JPH0435252B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a shell mold material used for forming the main mold and core of a casting mold, and a mold using the same. More specifically, it relates to shell molding materials that emit less smoke, formaldehyde, and other irritating odors, foreign odors, and toxic gases (hereinafter referred to as irritating gases) during overheating during casting, and molds using the same. It is. [Prior art and its problems] As a manufacturing method for the main mold and core of a casting mold (hereinafter simply referred to as the mold), sand molding has traditionally been used to incorporate the property of synthetic resins such as phenolic resins, which harden with heat, into The shell mold method used for curing is widely used. This is because, when manufactured using a mold manufactured by this shell molding method, a casting with extremely high dimensional accuracy and a beautiful casting surface can be manufactured. As a molding material used in this shell molding method, resin-coated foundry sand (coated sand), in which sand grains such as silica sand are coated with a thermosetting resin such as phenol resin, is generally used. However, when molds are manufactured using this resin-coated foundry sand as a raw material, irritating gases such as formaldehyde, phenol, and ammonia are generated during overheating during coating and molding processes, which poses a problem. Further, when casting using the obtained mold, the above-mentioned irritating gas is generated during overheating in the pouring process, which poses a problem. This causes a deterioration of the working environment within the foundry, and on the other hand, it requires enormous equipment costs to reduce the various irritating gases generated from the foundry, and this is not always sufficient. There is a strong need for countermeasures. Conventionally, as a method to solve these problems, mold materials using unsaturated polyester resin as the coating resin for resin-coated molding sand have been proposed (Japanese Patent Application Laid-Open No. 80234/1983, Japanese Patent Application Laid-Open No. 1983-80234). Publication No. 59560). However, although this unsaturated polyester resin-coated foundry sand reduces the generation of irritating gases compared to the case where phenolic resin-coated foundry sand is used, it has the problem of poor moldability. Furthermore, when the above-mentioned conventional resin-coated molding sand is used, there is a problem in that the disintegrability of the mold after casting is insufficient. That is, when casting materials such as cast iron, which have a high casting temperature, the mold disintegration property is relatively good, but when casting materials such as aluminum, magnesium, etc. and their alloys, which have a relatively low casting temperature, the mold disintegration property is poor. Therefore, it is a problem that it takes time and effort to remove sand after casting, especially to eject the core. In the case of iron-based metals, the internal temperature of the shell mold during pouring is 800 to 1000°C, so thermosetting resins such as phenolic resins used as binding materials are exposed to high temperatures and Thermal decomposition naturally reduces the strength of the shell mold after pouring and subsequent solidification, making it easy to remove the shell pour from the casting after casting. but,
In the case of casting low melting point metals such as aluminum,
Because the internal temperature of the shell mold during pouring is as low as 300 to 400°C, the thermosetting resin in the shell mold is not sufficiently decomposed, and since it maintains considerable strength even after casting, it has poor collapsibility. In particular, if the shell core is of a complicated shape, it may be extremely difficult to remove the shell core from the casting. Therefore, in such a case,
After casting, a sand baking process is required in which the mold is heated and maintained at a temperature of around 500℃ for a long period of time through a firing furnace, etc., causing it to collapse, which is time-consuming and reduces productivity, and consumes a large amount of energy, making it difficult to save energy. It was a problem. Therefore, the present inventors conducted intensive research to solve these conventional problems and conducted various systematic experiments, and as a result, the present invention was completed. [Object of the invention] The object of the present invention is that when manufacturing a casting mold,
