JP2010179542A - Degassing filter for carbon injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a degassing filter for carbon injection molding enabling a molded product to keep a dense and smooth appearance even in the vicinity of a degassing hole of the molded product and have improved strength and thermal conductivity. <P>SOLUTION: The degassing filter 10 for carbon injection molding is arranged in the final filling portion of a mold used for injecting a molding material or a mixture of a carbon particle and a binder as major components. In the case the filter has a hold part contacting the mold 2 to be held by the same and a body out of contact with the mold 2 and includes an outline forming holder 3 and a particulate resin 6 to be filling the body. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure of a mold for forming a carbon agglomerate for use in a cooking utensil such as a rice cooker capable of electromagnetic induction heating, and more specifically, a carbon particle and a binder that is a high carbon content substance. The present invention relates to a degassing filter for carbon injection molding that is used for decompression exhaust in a mold when a main molding material is injection molded.

  An electromagnetic heating cooker such as a stove or rice cooker is made by laminating a clad material in which a magnetic metal that generates heat due to eddy currents from an induction heating coil and aluminum or copper with high thermal conductivity is processed into a pan shape. It has the feature that uniform heating can be obtained by heat transfer. However, it is difficult to process the clad material into a shape such as a pan or a pot, and there is a problem that the respective laminated interfaces of the heat-resistant resin coating surface such as fluororesin are easily peeled off.

  For this reason, the use of carbon aggregates having high thermal conductivity in addition to excellent conductivity and dielectric properties has been proposed as a material for cookers for electromagnetic induction heating to replace conventional iron and stainless steel. (For example, refer to Patent Document 1).

  In addition, a cut product of a carbon compression body that has been pressed and condensed into a columnar shape has been introduced, and some describe that a carbon material is effective as a cooking utensil to be used at high temperatures (for example, patent documents) 2).

  According to the above-described cooking utensil manufacturing method, a compression molded product of a mixture of carbon particles such as coke and a high carbon content such as phenol or pitch as a binder is condensed at 1000 to 3000 ° C. in an oxygen-free atmosphere. After obtaining a compressed carbon body, it was cut into an arbitrary shape. However, cutting the carbon compression body into an arbitrary shape has a problem that a large amount of material is discarded in the concave portion of the container that occupies most of the cutting, and the number of processing steps is large.

  In addition, it is difficult to detect in advance defects existing in the carbon compression body, and the design and the various characteristics such as heat generation characteristics are adversely affected by being exposed after cutting.

  As a means to solve these problems, a molding material, which is a mixture of carbon particles and a binder material such as a phenol resin raw material liquid and tar pitch, is injected into a mold, pressed, and molded. Means have been devised to obtain a carbon aggregate formed into a pan shape by firing the formed product (see, for example, Patent Document 3).

  However, it is important to reduce the content of phenolic resin, which is a binder, in order to obtain a molded product with excellent strength, electrical conduction, and heat conduction, which are the characteristics required of cooking utensils capable of electromagnetic induction heating. is there. On the other hand, if the content of the phenolic resin in the molding material is reduced, the surface of the carbon powder particles is not sufficiently wet and tends to agglomerate, and the fluidity is lost and it becomes easy to form an unfilled portion. For this reason, in order to obtain a molding material that enables stable injection molding, it is important to sufficiently wet the surface of carbon powder particles with a binder such as phenol resin to reduce the apparent viscosity and improve the fluidity. It becomes.

  However, in molding materials with a large amount of binder added, the internal stress generated by shrinkage due to flow and curing in the mold tends to remain, and the weld is a weak part of the strain release behavior during the firing stage of the molded product. And cracks starting from the bubbles remaining in the inner layer where the coarse particles gather and the adhesion between the particles is insufficient, and a large amount of decomposition gas such as phenol resin collects to generate blisters There was a problem.

  In other words, in order to obtain uniform and high physical properties, it is important to ensure a good flow state of the molding material while discharging gas such as air in the mold, such as phenol resin that is a molten binder. While it is essential to improve the binder and molding pressure, air in the mold during the curing stage during injection molding and various by-product gases associated with the curing reaction of the binder interfere with filling and cause bubbles in the molded product. Will be promoted. For this reason, it is not sufficient to discharge gas from the mating surfaces of the molds according to the pressure at the time of molding, and it has been necessary to provide gas vent holes for performing vacuum exhaust at the final filling position of the molds.

  In order to solve the above-mentioned problems caused by increasing the amount of the binder such as phenol resin in order to improve fluidity in addition to increasing the injection pressure so that the carbon particles are in close contact with each other, the molding material For the purpose of suppressing the outflow of gas, means for suppressing by evacuating by providing pores in the mold or installing a filter having fine pores has been used.

