JP5779752B2 - Method for producing molded body, method for producing fired body - Google Patents

Description

  The present invention relates to a molded body obtained by combining finely divided inorganic materials as non-plastic materials with a condensed body made of a thermosetting resin, a fired body obtained by firing the molded body, a molded body, and a method for producing the fired body.

An inorganic material is a simple substance of a nonmetallic element such as silicon, an inorganic compound composed of a metallic element and a nonmetallic element such as alumina, and a carbonaceous material such as graphite. There are ceramics, graphite, and glass.
Powdered ceramics are shaped into a desired shape and used as dielectric ceramics, semiconductor sensors, adsorbents, and catalysts. Moreover, fibrous carbon is also shaped into a desired shape and used as an engineering part.

The shape of the shaped body is generally a ceramic particle or a raw material powder of metal particles brought into contact with each other and thermally bonded (sintered). Such a molded body can be produced by placing the raw material powder in a pressing mold and heating and sintering it while applying pressure in a high-temperature furnace, or placing the pre-formed raw material powder body in a rubber bag. There are methods such as degassing, sealing, and then putting in a pressure vessel containing the liquid to compress and compress the liquid.
In addition, as a molded body, there is an inorganic molded body in which raw material particles are bonded with a resin aggregate. Such a molded body is kneaded with raw material powder and resin, poured into a mold, cooled, and removed. Molded by molding.

What is formed by sintering is called a brittle material and has very low mechanical strength. On the other hand, an inorganic molded body obtained by combining raw material particles with a resin aggregate exhibits a mechanical strength greater than that of a brittle material, but has a problem that it is difficult to ensure a mechanical strength that can withstand practical use.
The cause is that inorganic materials that exist in nature are hydrophilic, but the resin is oleophilic, the affinity between the inorganic material and the resin is poor, and an effective interface to form a structure with mechanical strength. This is thought to be because it cannot be formed.

  As an example of an inorganic molded body, a carbonaceous material with severe restrictions and a thermosetting resin are kneaded and shaped into an arbitrary shape by a method such as compression molding, injection molding, extrusion molding, and then calcined by carbonization. A proposal has been made to obtain a carbonaceous structure suitable for an electromagnetic induction heating cooker (see Patent Document 1).

JP 2009-242176

Graphite has electrical conductivity in addition to mechanical strength, and if it is made into a molded body with as much graphite as possible, it forms an inner pot of an electromagnetic induction heating cooker with good mechanical strength and heating efficiency, such as an electromagnetic induction heating rice cooker. can do.
However, since the carbonaceous structure disclosed in Patent Document 1 is a material in which the molding material for producing the carbonaceous structure is simply kneaded with a polymer polymerized by polymerization and graphite, the separation of the graphite and the resin There is a problem that the strength is weak and it is difficult to obtain a mechanical strength that can withstand practical use as a carbonaceous structure.

  An object of the present invention is to obtain a molded article having strength enough for practical use and in which cracks and the like are not generated by firing, a fired body obtained by firing the molded body, and a method for producing the molded body and the fired body. .

The mechanical strength of compacts composed of aggregates of finely divided inorganic materials and thermosetting resins is considered to be governed by the physical properties of the components that make up the compacts and the adhesive structure between the finely divided inorganic materials and the aggregates. It is done. That is, it depends on the strength of the inorganic material itself, the strength of the thermosetting resin or its aggregate itself, and the peel strength of the adhesive surface between the inorganic material and the aggregate.
And regarding the peel strength of the adhesive surface between the inorganic material and the aggregate, whether the aggregate penetrates and adheres to the uneven details present on the surface of the inorganic material particles, and bonds the inorganic material particles together It is governed by whether or not the secondary bond (Van der Waals force) acting on the interface of the adhesive layer between the particles and the aggregate is large.

In order to increase the peel strength of the bonding surface between the inorganic material and the aggregate, the resin that becomes the aggregate may be infiltrated and adhered to the surface of the inorganic material. In order to infiltrate and attach the lipophilic resin composition component to the surface of the hydrophilic inorganic material, the affinity between the two may be increased using a surfactant.
However, simply using a surfactant does not allow the resin to sufficiently penetrate and adhere to the uneven details present on the surface of the inorganic material powder due to the viscoelasticity of the resin.
Therefore, the present inventor made the resin penetrate and adhere to the surface of the inorganic material from the state of the relatively permeable monomer, and gelled in that state to form a coagulated body. It is possible to obtain a coating of aggregates that penetrates and adheres to the uneven details present on the surface. Thereby, the peeling strength of the bonding surface between the aggregate and the inorganic material can be increased by the anchor effect of the aggregate coating.
The present invention has been made based on such knowledge, and specifically comprises the following configuration.

(1) The molded body according to the present invention is a molded body formed by bonding fine inorganic inorganic materials as non-plastic materials with a aggregate made of a thermosetting resin, and the aggregate is made of a thermosetting resin. The monomer and oligomer as composition components are gelled in a state where they penetrate and adhere to the surface of the particulate inorganic material.
The agglomerated material is a rough and uneven material in which the monomer and oligomer are present on the surface of the finely divided inorganic material by infiltrating and adhering the monomer and oligomer, which are the components of the thermosetting resin, onto the surface of the finely divided inorganic material. It penetrates and adheres to the details and gels in that state, thereby exerting an anchor effect, firmly bonding the finely divided inorganic material, and increasing the strength as a molded body.
The oligomer here is a molecule having 2 to 50 repeating units.

