JP2005074498A - Method for producing mold for shell mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making a mold having sufficient mold strength even at low temperature while securing the fluidity in producing the mold by using shell mold resin-coated sand (RCS) coated with binder. <P>SOLUTION: In the method for producing the mold for shell mold, this mold is composed of refractory grains and the binder which coats the grains. As this binder, novolak type phenolic resin (1) which contains ≤10% low molecular weight component (one-nuclide and two-nuclide) and (2) which has a dispersion ratio (Mw/Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of ≤3.0 in the measurement with gel filtration chromatography is used to obtain the RCS. The resultant RCS is pre-heated at a temperature higher than 70°C, and this RCS is filled up into a heated metallic mold to obtain the mold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improved method for producing a mold for a shell mold used in the production of a casting main mold and a core (hereinafter simply referred to as a mold), more specifically, even when the mold temperature during mold making is low. The present invention relates to a method for producing a mold for a shell mold, which exhibits mold strength and has mold characteristics that generate a small amount of dust during casting.

  Conventionally, as a mold for a shell mold, resin-coated sand for shell mold (hereinafter simply referred to as “RCS”) in which a refractory particle is coated with a binder such as a thermosetting novolac type phenol resin is heated in advance to 250 to 300 ° C. After filling in the adjusted mold, it is fired and shaped into a mold. Although the thin part of the mold obtained in this way is cured, the thick part is insufficiently cured, so the actual strength of the mold is weak, especially in the case of a mold with large thickness fluctuation. Had a problem in handling.

  In addition, when casting is performed using a mold that is insufficiently cured as described above, there is also a problem that a large amount of cracking occurs when an uncured portion is cured due to a heat history during casting.

  Furthermore, a temperature control unit composed of a heat exchanger composed of a hollow tube formed in a spiral shape for refluxing the thermal refrigerant and a gas distribution pipe for flowing the coated sand, and a temperature control device using the same are disclosed in the present patent applicant. (Patent Document 1), however, the problem described above was not solved even if this was simply used for a conventional RCS.

Japanese Patent No. 3355325

  In order to solve these problems, for example, if the mold temperature during mold making is increased to try to increase the number of cured parts, the smoke and odor during molding will become harder and the working environment will deteriorate. This is not preferable from the viewpoint of the problem that the strain caused by the expansion force increases, the mold cracks and the productivity decreases, and the dimensional accuracy of the casting. On the other hand, when trying to heat the RCS before filling the mold without changing the mold temperature at the time of mold making to a temperature higher than 70 ° C., in the conventional RCS coated with the novolak type phenol resin, Since the amount (unreacted phenol monomer and binuclear component) is large, the softening point of the resin is low, the RCS is likely to block, and the fluidity is deteriorated. As a result, there is a problem that defective filling of the mold occurs. Further, when a novolac type phenol resin having a small amount of low-nuclear component is used, there is a problem that the strength of the mold is remarkably lowered even if the problem of blocking property during heating of RCS is solved.

  Therefore, a mold for a shell mold that can exhibit sufficient mold strength even when the mold temperature at the time of mold making is low, using RCS that does not hinder the fluidity even if the RCS is heated to a temperature higher than 70 ° C. in advance. Improvement of the manufacturing method is demanded.

  As a result of intensive studies in view of these circumstances, the present inventors are effective to produce a mold by a specific method using refractory particles coated with a novolak type phenol resin that satisfies a specific condition. As a result, the present invention was completed through further research based on this knowledge.

That is, the present invention has a refractory particle and a binder that coats the refractory particles.
(1) The content of low molecular weight components (mononuclear and binuclear) is 10% or less, and (2) the dispersion ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 3.0 or less, preferably 2.0 or less,
This is a method for producing a mold for a shell mold, in which an RCS using a novolac type phenolic resin is heated to a temperature higher than 70 ° C. in advance, and the RCS is filled in a heated mold.

  Further, according to the present invention, when the RCS is heated in the above-described invention, a heat exchanger composed of a spirally formed hollow tube that recirculates the thermal refrigerant and a flow gas distribution pipe that supplies a gas that flows the RCS are provided. A method for producing a mold for a shell mold, characterized in that the RCS is heated to a temperature higher than 70 ° C. by a temperature control device having a temperature control unit configured, and then the heated mold is filled and molded. .

