JP2902479B2 - Smoke removal mold material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a casting mold used for casting metals such as cast steel, cast iron and aluminum, and a shell mold material used for manufacturing a core. . More specifically, the present invention relates to a degassing mold material that generates a small amount of smoke generated by heating during the production of a mold and a small amount of irritating odor, unusual odor, and toxic gas (hereinafter, irritating gas).

[Conventional technology and its problems]

2. Description of the Related Art Conventionally, as a method for manufacturing a main mold and a core (hereinafter simply referred to as a mold) of a casting mold, a shell mold method that uses a property of a synthetic resin such as a phenol resin to be cured by heat for curing a sand mold has been often used. Have been. By casting using a mold manufactured by this method, a casting having a beautiful casting surface with extremely high dimensional accuracy can be manufactured. As a mold material used in this shell mold method, resin-coated molding sand (resin coated sand: RCS) in which a thermosetting resin such as phenol resin, a hardening material, and a lubricant are coated on a mold material base such as silica sand in order. It is generally used, and if necessary, a curing accelerator and other additives are contained in the coating layer of the resin-coated molding sand, or are added to and mixed with the resin-coated molding sand.

However, when a mold is manufactured using this resin-coated molding sand as a raw material, the mold material is sealed in a heating mold and fired and consolidated, for example, when the heating mold is opened during heating in a molding process or the like. When the mold and the mold are taken out and carried out, strong irritating gases such as smoke, formaldehyde, phenol, and ammonia are generated, which significantly deteriorates the working environment. Recently, in the case of mass production in the manufacture of a mold, a blow method in which RCS is blown into a molding die using air pressure is used. In this method, calcium stearate is mainly used as a lubricant in order to improve the filling property into a molding die, and there is a problem that the calcium stearate is decomposed when producing a mold, and a large amount of smoke is generated.

As described above, in the conventional shell mold material, smoke and irritating gas generated in a manufacturing process of a mold in which it is difficult to install a smoke duct around a mold manufacturing machine cause deterioration of a working environment in a foundry. Therefore, enormous equipment costs are required for these reductions, and they are not necessarily sufficient measures, and a fundamental measure has been strongly desired.

As a method of solving these problems, a molding material obtained by mixing a porous material having a large number of pores such as activated carbon or activated alumina and a specific surface area of 50 m ² / g or more in a molding sand coated with a thermosetting resin ( JP-A-63-60042) has been proposed. From this, it is possible to reduce the amount of irritating gas generated during heating when molding a casting mold using the material or when performing casting using the mold by adsorption and catalysis. It is said that it was completed.

However, in this mold material, it is necessary to increase the mixing amount of the porous substance in order to completely remove the smoke and the irritant gas, and accordingly, the strength of the mold is greatly reduced, and the mold cracks in the casting process. Is generated. Further, when a mold material containing a large amount of the porous material is reused, the porous material excluding carbides such as activated carbon remains in a mold base material such as silica sand even after a regeneration treatment step, and is used as a mold. There was a problem that the mold strength was reduced to such an extent that it could not be performed.

The present inventors have conducted intensive research to solve these conventional problems, and have conducted various systematic experiments. As a result, the present invention has been accomplished.

[Object of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a demolding mold material that produces a small amount of smoke and irritating gas when producing a casting mold and has a required mold strength.

That is, the mold material used in the shell molding method of the prior art is a resin-coated molding sand in which a thermosetting resin or the like is coated on a mold material base such as silica sand, and further contained or included in the coating layer as necessary. It consists of a hardening accelerator and other additives added to and mixed with the resin-coated molding sand. In addition, a mold material obtained by mixing a porous substance with the resin-coated molding sand has an effect of reducing the irritating gas, but when the mixing amount of the porous substance is increased in order to enhance the effect, the mold material is produced from the material. However, there is a problem that the strength of the mold is reduced and the mold collapses during casting.

The present inventors have conducted various systematic experiments and studies in order to elucidate the generation mechanism of smoke and other irritating gases during mold production. As a result, the smoke generated during mold production
There are two types, smoke generated by the curing reaction of the thermosetting resin and smoke generated by the decomposition of calcium stearate used as a lubricant. It can be seen that the amount of generated smoke increases significantly when both occur simultaneously. Was.

Therefore, the smoke generated by the curing reaction of the thermosetting resin accelerates the curing reaction due to a decrease in the amount of components in the resin and a decrease in the ratio of the resin to the curing agent during the reaction, and the generation of unreacted gas is reduced. And smoke from lubricants, such as calcium stearate, was noticed to be broken down into smaller molecular weight gases by water or water vapor.

An inorganic water retention material having pores capable of absorbing a resin component in a fluidized state while having an appropriate water-containing capacity and releasing an appropriate amount of retained water at the time of heating in mold production to promote decomposition of unreacted gas and the like. The above problem has been solved by mixing an appropriate amount of resin-coated molding sand into a mold material.