(2) Moreover, the thing as described in said (1) WHEREIN: The average particle diameter of the said finely divided inorganic material is 500 micrometers or less, It is characterized by the above-mentioned.
By setting the average particle size of the finely divided inorganic material to 500 μm or less, it is necessary to bond the finely divided inorganic material particles to each other while maintaining the ratio of the finely divided inorganic material and the thermosetting resin as the aggregate. A surface area can be secured. In addition, even if the finely divided inorganic material is crushed and formed into finer particles in the molding process, it is possible to increase the proportion of aggregates that have permeated and adhered to details.

(3) Moreover, the thing as described in said (1) or (2) WHEREIN: The said thermosetting resin is carbonization rate 45-55%, and the mass ratio of the said particulate inorganic material and this thermosetting resin Is in the range of 90:10 to 50:50.
By making the mass ratio of the finely divided inorganic material and the thermosetting resin in the range of 90:10 to 50:50, the surface of the molded body can be smoothed, the fluidity of the molding material can be secured, and the residual stress can be reduced. Can be small.

(4) Further, in any of the above (1) to (3), the fine particulate inorganic material is graphite powder, and the thermosetting resin is a phenol resin. It is.
When the finely divided inorganic material is graphite powder, electromagnetic induction performance can be imparted to the molded body. Further, since the thermosetting resin is a phenol resin, when the molded body is baked, the carbonization rate of the resin is about 50%, which shows properties similar to graphite. Therefore, the same performance as an electromagnetic induction heater made of graphite alone can be exhibited. In addition, the phenol resin can form a large secondary bond at the interface of the adhesive layer with the graphite particles.

(5) In the above (4), the phenol resin is a resol type phenol resin.

(6) Further, in the above (5), the resol type phenolic resin has pressure-sensitive thermal self-curing property.
The pressure-sensitive thermal self-curing property contains a methylol group in the molecule and does not show fluidity only by heating, but has the property of being thermally fused and cured when pressure is applied. Since it has pressure-sensitive thermal self-curing property, it is possible to obtain a molded article having high mechanical strength that can be easily integrally molded by hot press molding such as transfer molding.

(7) A fired body according to the present invention is obtained by firing the molded body according to any one of (1) to (6) above.

(8) In the above (7), the firing is performed in a temperature range of 800 ° C. to 2000 ° C. in a vacuum or an inert gas atmosphere. Is.

(9) The method for producing a molded body according to the present invention comprises a step of adding a fine inorganic material while stirring a liquid containing a reaction component of a thermosetting resin, a reaction catalyst, an emulsifying dispersant and water, and reacting for a predetermined time. Removing the excess emulsifying dispersant with water, removing the solid produced by the reaction and drying it to prepare a molding material; placing the molding material in a mold of a molding machine; And a step of taking out the molded body after keeping the temperature and pressure for a predetermined time after putting in the mold.
In the present invention, since the fine inorganic material is added in the addition condensation process of the thermosetting resin, the addition composition is carried out in a state where the resin composition component permeates and adheres to the irregularities on the surface of the inorganic material powder. It is possible to improve the adhesion between the graphite and the polymer resin.

(10) In the above (9), the mold molding machine is a transfer molding machine, and the step of molding the molding material in a mold includes the molding material in a pot of the transfer molding machine, The molding material melted by heating and pressing is injected into a mold cavity.
In the present invention, since the molding material prepared as described above is molded by the transfer molding method, the molding material can be melted to increase the fluidity, and the molding material can be filled throughout the mold. The generation of pores during filling can be prevented. In addition, since the temperature and pressure are maintained for a predetermined time after filling, the curing reaction can be promoted.

(11) Further, in the above (9) or (10), the fine particle inorganic material has an average particle diameter of 500 μm or less.
Since the average particle size of the finely divided inorganic material is 500 μm or less, the surface area necessary for bonding the finely divided inorganic material particles to each other is maintained while maintaining the ratio of the finely divided inorganic material and the thermosetting resin as the aggregate. Can be secured. In addition, even if the finely divided inorganic material is crushed and formed into finer particles in the molding process, it is possible to increase the proportion of aggregates that have permeated and adhered to details. In addition, if the average particle diameter of the finely divided inorganic material is set to 100 μm or less, the ratio of the aggregate that has permeated and adhered to the details can be further increased.
Further, when graphite is used as the finely divided inorganic material, commercially available graphite powder can be used, and the powder particle size is large and dust disaster can be prevented.

(12) Moreover, in the thing in any one of said (9) thru | or (11), the said thermosetting resin is 45-55% of carbonization rate, and is the mass of a particulate inorganic material and a thermosetting resin. The ratio is in the range of 90:10 to 50:50.
Since the mass ratio of the particulate inorganic material having a carbonization rate of 45 to 55% and the thermosetting resin is in the range of 90:10 to 50:50, the fluidity is good and the residual stress after firing can be reduced. it can.

(13) Further, in any of the above (9) to (12), the fine inorganic material is graphite powder, and the reaction components of the thermosetting resin are phenols and aldehydes. It is characterized by this.
Since phenols and aldehydes are used as the reaction component of the thermosetting resin, the carbonization rate of the aggregate is high, and the mechanical strength after firing carbonization can be increased.

