JP2011212877A - Method of manufacturing molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for simply mold-releasing a molded body from a mold without causing mold-release failure while suppressing the cost of the mold without necessarily using an ejector pin or a seal material, and without complicating a mold shape.SOLUTION: First, the mold 10 having a core material 2 inserted therein is filled with a raw material 1, and the raw material 1 is heated, dried, and solidified. Then, the core material 2 is pulled out of the mold 10 to form an internal space N. Next, the molded body 3 is released by interposing a gas penetrated into the molded body 3 between the outer surface of the molded body 3 and the inner surface of the mold 10 by making the gas flow in the internal space N after being molded.

Description

  The present invention relates to a method for producing a molded body molded by a mold.

  A method for producing a molded body in which a dough-like raw material is heated and dried and solidified with a mold is known (Patent Document 1). In addition to such molded bodies, mold molded bodies may be difficult to release due to close contact with the inner surface of the mold after the molding. If the mold is forcibly opened, the molded body may be deformed or damaged. In such a case, as a method for releasing the molded body from the mold, there is a method in which a part of the molded body is pushed up by an ejector pin provided in the mold. In this method, the molded body is released from the mold, but the molded body may be damaged due to the disposition of the ejector pins and the unbalance of the protruding amount, or may not be sufficiently released due to malfunction of the ejector pin.

  As a method for releasing a molded body without using an ejector pin, Patent Documents 2 to 4 have been proposed. Patent Document 2 discloses a method in which a mold is released by slightly opening a mold after molding and allowing compressed air to flow between a cavity covered with an elastically deformable sealing material and a resin molded body. Are listed. However, in this method, it is necessary to cover the dividing surface in the mold including the cavity and the gate with an elastically deformable sealing material, and the manufacturing cost increases due to an increase in the number of parts. Moreover, since compressed air flows in the direction along the dividing surface of the slightly open molded object and the metal mold, that is, in the direction orthogonal to the direction of releasing, there is a limit as an effective releasing action.

  Patent Document 3 describes a method of releasing mold by blowing high-pressure air to a molded body using an air groove formed in a part of a mold. However, in this method, since the high pressure air does not hit the entire surface of the molded body, there is a possibility that a portion that is difficult to be released remains. Further, since the shape of the mold becomes complicated, the cost increases.

  In Patent Document 4, a mold having a hollow portion and formed of a porous member having a continuous pore portion is used, and after the molten resin injected into the hollow portion is solidified, a release agent and A method is described in which a molded product is released by injecting gas into a porous member and diffusing a release agent in the boundary between the cavity and the solidified resin. However, since a special mold is used, the manufacturing cost increases.

JP 2009-101553 A JP-A-4-140116 JP-A-9-314619 JP 2004-160825 A

  An object of the present invention is to not necessarily use an ejector pin or a sealing material, to suppress the cost of the mold by not complicating the mold shape, and to prevent the mold from being formed without causing a mold release defect. It is to provide a method for producing a molded article that is easily released from the mold.

  The present invention is a method of manufacturing a breathable molded body having an internal space by molding it on the inner surface of a mold composed of a plurality of mold members, and allowing gas to flow into the internal space after molding. There is a step of releasing the molded body from the mold by interposing the gas permeated through the molded body between the outer surface of the molded body and the inner surface of the mold.

  The molding method of the present invention does not necessarily use ejector pins or sealing materials, and does not complicate the shape of the mold, thereby reducing the cost of the mold and without causing mold release defects. It has become possible to remove the body from the mold.

FIG. 1 is a longitudinal sectional view (a), a longitudinal sectional view (b), a sectional view taken along line AA, and a sectional view taken along line BB, showing a state in which a mold is used in the method for producing a molded body of the present invention. is there. FIG. 2 is a schematic view showing the inflowing gas with arrows in the mold shown in FIG. FIG. 3 is a cross-sectional view taken along the line CC of FIG. 2 and shows a state in which the molded body is released from the mold.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to the illustrated embodiment.
1 (a) and 1 (b) show a state in which the mold 10 is used in the method for producing a molded body of the present invention, a longitudinal sectional view, a sectional view taken along line AA, and a sectional view taken along line BB. It shows with. In FIG. 2, the gas flowing into the mold 10 is indicated by arrows. FIG. 3 is a cross-sectional view of the mold 10 taken along the line CC.

