JP2006103099A - Method for producing molded article, and molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a molded article which can produce the molded article without spoiling its quality even when a large amount of a filler is contained in a molding material, and to provide the molded article. <P>SOLUTION: The molding material 1 in which the filler 3 is mixed with a powdered thermoplastic resin 2 to occupy at least 60 vol% of the total volume of the mixture is melted/pressurized by a mold 10 heated at the melting point of the resin 2 or above while being decompressed and cooled together with the mold 10, and the mold 10 is pressurized during the cooling to produce the molding comprising a radiation plate etc. Since the molding material 1 comprising the powdered thermoplastic resin 2 and the filler 3 is press-molded by approximately uniform force, the molding can easily be molded from the molding material 1 containing a large amount of the filler 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a molded article and a molded article comprising a separator for a fuel cell containing a large amount of filler, a heat radiating plate, an electromagnetic shielding casing, and the like.

  A molding material in which a large amount of filler is added and dispersed in a resin, specifically, a molding material in which a filler is added to a resin in a volume ratio of 60 vol% or more in terms of the volume ratio is considered to be used for molding various molded products. As one of the molded products, there is a fuel cell separator that has been attracting attention in recent years.

This fuel cell separator, which is a molded product, is not shown in the figure, but is molded into a thin plate with channels on both front and back surfaces using a molding material consisting of a predetermined resin and a large amount of graphite. Designed to satisfy corrosion resistance (see Patent Document 1). As a method for manufacturing this fuel cell separator, for example, an injection molding method in which a molding material is injected into a cold mold can be considered (see Patent Document 2).
JP 2002-373671 A Japanese Patent Laid-Open No. 2003-242994

  However, it is theoretically difficult to form a molded article such as a fuel cell separator by injection molding because it is not easy to knead a large amount of filler made of graphite into a resin from the viewpoint of fluidity of the molding material. In any case, there is a serious problem that it is extremely difficult in practice, and good characteristics such as conductivity cannot be obtained. In addition, when the molding material is injected into the mold, the cooling and solidification timing is shifted depending on the part, or the pressure distribution is non-uniform. There is often a risk that improvement cannot be achieved.

  The present invention has been made in view of the above, and an object of the present invention is to provide a method for producing a molded product and a molded product that can mold a molded product without impairing the quality even if the molding material contains a large amount of filler. Yes.

In order to solve the above-mentioned problems, the present invention is a method for producing a molded product, in which a molded product is obtained by compression molding using a molding material obtained by adding a filler to a powdered thermoplastic resin in a volume ratio of 60 Vol% or more. And
The molding material is melt-pressed with a mold having a temperature equal to or higher than the melting point of the thermoplastic resin, and the molding material is cooled together with the mold.

  The mold can be melted and pressurized while reducing the pressure. Further, it is possible to melt and press the mold while bumping it. Also, the mold can be pressurized during cooling.

  Moreover, in order to solve the said subject, in this invention, the molded article was manufactured with the manufacturing method of the molded article in any one of Claim 1 thru | or 4.

Further, in the present invention, in order to solve the above-mentioned problems, a method for producing a molded product is obtained by compression molding using a molding material obtained by adding a filler to a powdered thermoplastic resin in a volume ratio of 60 Vol% or more with respect to the whole. Because
The molding material is melt-pressed with a mold having a temperature equal to or higher than the melting point of the thermoplastic resin to primarily form a tablet, and the tablet is secondarily molded with a mold having a temperature equal to or higher than the melting point of the thermoplastic resin. It is characterized by cooling the molded tablet together with the mold.

  Note that the tablet can be primary molded while the mold is decompressed. In addition, the mold can be bumped during the primary molding and / or the secondary molding. It is also possible to pressurize the mold during cooling.

  Furthermore, in order to solve the above-mentioned problems, the present invention is characterized in that a molded product is manufactured by the method for manufacturing a molded product according to any one of claims 6 to 9.

