KR20110117745A - Device for manufacturing a separator of fuel cell, method for manufacturing a separator of fuel cell, and separator of fuel cell manufactured by the method - Google Patents

Abstract

A molding apparatus for a fuel cell separator, a molding method for a fuel cell separator, and a fuel cell separator molded by the molding method are disclosed. The method for forming a fuel cell separator according to the present invention comprises injection molding a thermoplastic resin composition in a molten state including 70 to 90% by weight of a conductive filler composed of carbon fiber and carbon graphite. A method of molding a separator, the method comprising: (a) heating a first mold and a second mold to form a cavity space; (b) when the first mold and the second mold are heated to 260 to 300 ° C., injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space; (c) pressing at least one of the first mold and the second mold in a direction in which the volume of the cavity space is reduced to fill the thermoplastic resin composition injected into the cavity space having the reduced volume; And (d) cooling the first mold and the second mold at a cooling rate of 200 to 400 ° C./min, respectively.

Description

Device for manufacturing a separator of fuel cell, method for manufacturing a separator of fuel cell, and separator of fuel cell manufactured by the molding apparatus of the fuel cell separator, the molding method of the fuel cell separator, and the fuel cell separator molded by the molding method the method}

The present invention relates to a molding apparatus for a fuel cell separator, a molding method for a fuel cell separator, and a fuel cell separator molded by the molding method, and more particularly, is provided in a fuel cell to function as a separation membrane of fuel gas and air. An apparatus for molding a separator, a molding method of a separator, and a fuel cell separator molded by the molding method.

Recently, fuel cells have been attracting attention from the viewpoint of environmental protection and energy saving, and in particular, development of fuel cells for automobiles has been actively performed. A fuel cell is a device that generates electricity by using an electrolysis reaction using a fuel gas containing hydrogen and air containing oxygen. Since such a fuel cell has a low voltage that can be taken out from a unit cell, it is generally configured by stacking tens to hundreds of unit cells in series. In such a structure in which each unit cell is stacked, a separator that functions as a separation boundary film of fuel gas and air is required.

In general, compression molding, milling machining, and the like are mainly used for molding the separator. However, when the compression molding or the milling machine is used, the separator is easily brittle and the corrosion resistance is weak. Furthermore, the secondary process is required for the processing of the flow path, and thus the manufacturing cost is very high. . Therefore, in order to form a separator not only having excellent mechanical strength and corrosion resistance but also having a low molding cost, research on a new molding method and apparatus is necessary. The starting point of the new research is injection molding, but the thermoplastic resin composition containing very low fluidity materials such as carbon fiber and carbon graphite as the conductive filler is very low in moldability, and thus the injection molding of the fuel cell separator which becomes thinner by injection molding alone. The specification could not be satisfied.

In the case of the thermoplastic resin composition composed of 80% by weight or more of conductive filler made of carbon fiber and carbon graphite and 20% by weight or less of organic material, the shape of the separator is perfectly formed because excessive injection pressure is required in general injection molding. There was a limit in obtaining even surface roughness. This non-uniformity of the surface roughness is caused by the protrusion of the filler, resulting in deterioration of corrosion resistance. For this reason, in the past, graphite (carbon black), or a mixture of carbon fiber and graphite, has been molded into a separator by compression molding or a milling machine while taking secondary processing.

The biggest problems in the conventional separator molding process are brittleness and high processing cost. Conventional separators are composed of pure graphite or a mixture of graphite and carbon fiber, and the compression process formed by heat and pressure alone is performed due to the low-flexural strength and impact strength of the molded product. It causes extremely weak problems in shock, and this problem has emerged as the biggest improvement in the development of fuel cells for automobiles, a key industry of fuel cell application. In addition, in the fuel cell for vehicles, it is essential to reduce the overall volume of the fuel cell, and further, even if the unit cells are stacked in a small amount, high electrical conductivity must be realized. For this purpose, a very thin separator is required. However, the conventional method has a limitation in that it is difficult to economically produce a very thin separator in large quantities. In particular, the milling process after the compression process has a disadvantage in that it is extremely vulnerable to the molding of the thin film type separator, such as the separator easily broken during the process.

The present invention has been made to solve the above problems, an object of the present invention is to apply a high-temperature mold heating technology and injection compression technology to heat and cool the mold rapidly to enable mass production of fuel cell separator at low cost It is to provide a molding apparatus for a fuel cell separator.

In addition, another object of the present invention is to provide a fuel cell separator molded by the molding method and the fuel cell separator molded by the molding method to enable the mass production of fuel cell separator at a low cost by applying a combination of ultra-high temperature mold heating technology and injection compression technology. It was to provide.