First, the raw material 1 is filled in the mold 10 in which the core material 2 is inserted, and the raw material 1 is heated and dried and solidified. Thereafter, the core material 2 is pulled out from the mold 10 to form a molded body 3 having an internal space N as shown in FIG.
Next, as shown in FIG. 2, the fluid supply source 30 is attached, and gas is caused to flow into the interior space N after molding. Thereby, as shown in FIG. 3, the gas which permeate | transmitted the molded object 3 exists between the outer surface of the molded object 3, and the inner surface of the metal mold | die 10, and the mold member 11 and the mold member 12 are separated. The molded body 3 can be released from the mold members 11 and 12 by applying a little force to the mold members 11 and 12. Hereinafter, materials, molds, process conditions, and the like in the above embodiment will be described in detail.

[material]
In the present embodiment, the raw material 1 used for producing the molded body is not particularly limited as long as it is used as this kind of dough-shaped raw material, but any one or more of inorganic particles, inorganic fibers, and organic fibers. It is preferable that the fluid is a viscous fluid having a fluidity obtained by kneading a solid having water and a liquid having at least one of water and an organic solvent. Here, preparation of the raw material in a dough shape means that the solid and the dispersion medium are kneaded and prepared so that the solid and the liquid are not easily separated while having fluidity. The method for preparing the raw material is not particularly limited. The solid content concentration of the raw material is not particularly limited, but is preferably 20 to 60% by mass, and more preferably 20 to 50% by mass. Further, when the raw material includes inorganic particles, it is preferable to use graphite from the viewpoint of moldability and cost. In this invention, it is more preferable to use at least 1 sort (s) chosen from earth-like graphite and artificial graphite from a viewpoint of improving the air permeability of a molded object. The inorganic particles preferably have an average particle size of 100 to 600 μm, more preferably 150 to 500 μm, and even more preferably 200 to 450 μm. In addition to graphite, obsidian, mica, mullite, silica, magnesia, talc and the like can be used as the inorganic particles within the range where the effects of the present invention are exhibited. These inorganic particles may be used alone or in combination of two or more. The content of the inorganic particles is preferably 40 to 90% by mass and more preferably 50 to 85% by mass in the molded product from the viewpoint of shape retention and surface property of the molded product.

  When inorganic fiber is included in the raw material, it mainly forms a skeleton of a molded body. For example, when used as a structure for casting production, the shape is maintained without being burned by the heat of molten metal during casting. Examples of the inorganic fibers include artificial mineral fibers such as carbon fibers and rock wool, ceramic fibers, and natural mineral fibers. One or two or more inorganic fibers can be selected and used. Among these, it is preferable to use polyacrylonitrile (PAN) -based carbon fibers that have high strength even at high temperatures from the viewpoint of effectively suppressing shrinkage associated with carbonization of the thermosetting resin. The inorganic fibers preferably have an average fiber length of 0.5 to 15 mm, particularly 1 to 8 mm from the viewpoints of moldability and uniformity. The content of the inorganic fiber is preferably 1 to 20% by mass and more preferably 2 to 16% by mass in the molded body from the viewpoint of moldability and shape retention of the molded body.

  When the thermosetting resin is included in the raw material, the normal temperature strength and hot strength of the molded body are maintained, the surface property of the molded body is improved, and the surface of the casting is used when the molded body is used as a structure for casting production. Improve roughness. Examples of the thermosetting resin include a phenol resin, an epoxy resin, and a furan resin. Among these, in particular, there is little generation of combustible gas, there is a combustion suppressing effect, the residual carbon ratio after pyrolysis (carbonization) is as high as 25% or more, and carbonization when the molded body is used for a structure for casting production. Phenol resin is preferably used from the viewpoint that a good cast surface can be obtained by forming a film. As the phenol resin, a novolak phenol resin that requires a curing agent or a resol phenol resin that does not require a curing agent is used. From the viewpoint of improving the air permeability, it is preferable to use a powdery phenol resin. From the viewpoint of improving the dispersibility of the raw material, it is preferable to use a liquid phenol resin. The said thermosetting resin can select and use 1 type, or 2 or more types.