  Here, the filler in the claims includes at least a conductive filler, aluminum oxide, aluminum hydroxide, boron nitrite, metal fiber, carbon fiber, carbon nanotube, and the like. The molded product includes at least a separator for a fuel cell, a heat radiating plate, an electromagnetic shielding housing, and the like.

  According to the present invention, even if a large amount of filler is contained in the molding material, there is an effect that a molded product can be manufactured without impairing the quality.

  Hereinafter, a preferred embodiment of the first invention of the present invention will be described with reference to the drawings. A method for manufacturing a molded article in this embodiment is described in FIG. 1 to FIG. The molding material 1 mixed with the filler 3 is melt-pressed while being decompressed by a mold 10 heated to a temperature equal to or higher than the melting point of the thermoplastic resin 2 to cool the molding material 1 together with the mold 10. Is pressed during cooling to produce a molded product 20 made of a heat sink or the like.

  The molding material 1 includes a predetermined thermoplastic resin 2 that has been pulverized, and a filler 3 that is pulverized and mixed without being kneaded with the thermoplastic resin 2. This molding material 1 is prepared by mixing 60 vol% or more of the filler 3 with the thermoplastic resin 2 in a volume ratio with respect to the whole.

  The thermoplastic resin 2 is not particularly limited as long as it is a powdered thermoplastic resin 2 that is softened by heating and exhibits plasticity, and examples thereof include polypropylene (PP) and polystyrene (PS). The thermoplastic resin 2 is finely pulverized into a size of about 50 to 200 mesh pass, preferably about 100 mesh pass (MAX 150 μm) from the viewpoint of ease of processing and prevention of secondary aggregation, and a required amount is weighed. .

  The filler 3 is made of, for example, powdered aluminum oxide or boron nitrite, and is formed to have an average particle diameter of 10 to 150 μm, preferably 10 to 100 μm, and a required amount is weighed. The reason why the average particle size of the filler 3 is in the range of 10 to 150 μm is that when it is less than 10 μm, the filler 3 rises upon mixing with the thermoplastic resin 2 and the working environment is deteriorated or the electrical characteristics are deteriorated. Conversely, if it exceeds 150 μm, the mechanical properties of the molded product 20 are degraded.

  In the above, when the molded product 20 is manufactured, first, the molding material 1 is put into a heated mold 10 (see FIG. 1), and the mold 10 is clamped and heat compression molded in a vacuum. Thus, the molding material 1 is melt-pressed (see FIG. 2). The mold 10 is connected to a vacuum device for pressure reduction, and is heated in advance to a temperature equal to or higher than the melting point of the thermoplastic resin 2 of the molding material 1 by a method such as hot air bath, infrared rays, and high frequency preheating before heat compression molding. The mold 10 can be heated after the molding material 1 is charged.

  At the time of this heat compression molding, in order to improve the strength of the molded product 20, to prevent deterioration of flatness, or to degas, the mold 10 that has been clamped is fixed a predetermined number of times (for example, 1 to 6 times). ) Open and close and bump (see Fig. 2).

  When the molding material 1 is melt-pressed and heat-compressed into a predetermined shape, the mold 10 is removed from the molding machine, and the mold 10 is transferred to a cooler having a pressurizing mechanism to transfer the molding material 1 to the mold 10. Then, the molded product 20 can be manufactured by opening the mold 10 and removing the mold 10 (see FIG. 3). Examples of the method for cooling the mold 10 include a method in which the mold 10 is left to cool to room temperature and a method in which cooling water is used.

  According to the above method, since the molding material 1 composed of the particulate thermoplastic resin 2 and the filler 3 is press-molded with a substantially uniform force, the molded product 20 is easily molded with the molding material 1 containing a large amount of the filler 3. can do. In addition, the compression molding method is used instead of the injection molding method in which the pros and cons of molding is greatly influenced by the fluidity of the molding material 1, so that the molded product 20 can be prevented from warping, bending, etc. Improvements can be made. Moreover, according to this method, since it cools in a pressurization state, the molded article 20 can be obtained, without causing the fall of the characteristic by loose contact of the fillers 3 and what is called a spring back.