In order to achieve the above object, the molding apparatus of the fuel cell separator according to the present invention is a thermoplastic resin composition in a molten state comprising a conductive filler of 70 to 90% by weight composed of carbon fiber and carbon graphite (carbon graphite) An apparatus for molding a fuel cell separator by injection compression molding, comprising: a first mold; A linear movement is possible in a direction approaching and spaced apart from the first mold, and when forming the first mold and forming a cavity space with the first mold, the volume of the cavity space is changed according to the distance to the first mold A second mold; Heating means for heating the first mold and the second mold at a heating rate of 400 to 800 ° C./min, respectively; A first cooling member capable of linearly moving between a contact position where thermal conductivity occurs in contact with the first mold and a spaced position spaced apart from the first mold; A second cooling member capable of linearly moving between a contact position where the thermal conductivity occurs in contact with the second mold and a spaced position spaced apart from the second mold; Cooling means for cooling the first cooling member and the second cooling member at a cooling rate of 200 to 400 ° C / min, respectively; Injection means for injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space when the first mold and the second mold are heated to 260 to 300 ° C; And at least one of the first mold and the second mold to linearly drive the first cooling member and the second cooling member and to reduce the volume of the cavity space so that the injected thermoplastic resin composition is filled in the cavity space. It is characterized in that it comprises a; pressing means for pressing in a direction approaching the other mold.

In addition, the molding method of the fuel cell separator according to the present invention by injection molding the thermoplastic resin composition in a molten state comprising a conductive filler of 70 to 90% by weight consisting of carbon fiber (carbon fiber) and carbon graphite (carbon graphite) A method of forming a separator for a fuel cell, the method comprising: (a) heating a first mold and a second mold to form a cavity space; (b) when the first mold and the second mold are heated to 260 to 300 ° C., injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space; (c) pressurizing at least one of the first mold and the second mold in a direction in which the volume of the cavity space decreases, thereby filling the injected thermoplastic resin composition in the reduced cavity space; And (d) cooling the first mold and the second mold at a cooling rate of 200 to 400 ° C./min, respectively.

In addition, the fuel cell separator according to the present invention is injection-molded a thermoplastic resin composition in a molten state including 70 to 90% by weight of a conductive filler composed of carbon fiber and carbon graphite to form a fuel cell separator. 1. A method of forming a metal mold comprising: (a) heating a first mold and a second mold to form a cavity space; (b) when the first mold and the second mold are heated to 260 to 300 ° C., injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space; (c) pressurizing at least one of the first mold and the second mold in a direction in which the volume of the cavity space decreases, thereby filling the injected thermoplastic resin composition in the reduced cavity space; And (d) cooling the first mold and the second mold at a cooling rate of 200 to 400 ° C./minute, respectively.

According to the present invention, it is possible to mass-produce a fuel cell separator at low cost by applying an ultra high temperature mold heating technique and an injection compression technique for rapidly heating and cooling a mold.

1 is a schematic cross-sectional view of a molding apparatus for a fuel cell separator according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a process of injecting a thermoplastic resin composition in the molding apparatus shown in FIG. 1.
FIG. 3 is a schematic cross-sectional view illustrating a process in which the volume of the cavity space is reduced in the state shown in FIG. 2 so that the thermoplastic resin composition is completely filled in the cavity space.
4 is a schematic cross-sectional view for explaining a process of taking out the molded separator.
5 is a flowchart of a method of forming a separator for a fuel cell according to the present invention.

The present invention relates to an apparatus, a method for forming a fuel cell separator by injection compression molding a thermoplastic resin composition, and a separator molded by the method.

In particular, in this embodiment, the thermoplastic resin composition is composed of 70 to 90% by weight of conductive filler and 10 to 30% by weight of thermoplastic resin composed of carbon fiber and carbon graphite. Here, the carbon fiber and carbon graphite is preferably contained in 10 to 20% by weight. If the carbon fiber is less than 10% by weight, the flexural strength and cracking improvement effect is remarkably inferior; if the carbon fiber exceeds 20% by weight, there is a problem in feeding the carbon fiber, so that the carbon fiber is not properly mixed. Because. In addition, the carbon graphite is preferably contained in 60 to 70% by weight. If carbon graphite is less than 60% by weight, D.O.E. It is impossible to realize the conductivity performance over the target index of 100S (Simense), and if the carbon graphite exceeds 70% by weight, it is impossible to make injection molding or to form a constant thickness depending on the carbon fiber content. For losing. Where D.O.E. indicates the U.S. Department of Energy.

