JP2006059683A - Washing method of rubber product for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing method of a rubber product for fuel cell capable of extraction removal of impurities or the like in a short time without affecting the physical property of rubber, and superior in washing efficiency. <P>SOLUTION: The rubber product for fuel cell formed of non-polar rubber is washed by a super-critical (subcritical) fluid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for cleaning a fuel cell rubber product.

  As a next-generation power generation method, a power generation method using a fuel cell system (in particular, a polymer electrolyte fuel cell) is considered promising. The energy obtained by this fuel cell system can be used very efficiently as, for example, the power of automobiles, household electricity and hot water. In the fuel cell system, energy is generated by a chemical reaction between hydrogen and oxygen, and a catalyst is used for the reaction. Therefore, if there are external contaminants such as catalyst poison components (sulfur, etc.) and various ions, these contaminants interfere with the reaction and poison the catalyst, resulting in a significant reduction in reaction efficiency. Therefore, in order to prevent this, it is necessary to use a product that does not extract or adhere to the above-mentioned external contaminants in the piping member (hose) and related members corresponding to the inflow lines of hydrogen and oxygen.

  In order to cool the heat generated during the chemical reaction in the fuel cell system, a water-cooled cooling system is usually introduced into the fuel cell system. And it is calculated | required that the cooling water (pure water and coolant) which flows through the cooling line should maintain insulation. That is, when the cooling water is conductive, an electrical short circuit is caused, which may cause an electric shock and a decrease in power generation efficiency due to the electric leakage. Therefore, in the piping member (hose) and related members used in the cooling water cooling line, a product that hardly extracts ions and does not increase the conductivity of the cooling water is required. For the cooling water, pure water having a low electrical conductivity or a mixture of pure water and coolant is usually used. However, pure water does not contain any disinfectant such as chlorine. For this reason, if there is a large amount of low molecular weight organic matter extracted from piping members (hoses) and related members, for example, There is concern that a large amount of bacteria will be generated.

For these reasons, conventionally, a stainless steel (SUS) pipe with less elution of ions and the like has been often used for a pipe of a fuel cell system. However, when SUS piping is used, since it has high rigidity, it lacks bending workability and the like, making molding and assembly difficult, and there are problems in layout and workability, as well as problems such as vibration durability. Therefore, in recent years, it has been proposed to use a rubber hose formed using rubber such as ethylene-propylene-diene terpolymer (EPDM). However, a release agent applied in the manufacturing process adheres to the inner peripheral surface of such a rubber hose, and further, a very small amount of impurities, etc. (contained in rubber compounding chemicals). Or impurities mixed in the manufacturing process of the hose, metal ions, sulfur components, low molecular organic substances, etc.), these may be gradually extracted. Therefore, there is a problem in using the rubber hose as it is for the piping of the fuel cell system. In addition to the hose, the fuel cell system includes, for example, rubber products such as packings and gaskets, and these related members have the same problem. Therefore, cleaning work is indispensable for rubber products for fuel cell system applications. For example, in the case of a hose, the above-described cleaning operation is performed by cleaning the release agent on the inner peripheral surface with water or a cleaning liquid, and then enclosing pure water (pure water with a specific conductivity of 20 μS / cm or less) in the hose. Then, extraction is performed for a long time (about 24 hours × 2 cycles) while keeping the water temperature at a high temperature (about 90 ° C.). And after that, it is commercialized through each process of water washing and drying (for example, refer to patent documents 1 or 2).
JP 2003-173803 A JP 2002-81581 A

  However, as described above, the conventional cleaning operation by filling pure water (extraction / removal operation of impurities in rubber) takes a considerable time at a high temperature and is not preferable in terms of work efficiency. In addition, in order to prioritize the efficiency of this cleaning work, for example, if the cleaning work is performed with an organic solvent, there is a risk of adversely affecting the physical properties of the rubber, and environmental concerns remain. The reality is that there is no practical solution.