Another object of the present invention is to provide a shell molding material that generates less smoke and/or irritating gas during overheating when casting is performed using these molds, and a mold using the same. Another object of the present invention is to provide a mold material that has good mold formability and has sufficient mold disintegration properties after casting even when the casting temperature is relatively low, such as aluminum casting or magnesium casting, and a mold using the same. is to provide. [Structure of the Invention] The shell molding material of the present invention is characterized by being formed by mixing molding sand coated with a thermosetting resin and hydrous magnesium silicate clay mineral coated with a thermosetting resin. (hereinafter referred to as the first invention). The shell molding material of the present invention is characterized by being made by mixing molding sand coated with a thermosetting resin and hydrous magnesium silicate clay mineral containing an acid and further coated with a thermosetting resin on the surface. (hereinafter referred to as this second discovery). The mold of the present invention is a mold consisting of a cavity for forming a casting and a wall for forming the cavity, in which the wall is made of molding sand at least partially coated with a thermosetting resin. It consists of a hydrated magnesium silicate clay mineral coated with a resin, a cavity formed between the resin-coated foundry sand and the resin-coated clay mineral, and the resin-coated foundry sand and the resin-coated clay mineral are bonded to each other. (hereinafter referred to as the third invention). The mold of the present invention is a mold comprising a cavity for forming a casting and a wall for forming the cavity, wherein the wall contains foundry sand and acid, at least a portion of which is coated with a thermosetting resin. It further comprises a hydrous magnesium silicate clay mineral whose surface is coated with a thermosetting resin, and a cavity formed between the resin-coated foundry sand and the resin-coated acid-containing clay mineral, and the resin-coated foundry sand and The resin-coated acid-containing clay mineral is characterized in that the resin-coated acid-containing clay minerals are bonded to each other (hereinafter referred to as the fourth invention). Below, the configuration of the present invention will be explained in more detail. The molding sand coated with a thermosetting resin in the shell mold material of the first invention is obtained by coating the surface of the molding sand as a base material of the material with a thermosetting resin as a caking agent. . Here, foundry sand is a refractory sandy substance that forms the base material of shell molds, and specifically includes silica sand, zircon sand, chromite sand, olivine sand, sea sand, river sand,
There are sands made by crushing rocks, and one type or a mixture of two or more of these types is used. The appropriate shape, size, and type of molding sand are selected in consideration of fluidity, filling properties, toughness, thermal expansion properties, solidification rate, etc. The particle shape of this foundry sand is preferably spherical, such as round or square. This is because, in this case, the sand has good fluidity, it is easy to obtain high mold strength with a relatively small amount of resin, and the mold has good air permeability. In addition, thermosetting resin is a caking material that has the function of mutually bonding foundry sand and hydrated magnesium silicate clay mineral, which serve as the base material of shell mold material, and molding it into a predetermined mold shape. are phenol formaldehyde resins, novolac type phenolic resins such as phenol and furfural resins, resol type phenolic resins such as resorcinol formaldehyde and ammonia resol resins,
Urea resin, silicone resin, melamine resin, etc. are used. The molding sand is coated with a resin by a conventional method such as a hot coating method, a dry hot coating method, a semi-hot coating method, a cold coating method, or a powder solvent method, by adding appropriate additives as necessary. Here, the blending amount of the resin is preferably 1 to 10 wt%. This amount varies depending on the purpose, the amount of hydrated magnesium silicate clay mineral and additives, and manufacturing conditions, but roughly speaking, it is 1 to 6 wt% when the foundry sand is silica sand, and 1 to 6 wt% when zircon sand is used. is preferably 1 to 4 wt%. In addition, the particle size of the resin-coated foundry sand is 50 μm to 1
Preferably, it is mm. Next, the hydrous magnesium silicate clay mineral coated with a thermosetting resin (hereinafter referred to as resin-coated clay mineral) is applied to the surface of the hydrous magnesium silicate clay mineral (hereinafter referred to as clay mineral) by thermosetting as a caking agent. It is coated with a synthetic resin. Here, the clay mineral is mainly composed of hydrated magnesium silicate and has highly reactive hydroxyl groups on its surface. In addition, this clay mineral
It consists of fibers with a diameter of about 0.005 to 0.6 μm, and pores (channels) with a rectangular cross section of about 10 to 6 mm are present parallel to the fibers. In this clay mineral, a part of magnesium or silicon may be replaced with aluminum, iron, nickel, sodium, etc. Specifically, sepiolite, Xylotile, Loughlinite, which is mainly composed of hydrated magnesium silicate,
There are falcondoite, palygorskite whose main component is hydrated aluminum silicate, etc., and one or a mixture of two or more of these is used. Further, these materials may be calcined within a temperature range of 400 to 800°C. Also known by common names: Mountain cork, Mountain wood, Mountain leather, Meerschaum.