[Description of the First Invention] Structure of the Invention The de-smoke mold material of the present invention comprises a mold material in which a thermosetting resin or the like is coated on a mold base material, and has a pore structure and a water content at 100 to 250 ° C. It is characterized by comprising an inorganic water retaining material having an adsorption / desorption capacity and a water content of 15% by weight or more, and a mixing amount of the inorganic water retaining material is 1.5 to 4.5% by volume of the mold base material.

Effects and Effects of the Invention The demolding mold material of the present invention has a small amount of smoke and irritating gas such as pungent odor, off-flavor, toxic gas and the like when producing a casting mold, and has a required mold strength. can get.

The mechanism by which the smoke-removing mold material of the present invention exerts the above-described excellent effects is not yet sufficiently clear, but is considered as follows.

That is, in the present invention, as a mold material used in the shell mold method, an inorganic water retaining material having further special properties is mixed with a constituent material generally used. This inorganic water retention material has a pore structure, has a water absorbing and desorbing ability even at 100 to 250 ° C., and has a water containing capacity of 15 to 15.
It is an inorganic water retention material by weight or more. Thus, during heating, such as during the manufacture of a mold, smoke caused by a lubricant such as calcium stearate is decomposed into smaller molecular weight gas by retained water released from the inorganic water retention material, and smoke and other irritants are generated. It is believed that gas generation is reduced. In addition, in a curing reaction of a resin such as a phenol resin, decomposition of a curing agent such as hexamethylenetetramine is promoted by water or water vapor, and the main component of the resin is contained in pores of a water retention material that supplies water. It is considered that the phenolic resin or the like is absorbed, the curing reaction is promoted by the change in the amount of the components in the resin and the change in the ratio of the resin and the curing agent, and the generation of unreacted gas is reduced.

[Description of Second Invention] Hereinafter, a second invention which is a more specific version of the first invention will be described.

The mold material in which the thermosetting resin or the like used in the present invention is coated on a mold material base material, that is, resin-coated molding sand, is thermally cured as a binder on the surface of the mold material base material (molding sand). In order to accelerate the curing of the resin, it is necessary to prevent the solidification of the particles of the molding sand in the molding material production process and to improve the fluidity. In order to increase the packing density, additives such as a lubricant such as calcium stearate are added.

Here, the mold material base material is a refractory sandy material that forms the base material of the shell mold, and specifically, crushes silica sand, zircon sand, chromite sand, olivine sand, sea sand, river sand, and rock. There is sand and the like, and one kind or a mixture of two or more kinds is used. This molding sand is appropriately selected in shape, size, and type in consideration of fluidity, filling property, toughness, thermal expansion property, solidification speed, and the like. The grain shape of the foundry sand is preferably spherical, such as round or polygonal.
This is because, in this case, the fluidity of the sand is good, high mold strength is easily obtained with a relatively small amount of resin, and the air permeability of the mold is improved.

Further, the thermosetting resin is a binder having a function of forming a predetermined mold shape by mutually bonding a molding sand and an inorganic water retention material as a base material of the shell mold material, and specifically,
Novolac phenol resins such as phenol / formaldehyde resin and phenol / furfural resin are used.

The resin is applied to the molding sand by a conventional method such as a hot coating method, a dry hot coating method, a semi-hot coating method, a cold coating method, a powdered solvent method, and the like, to which additives are appropriately added as necessary.

Here, the compounding amount of the resin is 1 to 10 wt.
%. The amount varies depending on the purpose, the amount of the inorganic water-retaining material and other additives, and the production conditions. However, when the molding sand is silica sand, it is generally 1 to 6 wt.
%, When zircon sand is used, 1-4 wt% is preferred. Further, the particle size of the mold base material is preferably 50 μm to 1 mm.

Next, the inorganic water retention material is an inorganic water retention material having pores capable of releasing an appropriate amount of retained water at the time of heating, such as at the time of mold production, to promote the decomposition of unreacted gas and the like and to absorb a resin component in a fluid state. The inorganic water retention material has a pore structure, has a water absorbing / desorbing ability even at 100 to 250 ° C., and has a water content of 15% by weight or more, preferably 20% by weight or more.
Specific examples include Kanuma soil, Akadama soil, hydrous magnesium silicate clay mineral, coconut charcoal, fir charcoal, zeolite, and one or more of these. Also,
Other than this, a substance having the adsorption / desorption ability and the water-containing ability, that is, a natural porous inorganic substance, or an inorganic porous substance obtained by heat-treating an inorganic substance or an organic substance containing a large amount of fibers,
Further, these fine powders may be used alone or in the form of a mixture with an inorganic binder such as clay. For example,
A mixture of coconut or charcoal charcoal and bentonite may be used. Further, those obtained by calcining these materials may be used.

Here, Kanuma soil and Akadama soil are clay minerals obtained by weathering volcanic ash soil. As the Kanuma soil, the main component may be allophane, and a mixture of halloysite in which the allophane is changed may be used. The Akadama soil is preferably a red soil which is a lower layer soil of the Ando soil in the Kanto region, and is preferably made of particles having improved drainage properties. In addition, since the Kanuma soil or the Akadama soil has a moderate water content, even if the used mold material is recycled to form the mold material according to the present invention, the same effect as that of the present invention is obtained. This is a suitable substance because the rate of decrease in mold strength can be within an allowable range.