  As phenols used in the present invention, phenol derivatives can be used in addition to phenol. Specifically, phenol, o-cresol, m-cresol, p-cresol, bisphenol A, styrenated phenol, alkylphenol substituted with an alkyl group having 2 to 9 carbon atoms, p-phenylphenol, xylenol, resorcinol, catechol, One or a mixture of two or more known phenol derivatives such as pyrogallol and halogenated phenol substituted with chlorine or bromine can be used. When using p-substituted phenols, it is preferable to use together with other phenols.

  Examples of the aldehydes used in the present invention include one or a mixture of two or more of formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, terephthalaldehyde, hydroxybenzaldehyde, furfural and the like, and formaldehyde and paraformaldehyde are particularly preferable.

(14) The process according to (13), wherein the reaction catalyst is an amine compound catalyst, the emulsifying dispersant is a polymer activator having a glucoside bond, and phenols and aldehydes undergo addition condensation. Is characterized by introducing a finely divided inorganic material.

  An amine compound is used as a reaction catalyst for the addition condensation reaction of phenols and aldehydes used in the present invention. For example, primary and secondary amines such as hexamethylenetetramine, ammonia, methylamine, dimethylamine, ethylenediamine, monoethanolamine, or ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, One or a mixture of two or more alkylamine compound catalysts containing at least two amino hydrogens such as N- (2-aminoethyl) ethanolamine, N- (2-aminoethyl) propanolamine, guanamine, and dicyandiamide Can be mentioned.

  As the emulsifying dispersant used in the present invention, a polymer activator having a glucoside bond is suitable, and hydroxyethyl cellulose, hydroxyethyl cellulose 2-hydroxypropyltrimethylammonium chloride added with 1.4 to 3.5 mol of ethylene oxide per glucose unit. Examples thereof include ethers, metal salts of alginic acid, and natural rubber metal salts of mucopolysaccharide skeleton, or a mixture of two or more thereof. Since these surfactants are polymerized, they swell in water but hardly dissolve, so it is desirable to prepare a 0.3 to 4% by mass aqueous solution in advance.

  As the addition condensation reaction of phenols and aldehydes proceeds in the presence of an addition condensation reaction catalyst and an emulsifying dispersant, a condensation reaction product containing finely divided inorganic materials reaches a stable state in which it is uniformly dispersed. This composition component promotes permeation and adhesion to the irregularities on the surface of the graphite particles, and is gelled in this state, so that the adhesive force between the resin and graphite can be increased.

(15) In the above (14), the phenol resin is a resol type phenol resin.

(16) Further, in the above (15), the resol type phenolic resin has pressure-sensitive thermal self-curing property.

(17) A method for producing a fired body according to the present invention is to produce a fired body by firing the molded body produced by the method for producing a molded body according to any one of (9) to (16). It is a feature.

(18) Further, in the above-described (17), the compact is fired in a temperature range of 800 ° C. to 2000 ° C. in a vacuum or an inert gas atmosphere. Is.

  The molded body according to the present invention is a molded body formed by bonding a fine inorganic material as a non-plastic material with a aggregate made of a thermosetting resin, and the aggregate is a composition component of a thermosetting resin. Since a certain monomer and oligomer are gelled in a state where they penetrate and adhere to the surface of the finely divided inorganic material, the fine particles of the finely divided inorganic material are firmly bound by the aggregates, and the molded body As a result, the mechanical strength is high. As a result, for example, cracking does not occur when fired.

It is explanatory drawing of the molded object which concerns on one embodiment of this invention. It is a SEM photograph of graphite used for a molding material of a forming object concerning one embodiment of the present invention. It is a SEM photograph of the molding material (molding material which consists of a graphite granular material and a phenol resin) which concerns on one embodiment of this invention. It is explanatory drawing of the manufacturing method of the molded object by transfer molding which concerns on one embodiment of this invention. It is an enlarged view of the A section enclosed with the circle of FIG. It is a figure which shows typically the molding material of the manufacture process in the manufacturing method of the molded object by transfer molding which concerns on one embodiment of this invention. It is a figure which shows typically one of the graphite granular materials which are the molding materials of the manufacture process in the manufacturing method of the molded object by transfer molding which concerns on one embodiment of this invention. It is a SEM photograph of the molding material in the cavity of the mold in the manufacturing process of the molded body according to one embodiment of the present invention.

  FIG. 1 is a view showing the appearance of a molded body according to the present embodiment, and is an inner pot of an electromagnetic induction heating rice cooker. As shown in FIG. 1, a molded body 47 according to the present embodiment is formed by combining graphite fine particles 49 as fine inorganic particles as non-plastic materials with a condensate 51 made of a thermosetting resin. In the aggregate 51, a monomer and oligomer, which are components of the thermosetting resin, gelled in a state where the monomer and oligomer penetrated and adhered to the surface 49a of the graphite fine particles 49 were heat-cured after molding. Is. In FIG. 1, a part 49 a of the outer peripheral portion of the graphite fine particle 49 is a double line because the monomer and oligomer, which are components of the thermosetting resin, are in the irregularities of the fine particle. It is shown that it is covered with a resin layer that has penetrated and adhered and gelled.