  For example, a tire vulcanization mold having a porous filter made of PTFE (polytetrafluoroethylene) particles has been proposed. The porous filter uses fine particles of 1 to 5 μm and has a void ratio of 40% or more (see, for example, Patent Document 4).

JP-A-9-75211 JP-A-9-70352 JP 2007-04257 A Japanese Patent Laid-Open No. 10-044154

  However, in order to prevent the molding material from leaking from the vent holes in the final filling portion, the flow resistance caused by the impregnation of the molding material into these filters is used to suppress the outflow. As a result, the productivity has been reduced.

  On the other hand, there is a means to prevent the molding material from flowing out by applying a compressive force to the porous filter and using a sponge-like material that compresses and eliminates the pores held by the filter. The stress load required for this increases the amount of deformation of the filter and relieves the stress applied to the flow end portion of the molded product. This results in inhibiting the close contact of particles and the elimination of residual bubbles.

  The present invention has been made to solve the above-described problems, and ensures a dense and smooth appearance even in the vicinity of the vent hole of a molded product, and the strength and heat conduction of the molded product. The present invention provides a degassing filter for carbon injection molding that can improve the rate.

The degassing filter for carbon injection molding according to the present invention includes a degassing hole for carbon injection molding disposed in a final filling portion of a mold for injection molding a molding material mainly composed of carbon powder and a binder. Filter for
A holder having a holding part that is held in contact with the mold and a body part that is not in contact with the mold, and forming an outline;
And a granular resin filled in the body.

  The degassing filter for carbon injection molding according to the present invention includes a degassing hole for carbon injection molding disposed in a final filling portion of a mold for injection molding a molding material mainly composed of carbon powder and a binder. Filter for use, comprising a holding part held in contact with a mold, a body part not in contact with the mold, a holder forming an outer shell, and a granular resin filled in the body part Therefore, by applying pressure when the molding material is completely filled in the mold, the granular resin in the softened state is deformed by being placed above the gas vent hole, and the voids between the particles are reduced and further blocked to form the molding material. It has the effect of suppressing the discharge of water.

FIG. 5 shows the first embodiment and is a cross-sectional view showing a state in which a gas vent hole filter 10 is installed in a mold 2. FIG. 5 shows the first embodiment, and is a cross-sectional view of the main part near the opening 2a of the mold 2. FIG. FIG. 3 shows the first embodiment, and is a cross-sectional view of the gas vent hole filter 10. It is a figure shown for the comparison, and sectional drawing which shows the structure of the filter 20 for degassing holes filled with porous bodies, such as the foaming urethane which has the conventional sponge form.

Embodiment 1 FIG.
First, an outline of the present embodiment will be described. The present embodiment relates to the production of a carbon aggregate molded product used for a cooking utensil capable of electromagnetic induction heating. As a means of obtaining a molded product by pressure filling by injection molding into a heated mold, a mixture of an uncured phenol resin and carbon particles of a molding material is placed in the bottom of the mold and placed in a reduced pressure state. In order to maintain, the structure of the gas vent filter (the gas vent filter for carbon injection molding) located at the final filling portion of the molding material is optimized.

  The degassing hole filter has a structure filled with resin granules such as PET (polyethylene terephthalate) having a diameter of 0.5 to 3.0 mm inside, and serves as a filter for preventing the molding material from flowing out. Bear.

  In the non-pressurized state in which the molding material is not filled, it is possible to evacuate from the gap between the granular resins. However, in the state in which the molding material is filled and pressurized in the mold, depending on the mold temperature and the applied pressure It is deformed so as to fill the gap, and the gap is closed, thereby preventing the molding material from flowing out. In other words, the portion that does not come into contact with the mold retains the gap, but the temperature of the portion that comes into contact with the mold reaches the softening point and deforms to close the gap between the granular resins.

  Even if the viscosity is high, such as injection molding, if the pressure is high, it is essential to use a high-strength porous member to suppress external outflow using small pores and long passage distances. In another example, the pores included in the filter were deformed and blocked to prevent outflow, but the injection pressure was dissipated during the deformation, leading to deterioration in the appearance and characteristics of the molded product.

  The present embodiment can exhibit a filter function that suppresses discharge of the molding material due to the clogging of the gap due to the deformation caused by the pressure received by the filter for vent hole. Since the deformation of the particles closes the gap between the particles only by exhibiting a slight displacement at the pressure when the molding material is completely filled in the mold, the pressure drop in the mold due to injection molding can be suppressed.

  As a result, even in the vicinity of the vent hole of the molded product, the pressure inside the mold by injection molding can be sufficiently maintained, so that bubbles remaining inside are crushed and miniaturized to ensure a dense and smooth appearance. In addition, it is possible to provide features that improve strength and thermal conductivity.