The hydrous magnesium silicate clay mineral is composed of fibers having a diameter of about 0.005 to 0.6 μm, and has pores (channels) having a rectangular cross section of about 10 to 6 mm in parallel with the fibers. And has a highly reactive hydroxyl group on the surface. Note that magnesium or silicon may be partially substituted with aluminum, iron, nickel, sodium, or the like. Also, these things
What was calcined in the temperature range of 400 to 800 ° C may be used. When used as a water retention material, it may be used in any form as long as it is pulverized to the extent that the pores remain, but its size is in the range of 50 μm to 1 mm, which is about the same as molding sand preferable. Among them, a size that is equal to or larger than the particle size indicating the maximum amount in the particle size distribution of the molding sand is preferable, and particularly 149 to 5
More preferably, it is 00 μm. This is because the temperature rise of the inorganic water retention material needs to be the same as the temperature rise of the resin-coated molding sand. Further, when the particle size is small, the strength of the obtained mold is reduced, and the effect of reducing smoke is reduced. The pulverization is performed by wet pulverization or dry pulverization using a jaw crusher, a hammer mill, a roller mill, a crushing granulator, a vibration mill, a pin mill, a beating machine, or the like.

Since coconut husk charcoal or fir-charcoal charcoal is a material that does not have self-adhesiveness, it uses a material obtained by mixing with strong caustic bentonite and then drying it after obtaining an appropriate viscosity. Try to be less. In the case of these mixtures, the water-containing capacity can be adjusted appropriately, so that even if the used mold material is recycled, the same effect as in the present invention can be obtained, and it is a suitable substance.

It is preferable to use an inorganic water retention material having a water content of 20% by weight to 35% by weight. This is because the absorption amount of the resin component such as phenolic resin into the inorganic water retention material becomes a fixed amount, so that smokelessness can be better achieved, and the mold strength can be reliably reduced within an allowable range. In addition, in order to reduce the generation of smoke at the time of firing, it is preferable that the inorganic water retaining material has predetermined water before firing. This is because water or water vapor is required to promote the decomposition of calcium stearate and the decomposition of hexamethylenetetramine. The water holding amount is preferably 5% by weight to less than the water content of the inorganic water retaining material. When the amount is less than 5% by weight, the water content is insufficient with respect to the mixed amount of calcium stearate and hexamethylenetetramine, and the effect of reducing smoke and irritating gas is not sufficiently obtained. Water is generated, and the resin-coated molding sand is solidified when the mold material is mixed, which causes a decrease in the strength of the mold, which is not preferable.

In addition, the inorganic water-retaining material is one having a particle size smaller than the particle size showing the maximum amount, particularly one having a size smaller than 145 μm in the particle size distribution of the molding sand before coating with the thermosetting resin or the like.
It is preferably a granular substance having a particle size distribution of 0% by weight or less. That is, in order to eliminate smoke in the curing reaction, it is necessary that the inorganic water retaining material absorbs the resin, but the strength of the mold is reduced due to the absorption of the resin. Therefore, when there are many particles having a small particle size, the resin is absorbed in many points, and the amount of resin absorbed is increased, and the strength of the mold is greatly reduced. It is preferable to reduce the number of particles having a small particle size.

The demolding mold material of the present invention comprises the above-mentioned mold material base material and the inorganic water retention material.

Here, the mixing ratio of the mold material (resin-coated molding sand) in which the mold material base material is coated with a thermosetting resin or the like and the inorganic water retention material is such that the inorganic water retention material is 1.5 to 4.5 vol. %. This is because if the mixing amount is less than 1.5% by volume, it is difficult to sufficiently reduce the amount of smoke and irritating gas generated during the production of a degassing mold or during casting. When the mixing amount of the inorganic water retention material exceeds 4.5% by volume, the strength of the mold manufactured using the material decreases, the mold strength reduction rate exceeds 20%, and the mold strength required for the casting operation is reduced. Is not obtained. In addition, this mixing amount,
When the content is 4.0 to 4.2% by volume, the effects of the present invention can be further exhibited, and thus it is more preferable.

Further, in the demolding mold material of the present invention, other additives can be appropriately added and mixed to such an extent that the excellent performance of the material is not impaired. Specifically, metal oxides such as zinc oxide, iron oxide, manganese oxide, and titanium oxide are used to promote the curing of the resin in the mold manufacturing process or the thermal decomposition of the resin in the casting process. Fillers such as steel balls, ballast, silica sand, etc., to prevent mold tension during casting, coal powder to secure the product casting surface, Pitch powder, coke powder,
There is a wetting agent such as kerosene for the combustible volatile substances such as graphite powder and Gilsonite to uniformly coat the surface of the molding sand such as silica sand with resin. These additives, depending on their purpose,
It may be included in the resin, or may be mixed at an appropriate time, for example, when coating the resin on the molding sand, and when mixing and adjusting the degassing mold material.

The following is a brief description of a typical method for adjusting the demolding mold material of the present invention.