  The low molecular weight components (mononuclear and binuclear) of the novolak-type phenolic resin have a low boiling point, and thus are easily chemically volatile, and are generated as irritating odors during molding at 250 to 300 ° C. Moreover, since heat resistance is also low, it becomes a spear generation source. On the other hand, these components physically have extremely low melt viscosity and are excellent in RCS wettability, so that the strength is increased. That is, when the amount of the low-nuclear component is increased from 10%, the novolac-type phenol resin is softened quickly, RCS blocks are likely to occur, and the amount of cracks increases, but the strength is improved.

  The dispersion ratio of the present invention defined above is a simple expression of the molecular weight distribution of the novolak-type phenol resin. However, when the dispersion ratio exceeds 3.0, the novolak-type phenol resin softens faster and the RCS Blocks are likely to occur, and the number of spears increases.

  Here, regarding the heating method (heating device) of RCS that has been conventionally used, so-called static heating in which RCS placed in an open container is simply heated (such as an electric furnace) is performed even if RCS is heated. The heat transfer to the inside is bad. As a result, the internal curability of the mold is poor and the strength tends to decrease and the amount of dust generated tends to increase. In addition, the conventional fluid heating is inferior in uniform and quick heating of the RCS because the RCS placed in the open container is only heated by aeration and local heating of the side and / or bottom of the open container. .

  In the present invention, in order to solve the difficult problems as described above, it is important that the RCS using the novolac type phenol resin as the coating binder is heated quickly and uniformly to a temperature higher than 70 ° C. in advance. Reached on a great deal of effort and based on that knowledge. Further, as a means for embodying it, a temperature control unit comprising a heat exchanger composed of a spiral hollow tube that recirculates the above-described thermal refrigerant and a flow gas distribution pipe that supplies a gas that flows RCS It has been conceived that it is optimal to use a temperature control device having

  As a result, the present invention achieves both of block resistance, strength, and spear reduction characteristics, and can heat RCS quickly and uniformly at a temperature higher than 70 ° C. In addition, the mold temperature at the time of mold making can be reduced. It can be lowered from the conventional 250-300 ° C. to 180-230 ° C.

  And by lowering the mold temperature at the time of mold making, 1. 1. The odor during molding is reduced. 2. Excellent mold dimensional stability due to reduced mold distortion. 3. A casting with high dimensional accuracy can be obtained by the above 2. Effects such as reduction of energy costs can be obtained.

  According to the present invention, even if the RCS is preheated to a temperature higher than 70 ° C., the RCS that does not hinder the fluidity can be used, and sufficient mold strength can be exhibited even when the mold temperature during mold molding is low. A method for producing a mold for a shell mold can be provided.

  The RCS used in the method for producing a mold for a shell mold of the present invention contains refractory particles and a binder for coating the refractory particles, and such refractory particles are aggregates for mold formation. The particles are not particularly limited as long as the particles have a fire resistance that can withstand casting and a particle size suitable for mold formation. Examples of such refractory particles include special sands such as silica sand, olivine sand, zircon sand, chromite sand, and alumina sand, slag system particles such as ferrochrome slag, ferronickel slag, and converter slag, Examples thereof include porous particles such as beads (trade name), iron sand, carbon particles, glass particles, ceramic particles, and regenerated particles thereof. These may be used alone or in combination of two or more.

  On the other hand, novolak-type phenol resin is used as the binder, but the phenol resin used in the present invention is a low molecular weight component (mononuclear and binuclear) by gel filtration chromatograph (hereinafter referred to as GPC) area method. The content of is 10% or less, preferably 5.0% or less. When the content exceeds 10%, the above-mentioned problems of RCS are solved without much difference from conventional resins. Can not.

  The second feature is that the dispersion ratio (Mw / Mn) of polystyrene-equivalent weight average molecular weight (Mw) and number average molecular weight (Mn) by GPC measurement is controlled to be 3.0 or less, preferably 2.0 or less. The smaller the dispersion ratio value, the narrower the molecular weight distribution width. In general, a high molecular weight compound has a weight average molecular weight (Mw) larger than a number average molecular weight (Mn), and a dispersion ratio (Mw / Mn) exceeds 1. When the dispersion ratio (Mw / Mn) exceeds 3.0, the novolac type phenol resin is quickly softened and RCS blocks are likely to occur, and there is a tendency to increase the amount of resin. The number average molecular weight of such a novolak type phenol resin is preferably 600 to 1500, and more preferably 700 to 1200. When the number average molecular weight is less than 600, the RCS fusion point is lowered, and there is a tendency that hot fluidity and fusion between sand grains are likely to occur. Conversely, if it exceeds 1500, the melt viscosity of the novolak type phenolic resin tends to increase and the mold strength tends to decrease.