  When the raw material contains a water-soluble polymer compound, the moldability of the molded body can be improved. Examples of the water-soluble polymer compound include thickening polysaccharides, polyvinyl alcohol, and polyethylene glycol. Examples of the polysaccharide include gum agents such as xanthan gum, tamarind gum, gellan gum, guar gum, locust bean gum and tara gum, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, carrageenan, pullulan, pectin, alginic acid and agar. Among these polysaccharides, non-natural products such as cellulose derivatives and chemically modified products such as carboxymethyl cellulose are more effective than small natural products such as agar. Good in terms of being able to do. These water-soluble polymer compounds preferably have a weight average molecular weight of 10,000 to 3,000,000, more preferably 20,000 to 1,000,000. One or two or more of the water-soluble polymer compounds can be selected and used.

  When heat-expandable particles are included in the raw material, the moldability of the molded body can be improved. The heat-expandable particles are preferably microcapsules in which an expansion agent that expands by vaporization is encapsulated in the shell wall of a thermoplastic resin. When the microcapsules are heated at 80 to 200 ° C., the diameter is preferably expanded to 3 to 5 times and the volume is expanded to 50 to 100 times, and the average particle diameter before expansion is preferably 5 to 80 μm, More preferred are particles of 20-50 μm. When the expansion of the thermally expandable particles is within such a range, the effect of addition can be sufficiently obtained while suppressing the adverse effect on the molding accuracy due to the expansion. The thermally expandable particles preferably have an average diameter before expansion of 5 to 80 μm, and more preferably 20 to 50 μm. Examples of the thermoplastic resin constituting the shell wall of the microcapsule include polystyrene, polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-vinylidene chloride copolymer, ethylene-vinyl acetate copolymer, or combinations thereof. Examples of the expanding agent contained in the shell wall include low-boiling organic solvents such as propane, butane, pentane, isobutane, and petroleum ether. The thermally expandable particles preferably include 0.5 to 10% by mass with respect to the total mass of the inorganic powder, the inorganic fiber, the thermosetting resin, and the water-soluble binder. It is more preferable to contain the mass%. When the thermally expandable particles are contained in such a range, the molding raw material is filled in the details of the mold by expansion, and the shape of the mold can be faithfully transferred, and the effect of addition can be sufficiently obtained. In the case of the above range, since a large amount of thermally expandable particles is not included, overexpansion can be prevented and no extra cooling time is required, so that high productivity can be maintained.

[Molding process]
Although the metal mold | die 10 may be a well-known thing which can be isolate | separated into the two metal mold | die members 11 and 12 by a division surface, it is not restrict | limited to this. In the present embodiment, the mold 10 includes two mold members 11 and 12 that are divided into two parts, but the present invention is not limited to this, and it may be divided into three or more parts. The inflow pressure of the raw material is not particularly limited, but when compressed air is used, it is preferably 0.15 to 5 MPa, and more preferably 0.2 to 3 MPa. After the raw material is filled in the mold 10, it is dried by heating and solidifying.
The heating temperature in the mold 10 is practically 120 to 300 ° C. as the mold temperature. As a result, the liquid is mainly evaporated, and a sufficiently strong porous and breathable molded article can be obtained. It is preferable to devise the heat generating part and its heat transfer mechanism so that it can be heated uniformly in order to obtain a homogeneous molded body. In the present embodiment, in consideration of simplification of illustration, a mold shape as a cylindrical molded body is shown, but any other shape can be used as necessary.

[Gas inflow process]
In this step, as shown by an arrow r in FIG. 2, gas is caused to flow into the internal space N of the molded body after the molding. From this point of view, when the mold 10 has a vent other than the dividing surface, it is possible to enhance the mold release effect by sealing the vent or the outlet of the vent. Furthermore, when the cavity of the mold 10 has a shallow and open shape so that the circumferential length πD of the cross section is longer than the length L, it can be effectively applied.
In the present embodiment, the inner space of the mold (not shown in the drawing but corresponding to the combined portion of the molded body 3 and the inner space N of the molded body) has a circular cross section, but has other shapes. It may be. Regarding the relationship between the length L and the circumferential length πD of the cross section, the ratio (L / πD) is preferably 2 to 50, and more preferably 5 to 20.