First, a resin-coated molding sand obtained by sequentially coating a mold material base material with a resin such as phenol / formaldehyde resin, a hardening agent such as hexamethylenetetramine, and a lubricant such as calcium stearate in accordance with a conventional method is prepared.

Next, an inorganic water retaining material having a pore structure, having a water absorbing / desorbing ability even at 100 to 250 ° C., and having a water content of 15% by weight or more is prepared and adjusted to have a predetermined water content. In addition, the shape and size of the inorganic water retention material may be appropriate shapes and sizes, and may be calcined at 400 to 800 ° C. before or after the pulverizing step.

Next, an inorganic water retention material having a predetermined moisture content is added so that the mixing amount is 1.5 to 4.5% by volume of the foundry sand base material, and mixed so as to be uniformly dispersed. Then, the resin and additives are appropriately added, and the mixture is kneaded using a kneader such as a mortar mixer, a speed maller, and a speed mixer so as to be uniformly dispersed, thereby obtaining a demolding mold material according to the present invention. The timing of adding the additive may be before the addition of the water retention material. Further, a necessary additive may be added to the resin and coated when the resin-coated molding sand is produced.

The demolding mold material according to the present invention obtained in this way is conceptually shown in FIG.
And an inorganic water retention material 3.

The demolding mold material of the second aspect of the present invention has good moldability, and the mold disintegration after casting is sufficient even at a relatively low casting temperature such as an aluminum casting or a magnesium casting.

[Description of Third Invention] A method of manufacturing the demolding mold material of the third invention suitable for producing the demolding mold materials of the first invention and the second invention will be described below.

The method for producing a smoke-free mold material according to the third invention is a method for producing a mold material by coating a mold material base material (casting sand) with a thermosetting resin or the like. A step of preparing an inorganic water retention material having a water absorption / desorption capacity and a water content of 15% by weight or more, and adjusting the water content of the inorganic water retention material to a predetermined amount; Immediately after the addition of the additive or after cooling the resin-coated molding sand by adding the additive, charging the inorganic water retention material whose water content has been adjusted, and mixing at a certain temperature or lower. And

Thereby, the defoaming mold materials of the first and second inventions can be easily manufactured.

In addition, it is possible to appropriately secure water required for decomposition and firing of the additive, and to uniformly disperse the water in the molding sand.

Further, since the addition of the inorganic water retention material is performed at a certain temperature or lower, it is possible to prevent solidification of resin-coated molding sand, additives, and the like.

[Description of Fourth Invention] Hereinafter, a fourth invention, which is a more specific example of the method for producing a demolding mold material of the third invention, will be described.

The first method is a method for producing a mold material by coating a molding sand with a thermosetting resin or the like.
A step of preparing an inorganic water retaining material having a water absorbing / desorbing ability even at a temperature of 15 ° C. and having a water content of 15% by weight or more, and adjusting the water content of the water retaining material to 5% by weight to less than the water content; A step of mixing the sand with a thermosetting resin such as a phenolic resin, and other additives such as a hardener such as hexamethylenetetramine and a lubricant such as calcium stearate to adjust the resin-coated molding sand; and Cooling the foundry sand, and adding and mixing the inorganic water retention material adjusted to have a water content of 5% to less than the water content.

Thus, in the mixed state of the resin-coated molding sand and the inorganic water-retaining material, the inorganic water-retaining material can secure the water necessary for decomposition of calcium stearate, hexamethylenetetramine, and the like, and can be uniformly dispersed in the molding sand. The operation during firing is as described above.

In this case, the addition of the inorganic water retention material is desirably performed in the cooling step in a state where the temperature of the resin-coated molding sand is 80 ° C. or lower. If the inorganic water retaining material is added in a state where the temperature exceeds 80 ° C., a large amount of water retained in the inorganic water retaining material is released, and there is a possibility that the resin-coated molding sand is solidified.
Note that, when the mold material to which the resin-coated molding sand is consolidated is fired, the mold strength of the obtained mold is significantly reduced, which is similar to a state where water is added to the resin-coated molding sand.

The second method is a method for producing a mold material by coating a molding sand with a thermosetting resin or the like.
A step of preparing an inorganic water retaining material having a water absorbing / desorbing ability even at 50 ° C. and having a water content of 15% by weight or more, and adjusting the water content of the inorganic water retaining material to 10% by weight or less; Thermosetting resin such as phenolic resin, a hardening agent such as hexamethylenehexamine, and additives such as a lubricant such as calcium stearate to adjust the resin-coated molding sand, and an additive such as the calcium stearate. Immediately after the addition, a step of adding the inorganic water retention material adjusted to a water content of 10% by weight or less and mixing with the resin-coated molding sand.

From this, the inorganic water retention material mixed with resin-coated molding sand,
The molding sand is coated with a thermosetting resin and a curing agent to absorb the water generated when the resin-coated molding sand is prepared, so that the water content required for firing can be kept from 5% by weight to less than the water content, and The water can be evenly dispersed in the foundry sand.

In this method, when the water retention amount of the inorganic water retention material exceeds 10% by weight, water in the inorganic water retention material is released due to high temperature, and the resin-coated molding sand is solidified in the cooling step. It is not preferable because it will do.