  Examples of the phenols used as one of the raw materials in the novolac type phenol resin include phenol, alkylphenols such as cresol and xylenol, bisphenols such as bisphenol A and bisphenol F, and phenol-based purification residues such as bisphenol A residues. Is mentioned. On the other hand, examples of aldehydes include, but are not limited to, formaldehyde and glyoxal.

There is no limitation on the production method of the novolac type phenol resin used in the present invention. However, as a preferred production method of the novolac type phenol resin, phenols and aldehydes can be used in the presence of an aqueous phosphoric acid solution in terms of production stability and good yield. In the reaction, a production method comprising a heterogeneous reaction step that satisfies the following reaction conditions is preferably used.
(I) The blending amount of aldehydes is 0.80 to 0.93 moles per mole of phenols (b) The blending amount of phosphoric acid is 25 parts by weight or more with respect to 100 parts by weight of phenols (c) Reaction system Water content is 15-40% by mass
(D) Reaction temperature is 70 ° C to reflux temperature

  More preferably, a reaction cosolvent is used in order to make the dispersion ratio (Mw / Mn) smaller. Specifically, the reaction auxiliary solvent is preferably at least one selected from the group consisting of alcohols, polyhydric alcohol ethers, cyclic ethers, polyhydric alcohol esters, ketones, and sulfoxides.

  Examples of alcohols include monohydric alcohols such as methanol, ethanol, and propanol, butanediol, pentanediol, hexanediol, ethylene glycol, propylene glycol, trimethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol. And dihydric alcohols such as polyethylene glycol and trihydric alcohols such as glycerin.

  Examples of polyhydric alcohol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, and ethylene glycol. Examples include glycol ethers.

  Examples of the cyclic ethers include 1,3-dioxane and 1,4-dioxane. Examples of the polyhydric alcohol ester include glycol esters such as ethylene glycol acetate. Examples include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of the sulfoxides include dimethyl sulfoxide and diethyl sulfoxide.

  The reaction auxiliary solvent is not limited to the above examples, and can be used as a solid as long as it is non-reactive and exhibits a liquid during the reaction, and each may be used alone or in combination of two or more. .

  Although it does not specifically limit as a compounding quantity of a reaction auxiliary solvent, It is 5 mass parts or more with respect to 100 mass parts of phenols, Preferably it is 10-200 mass parts.

  Novolac type phenol resins include silane coupling agents such as γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, which are conventionally used for the purpose of improving the physical properties of the mold, and ethylenebisstearic acid. It is desirable to include a lubricant such as amide and methylenebisstearic acid amide.

  For the production of RCS used in the present invention, any of the production methods conventionally practiced in the technical field, such as dry hot method, semi-hot method, cold method, powder solvent method, etc., can be applied. Therefore, the dry hot method is preferable. Further, if necessary, for example, a resol type phenol resin, a release agent, a deodorant, a bengara and the like may be added to the RCS.

  In the present invention, the novolac type phenolic resin is usually used at a ratio of 0.5 to 5 parts by weight with respect to 100 parts by weight of the refractory particles, and the curing agent is added to 100 parts by weight of the novolac type phenolic resin. On the other hand, it is usually used at a ratio of 5 to 30 parts by weight. As the curing agent, hexamethylenetetramine is preferable, but other known curing agents can be used.

  The RCS used in the present invention thus obtained is heated to a temperature higher than 70 ° C. using a method of static heating or fluid heating. The heating method is preferably fluid heating, and more preferably fluid heating using a temperature controller described later.

  As a method of static heating, specifically, the RCS placed in an open container is simply heated to a predetermined temperature in an electric furnace. In this case, since the RCS is always stationary, the heat transfer to the inside is poor and the uniform heating to the predetermined temperature is poor, so the internal curability of the mold is not good, the strength is reduced, and the amount of spear generation is low. It tends to increase.