Meanwhile, in the case of carbon fiber, it is preferable to coat the surface of the fiber with silane or stearic acid. This is because silane or stearic acid coatings increase compatibility, increase flexural strength, and improve cracking. In addition, it is preferable to contain a modified organic material grafted with 1 to 5% by weight of maleic anhydride, such as polypropylene or polyphenylene sulfide (PPS), as a compatibilizer for the thermoplastic resin and the conductive filler. As the compatibilizer, maleic anhydride is most preferably applied at 3% by weight. When the content of the maleic anhydride grafted modified organic material is less than 1%, the compatibility of carbon fiber with the base resin is lowered, and the effect of cracking is lowered. If the content is more than 5%, the flow length of the material is shortened by reducing the fluidity of the material. This reduces the moldability of the separator. If the compatibility is greatly improved in this way, brittleness and flexural strength are significantly improved.

When the separator is molded from the thermoplastic resin composition configured as described above, not only the electrical conductivity is significantly improved, but also the corrosion resistance is greatly improved, and further, the brittleness is remarkably improved.

In addition, the molding apparatus of the present embodiment implements injection compression molding, more specifically injection press molding. Here, in injection compression molding, the distance between the first mold and the second mold, which forms the cavity space from the start of molding to the end of molding, is varied. Therefore, a type called an injection press for advancing and compressing the first mold or the second mold after injection is also included in injection compression molding.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic cross-sectional view of a molding apparatus of a fuel cell separator according to an embodiment of the present invention, Figure 2 is a schematic cross-sectional view for explaining a process of injecting a thermoplastic resin composition in the molding apparatus shown in FIG. FIG. 3 is a schematic cross-sectional view illustrating a process in which the volume of the cavity space is reduced in the state shown in FIG. 2 so that the thermoplastic resin composition is completely filled in the cavity space, and FIG. 4 illustrates a process of taking out the molded separator. Is a schematic cross-sectional view.

1 to 4, the molding apparatus 100 of the separator for fuel cells according to the present embodiment includes a first mold 10, a second mold 20, heating means, and a first cooling member 40. ), A second cooling member 50, a cooling means, an injection means, and a pressing means.

The first mold 10 and the second mold 20 form a cavity space C through which the thermoplastic resin composition is injected during molding. The cavity space C is partitioned by the cavity face 11 of the first mold and the core face 21 of the second mold. Both the first mold 10 and the second mold 20 may be installed to be linearly movable in a direction approaching and spaced apart from each other, in this embodiment only the second mold 20 is installed to be linearly movable. The volume of the cavity space C is variable depending on the relative distance between the first mold 10 and the second mold 20. That is, as shown in FIG. 2, when the molds 10 and 20 are joined together, as shown in FIG. 3, the mold moves so that the distance between the first mold 10 and the second mold 20 is reduced. If it is reduced, the volume of the cavity space C is also reduced. The first mold 10 and the second mold 20 are formed with a first stopper 12 surface and a second stopper surface 22, respectively. The first stopper surface 12 and the second stopper surface 22 are disposed on a plane different from the cavity surface 11 and the core surface 21, respectively. The insertion hole 13 through which the nozzle 70 is inserted is formed in the center of the first mold 10.

In addition, the first mold 10 and the second mold 20 are coupled to the first support member 15 and the second support member 25.

The first support member 15 and the second support member 25 each have a plate shape. The first through hole 151 and the second through hole 251 are formed to step through the first support member 15 and the second support member 25, respectively. The stepped portions of the first support member 15 and the second support member 25 face each other, and the first mold 10 and the second mold 20 are inserted and supported in the stepped portions, respectively. Accordingly, the first support member 15 and the first mold 10 and the second support member 25 and the second mold 20 move together. The surface of the first support member 15 and the surface of the second support member 25 are disposed on the same plane as the first stopper surface 12 and the second stopper surface 22, respectively.