On the surface 49a of the graphite fine particles 49, the composition components of the monomer and oligomer thermosetting resin penetrated and adhered to the irregularities on the surface of the graphite and gelled, so that the graphite fine particles 49 And the thermosetting resin are strongly bonded. As a result, the graphite fine particles 49 including the uncoated portion 49b are also bonded to each other by the aggregate 51 between the adjacent fine particle surfaces that are firmly bonded to the irregularities of the fine particle surfaces. Therefore, the molded body 47 has a mechanical strength capable of withstanding a load such as a load.
In FIG. 1, the entire circumference of the fine particles is not indicated by a double line because graphite is pulverized during the transfer molding process and covered with monomers and oligomers which are resin components of the thermosetting resin. This is due to the appearance of a missing part.

  Next, the process in which the structure of the molded body 47 is generated is exemplified by the case where the inner pot as the molded body 47 is molded by a transfer molding machine. The molding material, molding apparatus, molding process, It demonstrates in order of a baking process and a coating process.

<Molding material>
376 grams of phenol,
360 grams of 50% aqueous formaldehyde,
40 grams of hexamethylenetetramine,
1064 grams of natural graphite with an average particle size of 100 μm
The graphite used for the molding material is one that has passed through a 1 mm square sieve, and those of 500 μm to 1 μm are mixed. Each graphite surface has a large number of irregularities on the surface (see the SEM photograph in FIG. 2).

A reactor equipped with a condenser, a thermometer, and a stirrer is charged with 680 grams of water and 800 grams of water in which 4 grams of hydroxyethyl cellulose as an emulsifying dispersant is dissolved in advance, and reacted at 85 ° C. for 1 hour 30 minutes. It was.
Graphite has excellent hygroscopicity and is hydrophilic. On the other hand, the resin is oleophilic and the affinity between the graphite and the resin is poor, and an effective interface for forming a structure having mechanical strength cannot be formed. Therefore, hydroxyethyl cellulose, which is an emulsifying dispersant, was added to make the composition component of the thermosetting resin and the inorganic material wet easily at the interface, and contact with the surface of the inorganic material powder.

The stirring mixture is initially in a state of flowing with stirring, but the viscosity of the system gradually increases as the reaction proceeds. The produced phenol resin is emulsified when the addition condensation has progressed to some extent, and the hydrophobic phenol resin is uniformly dispersed in water. Further, as the reaction proceeds, a stable state is reached, and a condensation reaction product of phenol and formaldehyde containing graphite is uniformly dispersed throughout the flask. When the reaction of the phenol resin proceeded to the desired degree, the reaction was stopped by cooling to 40 ° C., and 400 grams of water was added.
Next, the resin was filtered off with Nutsche, and the emulsifying dispersant was removed by washing with water. Further, washing with 900 g of water was repeated 5 times until the filtrate was completely colored by the anthrone reagent, and the emulsifying dispersant was completely removed to obtain a sludge product.
The sludge was air-dried and then subjected to a drying process at an internal temperature of 40 ° C. for 48 hours using a vacuum dryer to obtain a black powdery molding material. The water content of this molding material was 0.7% by mass, and the phenol resin adhesion rate in the molding material composed of graphite particles and phenol resin was 19.8% by mass. When the obtained molding material was magnified and observed with a microscope, it was confirmed that the graphite particles were agglomerated and composite particles having an average particle diameter of about 500 μm and formed into a lump (see the SEM photograph in FIG. 3).
The molding material obtained by the above method was coated with the surface of the graphite fine particles always wetted with the phenol resin raw material liquid, so that the outer peripheral surface of the graphite particles and the graphite fine particles were aggregated to form the graphite fine particles. Thus, the inside of the composite particles formed into a lump is a granular molding material in which the inside is held by a phenol resin film.

The molding material obtained as described above was evaluated as follows.
Gelation time: hot plate method (150 ° C.) JIS-K-6910 4.8
-Plate flow: Glass plate (125 ° C) JIS-K-6910 4.7
・ Blocking test equipment:
(1) Flat plate: 150 mm x 150 mm x 5 mm
(2) Cylindrical container: 71 mmφ × 120 mm
(3) Weight: 70mmφ × 160mm, total weight 5kg
(4) Wire mesh: 10 mesh (5) Constant temperature and humidity chamber: 25 ° C., set to 65% Operation: Place a cylindrical container on a flat plate and place it in a constant temperature and humidity chamber with a weight. Place 500 g of the sample in a cylindrical container, place the weight on it, and return to the constant temperature and humidity chamber. After 1 hour, the sample of the cylindrical container was gently taken out on paper, and the weight of the portion that was sieved and formed into a block through a 10-mesh wire mesh was calculated and the ratio (%) to the original weight was calculated.
-Single plate creation: 80g of molding material is charged into a mold (100mm x 100mm) and compression molded (160 ° C)
× 5 minutes × 105 kgf / cm ² ) to prepare a plate having a thickness of 4.0 mm. The bending strength (JIS-K-6911) of the obtained plate was measured.
As a result of the above evaluation test, the gelation time was short and could not be measured, the plate flow was 0 mm, and the blocking rate was 0%. The bending strength was 60 MPa. There was no uneven color or gloss on the surface of the molded product. As a result of visually confirming the cut cross section with a microscope, the dispersibility of graphite was good.