  As a fluidized heating method, conventional fluidized heating is performed by heating an RCS placed in an open container by heating the side surface and / or the bottom surface of the container, and flowing the RCS by aeration from the bottom surface. Until heated. Even in this case, even though the RCS is flowing, the heating part is a local heating only on the side surface and / or the bottom surface of the container. Takes a lot of time.

  Therefore, in the present invention, fluidized heating using a temperature adjusting device, which will be described later, is suitably used as a method that can be heated more quickly and uniformly than these heating methods and with controlled temperature. Hereinafter, fluidized heating using a temperature control device will be described in detail.

Moreover, the temperature control apparatus used for this invention is demonstrated, referring drawings. FIG. 1 shown as the first embodiment of the present invention is different in the passing diameter (mφ, nφ) in an existing circular powder storage tank T ₁ having a discharge port D provided with a shutter 7 at the bottom. And two independent helical heat exchangers A (A ₁ , A ₂ ) having a common thermal refrigerant inlet 5 and a thermal refrigerant outlet 6, and a flow having a gas inlet 4 and a gas outlet 3. It is a longitudinal cross-sectional view of the temperature control apparatus formed by installing the temperature control unit comprised by the gas distribution piping B, and forming the storage part 1 and the heat exchange part 2. FIG.

In the helical heat exchanger A, it is possible to arrange one having the same or different difference diameter, or one that sequentially expands or contracts, but a plurality of them are arranged in tandem, parallel, or concentric circles. By arranging in a shape, it is possible to structurally form a vertical and horizontal spread of the heat exchanger group (A ₁ , A ₂ ...), That is, a vertical and horizontal spread of the heat exchange unit 2 according to the shape of the RCS storage tank T. it can. Moreover, it has excellent heat exchange capacity (heat exchange area and heat exchange rate) derived from the spiral shape and material. Therefore, the RCS of the heat exchanging unit 2 receives heat exchange (heating or cooling) equally and efficiently regardless of the depth and spread, and the temperature rise / fall to the desired temperature is smoothly achieved. Also, by configuring the heat exchanger in a spiral shape, the RCS can effectively move downward due to its own weight, and the gas (air) distributed between the following gas distribution pipes B for flow and present between the RCSs. As a result, the RCS can be prevented from adhering to or coming into contact with a heat exchanger or the like as necessary, and the RCS can be discharged smoothly.

  The heat exchanger A here is composed of a spirally formed hollow tube, preferably from the viewpoint of heat exchange ability and workability, preferably using a copper tube having an inner diameter of 5 to 30 mm, especially 8 to 20 mm, For example, it is manufactured in a spiral shape as shown in FIG. 6 (for example, (a) conical shape, (b) cylindrical shape, (c) drum shape and other irregular coil shapes, and (d) planar spiral shape (e) column shape). However, among them, the one having an inclination in the spiral is preferable in terms of prevention of retention and distribution of the cooling medium. The material of the hollow tube is not particularly limited as long as it satisfies the above requirements. The length of such a copper tube is mainly determined in consideration of the RCS processing conditions (amount, temperature, cycle), but it is necessary to raise 26 Kg RCS from 5 ° C to 40 ° C per minute. The length of the 12 mmφ copper tube is approximately 80 m. Moreover, although the arrangement | positioning space | interval and spiral pitch of a helical heat exchanger are normally determined by observing the flow state of RCS, it is necessary to provide an interval of about 30 mm empirically.

  The heat exchange heat refrigerant flowing through the inside of the spiral heat exchanger 1 flows through the inside of the spiral heat exchanger from, for example, a heat refrigerant supply device through a flow rate adjustment valve, a flow meter, and an inlet end 5 and exits at the outlet end 6. While circulating through a circuit (partially not shown) returning to the thermal refrigerant supply device, heat exchange is performed with the gas blown from the blowout hole 3 of the flow gas distribution pipe B, and this gas further flows in contact with the RCS. The thermal refrigerant heats up or cools the RCS to a predetermined temperature by such indirect or direct heat exchange, such as by direct heat transfer with the stationary RCS in some cases, and controls the temperature. As such a thermal refrigerant, hot / cold water is optimal from the viewpoints of temperature control, ease of heating / cooling switching, device manufacturing and operating costs, but there is no particular limitation, and a heating medium or refrigerant is used instead of hot / cold water. May be. The temperature of the hot water is usually 40 to 90 ° C., particularly 50 to 80 ° C. is used when it is necessary to cope with block resistance. In the present invention, the RCS is higher than 70 ° C., preferably 70 ° C. The temperature of the hot refrigerant is circulated and adjusted so that it can be heated to a temperature higher than 100 ° C. and lower than 100 ° C., more preferably higher than 70 ° C. and lower than 90 ° C. On the other hand, in the case of cooling, of course, the ambient temperature or the use of cooled water is generally used. In particular, the helical heat exchanger used in the present invention can be easily stopped and restarted by heating and cooling when combined with a supply device capable of switching a thermal refrigerant (not shown). It is possible to contribute to the reduction of labor, such as being freed from troublesome work such as RCS discharge work.