Minerals called chaum, attapulgite, etc. fall under this category. This clay mineral may be used in the form of powder, granules, or plates, but it is best to crush it to the extent that the pores of the clay mineral remain, and the size of the pores is in the range of 50 μm to 1 mm. It is preferable that there be.
Among these, 100 to 500 μm is more preferable. The pulverization at this time is carried out by wet pulverization or dry pulverization using a geocrusher, hammer mill, roller mill, crushing granulator, vibration mill, pin mill, beater, or the like. In addition, the thermosetting resin used is the same as the molding sand coating resin described above, but if other properties such as strength improvement are required, a different type of thermosetting resin may be used. Good too. At this time, the coating amount of the resin is preferably 0.5 to 20 wt%.
This means that if the coating amount is less than 0.5wt%, the effect of resin coating during thermosetting is not seen, and 20wt%
This is because, if it exceeds the above, the effect of suppressing the generation of irritating gases and smoke during mold forming and casting will be reduced. More preferably, the amount of coating is about the same as the amount of resin blended into the foundry sand. When the coating amount is set to this ratio, the bond between the foundry sand and the clay mineral in the formed mold becomes good. The shell molding material of the first invention is made by mixing foundry sand coated with a thermosetting resin and hydrous magnesium silicate clay mineral coated with a thermosetting resin. Here, the mixing ratio of thermosetting resin-coated molding sand (resin-coated molding sand) and resin-coated clay mineral is 0.5 to 45 parts by weight of resin-coated clay mineral to 100 parts by weight of resin-coated molding sand. It is preferable that there be.
This means that if the mixing amount is less than 0.5 parts by weight,
This is because it is difficult to sufficiently reduce the amount of smoke and irritating gas generated when manufacturing shell molds or during casting. Furthermore, if the amount of resin-coated clay mineral mixed exceeds 45 parts by weight, it becomes difficult to form a shell mold. It is more preferable that the mixing amount is 1 to 10 parts by weight because the effects of the present invention can be further exhibited. Further, other additives can be appropriately added and mixed to the shell mold material of the first invention to the extent that the excellent performance of the material is not impaired. Specifically, metal oxides such as zinc oxide, iron oxide, manganese oxide, titanium oxide, and hexamethylenetetramine are used to promote hardening of the resin in the mold manufacturing process or thermal decomposition of the resin in the casting process. Halogen-based substances are added to the resin to improve the disintegration of the mold after casting, and fillers such as steel balls, ballast, and silica sand are used to prevent the mold from sticking during casting, and to ensure the product casting surface. In addition, combustible volatile substances such as coal powder, pitch powder, coke powder, graphite powder, and gilsonite are used, and wetting agents such as kerosene are used to uniformly coat the surface of casting sand such as silica sand with resin. Depending on the purpose, these additives may be included in the resin, or they may be mixed at an appropriate time, such as when coating molding sand with resin, or when mixing and adjusting shell mold materials. . A typical method for preparing the shell mold material of the first invention is briefly shown below. First, resin-coated molding sand obtained by coating molding sand with a resin such as phenol-formaldehyde resin is prepared according to a conventional method. Next, the hydrated magnesium silicate clay mineral is crushed using a diyoke crusher, hammer mill, etc. to obtain a clay mineral of an appropriate shape and size. In addition, it may be calcined at 400 to 800°C before or after this pulverization step. Next, the resin-coated foundry sand and clay minerals are mixed using a kneading machine such as a mortar mixer so that the clay minerals are uniformly dispersed. Appropriate additives are added thereto, and the mixture is kneaded using a kneader such as a speed muller or a speed mixer so that the clay mineral is uniformly dispersed, thereby obtaining the shell molding material according to the present invention. Here, in the above method, the resin-coated foundry sand was prepared in advance and the sand and clay mineral were mixed, but the resin may be added after mixing the foundry sand and the clay mineral, and then mixed and dispersed. . Alternatively, resin-coated foundry