Also, if the inorganic water retention material is mixed before adding the additive such as the calcium stearate, the resin component such as the phenol resin is still in a fluid state, so that the inorganic water retention material absorbs this resin component, which is desirable. Absent.

In these methods, the inorganic water retaining material may be sufficiently dried before use. In this case, by absorbing the moisture released when the molding sand is coated with the thermosetting resin and the curing agent, and by absorbing the moisture from the atmosphere at the time of storage, the water retained as an inorganic water retention material is used. It only needs to be able to hold the required amount of water by the time it needs to be released.

Experimental Example 1 First, silica sand, 2% by weight of phenolic resin based on the silica sand, 15% by weight of hexamethylenetetramine based on the phenolic resin as a curing agent, and 0.1% by weight of stearic acid based on the silica sand as a lubricant Calcium and 5-1 water
An inorganic water retention material containing 1, 21, 33, and 42% by weight was added to the silica sand at 4% by volume to prepare a mold material. Further, a comparative mold material to which the water retention material was not added was prepared. In order to evaluate the obtained mold material and the comparative mold material, gas components generated during firing were analyzed by GC-MS chromatography. As a result, the former mold material to which the water retention material was added contained fatty acids, alcohols, ketones, alkanes / alkenes, amides, and amines equivalent to C _{6 to} C _{18 as} compared with the comparative mold material without addition. Ring compounds (oxygen-containing compounds and nitrogen-containing compounds), which were not observed and were considered to be a reaction of the phenolic resin, were reduced to less than half. In particular, those with a water content of 21% by weight were the least, about 1/3.

From this, it is considered that smoke caused by a lubricant such as calcium stearate is decomposed into smaller molecular weight gas by water or steam.

On the other hand, quantitative analysis using gas detector tubes shows that CO, CO ₂ , and aldehydes are greatly reduced, and conversely, NH ₃ gas, which is said to be generated by the decomposition of hardeners such as hexamethylenetetramine, is said to be generated by condensation polymerization. As the amount of water vapor increases, the smoke generated by the curing reaction of the phenolic resin disappears because water or water vapor promotes the decomposition of the curing agent hexamethylenetetramine and releases the water Phenolic resin, which is the main component of the resin, is absorbed into the pores of the water retention material, and the curing reaction is accelerated by the change in the amount of components in the resin and the ratio of the resin to the curing agent, and the generation of unreacted gas is reduced. It is considered something.

Further, when a mold material is prepared by replacing the inorganic water retention material such as pearlite or vermiculite used in horticulture or horticulture having water of crystallization with the inorganic water retention material, a decrease in strength of the fired mold is small, The amount of smoke generated during firing cannot be reduced. These do not have pores or have a low water content (5.6 to 12.8% by weight) after water release. Therefore, the inorganic water retaining material to be added must be one that does not have a property of absorbing a predetermined amount of resin such as phenolic resin. It can be seen that the generation of smoke during heating cannot be reduced.

Further, in the performance evaluation of the mold material using the inorganic water retention material of the present invention, a differential thermal analysis was performed at a heating rate of 99 ° / min, which was close to actual use conditions. As a result, the inorganic water retention material of the mold material that does not generate smoke exhibits the maximum amount of water release per hour at about 90 to 105 ° C, and has the property of releasing 90% or more of the retained water by about 120 to 135 ° C. Was. In addition, even if the inorganic water retention material has this property, if the particle size becomes too small, the temperature at which the amount of water released per hour becomes maximum, and 90%
The temperatures at which the above moisture is released shift to the lower temperature side. These products do not show the effect of reducing smoke during firing,
It was found that the mold strength was also greatly reduced.

On the other hand, the comparative mold material produced by replacing the inorganic water retention material of the present invention with silica gel or the like which is a hydrate or a hygroscopic agent has some of the same water content and the same water release tendency as the inorganic water retention material. However, there was no smoke reduction effect during firing.

From the above, in the firing process, the inorganic water retention material of the present invention releases water retained in a temperature range up to about 135 ° C., and the water decomposes a lubricant such as calcium stearate or a curing agent such as hexamethylenetetramine. As the temperature rises, the inorganic water retention material absorbs resin components such as phenolic resin nearby and promotes the hardening of the resin near the molding sand such as silica sand, thereby significantly generating smoke during firing. It seems that it can be reduced.

Experimental Example 2 The temperature was increased in the presence of a dried inorganic water retention material of the present invention and a phenol resin. As a result, the phenolic resin is about 110
It becomes highly viscous at ℃ and forms a lump of inorganic water retention material.
It turned out to be in a fluid state at 130 ° C and was rapidly absorbed by the inorganic water retention material at about 140 ° C to 150 ° C.