Heating means for heating the first mold 10 and the second mold 20, as shown in Figure 1 is embedded in the first heat transfer heater 31 and the second mold embedded in the first mold The second electrothermal heater 32 is included. When power is applied to the first heat transfer heater 31 and the second heat transfer heater 32, heat is generated, and the temperature of the first mold 10 and the second mold 20 is increased. Here, the first mold 10 and the second mold 20 is preferably rapidly heated at a heating rate of 400 to 800 ℃ / min, in particular the first mold and the second mold at a heating rate of 600 ℃ / minute Most preferred is rapid heating. If the heating rate is less than 400 ° C./min, as the heating is delayed, the total cycle time becomes longer, resulting in lower productivity. A maximum of 28 seconds is required for heating to a temperature suitable for injection described later, and a heating time of 28 seconds or more increases unnecessary waiting time beyond the opening and closing time of the mold. In addition, it is not preferable to set the heating rate to 800 ° C / min or more because it is very difficult and uneconomical. In particular, it is preferable to heat the first mold 10 and the second mold 20 to a temperature suitable for injection, for example, 260 to 300 ° C, and most preferably to 280 ° C. When the first mold 10 and the second mold 20 are heated to below 260 ° C., the flow field of the formed separator may not be perfectly formed, and excessive thickness deviations, for example, between the vicinity of the gate and the opposite side of the gate, for example 0.5 It is not preferable because it occurs up to mm to 1.5 mm. In addition, when the first mold and the second mold are heated to 300 ° C. or higher, there is no problem in the flow field of the formed separator, but post-processing is required due to burr generation due to high temperature, and the filling amount in the cavity space is equal to the amount of burr generation. This deficiency causes a slight shrinkage from the outside of the molded article, and thus a thickness variation occurs to a level of 0.1 mm, and furthermore, the deformation of the first mold and the second mold is caused, which is not preferable. Here, it is preferable that the temperature of 260-300 degreeC or 280 degreeC is set to the temperature of the cavity surface 11 and the core surface 21. As shown in FIG.

The first cooling member 40 is for cooling the first mold 10. The first cooling member 40 is linearly movable between the separation position shown in FIG. 1 and the contact position shown in FIG. 2. When the first cooling member 40 is disposed at a spaced position, the first cooling member 40 and the first mold 10 do not contact each other. In this state, the first mold 10 is heated, and then injection is performed. When the first cooling member 40 is disposed at the contact position, the first cooling member 40 and the first mold 10 come into contact with each other. In this state, when the first cooling member 40 is cooled, the first mold 10 may be indirectly cooled through heat conduction.

Like the first cooling member 40, the second cooling member 50 may also be linearly moved between the spaced position shown in FIG. 1 and the contact position shown in FIG. 2. In the spaced position, the second mold 20 is heated, in the contacted position, the second cooling member 50 is cooled and the second mold 20 is indirectly cooled through heat conduction.

In addition, the first cooling member 40 and the second cooling member 50 are coupled to the first linear moving member 45 and the second linear moving member 55, and the first linear moving member 45 and the second linear member 55 are connected to each other. It linearly moves together with the linear member 55. The first linear moving member 45 and the second linear moving member 55 have a plate shape. In addition, insertion holes 41 and 451 through which the nozzles 70 are inserted are formed in the first cooling member 40 and the first linear movement member 41, respectively, and the insertion holes 41 and 451 are insertion holes of the first mold. It is arranged coaxially with (13).

In addition, linear movement of the first mold 10, the second mold 20, the first cooling member 40, and the second cooling member 50 may include a plurality of guide rods 80 and a plurality of guide cylinders 81. Guided by. Each guide rod 80 penetrates through the second supporting member 25 and is fixed to the second linear moving member 55. Each guide cylinder 81 penetrates through the first supporting member 15 and is fixed to the first linear moving member 45. Each guide cylinder 81 is formed with a guide hole 811 through which the guide rod 80 is inserted. In addition, a first compression coil spring 46 is installed between the first support member 15 and the first linearly movable member 45, and between the second support member 25 and the second linearly movable member 55. The second compression coil spring 56 is installed.

Cooling means is for cooling the first mold 10 and the second mold 20, as shown in Figure 1 inserted into the first cooling pipe 61 and the second mold inserted into the first mold The second cooling pipe 62 is included. The first cooling pipe 61 and the second cooling pipe 620 correspond to a flow path through which a cooling medium, for example, coolant, circulates, and instead of the first cooling pipe 61 and the second cooling pipe 62, the corresponding cooling pipe 61 and the second cooling pipe 62 correspond to each other. The flow path may also be formed in the first mold and the second mold, respectively. By circulating the second cooling pipe 62, the temperature of the first mold 10 and the second mold 20 can be lowered, where the first mold 10 and the second mold 20 are reduced. Rapid cooling at a cooling rate of 200 to 400 ° C./min is preferred, particularly at 300 ° C./min, most preferably cooling rate is the most important factor in determining cycle time. The longer the time for cooling the mold to the ejection temperature, for example 60 ° C., the lower the productivity and shrinkage As the size increases, it becomes difficult to manage the separator specifications, and if the cooling rate is less than 200 ° C / min, the thickness deviation will be greater than (-) 0.5 mm in the area between the gate and the opposite side as the shrinkage increases. In addition, this thickness variation corresponds to the tolerance of the contact surface in the stack structure of each unit cell of the fuel cell, and causes a problem of leakage of hydrogen, fuel, or water, which is a reactant thereof, and a cooling rate of 400 ° C / min or more. It is very difficult and uneconomical to set.