sand and resin-coated clay mineral may be prepared in advance, and the resin and additives may be added thereto and kneaded and dispersed. The shell mold material according to the first invention obtained in this manner is conceptually shown in the figure, and consists of molding sand 2 coated with resin 1 and hydrous magnesium silicate clay mineral 3 coated with resin 1. . Next, the shell mold material of the second invention will be explained in detail. The shell molding material of the second invention is obtained by containing an acid in the hydrous magnesium silicate clay mineral in the shell molding material of the first invention. That is, it consists of foundry sand coated with a thermosetting resin and a hydrous magnesium silicate clay mineral containing an acid and further coated with a thermosetting resin. Here, the thermosetting resin-coated molding sand (resin-coated molding sand) of the shell mold material of the second invention is:
Since it is the same as that described in detail in the first invention described above, detailed explanation will be omitted. In addition, hydrated magnesium silicate clay mineral containing an acid and coated with a thermosetting resin is a clay mineral containing an acid coated with a thermosetting resin. The method for coating minerals with resin is the same as that described in detail in the first invention described above, so detailed explanation will be omitted. Next, the acid-containing hydrated magnesium silicate clay mineral is obtained by impregnating the clay mineral in the first invention described above with an acid. Here, the acid contained in this clay mineral is used to neutralize this alkaline component and reduce the harm caused by the gas generated during manufacturing and casting of shell molding materials, which is strongly alkaline. It is used to prevent the formation of other toxic substances or gases with foreign odors when combined with other components. These acids also help maintain the required strength of the bonding resin when used as a shell molding material. Specifically, organic acids such as formic acid (HCOOH), acetic acid (CH ₃ COOH), and phthalic acid (HOOCC ₆ H ₄ COOH), phosphoric acid (H ₃
There are inorganic acids such as boric acid (H ₃ BO ₄ ), nitric acid (HNO ₃ ), and sulfuric acid (H ₂ SO ₄ ), and one _or a mixture of two or more of them is used. These acid impregnation methods include a method of gradually adding an acid aqueous solution while stirring the clay mineral, a method of spraying the acid aqueous solution with a sprayer while stirring the clay mineral, and a method of immersing the clay mineral in an acid aqueous solution. There are ways to do this. Here, the acid content of clay minerals is 10 ^-3 ~
Preferably it is 50wt%. This is because when the acid content is less than 10 ^-3 wt%, no effect is observed due to the inclusion of the acid. In addition, if the content exceeds 50 wt%, lumps of molding sand will be formed when the resin is coated and further mixed with resin-coated molding sand, and the fluidity and filling properties of the molding sand during molding may be reduced. Alternatively, the structure of clay minerals may be damaged due to the elution of cations such as magnesium (Mg) or aluminum (A1) from clay minerals due to acid, and the effect of reducing the amount of irritating gas and smoke generated may not be achieved. This is because there may not be any. Among these, it is more preferable that the acid content is 10 ^-2 to 30 wt%. In this range, the effect of reducing the amount of irritating gas and smoke generated is more excellent. Next, the mold of the third invention will be explained in detail. The mold of the third invention relates to a mold manufactured using the shell mold material of the first invention described above. That is, in a mold consisting of a cavity for forming a casting and a wall for forming the cavity, the wall is at least partially coated with molding sand coated with a thermosetting resin and a thermosetting resin. It consists of a hydrated magnesium silicate clay mineral, the resin-coated molding sand, and a cavity formed between the resin-coated clay mineral, and the resin-coated molding sand and the resin-coated clay mineral are bonded to each other. be. Here, a cavity is a space into which molten metal is poured in order to manufacture a casting, and this cavity is formed by walls. The wall forms a cavity and is a part of the mold body, at least a portion of which is made of foundry sand coated with a thermosetting resin and hydrated magnesium silicate clay mineral coated with a thermosetting resin. and a space formed between them. In the mold according to the third invention, the entire main mold or core may be made using the