The gas used for release may be compressed air that is generally used, and a release agent or the like may be further mixed therein. In the present embodiment, the lids 31 and 32 are attached to the mold 10 and a commercially available compressor is inserted as the fluid supply source 30 to supply gas to the internal space N of the molded body. The gas is supplied in a state where the mold member 11 and the mold member 12 are slightly opened or simultaneously with the opening.
The flow rate of the inflowing gas is not particularly limited, but is preferably 6 to 50 L / min and more preferably 10 to 50 L / min in consideration of the above-described molded body. At this time, it is preferable to increase the flow rate of the gas to be supplied as the air permeability of the molded body is low because it is easy to effectively interpose the gas between the molded body 3 and the inner surface S of the mold. By setting the flow rate to be equal to or less than the above upper limit value, it is easy to release without damaging the molded body, which is preferable. On the other hand, it is preferable by setting it as more than the said lower limit at the point from which the favorable mold release property of a molded object is obtained. Here, interposing the gas between the molded body 3 and the inner surface S of the mold may be in a state where the gas is permeated to such an extent that the mold 3 is effectively released. In addition, the molded body 3 may not be completely released only by the gas. When a part of the molded body 3 is not released from the inner surface S of the mold, the mold release may be completed by applying vibration to the mold member or slowly pulling the mold member away thereafter. Further, by repeating the minute opening and closing operations of the mold members 11 and 12, gas can be effectively interposed between the molded body 3 and the inner surface S of the mold.

  For example, it may be difficult to uniquely determine the relationship between the flow rate and the air permeability, and it is preferable to adjust the flow rate and the air permeability within a corresponding range in combination with other means as necessary. Specifically, when trying to release the mold from the mold by reducing the inflow of gas, the molded body may be partially released from the surface of the mold and may not be completely released. In such a case, the mold member can be completely released from the mold by applying vibration to the mold member.

  At this time, the type of gas to be supplied is not particularly limited, but is preferably air, nitrogen, carbon dioxide, helium, or argon, and more preferably air or nitrogen. The gas may be continuously supplied for a fixed time or may be supplied intermittently for a fixed time. Further, simultaneously with the gas supply, periodic or non-periodic vibration may be applied to the mold member 11 or the mold member 12 or both. Moreover, since the temperature of the molded body 3 is about 150 ° C. immediately after molding, the temperature of the gas to be supplied is set to 0 to 35 ° C. to cool the molded body 3 and promote thermal shrinkage, thereby efficiently releasing the mold. Can be done.

[Molded body]
The shape and dimensions of the molded body molded by the manufacturing method of the present embodiment are not particularly limited, but the internal space that is the inflow destination of the gas is introduced so as to release the adhesion from the inner surface of the mold by flowing in the gas. It is assumed that the molded body has. The size of the internal space is not particularly limited as long as the above-described effect is obtained, but it is preferably a shape similar to the internal shape of the mold, and in the illustrated example, it is preferably a cylindrical shape. The thickness t of the molded body is not particularly limited, and is preferably set to have a predetermined air permeability in relation to the characteristics of the material. Considering the use of this type of molded article, it is practical that the thickness t is 1 to 50 mm in the case of the molded article. The air permeability when releasing the adhesion from the inner surface S of the mold is not particularly limited, but is preferably 1 to 1200 and more preferably 3 to 1000 in the thickness direction of the molded body. The air permeability at this time may be a value at the gas flow rate applied in the manufacturing process, but can typically be evaluated as a value at 2 L / min. In order to increase the air permeability of the molded body, for example, it is preferable to adjust the particle diameter of the inorganic particles to be blended in the raw material and to make the solid content concentration of the raw material 20 to 60% by mass, preferably 20 to 50% by mass. Is more preferable. In order to make the particle diameters of the inorganic particles uniform, the particles are sized using a sieve having a predetermined opening beforehand.
In the present invention, the air permeability means a value measured by the method described in Examples unless otherwise specified.

  The method for producing a molded body of the present invention is suitable when the molded body has a bottomed cylindrical shape, but may have a cylindrical shape without a bottom. In this case, the form which seals the part used as the bottom in the said gas inflow process with a predetermined | prescribed jig | tool, and interrupts | blocks gas leakage is mentioned. Moreover, it is suitable for manufacture of the structure for casting manufacture. Further, as in the prior art, it is possible to use in combination with other mold release methods such as using an ejector pin or using a sealing material.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.
[Example 1]
Using the mold shown in FIG. 1, the illustrated bottomed cylindrical molded body was produced as follows.

  First, the raw material 1 which consists of a mixing | blending shown in Table 1 was prepared.