  The adhesion rate of the phenol resin in the molding material composed of the graphite particles and the phenol resin is 18% by mass to 35% by mass, and preferably 18% by mass to 20% by mass. By setting the adhesion rate to 18% by mass to 20% by mass, the phenolic resin coats the surface of the graphite particles when pressed under heating at the melting temperature or higher, and the graphite particles are placed in a suitable position due to the fluidity of the resin. It becomes easy to move. As a result, the state shifts from a state where the bubbles are large to a state where the bubbles are filled. If the bubble is an open cell, the air contained in the molding material by being filled is discharged by a gap between the pot 15 and the plunger 37 or a vacuum ejector as will be described later. For this reason, the gas contained in the molded object 47 can be suppressed to the minimum, and the smoothness of the surface of the molded object 47 can be improved.

Here, the significance of setting the adhesion rate of the phenol resin to the graphite particles within a predetermined range will be described.
When the graphite content is increased, the resin amount is relatively decreased and the mechanical strength is increased, but the fluidity when the molding material is melted and filled in the mold is deteriorated and air is embraced. For this reason, bubbles may remain in the carbonaceous structure obtained by the firing treatment. As a result, the conductivity may be uneven, or the strength may be insufficient to cause cracks or cracks.
In addition to this, if the fluidity deteriorates, uneven distribution of graphite occurs when filling the molding material into the mold, and the electric resistance is high in the flow direction at the time of filling, and the electric resistance is low in the direction perpendicular to the flow direction. Anisotropy of electrical properties may appear. When a carbonaceous molded body having such an electric anisotropy is used for electromagnetic induction heating, heat generation unevenness appears.
In addition, if the flowability of the molding material is poor, friction occurs between the graphite particles during molding that is forcibly filled into the mold at high pressure, and the graphite is crushed into fine particles, and is not crushed. However, it has a large residual stress inside. When such a molded body is removed from the mold, a springback that releases residual stress is generated, and expansion occurs in the flow direction, resulting in distortion. The quality structure may break.
Thus, in the case of molding a molded body having many graphite fine particles, the fluidity of the molding material composed of the graphite fine particles and the resin is important.
In this Embodiment, the adhesion rate of the phenol resin in the molding material which consists of a graphite granular material and a phenol resin is 18 mass%-35 mass%, Preferably it is 18 mass%-20 mass%, The fluidity of the molding material is secured.

<Molding device>
The main part of the transfer molding machine 1 used in this embodiment will be described with reference to FIGS. In FIG. 4, the transfer molding machine 1 is provided with a mold for molding an inner pot of a rice cooker for electromagnetic induction heating. The transfer molding machine 1 is a male which can be moved up and down by being guided by a hydraulic cylinder installed on a base (not shown) and a pole (not shown) fixed to the rod 3 of the hydraulic cylinder and standing on the base. A mold receiver 5, a male mold 7 fixed to the upper surface of the male mold receiver 5, a protruding pin 9 that can move up and down through the male mold 7, and a pole (not shown) erected on the base ) And a female die 13 installed on the lower side of the floating plate 11 and an upper side of the floating plate 11. A pot 15 is provided.

  The top of the female mold 13 and the bottom of the pot 15 are communicated with each other through a communication passage 17 that communicates the two. As shown in FIG. 2, the communication path 17 is gradually reduced in diameter from the bottom side of the pot 15 toward the lower side, and a minimum diameter part 19 is formed in the middle of the communication path 17 so that the path diameter is minimum. The diameter is increased from the minimum diameter portion 19 toward the female mold 13 side so as to reach the female mold 13. That is, the communication path 17 has a funnel shape from the bottom of the pot 15 to the minimum diameter portion 19, and has a trumpet shape from the minimum diameter portion 19 to the female die 13.

  The communication path 17 as described above is formed by a hole 21 formed in the bottom of the pot 15 and a through hole 25 provided in a gate insert 23 installed between the pot 15 and the female mold 13. . As shown in FIG. 5, the hole 21 formed in the bottom of the pot 15 is gradually reduced in diameter downward to form a trumpet shape, and a through hole 25 provided in the gate insert 23 in the hole 21. Is continuous. The gate insert 23 has a head portion 27 whose upper end is enlarged in diameter, and a main body portion 29 is formed in the lower portion of the head portion 27. The vertical section has a substantially T-shape. The gate insert 23 is inserted into the opening 15 provided in the female mold 13 so that the main body 29 is inserted and the head 27 is fitted into the recess 33 provided in the bottom surface of the pot 15. It is installed between the molds 13. The gate insert 23 is formed with a through hole 25 that forms a part of the communication path 17 at the center thereof. The shape of the through-hole 25 is gradually reduced from the head 27 side downward, and a minimum diameter portion 19 having a minimum hole diameter is formed on the way, and a wrapper is formed from the minimum diameter portion 19 toward the lower end. The diameter is expanded.

  The inner diameter of the minimum diameter portion 19 in the communication path 17 is related to the particle size of the inorganic material. When the inorganic material having a maximum length of 500 μm is used, the inner diameter is 4.0 to 7.0 mm, preferably Is from 5.0 to 6.5 mm. Further, the opening angle and length of the trumpet shape of the hole from the smallest diameter portion 19 to the female mold 13 may be determined in consideration of fluctuations in actual molding conditions and lot fluctuations in the molding material. Is practically 30 to 50 degrees and the length is 5 to 15 mm.