The injection means is for injecting the molten thermoplastic resin composition into the cavity space C through the nozzle 70. The injection means is composed of an injection molding machine (not shown) including a thermoplastic resin composition injection cylinder, an injection screw installed in the injection cylinder, and a hydraulic motor for driving the injection screw. Let's do it. Injection is preferably performed when the first mold 10 and the second mold 20 are heated to 260 to 300 ° C, and most preferably, when heated to 280 ° C. In addition, the volume of the thermoplastic resin composition in the molten state to be injected is preferably 75% to 85%, and most preferably 80% of the volume of the cavity space (C) shown in FIG. If the injection amount is less than 75%, the surface roughness of the molded article becomes bad due to excessive injection compression process, causing a problem in the surface roughness, and when the injection amount is more than 85%, it causes the unmolding according to the flow field distance of the injection molding.

The pressurizing means may be spaced apart from each other in a direction and spaced apart from each other in order to drive the first cooling member 40 and the second cooling member 50 in a straight line, respectively. In the direction of pressure. In addition, the pressing means pressurizes the second linear moving member 55 in the direction approaching the first mold 10 even when the second cooling member 50 is disposed at the contact position. As such, when the second linear movement member 55 is pressurized even in the contact position, the volume of the cavity space C is reduced, whereby the thermoplastic resin composition injected into the cavity space C is a cavity space ( It is filled in the whole of C). Here, the linear movement of the second linear moving member 55 is made until the moment when the first stopper surface 12 of the first mold and the second stopper surface 22 of the second mold contact each other.

Pressing means is for pressing the first linear movement member 45 and the second linear movement member 55, a pair of driving the first linear movement member 45 and the second linear movement member 55, respectively It may be configured in a known configuration such as a hydraulic cylinder, such a configuration is already well known, so a detailed description thereof will be omitted.

On the other hand, in order to control the heating means, the cooling means and the pressurization means according to the process conditions, a control means is further required. Since the configuration of such control means is already well known, a detailed description thereof will be omitted.

Hereinafter, an example of a process of manufacturing a separator using the molding apparatus 100 of the fuel cell separator configured as described above will be described with reference to FIG. 5.

As shown in FIG. 1, in a state where the first mold 10 and the second mold 20 are spaced apart from each other, and the first cooling member 40 and the second cooling member 50 are disposed at a spaced position, respectively. By applying power to the first heat transfer heater 31 and the second heat transfer heater 32, the first mold 10 and the second mold 20 by heating at a heating rate of 400 to 800 ℃ / min, The temperature of the mold and the second mold is to be 260 to 300 ℃ (S100).

As described above, in the state in which the mold is heated, the hydraulic cylinder is operated to move the first linear moving member 45 and the second linear moving member 55 in a direction approaching each other. In this process, the first cooling member 40 and the second cooling member 50 are respectively disposed in the contact position (S110). Thereafter, the hydraulic cylinder for the first linear movable member does not operate any more and only the hydraulic cylinder for the second linear movable member is operated so that the second linear movable member 55 approaches the first linear movable member 45. Keep moving. As such, when the second linear movement member 55 is linearly moved, the first mold 10 and the second mold 20 are combined to form a cavity space C as shown in FIG. 2 (S120). Then, the thermoplastic resin composition is injected into the cavity space (C) shown in FIG. 2 (S130), but only by 75% to 85% of the volume of the cavity space, and the injection part is converted to the pressure holding process.

Thereafter, the operation of the first heat transfer heater 31 and the second heat transfer heater 32 is stopped and the coolant is circulated in the first coolant pipe 61 and the second coolant pipe 62 (S140). Of course, during the circulation of the cooling water, the first mold 10 and the second mold 20 are no longer heated. When the coolant is circulated in this manner, the first mold 10 and the second mold 20 are cooled by heat conduction. At this time, the first mold 10 and the second mold 20 are quenched at a cooling rate of 200 to 400 ° C / min by adjusting the circulation rate of the cooling water or the temperature of the cooling water. Here, the first mold and the second mold are quenched until they reach 60 ° C.

Then, during the cooling of the first mold and the second mold, the second linear moving member 55 is linearly driven toward the first linear moving member, and as shown in FIG. 3, the first stopper surface 12 of the first mold is shown. ) Is linearly driven until it comes into contact with the second stopper surface 22 of the second mold. As such, when the second linear movement member 55 is driven, the injected thermoplastic resin composition is filled in the entirety of the reduced cavity space C while the volume of the cavity space C is reduced (S140). When the molding is completed after a predetermined time, the first mold 10 and the second mold 20 are moved in the mutually open direction to take out the molded separator (S150).

