to 10, which use a single modified linear phenolic resin or a combination of modified linear phenolic resin and methyl phenolic resin as binder resin, and whose cured binder resin has a volatility of 45 to 60%, the occurrence of casting sand sintering can be effectively suppressed or even prevented, and the surface of the obtained castings becomes better, resulting in castings of excellent quality.

[0119] In contrast, in the mold material of Comparative Example 1, which uses a conventional unmodified linear phenolic resin as a binder resin, the casting sand sintering and the surface of the casting became unsatisfactory. Furthermore, in the cases of the mold materials of Comparative Examples 2 and 3, where even when a modified linear phenolic resin or a combination thereof with a first-order phenolic resin is used as a binder resin, the volatility of the cured product is less than 45%, and in the case of the mold material of Comparative Example 4, which uses a benzyl ether type phenolic resin (phenolic polyurethane resin) and whose cured product has a volatility of more than 60%, sufficient improvement effects could not be confirmed in the evaluation of the characteristics of the casting sand sintering and the surface of the casting.

[0120] Explanation of reference numerals in the attached figures

[0121] 2. Molten metal inlet 4. Core head fixing part

[0122] 6 main molds, 8 cores head

[0123] 10 cores, 12 sand molds

[0124] 14 Waste core discharge port 16 Castings

Claims

1. A molding material with excellent resistance to casting sand sintering, characterized in that, It is formed from a mixture comprising refractory aggregate and a single modified linear phenolic resin, or a combination of modified linear phenolic resin and methyl phenolic resin, wherein the volatilization rate of the cured product of the single resin or combination after heat exposure at 500°C for 1 hour under a nitrogen atmosphere is 45-60%, and the mixture further contains a volatilization accelerator that promotes the volatilization of the cured product, and the volatilization rate is determined in the presence of the volatilization accelerator, wherein the volatilization accelerator is selected from the group consisting of aliphatic condensed phosphate esters and / or organohalides.

2. The casting mold material with excellent resistance to casting sand sintering as described in claim 1, characterized in that, The modified linear phenolic resin was modified with at least one of polyphenols, polycyclic phenols, and alkylphenols.

3. The molding material with excellent resistance to casting sand sintering as described in claim 1 or claim 2, characterized in that, The first-order phenolic resin has a weight-average molecular weight of less than 3000.

4. The casting mold material with excellent resistance to casting sand sintering as described in claim 1 or claim 2, characterized in that, The mixing ratio of the modified linear phenolic resin to the alpha-phenolic resin is 10:90 to 95:5 by mass.

5. The molding material with excellent resistance to casting sand sintering as described in claim 1 or claim 2, wherein, The volatility is 48.4% to 60%.

6. The casting mold material with excellent resistance to casting sand sintering as described in claim 1 or claim 2, characterized in that, The organohalide is tetrabromobisphenol A.

7. The casting mold material with excellent resistance to casting sand sintering according to claim 1 or claim 2, characterized in that, It also contains carbon materials.

8. The casting mold material with excellent resistance to casting sand sintering according to claim 1 or claim 2, characterized in that, A covering layer comprising the individual resin or combination thereof is formed in such a way as to cover the surface of the refractory aggregate.

9. The casting mold material with excellent resistance to casting sand sintering according to claim 1 or claim 2, characterized in that, Molding molds used for casting molten iron.

10. A casting mold with excellent resistance to casting sand sintering, characterized in that, It is formed by molding and heating with a molding material that has excellent resistance to casting sand sintering, as described in any one of claims 1 to 9.

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