From these results, regarding the strength after firing of the resin-coated molding sand and the strength after firing of the mold material mixed with the inorganic water retention material,
It is considered as follows. That is, with reference to FIGS. 2 (a) to 2 (c), the phenol resin and the curing agent [shown in FIG. 2 (a)] coated on the molding sand such as silica sand are approximately equivalent. Increases fluidity above 140 ° C,
As shown in FIG. 5B, it is considered that the resin gathers at the contact points between the particles, the thickness of the cured resin increases, and the fired mold exhibits higher strength. Therefore, in this case, it is considered that the mold strength is greatly reduced when the amount of the phenol resin is reduced and the amount of the resin collected at the contact is reduced. On the other hand, as shown in FIG. 2 (c), when a large amount of the inorganic water retaining material is mixed, the phenol resin is absorbed by the inorganic water retaining material when the temperature reaches about 140 ° C. or higher, and the resin-coated molding sand and the inorganic water retaining material are mixed. It is considered that a defective state without a phenolic resin cured body was formed at the contact of No. 3 and the mold strength was reduced.

Therefore, when mixing the inorganic water-retaining material, if the mixing amount is too large, the mold strength is reduced, and also, if the particle size of the inorganic water-retaining material is too small, the number of defective portions increases and the mold strength is reduced. it is conceivable that.

From the results of Experiments 1 and 2 above, smoke during firing was eliminated,
In order to make the strength of the mold fall within an acceptable range, the inorganic water retention material must have the necessary water, have a predetermined amount of water and fine pores to absorb phenolic resin, It is understood that it is necessary to have a diameter of a predetermined size with respect to the diameter of the sand and to raise the temperature to the same degree as that of the resin-coated molding sand.

Experimental Example 3 As a result of coexistence of resin-coated molding sand and water, the resin-coated molding sand was solidified in a ball shape. From this, it is necessary to make the water necessary for sintering not only coexist, but also to contain an appropriate amount in the pores of the inorganic water retention material so that water does not come out on the surface when mixed with resin-coated molding sand. It is considered to be. Further, in general, the pore size of the adsorbent required for adsorbing the offensive odor gas is required to be very small in angstrom (Å) units. On the other hand, the inorganic water retention material of the present invention only needs to be a hole having a size capable of sucking water by capillary action, and it is considered that it is sufficient if the hole has a unit of μ or more.

〔Example〕

 Hereinafter, examples of the present invention will be described.

First Example After a mold material was manufactured using a casting sand novolak-based phenol resin and an inorganic water retaining material, a mold was molded using the material, and a performance evaluation test was performed by casting.

First, as an inorganic water-retaining material, a particle size of 149-297 μm Kanuma soil, Akadama soil, sepiolite, and a mixture of coconut shell activated carbon or coconut charcoal and bentonite, coconut shell activated carbon, zeolite, coconut charcoal, and adjust the water content. To obtain the inorganic water retention materials shown in Table 1 (Sample Nos. 1 to 1).
8).

Next, commercially available quartz sand (Mikawa Silica Co., Ltd .: particle size No. 6)
2% by weight of novolak phenolic resin with respect to the silica sand,
15% by weight of hexamethylenetetramine based on the resin,
0.1% by weight of calcium stearate with respect to the silica sand was sequentially mixed by a speed muller to obtain a resin-coated molding sand. Then, the resin-coated molding sand was placed in a small mortar mixer, and the inorganic water-retaining material shown in Table 1 was mixed with a sample No. 1 by 2.0%.
By volume, Sample Nos. 2 to 18 were added at 4.0% by volume under the conditions shown in Table 1 and mixed to obtain a demolding mold material of this example. Table 1 shows the content of the water retention material.

Next, the demolding mold material is placed in an iron mold for a cup-shaped product having an outer diameter of 80 mm, an inner diameter of 60 mm, a height of 135 mm, a bottom thickness of 15 mm and a draft angle of 2 degrees, which has been previously heated to 250 ° C. After the mold was heated and held at 400 ° C. for 2 minutes in a siliconit furnace, it was taken out of the furnace and the mold was removed to obtain a mold.

The moldability of these molds was determined by sample numbers 1-4, 6-12, 14
~ 18 were good. However, for sample numbers 5 and 13, the resin-coated molding sand was partially solidified. In addition, the measurement was carried out by observing the amount of smoke generated during heating in the production of the mold and conducting a sensory test of the generated odor. Table 2 shows the results. In the table, the smoke emission status "◎" indicates "no smoke emission",
“△” indicates “smoke is slightly observed”, “×” indicates “a small amount of smoke”, and “XX” indicates “a large amount of smoke”.

In the table, the irritating odor "◎" indicates "no irritating odor", "△" indicates "irritating odor slightly", "x" indicates "irritating odor", and "xx" indicates "irritating odor". The pungent odor is very strong. " As is evident from Table 2, none of the samples according to this example except for Sample No. 12, which had a low water content, showed no smoke and no irritating odor or off-flavor was observed.

Next, a mold strength test was performed. Table 2 shows the results. As in Sample Nos. 5 and 13, when the mixing temperature of the inorganic water-retaining material was high, or when the content of water was large, the strength of the resulting mold deviated greatly from the allowable range. In addition, in the case of using the coconut shell activated carbon, zeolite, and shrimp charcoal as the inorganic water retention material of Sample Nos. 16 to 18, the strength of the obtained mold slightly exceeded the allowable range.