shell mold material according to the first invention, or a part of the mold may be made from the material. good. The effect of the present invention is exhibited in the portion made of this material. This resin-coated foundry sand and resin-coated hydrated magnesium silicate clay mineral are similar to those detailed in the first invention, and are bonded to each other by heating, but there is no particular structural change in them. A space is appropriately formed between the resin-coated foundry sand and the resin-coated clay mineral. A typical manufacturing method of the mold of the third invention will be briefly described below, taking the main mold of the mold as an example. First, a mold model made of aluminum, cast iron, or the same alloy in the desired shape is heated with gas or electric heat in a furnace at 200 to 300 degrees Celsius, and then a silicone liquid or the like is sprayed on the mold to make it easier to release the mold. Clean the model. Next, the shell mold material according to the first invention is uniformly poured into the mold model to the corners of the model, and heated to a predetermined temperature (300 to 450°C) for a predetermined time (several minutes to several tens of minutes) in a siliconite furnace, etc. After heating and holding, the mold is taken out from the furnace and the mold model is removed to obtain a mold according to the present invention. Next, the mold of the fourth invention will be explained in detail. The mold of the fourth invention relates to a mold manufactured using the shell mold material of the second invention described above. That is, in a mold consisting of a cavity for forming a casting and a wall for forming the cavity, the wall contains foundry sand and acid, at least a portion of which is coated with a thermosetting resin, and the wall is further coated with a thermosetting resin. The composition consists of a hydrated magnesium silicate clay mineral coated with a synthetic resin, a cavity formed between the resin-coated foundry sand and the acid-containing resin-coated clay mineral, and the resin-coated foundry sand and the acid-containing resin-coated clay. Minerals are things that are joined together. Here, a cavity is a space into which molten metal is poured in order to manufacture a casting, and this cavity is formed by walls. The wall forms the cavity, and is the main body of the mold, and is made of foundry sand coated with a thermosetting resin, hydrated magnesium silicate clay mineral containing acid, and further coated with a thermosetting resin. and a space formed between them. In the mold according to the fourth invention, the entire main mold or core may be made from the shell mold material according to the second invention, or a part of the mold may be made from the material. In the part made of this material,
The effect according to the fourth invention is achieved. The resin-coated foundry sand and the acid-containing resin-coated hydrated magnesium silicate clay mineral are similar to those detailed in the second invention, and are bonded to each other by heating. Spaces are appropriately formed between the covered clay minerals. Note that the method for manufacturing a mold according to the fourth invention includes:
This is the same as that in the third invention and is carried out by a conventional method, so detailed explanation will be omitted. [Operations and Effects of the Invention] The shell mold material of the present invention generates a small amount of irritating gases such as irritating odors, foreign odors, and toxic gases when manufacturing molds. Also, the amount of smoke generated is small. Furthermore, when a mold is manufactured using the shell mold material of the present invention, the mold has good formability. The mold of the present invention generates less irritating gas and smoke during casting. Furthermore, when casting is carried out using the shell mold of the present invention, the disintegration of the mold after casting is good even when the casting temperature is relatively low, such as when casting aluminum or magnesium castings. Therefore, post-processes such as sand baking are not required. As described above, the mechanism by which the shell molding material and the mold using the same according to the present invention exhibit such effects is not necessarily clear yet, but it is thought to be as follows. That is, the shell molding material of the present invention is made by mixing resin-coated clay minerals with molding sand as a base material coated with a thermosetting resin. has a pore with a rectangular cross section. This pore has OH on the surface