  The gas distribution pipe B constituting the temperature control unit used in the present invention is a gas having a pressurized ambient temperature supplied from a pressurized gas supply device (for example, a blower, a compressor, a pressure cylinder), not shown, In particular, air or air obtained by dehumidifying or cooling the air, and in some cases, a mixed gas or an inert gas of an inert gas such as nitrogen gas or air (hereinafter, these gases are simply referred to as “gas”). It has a plurality of gas blowout holes 3 communicating with the gas receiving port 4 to be received and the inside of the pipe provided at a desired interval.

  When the supply of pressurized gas is stopped, the gas blowing hole 3 is opened in an angle and a direction in which it is difficult to cause clogging due to inflow of RCS into the pipe or a short path of gas, or a cover structure (for example, twy) is used. Consideration is given. Especially, as shown in FIG. 4, the blow-out hole 3 drilled below the horizontal center line of the pipe, for example, obliquely below or directly below is preferable. The shape of the gas blowing hole is preferably a circle from the viewpoint of blowing resistance (pressure loss) and ease of processing, but is not limited thereto. The hole diameter is preferably 1 to 6 mmφ, considering flow state and blowing pressure adjustment, prevention of gas short path, variation in the amount of blowing gas, increase in supply capability of the gas supply device, and the like. In addition, the arrangement and number of gas blowout holes can be made small or small when the gas pressure is high, and large or large when the pressure is low, so that uniform heat exchange can be realized. It is preferable to make it. In addition, the hole can be provided in the longitudinal pipe of the flow distribution pipe at a position where clogging due to RCS does not occur.

  The shape of the flow gas distribution pipe is not particularly limited because it is determined according to the shape of the RCS storage tank. For example, in addition to the conical structure as shown in the embodiment, an annular shape, a circular shape, a cylindrical shape, a rectangular tube shape, Examples thereof include a pyramid shape, a radial shape, and a composite or multiple column structure thereof. The gas distribution pipe for flow is generally made of metal, but the material is not particularly limited, and may be ceramic, fiber reinforced plastic, plastic, or the like.

The flow gas blown out from the blow hole 3 of the flow gas distribution pipe B functions as a fluidization and heat exchange medium for the RCS, but this gas is generally continuous or intermittent depending on the properties of the RCS. To be blown. In addition, in the present invention, as described above, the spiral heat exchanger having excellent heat exchange capability and hot / cold water as the heat refrigerant are preferably used, so that floating flow and gas short path often observed in conventional apparatuses are used. Air flow and discharge pressure are not required, and at least the amount of air satisfying the space between the RCSs as a heat exchange medium, and the microfluidity or flow state of causing RCS replacement or mixing from the extent of preventing the RCS from stopping, that is, It is only necessary to supply a gas having a discharge pressure that does not cause floating although the RCS moves. The gas discharge pressure in the gas supply device is not limited because it varies depending on the type and processing amount of the RCS, the structure of the RCS storage tank, the diameter of the blowout hole, and the like. 0.02 MPa, intermittent blowing by a compressor is about 0.2 to 0.4 MPa, and the amount of gas is about 1 to 1.5 m ³ per minute. For this reason, there are provided advantages such as prevention of peeling and dust generation of the resin film during the flow treatment. The gas used in the heat exchange section is exhausted as waste heat after exchanging heat with the RCS to be processed while rising and diffusing from the heat exchanger into the storage section. For this reason, it can contribute to shortening of a heat treatment cycle and reduction of energy cost. From the viewpoint of further utilization of waste heat and prevention of dust generation, the RCS storage tank is preferably provided with an outer lid provided with an exhaust port (not shown) and an opening such as an untreated RCS receiving port. In addition, by installing a vibration part or a vibration transmission part in the gas distribution pipe for flow, it is possible to smoothly discharge the RCS from the outlet D by continuing to vibrate or oscillating whenever it tends to stay. It becomes.