  In the means for forming the inner pot of a rice cooker by injection molding in which a mixture of carbon powder and binder is used as a raw material, the structure of a gas vent filter disposed in the mold and used for vacuum exhaust and The mechanism will be described in detail below.

  FIGS. 1 to 3 are diagrams showing the first embodiment. FIG. 1 is a cross-sectional view showing a state where the gas vent hole filter 10 is installed in the mold 2. FIG. 2 is a schematic view of the vicinity of the opening 2a of the mold 2. FIG. FIG. 3 is a sectional view of the degassing hole filter 10.

  FIG. 4 is a view for comparison, and is a cross-sectional view showing a structure of a conventional vent hole filter 20 filled with a porous body 5 such as foamed urethane having a sponge shape.

  Use as a molding material a mixture of carbon granules obtained by pulverizing petroleum coke in the oxygen-free state by calcination at high temperature (about 3000 ° C) and pulverizing to 0.3 mm or less and uncured phenol resin It was.

  Next, this molding material was injection-molded in a mold heated to about 160 ° C., cured after a holding time of 3 minutes, and then a molded product serving as an inner pot of the rice cooker was taken out of the mold. .

  The obtained molded product was left in an oxygen-free atmosphere at about 1200 ° C. to carbonize the phenol resin, thereby obtaining a carbon aggregate molded product having a pan shape. At this time, the phenol resin was completely cured in a low temperature region of about 250 ° C. and then carbonized in an oxygen-free atmosphere in a further high temperature region. At this time, the decomposition of the phenolic resin becomes active and sudden weight loss occurs in order to prevent local bulging caused by the cracked gas staying inside the molded product without being diffused from the molded product and generating fault cracks. In the vicinity of 350 ° C., 500 ° C., and 800 ° C., it is effective to raise or hold the temperature slowly.

  In the production process of these series of inner pots (panned carbon aggregate molded products), the air in the mold when the molding material flows in the mold to suppress cracks and blisters in the firing process. Therefore, it is important to discharge the air smoothly so that it does not become a load, and to make it fine by crushing the air entrained during the flow with the injection pressure. I made it.

  A gas vent filter 10 installed in the mold 2 will be described with reference to FIGS. 1 to 3. The degassing hole filter 10 is arranged substantially at the center of the bottom surface 2b portion of the mold 2 that is finally filled with the injected molding material, and maintains an exhausted state in which the inside of the mold is decompressed.

  Next, the molding material that has melted the binding material and has flowed is injected into the mold. Since the inside of the mold is maintained at a reduced pressure, the remaining air is compressed and reaches the degassing hole filter 10 in the final filling portion without causing flow resistance.

  The degassing hole filter 10 is installed in an opening 2 a formed substantially at the center of the bottom surface 2 b of the mold 2.

  As shown in FIG. 3, the holder 3 forms an outer shell of the gas vent hole filter 10. The holder 3 has a trunk portion 3a and a holding portion 3b.

  The holding portion 3b has an exhaust hole 7 having a honeycomb structure inside, and is fixed in contact with the mold 2. The outer diameter of the holding part 3b is 8 mm in an example. The holding | maintenance part 3b is comprised with a highly heat conductive metal.

  As shown in FIG. 1, the body 3 a constituting the lower part of the gas vent hole filter 10 is held without being in contact with the mold 2. Between the trunk | drum 3a and the metal mold | die 2, the space | gap 4 of 1.0-2.5 mm is provided and arrange | positioned. The inside is filled with granular resin 6 having a diameter of 0.5 to 1.0 mm and a softening point of 155 ° C. The trunk portion 3a is made of a low thermal conductivity material having lower thermal conductivity than the holding portion 3b.

  The degassing hole filter 10 installed in the mold evacuates using a depressurization device (not shown) connected thereto, but when the mold 2 is opened, the outside air is degassed. The cooling effect is produced by passing through the filter 10. Accordingly, the holding part 3b of the gas vent hole filter 10 fixed to the mold 2 is transferred to heat and reaches the vicinity of the mold temperature, but the body part 3a remains at a temperature lower by about 15 ° C.

  When the mold 2 was closed in this state and the inside was kept in a reduced pressure state, the molding material was injected and filled in the mold 2. At this stage, the temperature of the granular resin 6 filled inside and located in the vicinity of the holding portion 3b reaches the temperature of the mold 2, but the granular resin 6 in the body portion 3a is held at a sufficiently low temperature. .

  The injected molding material reaches the gas vent hole filter 10 at the final filling position while filling the gap in the mold 2. Since the molding material needs to have the characteristics of heat generation efficiency and heat transfer by electromagnetic induction heating, the addition amount of the substance to be melted such as a phenol resin which is a binder mixed with the carbon particles is about 20 to 35%. It is. As a result, the molding material has a very high viscosity and is heated in the flow process to be in a temperature state close to the temperature of the mold 2.