  Further, when using a thermosetting resin, after the resin flows and fills the space between the fillers 3, the mold cannot be opened until the curing is completed. As a result, the molding cycle may be lowered. Not a few. In view of this point, when adopting a formulation that accelerates the curing time in order to increase the molding cycle, curing starts before the resin fills the filler 3, resulting in a decrease in strength due to the occurrence of voids, unfilled in a complicated shape, etc. There may be drawbacks.

  On the other hand, according to the present embodiment, since the time for curing is not required by using the thermoplastic resin 2, the molding cycle can be shortened, and the molding material 1 has a temperature equal to or higher than the melting point. During this period, fluidity is maintained, so that generation of voids and unfilling can be suppressed. Furthermore, such an effect can be increased by molding under vacuum.

  Next, a preferred embodiment of the second invention of the present invention will be described with reference to the drawings. A method for manufacturing a molded article in this embodiment is shown in FIG. 4 to FIG. The molding material 1 in which a large amount of electrically conductive filler 3A is mixed with the plastic resin 2 is melt-pressed while being decompressed by a primary molding die 11 having a temperature equal to or higher than the melting point of the thermoplastic resin 2 to primary-mold the tablet 4; The tablet 4 is subjected to secondary molding by a secondary molding die 12 having a temperature equal to or higher than the melting point of the thermoplastic resin 2, and the secondary molded tablet 4 is cooled together with the secondary molding die 12, and the secondary molding is performed. The mold 12 is pressurized during cooling to manufacture a fuel cell separator 21 which is a molded product 20.

  The molding material 1 includes a predetermined powdered thermoplastic resin 2 and a conductive filler 3A that is powdered and mixed without being kneaded into the thermoplastic resin 2. In order to ensure the conductivity of the fuel cell separator 21, the thermoplastic resin 2 and the filler 3 </ b> A have a volume ratio of the filler 3 </ b> A of 60 vol% or more, preferably about 60 to 85 vol%, more preferably about 75 vol%. To be mixed.

  The thermoplastic resin 2 is not particularly limited as long as it is a powdered thermoplastic resin 2 that is softened by heating and exhibits plasticity. For example, LCP, polyacetal, polyoxymethylene, polyformaldehyde (POM), Polypropylene, polyphenylene ether (PPE), polyphenylene sulfide (PPS), polystyrene, polyvinylidene fluoride (PVDF), vinyl chloride (VC) and the like are used. The thermoplastic resin 2 is finely pulverized into a size of about 50 to 200 mesh pass, preferably about 100 mesh pass, from the viewpoint of ensuring conductivity, ease of processing, and preventing secondary aggregation, and the required amount is weighed. The

  The filler 3A is not particularly limited as long as it is a conductive particle material. For example, natural graphite, artificial graphite, carbon fiber, metal fiber, carbon fiber, carbon nanotube, or the like is used. Among these, natural graphite and artificial graphite are optimal from the viewpoint of reducing the resistance value and preventing the mechanical strength from being lowered.

  The filler 3A is adjusted to an average particle size of 10 to 150 μm, preferably 10 to 100 μm, and a required amount is weighed. The average particle size of the filler 3A is in the range of 10 to 150 μm because, when the average particle size is less than 10 μm, it soars when mixed with the thermoplastic resin 2 and the working environment is deteriorated and the electrical characteristics are deteriorated. is there. Conversely, when the average particle diameter exceeds 150 μm, the mechanical characteristics of the fuel cell separator 21 deteriorate.

  In the above, when manufacturing the fuel cell separator 21, first, the molding material 1 is put into the primary molding die 11 having a predetermined temperature (see FIG. 4), and the primary molding die 11 is used under vacuum. The tablet 4 of the fuel cell separator 21 is melt-pressed and molded into a predetermined shape, and the primary molding die 11 is cooled to a temperature not higher than the melting point and taken out from the primary molding die 11 for primary molding (see FIG. 5). ).