  The present invention has been made in view of such circumstances, and provides a method for cleaning a fuel cell rubber product that can extract and remove impurities and the like in a short time without adversely affecting rubber physical properties and has excellent cleaning efficiency. Objective.

  In order to achieve the above object, a method for cleaning a fuel cell rubber product according to the present invention is a method for cleaning a fuel cell rubber product formed of non-polar rubber, which is described above with a supercritical (subcritical) fluid. The rubber product is cleaned.

  That is, the present inventors have intensively studied to solve the above problems. In the course of the research, if the rubber is washed with a supercritical (subcritical) fluid such as carbon dioxide (a fluid in which the liquid and gas are in a single phase), the load on the environment is low. Because of its high permeability to rubber, it has been found that it can easily enter and exit the rubber, and when it moves out, impurities inside the rubber can be pulsated and efficiently removed (extracted) from the rubber. . Therefore, by using the supercritical (subcritical) fluid, it is possible to efficiently extract and remove impurities and the like inside the rubber at a low temperature and in a short time. However, in the course of this research, if the rubber product to be applied is made of polar rubber, it tends to swell due to the supercritical (subcritical) fluid, and the fluid is vaporized while being swelled in this way. Then, it became clear that foaming is likely to occur in the rubber product. Therefore, when the rubber product to be applied is made of a non-polar rubber and the specific cleaning method is applied thereto, the above-mentioned cleaning can be advantageously performed without causing the above-mentioned foaming problem. It became so. Thus, it has been found that this cleaning method can provide a rubber product useful in a fuel cell system that dislikes impurities and the like, and has reached the present invention.

  As described above, in the present invention, a rubber product for a fuel cell formed of nonpolar rubber is brought into contact with a supercritical (subcritical) fluid for a predetermined time to extract and remove (wash) impurities and the like inside the rubber. The target fuel cell rubber products have been obtained. Therefore, if it wash | cleans by this method, it can wash | clean efficiently at low temperature and a short time, without deteriorating a rubber physical property. In addition, by this cleaning, not only various ions that promote the conduction of fluid flowing in the fuel cell system, but also low molecular organic substances can be positively removed. Therefore, the fuel cell rubber product washed in this manner has almost no elution of impurities, various ions, sulfur components, low molecular organic substances, etc., and can be applied to all piping members (hoses) and related members in the fuel cell system. This can be used to reduce the power generation efficiency due to the short circuit of the fuel cell system due to the increased conductivity of the fluid flowing in the fuel cell system, the poisoning of the catalyst, and the like. The generation of bacteria due to the extraction of low molecular organic substances can be eliminated.

  In particular, the nonpolar rubber is ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR), or brominated butyl rubber (Br-IIR). Thus, foaming does not occur more and the cleaning operation in the present invention can be carried out more advantageously.

  Further, when the supercritical (subcritical) fluid is derived from carbon dioxide in a supercritical (subcritical) state, the extraction efficiency is higher, and the environmental load due to its use can be further reduced. .

  Furthermore, if the cleaning with the supercritical (subcritical) fluid is an extraction process within 24 hours with a supercritical (subcritical) fluid having an ambient temperature of 32 to 80 ° C., the conventional rubber properties are not deteriorated. Thus, it is possible to obtain an extraction effect (cleaning effect) equivalent to or higher than the extraction treatment with pure water at a high temperature and for a long time.

  Next, embodiments of the present invention will be described in detail.

  In the present invention, as described above, a rubber product for a fuel cell formed of nonpolar rubber is brought into contact with a supercritical (subcritical) fluid for a predetermined time, thereby cleaning the rubber product. Has obtained rubber products for fuel cells. The term “cleaning” as used herein does not only indicate the surface cleaning of a rubber product, but also includes cleaning the inside of the rubber, that is, extracting and removing a small amount of impurities contained in the rubber. It is.