  The granular resin 6 filled in the degassing hole filter 10 reached by the molding material is subjected to the injection pressure of the molding material, and the granular resin 6 located in the vicinity of the holding portion 3b is deformed so that the voids between the particles are formed. Will be blocked. On the other hand, since the granular resin 6 in the trunk portion 3a has not reached the softening point, it is possible to keep the mode and minimize deformation.

  The granular resin 6 is a composite granular processed product in which 40 wt% pulp fiber is mixed and uniformly dispersed in high-viscosity polypropylene, and has a softening point near the mold temperature and has a very high viscosity. Since it has thixotropy, even if it softens, it only deforms and does not flow. Therefore, if the granular resin 6 in the body portion 3a maintains the condition that does not exceed the softening point, the molding material does not pass through the voids between the particles because it stops in the body portion 3a without flowing. .

  From the gate part provided in the outer peripheral part of the opening part with which the inner pot of a rice cooker is arranged in the metal mold | die 2 used as the final filling part of the molding material with the gas vent hole filter 10 mentioned above, carbon particle and The molding material kneaded with the uncured phenol resin is injected into the mold, and the molding material is overfilled so that the molding material slightly leaks from the mating surface of the mold. The leakage state of the material and the appearance state around the vent hole of the obtained molded product were observed.

  As a result, in the case of the gas vent hole filter 20 filled with the porous body 5 such as urethane foam having a conventional sponge shape shown in FIG. 4, the molding material is contained in the pores having a diameter of about 0.1 mm. Although impregnation was observed, it was confirmed that a void was formed in the outer peripheral portion in contact with the opening 2a of the mold 2 holding the porous body 5, and the air flowed out from the gap to the reduced pressure exhaust pipe path.

  On the other hand, according to the degassing hole filter 10 having the structure of the present embodiment shown in FIGS. 1 to 3, the granular resin 6 in the vicinity of the holding portion 3b on the holder 3 is accompanied by excessive filling of the molding material. Since it is heated and deformed near the softening point by pressurization and pressed against the outer periphery of the mold 2 in contact with the holder 3 and the voids between the particles are reduced, the flow path of the molding material is blocked to prevent leakage. I confirmed that

  Further, since the granular resin 6 in the lower body portion of the holder 3 is significantly lower than the softening point, it hardly deformed and supported the granular resin 6 subjected to deformation in the vicinity of the holding portion 3b.

  The sponge-like porous body 5 in the conventional gas vent hole filter 20 is compressed from the original thickness of 10 mm to 2 mm, whereas the gas vent hole filter having the structure of the present embodiment is used. In No. 10, it was confirmed that the depression was 1 mm or less.

  As a result, in the vicinity of the conventional vent hole filter 20, many bubbles remained on the surface to form a fluffy and no gloss, but the vent hole filter 10 according to the present embodiment is not glossy. It was confirmed that the vicinity had a smooth appearance with a gloss that was not different from other parts.

  The gas vent hole filter 10 according to the present embodiment does not require the entire filter to be replaced every time it is molded. It is only necessary to replace part of the granular resin 6 in the vicinity of the holding part 3b where the molding material remains and the holding part 3b heated and deformed in the vicinity of the softening point.

  Here, the granular resin 6 is made of a composite of pulp fibers with high viscosity PP, but instead of this, PS (polystyrene) or ABS resin (acrylonitrile, butadiene, styrene) may be used. It is also possible to use a fiber obtained by defibrating glass fiber or rock wool instead of pulp fiber, and the same effect can be obtained.

  2 Mold, 2a Opening, 2b Bottom, 3 Holder, 3a Body, 3b Holding part, 4 Air gap, 5 Porous body, 6 Granular resin, 7 Exhaust hole, 10 Degassing hole filter, 20 Degassing hole filter .

Claims (4)

A gas injection hole filter for carbon injection molding disposed in a final filling portion of a mold for injection molding a molding material mainly composed of carbon particles and a binder,
A holder having a holding part held in contact with the mold and a body part not in contact with the mold, and forming an outer shell;
A carbon injection degassing filter, comprising: a granular resin filled in the body portion.   2. The degassing filter for carbon injection molding according to claim 1, wherein the holding portion fixes and holds the body portion below the holding portion without coming into contact with the mold.   The said holding | maintenance part contact | abutted with the said metal mold | die is comprised with a high heat conductive metal, and the said trunk | drum part which is not contact | abutted with the said metal mold | die is comprised with a low heat conductive substance, The Claim 1 or Claim 2 characterized by the above-mentioned. Filter for degassing carbon injection molding.   The degassing filter for carbon injection molding according to any one of claims 1 to 3, wherein the granular resin is a composite with a fibrous material having a softening point near the mold temperature.

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