  The arrangement of the flow gas distribution pipe B is a relatively helical heat exchanger in order to easily discharge the RCS controlled to a predetermined temperature and to efficiently exchange heat between the RCS and the cooling medium. It is preferable to be below A. For example, even if a part of the gas distribution pipe B for flow (or one of the plurality of gas distribution pipes B for flow) is provided at a position where it overlaps the spiral heat exchanger A, It is preferable that the gas blowing hole 3 provided below the gas distribution pipe B is disposed so as to be closer to the RCS discharge port D than the lower end portion of the helical heat exchanger A. The flow gas distribution pipe is effective in consideration of the arrangement interval with the spiral pipe so that the RCS does not stay or inclining the horizontal pipe surface. Furthermore, a plurality of gas distribution pipes for flow can be provided in a vertical relationship or a plurality of gas distribution pipes can be arranged in parallel. The number and arrangement of these flow gas distribution pipes B, spiral heat exchangers A, and RCS pressure buffers C can be set in consideration of the mutual relationship.

Next, FIG. 2 showing a second embodiment of the temperature control apparatus for use in the present invention, the reduced diametrical RCS reservoir T in ₂ in order to provide a suitable continuous processing of RCS, the across the diameter (mφ, nφ ) Of two spiral heat exchangers A ₁ and A ₂ , and one heat exchanger having one heat refrigerant inlet 5 and one heat refrigerant outlet 6, and a flow gas component FIG. 3 is a longitudinal sectional view of a reduced-diameter temperature control apparatus configured with a pipe B, a pair of level controllers L (L ₁ , L ₂ ) and an RCS pressure buffer C in the storage unit 1.

  The pair of level controllers L attached to the storage unit 1 includes a level controller L1 that adjusts the upper limit amount of RCS that is carried in by a transport device such as a bucket elevator (not shown), and a level controller L2 that adjusts the lower limit amount. These enable the RCS automatic acceptance for controlling the said conveying apparatus and maintaining RCS in the storage part 1 in fixed quantity. The RCS can be supplied to the storage unit 1 of the RCS storage tank T in a batch type or a continuous type.

The RCS pressure buffer C provided near the upper portion of the spiral heat exchanger A is not affected by the weight of the RCS that is controlled by the level controller L (L ₁ , L ₂ ) to be carried into the storage unit 1. It functions so that a good flow state of RCS in the heat exchanging unit 2 is formed, and the RCS supply from the storage unit to the heat exchanging unit can be performed without any trouble after the RCS is discharged. By providing near the lower part of the gas distribution pipe B for flow suppression, the temperature of the RCS can be made uniform by the mixing action at the time of discharge. It is also possible to install both of them. By connecting a vibration part or a vibration transmission part to these RCS pressure buffers C, it is possible to prevent the RCS from staying and promote smooth cooling (heating).

  The shape of the RCS pressure buffer C is not particularly limited as long as the RCS pressure buffer C has the above-described function. However, from the viewpoint of the RCS replenishment ability from the storage part after the RCS discharge to the heat exchange part, the flowability of the RCS is particularly taken into consideration. For example, surface lubrication treatment such as fluorine resin processing may be performed with a plurality of openings provided with a gradient equal to or greater than the angle of repose at which RCS naturally flows and / or through which RCS passes. Specifically, various shapes such as a plate shape, a lattice shape, a saw shape, a Jinka shape, a mountain shape, a cone shape, a pyramid shape, a trumpet shape, and a cone shape can be exemplified. Of these, a cone shape as shown in FIG. 2 is preferable. A plurality of these RCS pressure buffers C may be provided in parallel. The RCS pressure buffer C is generally made of metal, but the material thereof is not particularly limited, and may be ceramic, fiber reinforced plastics, plastics, wood, or the like. Attachment of the spiral heat exchanger A, the flow gas distribution pipe B, and the RCS pressure buffer C to the RCS storage tank T can be appropriately performed by conventionally known fixing means such as welding, bolts, and jigs.