The conditions in each process were set as follows.
[Molding process]
Molded body dimensions: length L = 385 mm, diameter D = 12 mm, thickness t = 3 mm
・ Inflow pressure: 0.5 MPa
・ Heating temperature: 200 ℃
・ Heating time: 2 minutes [gas inflow process]
Inflow gas: Compressed air (room temperature)
・ Inflow rate: 30L / min

[Measurement of air permeability]
About the molded body obtained in Example 1, “Standard test method for coating agent for disappearance model” defined based on JISZ2601 (1993) “Testing method of foundry sand” (March 1996, Japan According to “5. Air permeability measurement method” of Kansai branch of the casting engineering society), using an apparatus of the same principle as the air permeability measurement device (compressor air ventilation method, FIG. The air permeability was measured.
The air permeability P is determined by “P = (h) by the specimen thickness h (cm), the specimen cross-sectional area a (cm ² ), the ventilation resistance p (cmH ₂ O), and the air flow rate V (cm ³ / min). / (A × p)) × V ”. However, in this specification, the test piece thickness h is the wall thickness, that is, “(outer diameter−inner diameter) / 2”, and the test piece cross-sectional area a is “inner diameter × circumferential ratio × length”.
The air permeability of the molded body obtained in this example was 3.79.

[Example 2]
As shown in Table 1, a molded body was obtained in the same manner as in Example 1 except that the type of phenol resin was changed, and then released from the mold.
In the present example also, the entire molded body could be released from the mold without causing defective release.

  Furthermore, when the air permeability was measured in the same manner as in Example 1, the air permeability of the molded body obtained in this example was 14.08.

[Example 3]
As shown in Table 1, after obtaining the molded body in the same manner as in Example 1 except that the type of phenol resin was changed and the amount of water was changed, the molded product was released from the mold.
In the present example also, the entire molded body could be released from the mold without causing defective release.

  Furthermore, when the air permeability was measured in the same manner as in Example 1, the air permeability of the molded product obtained in this example was 18.95.

[Example 4]
As shown in Table 1, molding was carried out in the same manner as in Example 1 except that the type of phenol resin was changed, the inorganic particles were changed from earth graphite to artificial graphite, and the amount of water was changed. After obtaining the body, it was released from the mold.
In the present example also, the entire molded body could be released from the mold without causing defective release.

  Furthermore, when the air permeability was measured in the same manner as in Example 1, the air permeability of the molded product obtained in this example was 985.77.

[Comparative Example 1]
As shown in Table 1, except that the inorganic particles were changed from earthy graphite to scaly graphite, a molded body was obtained in the same manner as in Example 1, and then the mold was released from the mold. It was in close contact with the mold and could not be released.

The air permeability of the molded product obtained in Comparative Example 1 was measured in the same manner as in Example 1. As a result, the air permeability was 0.
Table 2 summarizes the results of Examples 1 to 4 and Comparative Example 1.

  As can be seen from the examples, the manufacturing method of the molded body of the present invention does not necessarily use an ejector pin or a sealing material, and does not complicate the mold shape, thereby reducing the cost of the mold and releasing the mold. It was possible to remove the molded product from the mold without causing defects.

DESCRIPTION OF SYMBOLS 1 Raw material 2 Core material 3 Molded body 10 Mold 11, 12 Mold member 30 Fluid supply source 31, 32 Cover body N Internal space of molded body S Inner surface L of mold D Length of mold cavity D Mold cavity Diameter t Thickness of molded body

Claims (5)

  A method for producing a molded article having air permeability and having an inner space formed on an inner surface of a mold constituted by a plurality of mold members, wherein a gas is caused to flow into the inner space after molding, and the molding is performed. The manufacturing method of a molded object which has the process of releasing the said molded object from this metal mold | die by interposing the gas which permeate | transmitted this molded object between the outer surface of a body and the inner surface of the said metal mold | die.   The method for producing a molded body according to claim 1, wherein the molded body has a bottomed cylindrical shape.   The mold is released from the mold member while separating the mold from a mold member after the gas is interposed between the outer surface of the molded body and the inner surface of the mold. A method for producing the molded article according to 1 or 2.   The manufacturing method of the molded object of Claim 3 which gives a vibration to a metal mold | die member in the operation | movement which isolate | separates the said metal mold | die into a metal mold | die member.   The said molded object is a structure for casting manufacture, The manufacturing method of the molded object of any one of Claims 1-4.

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