It is thought that it has a group and functions as a site that adsorbs or absorbs odors of smoke-like substances and irritating gaseous substances. When a mold is manufactured using this shell molding material, and when casting is performed using this mold, the pore structure of this clay mineral is maintained without being destroyed, and smoke-like substances and irritating gases are removed. It is thought that the substance effectively adsorbs or absorbs odors, reducing the generation of smoke and irritating gases. In addition, the clay minerals in the mold play the role of a catalyst during heating during the casting process, decomposing toxic gases and irritating and off-odor components, and promoting thermal decomposition of the resin to bond the mold. It is thought that this weakens the disintegration property after casting. In addition, if the clay mineral contains acid, it will actively neutralize the alkaline components of the gaseous substances generated during mold manufacturing or casting using the mold, which will further improve the deodorizing effect. It seems to be improving. [Examples] Examples of the present invention will be described below. Example 1 A shell mold material was manufactured using foundry sand, sepiolite, and novolak phenolic resin, and then a shell mold was molded using the material, and a performance evaluation test by casting was conducted. First, sepiolite from Turkey was coarsely crushed using a geo crusher, and then further crushed using a crushing granulator to obtain sepiolite powder with an average particle size of 200 μm. Next, commercially available silica sand (Mikawa Siliceki Co., Ltd.: particle size 6) and sepiolite powder in the amount shown in Table 1 (water content 2wt) were used.
%) in a mortar mixer and mixed for 5 to 10 minutes. Furthermore, 100 parts by weight of the resulting mixture was heated to about 150°C, and 3 parts by weight of novolak-based phenolic resin (manufactured by Asahi Yokuzai Kogyo Co., Ltd.) was added to this. After 50 seconds of kneading, 0.45 parts by weight of hexamethylenetetramine and 1.5 parts by weight of cooling water were added, and after 30 seconds, 0.1 part by weight of calcium stearate was added and kneaded to obtain a shell molding material according to the first invention. Next, this shell mold material is placed in an iron mold, and the mold is heated and held at 400°C for 2 minutes in a silicone furnace.The mold is then removed from the furnace and the mold according to the third invention (shell mold material) is placed in an iron mold. A mold was obtained.
Here, the mold consists of an inner mold and an outer mold, and the inner mold is a truncated cone with an upper diameter of 52 mm x a lower diameter of 60 mm and a diameter of 110 mm.
mm, with a base of 20 mm thickness, the outer diameter of the outer mold is 90 mm.
It is a hollow cylindrical body with an upper inner diameter of 71 mm, a lower inner diameter of 79 mm, and a height of 137 mm. Furthermore, the moldability of these shell molds is good;
Furthermore, no smoke was observed during heating during the production of the shell mold, and the degree of generation of irritating and off-flavor odors was also low. Next, the performance of the obtained shell mold was evaluated by observing the amount of smoke generated after casting, a sensory test for the odor generated, and a detection test for the concentration of ammonia (NH ₃ ) in the generated gas.
This was done through a quantitative test of formaldehyde (HCHO) in the generated gas. First, an aluminum alloy (JISAC2B) melted at 750°C was poured into a shell mold, the amount of smoke emitted after casting was visually observed, and the degree of odor generation was determined through a sensory test. The results obtained are shown in Table 1.

[Table] In the table, regarding the smoke generation status, "-" indicates "no smoke is observed,""△" indicates "smoking is present," and "x" indicates "a large amount of smoke is present." As is clear from the table, the products according to the present invention generate less smoke after casting. In particular, the mixing ratio of sepiolite is
In the case of 5.0 to 10.0 wt%, some smoke was observed for up to 30 seconds after casting, but after that, almost no effect was observed. Furthermore, the degree of generation of irritating odor was also low. In addition, ammonia (NH ₃ ) concentration detection tests and formaldehyde (HCHO) quantitative tests are conducted using a 400 mm inner diameter x
A shell mold filled with aluminum alloy (JISAC2B) is placed in a cylindrical airtight container with a depth of 460 mm.
After 25 minutes had elapsed after casting, the generated gas inside the closed container was collected. Ammonia concentration was detected using a Kitagawa gas detection tube (manufactured by Komei Rikagaku Kogyo Co., Ltd.).