For comparison, those using only the resin-coated molding sand described above (Sample No. C1), those using perlite as a water retention material (Sample No. C2), those using bentonite (Sample No. C3), and those using vermiculite (Sample No. C
4) A sample using sepiolite whose addition amount is out of the range of the invention (Sample Nos. C5 and C6) was used as a comparison mold material, and conditions other than those in Tables 3 and 4 were prepared as described above. A comparative mold was produced using the same, and a similar performance evaluation test was performed. Table 5 shows the results. As is clear from Table 5, in the case of the comparative example of sample No. C1, the amount of smoke generated after casting was considerably large during the production of the mold, and the generation of pungent odor was also quite strong. On the other hand, in the case of sample numbers C2 to C4, during the production of the mold, the amount of smoke generated after casting and the degree of generation of irritating odor are not as large as those of sample number C1, but are larger than in this example. Sample No. C5 does not have a sufficient effect of reducing the amount of smoke produced after casting and the amount of pungent odor during casting, and Sample No. C6 shows that the mold strength is significantly reduced.

Further, for the sample numbers 1 to 4, 6 to 8, and 10 to 12, the cast materials were collected and evaluated as recycled sand. That is, in the resin-coated molding sand making step, 40% of the silica sand was replaced with this reclaimed sand, and otherwise, a smoke-free mold material was manufactured in the same manner as described above, and a mold was manufactured using the same. The test was performed. As a result, in Sample Nos. 1 to 4 and 6 to 8, both during the production of the mold and during the casting, the smoke generation state and the degree of the irritating odor were almost the same as those without using the regenerated sand, and were good. The degree of decrease in mold strength also showed substantially the same value. On the other hand, the sample number
In the case of 10 to 12, the decrease in mold strength was remarkable at 50% or more.

Second Example A molding material was produced using casting sand, an inorganic water retaining material and a novolak-based phenolic resin, while changing the charging time of the inorganic water retaining material from the first example.

First, as an inorganic water retention material, Kanuma soil, Akadama soil, and sepiolite having a particle size of 149 to 500 μm were prepared, dried at 100 ° C., and adjusted for moisture to obtain an inorganic water retention material shown in Table 6. Numbers 19-28).

Next, commercially available quartz sand (Mikawa Silica Co., Ltd .: particle size No. 6)
2.5% by weight of the novolak phenolic resin based on the silica sand and 15% by weight of hexamethylenetetramine based on the resin were mixed in a mixing mara, and then mixed.
0.1% by weight of calcium stearate based on silica sand was added to the mixture, and immediately after the addition, 4.2% by volume of an inorganic water retention material shown in Table 6 was added and mixed to obtain a demolding mold material of this example. Was. Sample Nos. 22, 26 and 28 having a water content exceeding 10% by weight were solidified when the mold material was cooled, and crushed to form a mold material.

Next, a mold was obtained using this smoke-free mold material in the same manner as in the first embodiment.

In addition, the moldability of these molds was good, and the evaluation was carried out by observing the amount of smoke generated during heating in the production of the molds and performing a sensory test of the generated odor. Table 7 shows the results. The symbols in the table are the same as those in Table 2. As is evident from Table 7, none of the samples according to the present example produced smoke and no irritating odor or off-flavor was observed.

Next, a mold strength test was performed. The results are also shown in Table 7. As is evident from Table 7, the mold strength of any water retention material having a water content of 10% by weight or less at the time of addition was within the allowable range.

Further, for the sample numbers 19 to 21 and 23 to 25, the cast material was recovered after casting, and 40% of the silica sand was replaced with this recycled sand.
Using this, a mold was prepared, and an evaluation test was performed in the same manner.
As a result, both during the production of the mold and during the casting, the generation of smoke and the degree of irritating odor were almost the same as those without the use of recycled sand, and were almost the same. showed that.

Third Example Using a molding sand, a novolak-based phenol resin, and an inorganic water-retaining material, a mold material was manufactured in the same manner as in the second example, and then a mold was formed using the material, and a performance evaluation test was performed by casting. .

First, Kanuma soil, Akadama soil, and sepiolite having a particle size of 149 to 500 μm are prepared as inorganic water retention materials, and the water content is 5% by weight.
To obtain the inorganic water retention materials shown in Table 8 (Sample Nos. 29 to
42).

Next, commercially available quartz sand (Mikawa Silica Co., Ltd .: particle size No. 6)
The novolak phenol resin in the amount shown in Table 8 and 15% by weight of hexamethylenetetramine based on the resin were mixed into the mix mara and mixed with the silica sand, and then 0.1% by weight based on the silica sand was added to the mixture. Was added, and immediately after the addition, the inorganic water retaining material shown in Table 8 was added under the conditions shown in the same table, and the mixture was stirred and mixed for 10 to 15 seconds to obtain a demolding mold material of this example. .

When the performance evaluation test of the obtained mold was performed in the same manner as in Example 1, the mold according to this example did not emit any smoke at the time of heating for the production of the mold, and produced no irritating odor or off-flavor. The degree was extremely weak. The test was performed by a mold strength test. The results are also shown in Table 9. In the case of this example, the decrease in mold strength was small.