  The primary molding die 11 is connected to a vacuum device for pressure reduction, and is preheated to a temperature equal to or higher than the melting point of the thermoplastic resin 2 in advance before heat compression molding. Examples of a method for preheating the primary molding die 11 include a hot air bath, infrared rays, and high frequency preheating. The primary molding die 11 can be heated after the molding material 1 is introduced. By performing such primary molding, it is possible to prevent voids and unfilled materials from being formed when molding a low-fluidity material containing a large amount of filler, such as the molding material of the fuel cell separator 21. .

  Next, the tablet 4 is transferred from the primary molding die 11 to a secondary molding die 12 having a predetermined temperature, and is heated and compressed by the secondary molding die 12 to perform secondary molding (see FIG. 6). The secondary molding die 12 is preheated to a temperature equal to or higher than the melting point of the thermoplastic resin 2 before heat compression molding. Examples of a method for preheating the secondary molding die 12 include the hot air bath, infrared rays, high frequency preheating and the like.

  In the case of secondary molding, in order to further improve the strength of the fuel cell separator 21 or to reduce the resistance value, the compression / decompression is repeated several times (bumping) during compression molding, and the filler 3A is densely filled. It is preferable.

  When the tablet 4 is secondary molded, the tablet 4 is transferred from the molding device to a cooling press device, which is another dedicated device, together with the secondary molding die 12 and subjected to secondary molding in a compression-pressed state from the viewpoint of preventing spring back. If the mold 12 is cooled and then removed from the secondary molding mold 12, a fuel cell separator 21 as the molded article 20 can be manufactured (see FIG. 7). Examples of the method for cooling the tablet 4 together with the secondary molding die 12 include a method in which the tablet 4 is left to cool to room temperature and a method in which cooling water is used.

  As shown in FIG. 8, the fuel cell separator 21 is formed into a flat rectangular thin plate provided with a surpane-type flow path 22 on the front and back surfaces, and satisfies gas impermeability, conductivity, and corrosion resistance. .

  According to the above, since the particulate molding material 1 is press-molded with a substantially uniform force, the fuel cell separator 21 can be easily molded using the filler 3A made of a large amount of graphite. Good conductivity can be obtained. In addition, the fuel cell separator 21 can be prevented from warping or bending while achieving both electrical properties and mechanical properties, and quality can be improved.

  In addition, when using a thermosetting resin, after the resin flows and fills the space between the fillers 3A, the mold cannot be opened until the curing is completed. As a result, the molding cycle may be lowered. Not a few. Therefore, if a prescription that accelerates the curing time is adopted in order to increase the molding cycle, curing starts before the resin fills the filler 3A. As a result, there are defects such as a decrease in strength due to the generation of voids and unfilling in a complicated shape. It sometimes occurred.

  On the other hand, according to the present embodiment, since the time for curing is not required by using the thermoplastic resin 2, the molding cycle can be shortened, and the molding material 1 has a temperature equal to or higher than the melting point. During this period, fluidity is maintained, so that generation of voids and unfilling can be suppressed. Furthermore, an increase in the effect can be expected by molding under vacuum.

  Further, since the molding is performed twice, that is, the primary molding and the secondary molding, the gap between the thermoplastic resin 2 and the filler 3A can be filled to further improve the mechanical strength. In addition, since the primary molding is performed before the secondary molding, there are few burrs and the handling is really simple. Furthermore, since the primary molding is performed under vacuum, it is possible to effectively remove bubbles between the thermoplastic resin 2 and the filler 3A, improve the strength, or prevent deterioration of the value of the required characteristics such as conductivity. It becomes possible.

  In the above embodiment, the secondary molding is simply performed, but the pressure may be reduced during the secondary molding. Further, when it is desired to lower the resistance value of the fuel cell separator 21, carbon fibers or carbon nanotubes may be positively used. Further, the shape and size of the fuel cell separator 21 can be appropriately changed. Furthermore, the molded product 20 other than the fuel cell separator 21 can be manufactured by the above manufacturing method.