  A fixed platen 35 is fixed above the floating plate 11 at an upper position of a pole (not shown), and a plunger 37 is installed on the lower surface of the fixed platen 35. A take-out groove 39 having an inverted trapezoidal vertical cross section is formed at the center of the top surface of the plunger 37. A gap of about 0.01 to 0.02 mm is formed between the plunger 37 and the pot 15. Further, in order to prevent an excessive pressure from being applied to the molded body 47, a gap of 1 to 2 mm is formed between the distal end surface of the plunger 37 and the bottom surface of the pot 15 when the plunger 37 is moved most downward. It has become so.

<Molding process>
A molding method for molding the inner pot of the electromagnetic induction heating rice cooker using the transfer molding machine 1 and the molding material will be described.
The male and female molds 7 and 13, the pot 15, and the plunger 37 are heated in advance to a temperature suitable for the molding material, the rod 3 of the hydraulic cylinder is extended to raise the male mold receiver 5, and the male mold receiver 5 Is brought into contact with the floating plate 11 to form a cavity. When the cavity is formed, the vacuum ejector starts to discharge the gas in the cavity. By further extending the rod 3 of the hydraulic cylinder, the male mold receiver 5 and the floating plate 11 are raised together, the mold is closed, and the molding material formed into a tablet is put into the pot 15.
FIG. 6A schematically shows the molding material stored in the pot 15 of the transfer molding machine 1. The graphite fine particles 49 in the molding material have irregular particle diameters, and large and small particles are mixed. All the surfaces 49 a of the graphite fine particles 49 are covered with a phenol resin layer 53 formed by gelling the short thoughts and oligomers that are resin composition components, and the surface of the graphite fine particles 49 is covered with the phenol resin layer 53. There are air bubbles 55 in between. FIG. 7A is a view focusing on one of the graphite fine particles 49 in this state.

  When the pot 15 is heated, the phenol resin covering the surface of the graphite fine particles is melted to form a molten resin 57. FIG. 6B shows this molten state. As shown in FIG. 6B, the resin layer melts and the graphite fine particles 49 move downward to reduce the particle mutual distance. In this state, the graphite fine particles are still covered with the resin layer formed by gelation. A part of the bubbles 55 is discharged from the gap between the pot 15 and the plunger 37, and a part remains as internal bubbles. By releasing the bubbles 55, the volume of the entire molding material is reduced. That is, L2 in FIG. 6B is shorter than L1 in FIG.

The molding material formed on the tablet is put into the pot 15, and the plunger 37 is inserted into the pot 15. The molding material that is easy to flow due to the heat of the pot 15 is gradually injected into the cavity via the communication path 17. In the process of this injection, as described above, the pores in the molding material become small, and the gas pushed out thereby is discharged by the gap between the pot 15 and the plunger 37 or by the vacuum ejector.
The molding material is pulverized as it passes through the communication path 17 to be in the state shown in FIG.

  The molten molding material that passes through the communication path 17 is compressed at the minimum diameter portion 19 and is released at once in a trumpet-shaped passage immediately after passing through the minimum diameter portion 19 to maintain high fluidity. However, it flows toward the mold end. In a state where the melted molding material is filled in the mold, it is cured by holding the pressure for about 6 to 8 minutes. The lowest movement position of the top surface of the plunger 37 with respect to the bottom surface of the pot 15 is set to be 1 to 2 mm above the bottom surface of the pot 15, and the bottom surface of the pot 15 even when the plunger 37 is moved to the lowest position. A gap is formed between the two. A cull portion 41 made of a cured product of the molding material is formed by the gap. The cull portion 41 refers to a portion in the drawing that is higher than the portion indicated by the broken line in the diagram showing the cull portion 41 in FIG. Cull thickness (material charge) is typically 1 to 2 mm, and if it is thicker than this, excessive pressure is applied, resulting in increased internal stress of the molding material to be filled. When it is thin, insufficient filling occurs and the density of the molding material to be filled is lowered.

Here, the behavior until the molding material accommodated in the pot 15 is injected into the mold cavity will be described by focusing on one of the graphite fine particles 49. The graphite fine particles 49 of the molding material in the pot 15 are covered and covered with a phenol resin layer 53 that has been subjected to permeation and adhesion in the form of monomers and oligomers and subjected to addition condensation (FIG. 7 (a)). In this state, the phenol resin monomer and oligomer penetrate and adhere to the uneven details on the surface 49 a of the graphite fine particles 49.
When the molding material is melted and injected into the mold cavity, the graphite fine particles 49 are pulverized by pressure to become strips having a portion 49a covered with phenol resin and a portion 49b not covered with phenol resin. (FIG. 7 (b)). A melted molten resin 57 exists around the pulverized graphite fine particles 49 (around the portions 49a and 49b). The finely divided graphite fine particles 49 flow in the mold cavity and are filled to the end of the mold. Then, by the heat and pressure maintaining process after filling the mold cavity, the phenol resin and the other resin that have entered the irregularities of the graphite fine particles 49 are adsorbed and hardened to form the aggregate 51, and the graphite fine particles 49 as a whole. The block body is shaped (FIG. 7C).