  The RCS heated to a temperature higher than 70 ° C. by the heating method or the temperature control device is subsequently blow-filled into a mold heated to a temperature lower than the conventional temperature of 180 to 230 ° C., preferably 190 to 210 ° C. After baking for -100 seconds, the mold is removed to obtain a mold.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. The following test methods are used for the dispersion ratio of the novolak-type phenolic resin, the content of the low molecular weight component, the blocking property of the RCS, the odor, the bending strength of the mold, and the amount of spear generation when the shell mold mold of the present invention is produced. Measurement was carried out by

(1) Dispersion ratio (Mw / Mn)
Weight average molecular weight (Mw) in terms of standard polystyrene measured by Tosoh Corporation gel filtration chromatograph SC-8020 series build-up system (column: G2000Hxl + G4000Hxl, detector: UV254 nm, carrier: tetrahydrofuran 1 ml / min, column temperature: 38 ° C.) And the number average molecular weight (Mn) was calculated | required and the dispersion ratio (Mw / Mn) was computed.

(2) Content of low molecular weight components (mononuclear and binuclear components) (%)
The total amount of each component content measured by the area method displaying the area of the mononuclear component and the binuclear component as a percentage with respect to the total area of the molecular weight distribution by the gel filtration chromatograph is low in the novolak type phenol resin. The content of molecular weight component. “ND” in Table 1 means that no mononuclear component was detected.

(3) Blocking property of RCS When the RCS was heated by each heating container and heating device, the state of RCS in the container and the device was evaluated according to the following evaluation criteria.
○: Level in which the RCS block is hardly confirmed in the container and the apparatus, and there is no practical problem. Δ: Although a slight block of RCS is confirmed in the container and the apparatus, a level that does not hinder the heating. : Level at which the RCS block is confirmed in the container and the apparatus and causes a practical problem

(4) Odor sensory test The mold heated to the set temperature shown in Table 1 was blow-filled with RCS preheated to the preheat temperature shown in Table 1, and then fired for 60 seconds to form a cylindrical mold ( The odor when molding a 47 mm diameter x 49 mm height was evaluated by a sensory test based on the following evaluation method and evaluation criteria.
(I) Evaluation method The odor panelists of 15 persons (including 5 women) performed sensory evaluation based on the following evaluation criteria, and evaluated superiority or inferiority by the average of the obtained sensory evaluation.
(Ii) Evaluation criteria ○: The irritating odor is hardly felt.
(Triangle | delta): Although an irritating odor is somewhat felt, there is no practical problem.
X: The pungent odor is felt strongly.

(5) Bending strength (N / cm ² )
In accordance with JIS K-6910, a mold (test piece) was prepared and measured. If the bending strength is 250 N / cm ² , there is no practical problem.

(6) Generated amount of spear (mg)
After placing a test piece for bending strength measurement (size 10 mm x 10 mm x 60 mm) in a glass test tube (inner diameter 27 mm x length 200 mm), pre-weighed glass wool (2.50 g) is placed near the opening of the test tube. Inserted to make a measuring device for the amount of spear generation. Next, the measuring device was placed in a tubular heating furnace maintained at 600 ° C., subjected to an explosion heat treatment for 6 minutes, and then taken out and allowed to cool to room temperature. Thereafter, the glass wool was taken out from the measuring instrument, and its mass was measured. In addition, the generation amount (mg) of spear was calculated by subtracting the glass wool mass (mg) before the explosion heat treatment from the glass wool mass (mg) after the explosion heat treatment.
[Example 1]

-Production of novolac-type phenolic resin-
In a reaction vessel equipped with a thermometer, a stirrer, and a condenser, 300 g of phenol (P), 88.5 g of 92% by mass paraformaldehyde (F) (F / P = 0.85), and 89% by mass phosphoric acid. After charging 180 g (60.0% / P) and 17.6 g (5.87% / P) of methanol, the mixture was gradually refluxed under a cloudy state (two-phase mixture) formed by stirring and mixing. The reaction was stopped after a condensation reaction was carried out at the same temperature for 10 hours.