Hereinafter, the manufacturing method of the molded product of the first invention according to the present invention and examples of the molded product will be described together with comparative examples.
Example

First, a molding material is prepared by mixing graphite as a filler with a powdery PP, which is a thermoplastic resin, at a volume ratio of 70 vol% with respect to the whole, and the molding material is heated to a temperature equal to or higher than the melting point of PP. The molding material was melt-pressed by closing the mold and heat compression molding under vacuum. As graphite, 8020S [manufactured by Tokai Carbon Co., Ltd .: trade name] was used. The compression molding was performed under conditions of a molding pressure of 200 kgf / cm ² (200 kgf / cm ² = 19.6 MPa) 240 ° C. for 5 minutes.

Once the molding material is melt-pressed and heat-compressed into a predetermined shape, the mold is removed from the molding machine, the molding material is cooled together with the mold while the mold is still pressed, and then the mold is molded. It was opened and demolded to produce a molded product made of a heat sink. The cooling was allowed to stand until the mold reached 50 ° C.
When a molded product composed of a heat radiating plate was manufactured, the thermal conductivity of the molded product was measured based on the disc heat flow meter method and summarized in Table 1.

Comparative Example A molding material was prepared so that the volume ratio of 70% by volume of graphite as a filler to PP as a thermoplastic resin was used as a filler, and injection molding was attempted. However, graphite could not be filled. Therefore, a molding material was prepared by mixing graphite with PP at a volume ratio of 30 Vol% so that graphite could be filled. Others were the same as in the Examples, and the thermal conductivity was measured and summarized in Table 1.

Results According to the present example, unlike the comparative example, good thermal conductivity was confirmed for the molded product made of the heat sink.

Next, a method for manufacturing a molded product according to the second invention of the present invention and an example of the molded product will be described together with a comparative example.
Example 1

Powdered thermoplastic resin, PPS, is mixed with graphite as a filler at a volume ratio of 75% by volume with respect to the whole to prepare a molding material, and the mixed molding material is subjected to primary molding having a temperature equal to or higher than the melting point of PPS. While being decompressed by a mold, it was melt-pressed to primarily form a fuel cell separator tablet. Torelina E2180 (manufactured by Toray Industries, Inc .: trade name) having an average particle diameter of 70 μm was used as PPS, and 8020S (manufactured by Tokai Carbon Co., Ltd .: trade name) was used as graphite. Primary molding was performed under conditions of a molding pressure of 100 kgf / cm ² (100 kgf / cm ² = 9.8 MPa), 370 ° C., and 5 minutes.

  Next, the tablet is subjected to secondary molding while being bumped five times by a secondary molding die having a temperature equal to or higher than the melting point of PPS. The secondary molded tablet is cooled together with the secondary molding die, and the secondary molding die is cooled. The mold was pressurized during cooling to produce a fuel cell separator measuring 160 mm long × 120 mm wide × 2 mm thick.

The bumping was performed in a range of a pressurizing pressure of 0 to 200 kgf / cm ² . Secondary molding was performed under conditions of a molding pressure of 200 kgf / cm ² and 370 ° C. for 5 minutes. Further, for cooling, the secondary molding die was transferred to another cooling press apparatus, and the secondary molding die was left to be 100 ° C. in a pressurized state of 100 kgf / cm ² .
When a fuel cell separator was manufactured, the electrical resistance value, bending strength, bending strain, thickness variation, and warpage of the fuel cell separator were measured and summarized in Table 2.

In measuring the electrical resistance value, first, four fuel cell separators are cut into a size of 5 cm × 5 cm, and the four pieces to be measured are stacked in the vertical direction, and the resistance value R ₁ is set as the resistance. as measured by instrumental, in four of the measured piece, its after the resistance value R ₂ was measured by the resistor was calculated by R 1 _{-R 2/2} stacked two of the measured pieces vertically.

Example 2
Basically, it was the same as in Example 1, but the tablet was secondarily molded without bumping with a second molding die having a temperature equal to or higher than the melting point of PPS.

Comparative Example 1
Powdered thermosetting resin, PF (phenol resin), is mixed with graphite at a volume ratio of 75% by volume with respect to the whole to prepare a molding material. This molding material is a mold having a temperature equal to or higher than the melting point of PF. After the molding, the molded tablet was cooled together with the mold and demolded to obtain a fuel cell separator. Bell pearl S99W [manufactured by Kanebo Co., Ltd .: trade name] was used as the PF. The other parts were the same as in Example 1.