What is important here is that the peel strength of the portion 49 a covered with the phenol resin layer 53 is high, so that the graphite fine particles 49 are covered with the phenol resin layer 53 as much as possible. For this purpose, it is preferable that the molding material is not atomized when passing through the communication path 17 but is atomized in a state in the pot 15. That is, it is preferable that the graphite used has a small particle size.
In order to maintain the mechanical strength of the compact 47 high, the particle size of the graphite fine particles 49 is reduced so that the graphite fine particles 49 are not crushed when pressurized or passed through the nozzle, so that all the surfaces of the particles It is good to be comprised only by the part coat | covered with the phenol resin layer 53. FIG.
The optimum particle size of the graphite fine particles 49 is determined by the minimum diameter of the communication passage 17 and the injection pressure.

  The cured product that has become insoluble and infusible by the curing reaction is connected to the bottom of the pot 15, the communication path 17, and the cavity. When the hydraulic cylinder is operated in this state and the floating plate 11 and the male mold receiver 5 are lowered together, the cull portion 41 is fixed to the plunger 37 by the take-out groove 39. The upper part is fixed and pulled downward, and as a result, it breaks at the smallest diameter part 19 having the smallest cross section. As a result, the reverse frustoconical cured product 43 formed by the portion above the minimum diameter portion 19 in the cull portion 41 and the communication path 17 is held on the plunger 37 side, and the flow below the minimum diameter portion 19 is maintained. The frustoconical protrusion 45 formed by the path is held on the floating plate 11 side together with the molded body 47.

  The communication path 17 has a trumpet-shaped diameter that is downstream of the minimum diameter portion 19, and after being expanded, communicates with the cavity via a truncated cone-shaped channel. For this reason, when the mold is opened, cutting of the communication path 17 causes a molding failure near the minimum diameter portion, but does not affect the molded body 47 side. And since the truncated cone-shaped convex part 45 formed by the flow path below the minimum diameter part 19 is removed after demolding, the mechanical strength due to poor molding is lowered in the vicinity of the communication flow path in the molded body 47. There is nothing.

Next, when the floating plate 11 is fixed at an intermediate position of the pole and the hydraulic cylinder is further operated to move the male mold receiver 5 downward, a molded body 47 in which the truncated cone-shaped convex portion 45 is integrally formed. Is exposed in a state of being fixed to the male mold 7 side. In this state, the projecting pin 9 is projected to remove the molded body 47. The molded body 47 is removed from the mold and then left to cool. Thereafter, the truncated cone-shaped convex portion 45 is cut off at the base to form a molded body 47. As described above, even if a defective molding portion occurs, the defective molding portion is concentrated on the top of the truncated cone-shaped convex portion 45, and by removing the convex portion 45, defective molding occurs on the molded body 47 side. There is nothing. For this reason, it becomes possible to increase the injection pressure at the time of molding, and a molded body 47 having a bent portion between the distal end portion of the molded body 47 having a long flow length or the communicating path 17 and the distal end portion of the molded body 47 (for example, a pot Can be molded.
The molding material in the mold cavity is kneaded when passing through the communication passage 17 at the time of injection and is further fragmented, and the phenol resin undergoes a curing reaction due to heat retention pressure after filling the mold. It is an inner pot (see SEM photo in Fig. 8).

  In the present embodiment, the pot 15 and the cavity are arranged in the vertical direction via the communication path 17, and the communication path 17 is arranged in the center of the cavity. The molded body 47 having a bent portion between the communication passage 17 and the tip portion of the molded body 47 can be injected evenly into each part. Further, in the present embodiment, the adhesion rate of the thermosetting resin in the molding material is set to 18% by mass to 20% by mass, and the gas in the cavity is forcibly exhausted by the vacuum ejector 53. Therefore, the gas remaining in the molded body 47 can be reduced and the surface of the molded body 47 can be smoothed.

<Baking process>
The obtained molded body 47 is left to stand in an atmosphere of 1000 to 1200 ° C. in a vacuum or an inert gas atmosphere to carbonize the phenol resin that has become an insoluble and infusible cured product. By connecting, a fired body of an inner pot having a pot shape was obtained. At this time, if there is a cracked gas staying in the molded body 47 without condensing from the molded body 47 due to the condensation or carbonization of the phenol resin, the cracked gas causes a local blistering. In order to prevent this, the temperature is gradually raised over one month. The phenol resin used as the binder generates a shrinkage due to the curing reaction, that is, a curing stress accompanying the curing shrinkage in the reaction curing process at the time of molding. In the molding material which is a combination of graphite particles and resin, the generated curing stress is large. If the curing stress is excessive, it is released during the firing process, causing a phenomenon of explosion, resulting in a defective product.

<Coating process>
The inner surface painting process of the inner pot will be described. First, the base coating for cooking is performed. 10 vol% of tetrafluoroethylene / hexafluoropropylene copolymer (4.6 fluoride) (FEP) fine powder is dispersed in an aqueous dispersion of polyethersulfone (PES) to form an undercoat having a low viscosity of 200 centipoise The resin is sprayed several times using a spray until it remains thin on the surface.

Next, surface coating is performed. The liquid resin used for the base coating is in an undried state, and a fine powder of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) compatible with FEP is uniformly adhered to the surface of the liquid resin to absorb the liquid resin. And fix. Thereafter, drying is performed in a 200 ° C. oven for 10 minutes.
Subsequently, it is put into a 360 ° C. furnace in order to perform the fusion treatment. As a result, PES and FEP are melted and joined so as to fit into the pores of the graphite aggregate, and a coating film not containing pores such as pinholes is formed, so that liquid ingredients used for cooking do not penetrate during cooking. Form an embodiment.