As described above, according to the present embodiment, a fuel cell separator can be produced in large quantities at low cost by using a thermoplastic resin composition containing 70 to 90% by weight of a conductive filler composed of carbon fiber and carbon graphite as a raw material. In particular, the produced separators are significantly improved in electrical conductivity, cracking and corrosion resistance compared to the conventional.

In addition, by coating carbon fibers with silane or stearic acid or by adding a modified organic material grafted with maleic anhydride, for example, a thermoplastic resin such as polypropylene or PPS, cracking and bending strength can be greatly improved. do.

And, for the implementation of the present embodiment, it is preferable to use the ultra-high temperature mold heating technology (E-MOLD) method developed by the applicant. Here, the ultra-high temperature mold heating technology rapidly heats a mold by using a pair of molds that form a cavity space and a relative movement with respect to each mold, and a cooling member that cools the mold by thermal conduction, as shown in FIG. 1. The technique which improved the moldability by cooling is referred to. In addition, in order to overcome the limitation of the moldability by injection molding, by utilizing the injection compression molding and the double-sided heating of the cavity space, it is possible to reduce the thickness variation of sex products.

In particular, when the ultra-high temperature mold heating technology is used as in this embodiment, the carbon fiber and the carbon graphite are completely wrapped by the thermoplastic resin, unlike the molding itself, which is difficult in the general injection molding technology. Since graphite is not exposed, the corrosion resistance of the molded article can be significantly improved. In addition, since the first mold and the second mold can be rapidly heated to the melting temperature (Tm) of the organic material or higher, for example, 260 to 300 ° C., the surface roughness can be made uniform, and the thickness of the molded article is also uniform. I can do it.

Example

In order to verify the formability according to the conductive filler content, the PPS resin is carriered and contains 60 wt% (type A), 70 wt% (type B) and 80 wt% (type C) conductive filler, respectively. A thermoplastic resin composition was prepared. Then, injection compression molding is performed for each type using E-MOLD (a mold commercialized as an E-MOLD by the applicant) and a high speed electric injection machine (product of NIIGATA MACHINE TECHNO Co., Ltd.) to which the ultra-high temperature mold heating technology shown in FIG. 1 is applied. In addition, injection molding was performed up to 80% of the flow length of the molded products, and the remaining 20% were simultaneously subjected to injection compression molding. Here, the length of the flow field means the distance from the gate to the end of the molded article. The design size of the molded article was 100 * 100 * 1.1 mm (channel thin film part 0.4 mm) [width * length * thickness], and detailed process conditions were set as follows.

1. Mold heating heat source: E-MOLD Electric Heater

2. Mold temperature: injection time 280 ℃, ejection time 60 ℃

3. Injection Molding Machine: NIIGATA MD-350X (Clamping Force 350 Ton)

4. Injection machine cylinder temperature

   300/350/340/330/320/290/270 (N1 / N2 / C1 / C2 / C3 / C4 / C5)

5. Injection pressure: 250MPa in all sections

6. Injection speed: 150mm / sec for all sections

7. V-P switching position: 15㎜

8.V-P pressure (injection compression): 60% (Clamping Force 350Ton)

9. VP speed (speed of injection compression): 200㎜ / sec

And, in order to compare the results for the above example, three comparative examples were experimented together as follows.

Comparative example  One

For each type, the molded article was molded by injection molding. At this time, the mold was heated to 110 ° C using warm oil, and a high speed electric injection machine (NIIGATA Machine Techno) was used as the injection molding machine. Detailed process conditions are as follows.

1. Mold heating heat source: warmer

2. Mold temperature: injection point, 110 ℃ / blowout temperature, 60 ℃

3. Injection Molding Machine: NIIGATA MD-350X (Clamping Force 350Ton)

4. Injection machine cylinder temperature

   300/350/340/330/320/290/270 (N1 / N2 / C1 / C2 / C3 / C4 / C5)

5. Injection pressure: 250MPa in all sections

6. Injection speed: 150mm / sec for all sections

Comparative example  2

For each type, the molded article was molded by injection molding. At this time, E-MOLD (mould commercialized by E-MOLD by the applicant) and high-speed electric injection machine (product of NIIGATA MACHINE TECHNO Co., Ltd.) to which ultra high temperature mold heating technology was applied were used, and the mold was heated to 280 ° C. Detailed process conditions are as follows.