This was done by suctioning 100 ml of generated gas per minute. The results are shown in Table 1. As is clear from the table, the product according to the present invention has a low concentration of ammonia (NH ₃ ).In addition, in the quantitative test of formaldehyde (HCHO) in the generated gas, the generated gas was extracted from a closed container and the aldehyde The hydrazine was collected in a hydrochloric acid solution of 2-4 dinitrophenylhydrazine, the produced hydrazine was extracted with chloroform, and the chloroform concentrated solution of hydrazine was determined by gas chromatography. The results are shown in Table 1, and the analysis conditions at that time are shown in Table 2.
As is clear from the same table, it can be seen that the products according to the present invention generate less aldehyde. Also,
The disintegration property of the shell mold according to the present invention after casting was good. Table 2 Aldehyde analysis conditions Column: 2% Silicone OV-17 on
Chromosor WAW ・DMCS 80−100
Mesh, 3mmφ x 3m glass Column temperature: 200→300℃ (3℃/min) Inlet temperature: 230℃ Carrier gas: Helium 60ml/min Detector: Flame ionization detector (FID) Hydrogen pressure 0.6Kg /cm ² Air pressure 0.2Kg/cm ² Equipment: Shimadzu GC-9A gas chromatograph For comparison, only the resin-coated molding sand mentioned above was used as a comparison mold material, and a comparison mold was made using this ( Sample number C1), a similar performance evaluation test was conducted. The results are also shown in Table 1. As is clear from Table 1, the comparative example of the conventional product produced a considerably large amount of smoke after casting, and
It can be seen that the degree of generation of irritating odor is also quite strong.
Incidentally, during heating during production of the comparison mold, smoke was observed, and the degree of generation of irritating odor and off-odor was also stronger than that of the product of the present invention. Moreover, the disintegration property of the mold after casting was also poor compared to the product of the present invention. Example 2 After producing a shell mold material consisting of resin-coated foundry sand and sepiolite containing acid and whose surface was further coated with resin, a shell mold was formed using the material, and a performance evaluation test by casting was conducted. . First, sepiolite from Turkey was crushed to obtain sepiolite powder with an average particle size of 200 μm. Next, this sepiolite powder was impregnated with acetic acid (CH ₃ COOH) in the concentration and amount shown in Table 3 to obtain acid-containing sepiolite. The acid content is shown in the same table. Next, commercially available silica sand (Mikawa Silica Co., Ltd.: particle size No. 6)
95wt% and the prepared acid-containing sepiolite 5wt% were placed in a mortar mixer, mixed for 5 to 10 minutes, and the resulting mixture was further mixed with novolac type phenolic resin (Asahi Yokuzai Kogyo Co., Ltd.) in the same manner as in Example 1. A shell mold material according to the second invention was obtained.

[Table] Next, this shell mold material was placed in the same mold as in Example 1, and the mold was heated and held at 400°C for 2 minutes in a siliconite furnace, taken out from the furnace, and the mold was removed. Four molds (shell molds) according to the invention were obtained (sample numbers 4 to 6). In the production of shell molds, the moldability of these shell molds is good, no smoke is observed, the generation of carbon monoxide is below the detection limit of gas detection tubes, and there is no generation of irritating or unusual odors. The degree was also weaker than in the case of the first invention. Next, the performance of the obtained shell mold was evaluated by observing the amount of smoke generated after casting, a sensory test for the odor generated, a detection test for the ammonia (NH ₃ ) concentration in the generated gas, and a test for detecting the concentration of formaldehyde (HCHO) in the generated gas. This was done through a quantitative test. First, an aluminum alloy (JISAC2B) melted at 750°C was poured into a shell mold, the amount of smoke emitted after casting was visually observed, and the degree of odor generation was determined through a sensory test. The results obtained are shown in Table 3.