  As described above, the compact 47 according to the present embodiment is obtained by combining the graphite fine particles 49 with the aggregate 51 made of a phenol resin that is a thermosetting resin. Since the resin monomers and oligomers are gelled in a state where they penetrate and adhere to the surface of the graphite fine particles 49, the graphite fine particles 49 are firmly bonded to each other, and the mechanical strength of the entire compact 47 is obtained. Is excellent.

Graphite particles in the molding material with respect to falling ball strength and surface smoothness after firing for carbonaceous moldings molded with a transfer molding machine with different types of graphite, particle size, resin blending ratio and molding method Table 1 summarizes the relationship between the amount of phenolic resin and the proportion of phenolic resin. Chinese graphite is granular and Japanese graphite is acicular. In the table, ◯ indicates that the appearance is good and Δ indicates that the surface is rough.
In Table 1, when the molding conditions shown in Table 1 are the same (No. 3-4, No. 5-8, No. 9-11), there is a difference in weight after molding and falling ball strength. This is because the molding was carried out while slightly changing the reaction rate and the reaction time.

As shown in Table 1, when the phenol resin content in the molding material was in the range of 19.5 mass% to 30 mass%, the appearance after firing was beautiful. Moreover, if it is the thing of number 1-10, since falling ball intensity | strength is also 100 mm or more, it can endure practical use.
On the other hand, in the thing of the number 11 which made the resin compounding ratio 18 mass%, the falling ball strength was 50 mm and the appearance was a little inferior, but all were acceptable. The reason why such falling ball strength is obtained even if the resin blending ratio is reduced is that the aggregate that binds the graphite fine particles penetrates the surface of the graphite fine particles with the monomers and oligomers that are the components of the phenol resin. It is considered that the gelation was caused in the attached state.
Regarding the particle size of graphite, 20 μm and 20 μm tend to be slightly better in falling ball strength, but the phenol resin compounding ratio in the molding material is in the range of 18% by mass to 30% by mass. If so, both the falling ball strength and the appearance after firing are acceptable for any particle size.

  From the above considerations, it can be seen that when the phenol resin blending ratio in the molding material is in the range of 18% by mass to 30% by mass, at least the appearance is suitable for practical use. On the other hand, regarding the strength, whether or not it is appropriate is determined according to the intended use. Therefore, when high strength is required, it is desirable to increase the resin blending ratio.

  A molding material having a resin blending ratio of 18% by mass to 30% by mass easily moves graphite particles to a suitable position in the mold when pressed under heating at a melting temperature or higher, that is, has excellent fluidity. Therefore, the appearance of the surface of the molded product after firing is considered good. In addition, the molding material according to the present embodiment in which the resole resin is arranged on the surface of the graphite particles is excellent in fluidity because it is homogeneous, and also in this respect, the appearance of the surface of the molded product after firing is improved. It is done.

In addition, in said embodiment, it demonstrated in detail taking the inner pot of the electromagnetic heating rice cooker shape | molded by the transfer molding method using the graphite particle | grains as an inorganic material.
However, the fired body of the present invention includes not only the inner pot of the electromagnetic induction heating rice cooker but also a plate for frying pan, pan, yakiniku, takoyaki cooker, and the like as an electromagnetic cooker. Moreover, as a molded object before baking, it can be used also as a separator of a hydrogen fuel cell.

DESCRIPTION OF SYMBOLS 1 Transfer molding machine 3 Rod 5 Male die receiver 7 Male die 9 Projection pin 11 Floating board 13 Female die 15 Pot 17 Communication path 19 Minimum diameter part 21 Hole 23 Gate insert 25 Through hole 27 Head 29 Main body part 31 Opening hole 33 Concave portion 35 Fixed platen 37 Plunger 39 Extraction groove 41 Cal content 43 Molten solidified product 45 Convex portion 47 Molded body 49 Graphite fine particle 51 Condensed body 53 Phenolic resin layer 55 Bubble 57 Fusion

Claims (4)

Stirring a liquid containing phenols and aldehydes as reaction components of a resol-type phenolic resin having pressure-sensitive thermal self-curing property, an amine compound as a reaction catalyst , a polymer activator having a glucoside bond as an emulsifying dispersant , and water While adding graphite powder having an average particle diameter of 200 μm or less in the process of addition condensation of the phenols and the aldehydes, and reacting for a predetermined time;
Removing the excess emulsifying dispersant by washing and removing the solid content produced by the reaction and drying to prepare a molding material; and
Placing the molding material in a pot of a transfer molding machine, injecting the molding material melted by heating and pressing into a mold cavity, and molding;
And a step of taking out the molded body after being kept warm and maintained for a predetermined time after being placed in a mold. 2. The method for producing a molded body according to claim 1, wherein a mass ratio of the graphite particles to the resol type phenol resin is in a range of 80.5: 19.5 to 70:30 .   A method for producing a fired body comprising firing a shaped body produced by the method for producing a molded body according to claim 1 or 2 to produce a fired body. The method for producing a fired body according to claim 3, wherein the firing of the formed body is performed in a temperature range of 800 ° C to 2000 ° C in a vacuum or an inert gas atmosphere.