1. Mold heating heat source: E-MOLD Electric Heater

2. Mold temperature: Injection time, 280 ℃ / Blowing temperature, 60 ℃

3. Injection Molding Machine: NIIGATA MD-350X (Clamping Force 350Ton)

4. Cylinder temperature

   300/350/340/330/320/290/270 (N1 / N2 / C1 / C2 / C3 / C4 / C5)

5. Injection pressure: 250MPa in all sections

6. Injection speed: 150mm / sec for all sections

Comparative example  3

As in Example, molded articles were molded by injection compression for each type. The injection molding was performed up to 80% of the flow length of the molded products, and the remaining 20% were injection-molded simultaneously. Detailed process conditions are as follows.

1. Mold heating heat source: warmer

2. Mold temperature: injection point, 110 ℃ / blowout temperature, 60 ℃

3. Injection Molding Machine: NIIGATA MD-350X (Clamping Force 350Ton)

4. Injection machine cylinder temperature

   300/350/340/330/320/290/270 (N1 / N2 / C1 / C2 / C3 / C4 / C5)

5. Injection pressure: 250MPa in all sections

6. Injection speed: 150mm / sec for all sections

7. V-P switching position: 15㎜

8.V-P pressure: 60% (Clamping Force 350Ton)

9.VP speed: 200㎜ / sec

As described above, <Table 1> can be obtained by measuring the flow field length of sex products for Examples, Comparative Examples 1, 2 and 3, respectively.

division Flow field length (mm) Mold temperature A Type (60%) B Type (70%) C Type (80%) Comparative Example 1 46 21 11 110 ℃ Comparative Example 2 85 76 69 280 ℃ Comparative Example 3 78 65 58 110 ℃ Example 100 100 100 280 ℃

Table 1 shows that mold temperature and injection compression molding are directly linked to moldability improvements. As PPS resin, resin with high melting point (melting point: 280 ℃) is used, and when the content of filler is very high, if the mold temperature is set high, the frictional stress due to the temperature variation between the resin front end and the mold surface is minimized. It can be seen that the moldability can be improved. This can be easily seen through the results of Comparative Example 1 and the examples. In addition, the injection speed and the injection pressure of the high-speed electric injection machine alone, the moldability is insufficient, it can be seen that injection compression molding can be used to solve this lack of moldability. This can be easily seen through the results of Comparative Example 3 and the examples.

<Table 2> is a table summarizing the results of molding the molded article of the C type material having the highest filler content among the three types of materials and analyzing the properties thereof.

Properties unit D.O.E Standard Comparative Example 1 Comparative Example 2 Comparative Example 3 Example Electrical conductivity S / Cm More than 100 89.3 108.7 75.8 109.9 Contact resistance Ohm / Cm 0.01 or less 0.011 0.0092 0.0132 0.0091 Flexural strength psi More than 3,625 3,109 4,196 3,082 4,303 Product appearance - - X △ X ○ Thickness deviation Mm - 0.28 0.16 0.21 0.04

Here, the thickness deviation refers to the thickness deviation between the gate portion and the end of the molded article.

Referring to Table 2, in the embodiment according to the present invention, the ultra-high temperature mold heating technology and the injection compression technology are used together, so that the physical properties of the molded separator can be remarkably improved compared to other comparative examples.

In particular, since the molded separator is stacked in a stack form, minimizing thickness variation is most important to meet the external characteristics of the separator. In addition, according to the present invention, it can be seen that the electrical conductivity is also excellent.

As described above, according to the present embodiment, the carbon graphite and the like are prevented from protruding from the surface due to the uniform transfer of the surface resin layer, and as a result, the bending strength is very excellently measured. This is because carbon graphite prevents the starting point of cracking at the surface.

As mentioned above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the technical idea of the present invention. It is obvious.

1. 1st mold 11 ... cavity surface
12 1st stopper face 13,41,451 Insert hole
15 ... 1st support member 20 ... 2nd mold
21 core surface 22 second stopper surface
25.2nd support member 31 ... 1st electric heater
32.2nd electric heater 40 ... 1st cooling member
45 ... 1st linear moving member 46 ... 1st compression coil spring
50 ... 2nd cooling member 55 ... 2nd linear moving member
56 2nd compression coil spring 61 ... 1st cooling pipe
62.2nd cooling pipe 70 ... nozzle
80.Guide rod 81 ... Guide cylinder
151 ... first through hole 251 ... second through hole
811 guiding hole C ... cavity space
Molding apparatus for fuel cell separator

Claims (16)