Comparative Example 2
A molding material was prepared in such a manner that the volume ratio of graphite to PPS was 75% by volume, and injection molding was attempted using this molding material. However, the molding material was insufficient in fluidity and could not be filled. Therefore, a molding material was prepared in a volume ratio of 55 Vol% with respect to the whole graphite in PPS so that the graphite could be filled, and this molding material was injection molded into a mold to obtain a fuel cell separator. The other parts were the same as in Example 1.

Results In the case of Examples 1 and 2, it was possible to obtain fuel cell separators having good electrical and mechanical properties.
On the other hand, in the case of Comparative Examples 1 and 2, there were cases where electrical properties and mechanical properties could not be made compatible in a good state. In Comparative Example 2, PPS and graphite could not be kneaded so that the most important electrical resistance value was less than 100 mΩ · cm.

It is a section explanatory view showing typically the state where a molding material is thrown into a metallic mold in an embodiment of a manufacturing method of a molded product of the 1st invention concerning the present invention. FIG. 2 is an explanatory cross-sectional view schematically showing a state in which the mold of FIG. 1 is clamped and heated and compressed under vacuum. It is explanatory drawing which shows typically the state which opens the metal mold | die of FIG. 2 and demolds a molded article. It is explanatory drawing which shows typically the state which throws into the primary molding die the molding material in embodiment of the manufacturing method of the molded article of 2nd invention which concerns on this invention. It is explanatory drawing which shows typically the state which preforms the tablet of the separator for fuel cells under vacuum with the primary shaping die of FIG. It is explanatory drawing which shows typically the state which moves a tablet from the primary shaping | molding die of FIG. 5 to a secondary shaping | molding die, and performs this shaping | molding. It is explanatory drawing which shows typically the state which cools a tablet with the secondary shaping | molding die of FIG. 6, and demolds. It is a perspective explanatory view showing typically the separator for fuel cells in the manufacturing method of the 2nd invention concerning the present invention, and the embodiment of a molded product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding material 2 Thermoplastic resin 3 Filler 3A Filler 4 Tablet 10 Mold 11 Primary molding die 12 Secondary molding die 20 Molded product 21 Fuel cell separator (molded product)

Claims (10)

A method for producing a molded product, which is compression-molded using a molding material in which a filler is added to a powdered thermoplastic resin in a volume ratio of 60 vol% or more with respect to the whole, to obtain a molded product,
A method for producing a molded product, characterized in that a molding material is melt-pressed with a mold having a temperature equal to or higher than a melting point of a thermoplastic resin, and the molding material is cooled together with the mold.   The method for producing a molded article according to claim 1, wherein the mold is melt-pressed while the pressure is reduced.   The method for producing a molded article according to claim 1 or 2, wherein the mold is melt-pressed while bumping.   The method for producing a molded article according to claim 1, 2 or 3, wherein the mold is pressurized during cooling.   A molded product produced by the method for producing a molded product according to claim 1. A method for producing a molded product, which is compression-molded using a molding material in which a filler is added to a powdered thermoplastic resin in a volume ratio of 60 vol% or more with respect to the whole, to obtain a molded product,
The molding material is melt-pressed with a mold having a temperature equal to or higher than the melting point of the thermoplastic resin to primarily form a tablet, and the tablet is secondarily molded with a mold having a temperature equal to or higher than the melting point of the thermoplastic resin. A method for producing a molded product comprising cooling a molded tablet together with a mold.   The method for producing a molded product according to claim 6, wherein the tablet is primary molded while the mold is decompressed.   The method for producing a molded product according to claim 6 or 7, wherein the mold is bumped during primary molding and / or secondary molding.   The method for producing a molded product according to claim 6, 7 or 8, wherein the mold is pressurized during cooling.   A molded product manufactured by the method for manufacturing a molded product according to any one of claims 6 to 9.

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