For the sample numbers 29 to 42, the cast material after casting was collected and used as recycled sand, and 40% of the silica sand was replaced with this recycled sand.
Using this, a mold was prepared, and an evaluation test was performed in the same manner.
As a result, both during the production of the mold and during the casting, the generation of smoke and the degree of irritating odor were almost the same as those without the use of recycled sand, and were almost the same. showed that.

Next, 350 kg of the demolding mold materials of Sample Nos. 31 and 39 were prepared in large quantities by a speed marula for production, and 250 ° C.
An automatic baking machine (one that can bake 1.94 kg of front cover core, 3.08 kg of rear cover, and 1.72 kg of slab core at one time) is manufactured by the air blow method. After heating and holding at 250 ° C. for 1 minute, the mold was automatically opened and the mold was taken out.

In addition, the moldability of these molds was good, and the evaluation was carried out by observing the amount of smoke generated during heating in the production of the molds and performing a sensory test of the generated odor. As a result, as in Table 9, no fuming was observed at all, and the degree of generation of irritating odor and off-flavor was extremely weak. As a result of producing a strength test specimen for each production lot and performing a die strength evaluation test, the strength reduction rate was 20% or less.
In the manufacturing process, no problem such as destruction of the mold occurred. In order to compensate for the decrease in strength of the mold, even when the amount of the resin added was 3.2% by weight, no smoke was observed at the time of the production of the mold with the same amount of the inorganic water retention material, and the irritating odor and the off-flavor were extremely weak.

Fourth Embodiment Silica sand, 2% by weight of phenol resin with respect to the silica sand, 15% by weight of hexamethylenetetramine with respect to the phenol resin as a hardening agent, and 0.1% with respect to the silica sand as a lubricant.
1% by weight of calcium stearate and a hydrous magnesium silicate clay mineral as an inorganic water-retaining material were added to the silica sand in an amount of 4%.
A mold material was prepared by adding volume%. The water content of the inorganic water retention material was 3, 5, 11, 21, 33, 42, and 47% by weight. Using the resulting mold material, a mold was prepared, the mold strength of the obtained mold was measured, and the mold strength reduction rate was examined. The result is shown in FIG. As a result, when the water content of the inorganic water retaining material was 5 to 42% by weight, no smoke was generated and the mold strength reduction rate was 20% or less. On the other hand, in the case of 3% by weight, a small amount of smoke is generated and the mold strength reduction rate is also low.
It was as high as 27%. In the case of 47% by weight, although no smoke was generated, the mold strength reduction rate was extremely high at 40%.

Fifth Embodiment Silica sand and 2.5% by weight of phenol resin with respect to the silica sand,
15% by weight of hexamethylenetetramine with respect to the phenol resin as a hardener, and the silica sand as a lubricant
0.1% by weight of calcium stearate and 5% by weight of water
4% by volume of the contained inorganic water retention material was added to the silica sand to prepare a mold material. At this time, the addition time of the water retention material,
After mixing in silica sand (I), charging phenolic resin (II), charging hexamethylenetetramine (III), charging calcium stearate (IV), and charging in the cooling step (V),
Each mold material was obtained. Using the obtained mold material,
A mold was prepared, the mold strength of the obtained mold was measured, and the mold strength reduction rate was examined. The result is shown in FIG. As a result, the mold strength was reduced by 34% or more in all cases when the water retention material was charged at the timings I to III, that is, before calcium stearate was charged. On the other hand, when the water retention material was charged after the addition of IV calcium stearate and during the V cooling step, the mold strength reduction rate was 20% or less.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a demolding mold material according to the present invention, FIG. 2 is a conceptual diagram schematically showing a resin-coated molding sand and a cross-sectional structure thereof after firing, and FIG. 2 (a) is a resin-coated molding. FIG. 2 (b) is a cross-sectional view schematically showing the structure of the resin-coated molding sand obtained by firing the resin-coated molding sand. FIG. 2 (c) is a cross-sectional view schematically showing the structure of the resin-coated molding sand. Sectional view schematically showing the structure of a fired smoke removal mold material mixed with
The figure is a diagram showing the relationship between the water content of the inorganic water retention material and the mold strength reduction rate of the demolding mold material obtained in the fourth embodiment, and FIG. 4 is the water retention of the demolding mold material obtained in the fifth embodiment. FIG. 3 is a diagram showing a relationship between a material addition time and a mold strength reduction rate. 1. Thermosetting resin 2. Casting sand base material 3. Water retention material

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Haruyoshi Hirano 2-1-1 Toyota-cho, Kariya-shi, Aichi Examiner, Toyoda Automatic Loom Works Ltd. Wakako Okada

Claims (1)

(57) [Claims] 1. A mold material in which a thermosetting resin or the like is coated on a mold base material, having a pore structure, having a water absorbing / desorbing ability even at 100 to 250 ° C., and having a water content of 15% by weight or more. A smoke removing mold material comprising an inorganic water retaining material, wherein the mixing amount of the inorganic water retaining material is 1.5 to 4.5% by volume of the mold material base material.