An apparatus for molding a fuel cell separator by injection molding a thermoplastic resin composition in a molten state comprising 70 to 90% by weight of a conductive filler composed of carbon fiber and carbon graphite.
First mold;
A linear movement is possible in a direction approaching and spaced apart from the first mold, and when forming the first mold and forming a cavity space with the first mold, the volume of the cavity space is changed according to the distance to the first mold A second mold;
Heating means for heating the first mold and the second mold at a heating rate of 400 to 800 ° C./min, respectively;
A first cooling member capable of linearly moving between a contact position where thermal conductivity occurs in contact with the first mold and a spaced position spaced apart from the first mold;
A second cooling member capable of linearly moving between a contact position where the thermal conductivity occurs in contact with the second mold and a spaced position spaced apart from the second mold;
Cooling means for cooling the first cooling member and the second cooling member at a cooling rate of 200 to 400 ° C / min, respectively;
Injection means for injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space when the first mold and the second mold are heated to 260 to 300 ° C; And
At least one mold of the first mold and the second mold is linearly driven to drive the first cooling member and the second cooling member, and the volume of the cavity space is reduced so that the injected thermoplastic resin composition is filled in the cavity space. And pressing means for pressing in a direction approaching another mold. The method of claim 1,
The first mold and the second mold are respectively formed with a stopper surface,
And reducing the volume of the cavity space until the stopper surface of the first mold and the stopper surface of the second mold are in contact with each other. The method of claim 1,
And said pressurizing means pressurizes the cooling member disposed at said contact position of said first cooling member and said second cooling member and a metal mold in contact with said cooling member together. The method of claim 1,
The heating means heats the first mold and the second mold at a heating rate of 600 ° C./min, respectively,
The injection means inject the thermoplastic resin composition when the first mold and the second mold is 280 ℃,
And said cooling means cools said first mold and said second mold at a cooling rate of 300 deg. C / min, respectively. The method of claim 1,
When the volume of the cavity space is reduced, the first mold and the second mold are not heated,
And a volume reduction of the cavity space and cooling of the first mold and the second mold are simultaneously performed. A method of molding a fuel cell separator by injection molding a thermoplastic resin composition in a molten state containing 70 to 90 wt% of a conductive filler composed of carbon fiber and carbon graphite,
(a) heating the first mold and the second mold to form a cavity space;
(b) when the first mold and the second mold are heated to 260 to 300 ° C., injecting the thermoplastic resin composition into the cavity space by a volume smaller than the volume of the cavity space;
(c) pressurizing at least one of the first mold and the second mold in a direction in which the volume of the cavity space decreases, thereby filling the injected thermoplastic resin composition in the reduced cavity space; And
(d) cooling the first mold and the second mold at a cooling rate of 200 to 400 ° C./min, respectively. The method of claim 6,
The carbon fiber and the carbon graphite are formed in the fuel cell separator, characterized in that contained in 10 to 20% by weight and 60 to 70% by weight with respect to the thermoplastic resin composition, respectively. The method of claim 6,
In the step (a), the first mold and the second mold is a molding method of a separator for a fuel cell, characterized in that each is heated at a heating rate of 400 to 800 ℃ / min. The method of claim 6,
In the step (a), the first mold and the second mold are each heated at a heating rate of 600 ℃ / min,
In the step (b), the thermoplastic resin composition is injected when the first mold and the second mold is 280 ℃,
In the step (d), wherein the first mold and the second mold are respectively cooled at a cooling rate of 300 ℃ / min. The method of claim 6,
In the step (c), the thermoplastic resin composition is molded in a fuel cell separator, characterized in that the injection of 75% to 85% of the cavity space volume. The method of claim 6,
When the volume of the cavity space is reduced, the first mold and the second mold are not heated,
Step (c) and step (d) is a molding method of a separator for a fuel cell, characterized in that at the same time. The method of claim 6,
The carbon fiber is a molding method of a separator for fuel cells, characterized in that the coating with silane or stearic acid. The method of claim 6,
The thermoplastic resin composition comprises a modified organic material grafted with 1 to 5% by weight of maleic anhydride as a compatibilizer of the thermoplastic resin and the conductive filler. The method of claim 13,
The organic material is a polypropylene or polyphenylene sulfide (PPS) forming method of a fuel cell separator, characterized in that. The method of claim 6,
The second mold may be linearly moved in a direction approaching and spaced apart from the first mold, wherein the first mold and the second mold form the cavity space when the mold is joined, and the volume of the cavity space is the first mold and Changes according to the distance between the second mold,
Contacting the first cooling member and the second cooling member with the first mold and the second mold spaced apart from the first mold and the second mold, respectively, to the first cooling member and the second cooling member cooled by the cooling means. And the first mold and the second mold are cooled by the method of forming a separator for a fuel cell. A fuel cell separator molded by the method for forming a fuel cell separator according to any one of claims 6 to 15.

Images