  Next, methyl isobutyl ketone is added with stirring and mixing to dissolve the condensate. Then, stirring and mixing are stopped, and the contents are transferred into a separating flask and allowed to stand, and the methyl isobutyl ketone solution layer (upper layer) and phosphorus are mixed. Separated into an acid aqueous solution layer (lower layer). Next, after removing the phosphoric acid aqueous solution layer and washing the methyl isobutyl ketone solution with water several times to remove phosphoric acid, the contents are returned again into the reaction vessel, and methyl isobutyl ketone is completely removed by vacuum distillation to remove the novolak. 330 g of type phenol resin was obtained.

-Production of RCS, preheating and mold evaluation-
In a laboratory speed mixer, add 5000 g of futtery sand preheated to about 140 to 150 ° C. and 75 g of the above novolac phenol resin, knead for 50 seconds, and then dissolve 11.3 g of hexamethylenetetramine in 75 g of cooling water in advance. The entire amount of the curing agent aqueous solution prepared in this manner was added, and air cooling was performed until the formed mass collapsed into particles. Finally, 5 g of calcium stearate was added and mixed for 15 seconds to obtain RCS.

The obtained RCS was preheated to 80 ° C. by static heating, and then the RCS blockability, the sensory test of odor during mold molding, the bending strength of the mold, and the amount of spear generation were evaluated by the above test methods. . The results are shown in Table 1.
[Examples 2-8, Comparative Examples 1-3]

  In Example 1, the same operation as in Example 1 was performed except that the novolac type phenol resin, the preheating method, the preheating temperature, and the mold temperature described in Table 1 were used.

  From Table 1, those obtained in Examples 1 to 8 were solved with the problems of RCS blockability during preheating, odor during mold molding and mold casting, and even when the mold temperature during mold molding was low. It can be seen that it has sufficient mechanical strength. On the other hand, what was obtained in Comparative Example 1 has the problem of the blockiness of the RCS and the odor during mold molding. Further, it can be understood that all of the samples obtained in Comparative Examples 1, 2, and 3 have a problem associated with the occurrence of spears.

FIG. 1 is a longitudinal cross-sectional view of a temperature control device manufactured by installing a temperature control unit according to one embodiment of the temperature control device used in the present invention in an existing circular RCS storage tank T ₁ . FIG. 2 is a longitudinal cross-sectional view of a temperature control device manufactured by installing a temperature control unit according to another embodiment in the temperature control device used in the present invention in an existing circular reduced-diameter RCS storage tank T ₂ . is there. FIG. 3 is a plan view of the conical flow gas distribution pipe B used in FIGS. FIG. 4 is a front view of FIG. FIG. 5 is a cross-sectional explanatory view showing a preferred position of the gas blowing hole 3 along the line XX of the flow gas distribution pipe B shown in FIG. 6 (a), (b), (c), (d), and (e) are explanatory views showing examples of the shape of the spiral heat exchanger A, and (e) is a plane spiral in the structural unit of (d). It is.

Explanation of symbols

A (A ₁ , A ₂ ) ... spiral heat exchanger B ... gas distribution pipe C for flow ... RCS pressure buffer D ... outlet T ... RCS reservoir tank L (L ₁ , L ₂ ) ... level controller 1 ... reservoir 2 ... Heat exchanger 3 ... Gas outlet 4 ... Gas inlet 5 ... Thermal refrigerant inlet 6 ... Thermal refrigerant outlet 7 ... Shutter

Claims (2)

  It has a refractory particle and a binder that coats it, and, as the binder, in the measurement by gel filtration chromatography, the content of (1) low molecular weight components (mononuclear and binuclear) is 10% or less And (2) a resin-coated sand for a shell mold using a novolac-type phenolic resin having a dispersion ratio (Mw / Mn) of 3.0 or less of the weight average molecular weight (Mw) and the number average molecular weight (Mn), A method for producing a mold for a shell mold, which is preliminarily heated to a temperature higher than 70 ° C. and filled with the coated sand in a heated mold.   When the shell-coated resin-coated sand is heated, the shell-molded resin is composed of a heat exchanger composed of a spiral hollow tube that recirculates a thermal refrigerant and a flow gas distribution pipe that supplies a gas that flows the coated sand. 2. The shell mold according to claim 1, wherein the coated sand is heated to a temperature higher than 70 ° C. by a temperature regulating device having a temperature regulating unit, and the coated sand is filled in a heated mold to form the shell mold. A method for manufacturing a mold for use in a process.

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