In the table, regarding the smoke generation status, "-" indicates "no smoke generation", "△" indicates "smoke generation", and "x" indicates "a large amount of smoke generation". As is clear from the table, the product according to the present invention emitted some smoke for up to 30 seconds after casting, but no smoke was observed after that, indicating that the amount of smoke emitted after casting was quite small. . Furthermore, the degree of generation of irritating odor was also low. In addition, ammonia (NH ₃ ) generated after casting
The concentration of formaldehyde (HCHO) and formaldehyde (HCHO) were detected by the same method as in Example 1. The results are shown in Table 3. As is clear from the same table, the sample according to the present invention has a low concentration of detected gas. Further, the disintegration property of the shell mold according to the present invention after casting was good. For comparison, only the resin-coated foundry sand described above was used as a comparative mold material, a comparative mold was made using this (sample number C2), and the same performance evaluation test was conducted. The results are also shown in Table 3. As is clear from the table, it can be seen that the comparative example of the conventional product produced a considerably large amount of smoke after casting, and also produced a considerably strong irritating odor. As is clear from the above results, the mold material and mold according to the present invention generate less smoke and irritating gas during mold molding and casting, and also have good disintegration properties of the mold after casting. I understand that there is something.

[Brief explanation of drawings]

The figure is a conceptual diagram of the shell mold material according to the first invention. 1... Resin, 2... Foundry sand, 3... Hydrous magnesium silicate clay mineral.

Claims (1)

[Scope of Claims] 1. A shell molding material comprising a mixture of foundry sand coated with a thermosetting resin and hydrous magnesium silicate clay mineral coated with a thermosetting resin. 2. The shell mold material according to claim 1, wherein the thermosetting resin is a novolak type phenolic resin or a resol type phenolic resin. 3. The shell molding material according to claim 1, wherein the hydrated magnesium silicate clay mineral is sepiolite, scillotile, palygorskite, or roughinite. 4. A shell mold material comprising a mixture of foundry sand coated with a thermosetting resin and a hydrous magnesium silicate clay mineral containing an acid and whose surface is further coated with a thermosetting resin. 5. The shell mold material according to claim 4, wherein the thermosetting resin is a novolak type phenolic resin or a resol type phenolic resin. 6. The shell molding material according to claim 4, wherein the hydrated magnesium silicate clay mineral is sepolite, scillotile, palygorskite, or roughinite. 7. The shell mold material according to claim 4, wherein the acid is an organic acid such as formic acid, acetic acid, or phthalic acid. 8. The shell mold material according to claim 4, wherein the acid is an inorganic acid such as phosphoric acid or boric acid. 9 In a shell mold consisting of a cavity for forming a casting and a wall for forming the cavity, the wall is made of molding sand at least partially coated with a thermosetting resin, and a molding sand coated with a thermosetting resin. The resin-coated molding sand and the resin-coated clay mineral are bonded to each other. A mold characterized by: 10. The mold according to claim 9, wherein the thermosetting resin is a novolak type phenolic resin or a resol type phenolic resin. 11. The mold according to claim 9, wherein the hydrated magnesium silicate clay mineral is sepiolite, scillotile, palygorskite, or roughinite. 12. A mold consisting of a cavity for forming a casting and a wall for forming the cavity, at least a part of which contains foundry sand coated with a thermosetting resin, and an acid. It consists of a hydrous magnesium silicate clay mineral whose surface is coated with a thermosetting resin, and a cavity formed between the resin-coated foundry sand and the resin-coated acid-containing clay mineral. A mold characterized in that resin-coated acid-containing clay minerals are bonded to each other. 13. The mold according to claim 12, wherein the thermosetting resin is a novolak type phenolic resin or a resol type phenolic resin. 14. The mold according to claim 12, wherein the hydrated magnesium silicate clay mineral is sepiolite, scillotile, palygorskite, or roughinite. 15. The mold material according to claim 12, wherein the acid is an organic acid such as formic acid, acetic acid, or phthalic acid. 16. The mold according to claim 12, wherein the acid is an inorganic acid such as phosphoric acid or boric acid.