  The non-polar rubber which is a material for forming the rubber product is not particularly limited as long as it is a rubber having no polar group in the molecule. Among them, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR) and brominated butyl rubber (Br-IIR) have a lower degree of swelling of supercritical (subcritical) fluids, and are therefore supercritical (subcritical). Since foaming due to fluid swelling is less likely to occur, the cleaning operation in the present invention can be carried out more advantageously, which is preferable. These nonpolar rubbers may be used alone or in combination of two or more. Among these, ethylene-propylene-diene rubber (EPDM) can be preferably used in the fuel cell hose application. Along with these nonpolar rubbers, a filler such as carbon black and talc, a crosslinking agent, a co-crosslinking agent, a process oil, an anti-aging agent and the like are appropriately blended. In addition, in this invention, the nonpolar rubber includes not only the whole being composed of a nonpolar rubber but also the one containing a small amount (for example, 20% by weight or less) of a polar rubber.

  These components are kneaded using a kneader such as a kneader, Banbury mixer, roll, etc. to prepare a rubber compound, which is then extruded into a hose shape and heat vulcanized, or press vulcanized. The rubber product for a fuel cell to which the present invention is applied can be produced by vulcanization. Even if this rubber product is partly made of such rubber and the rest part is made of resin, fiber (reinforcing thread, etc.), metal, etc. It may be formed of such rubber.

  The rubber product for the fuel cell thus obtained is first cleaned with water or a conventionally known cleaning solution (especially, when the rubber product is a hose, mainly on its inner peripheral surface). Is done. Thereafter, the rubber product is brought into contact with the above-mentioned supercritical (subcritical) fluid for a predetermined time, whereby the rubber product is extracted and washed. Here, when the rubber product is a hose, the extraction cleaning may be performed with both ends of the hose plugged, and the hose is connected to a circulation system so that the supercritical (subcritical) fluid can be used. May be circulated in the hose. Further, when only cleaning by impregnating the entire hose with a supercritical (subcritical) fluid or the like is performed, it is necessary to distribute the supercritical (subcritical) fluid in the hose.

  As described above, the supercritical (subcritical) fluid is a fluid in which a liquid and a gas are in a single phase. Specifically, carbon dioxide, helium, argon, nitrogen, ammonia, water, Alkanes (ethane, propane, butane, etc.), alcohol solvents (methanol, ethanol, propanol, isopropanol, butanol, isobutanol, etc.), etc. are made fluids exceeding the critical point at a predetermined temperature and pressure. That is, for example, in the case of carbon dioxide, the critical point is a temperature of 31.3 ° C. and a pressure of 7.4 MPa. Therefore, in order to obtain a supercritical (subcritical) fluid, the conditions are set to exceed these values. Need to work. These supercritical (subcritical) fluids are used alone or in combination of two or more. Among them, the use of supercritical (subcritical) fluids with carbon dioxide has higher extraction efficiency for non-polar rubbers such as EPDM and EPM, and can further reduce the environmental burden due to its use. preferable.

  And by using the supercritical (subcritical) fluid as described above, it is possible to remove impurities contained in the rubber that cannot be removed unless pure water requires a high temperature and a long time at a low temperature and a short time. . Specifically, if the cleaning with the supercritical (subcritical) fluid is an extraction treatment within 24 hours with a supercritical (subcritical) fluid having an ambient temperature of 32 to 80 ° C., the physical properties of the rubber are deteriorated. In addition, it is possible to obtain an extraction effect (cleaning effect) equivalent to or higher than the conventional extraction treatment with pure water at a high temperature and for a long time. In addition, this range is the meaning that the cleaning effect can be expected more, and in the present invention, the extraction process is not particularly excluded in the condition of the atmospheric temperature or time exceeding the range. Then, after performing the cleaning process with the supercritical (subcritical) fluid, an appropriate cleaning process such as air drying or vacuum drying can be performed to obtain a target cleaned fuel cell rubber product.

  The cleaning treatment as described above can be suitably used for a fuel cell hose such as a fuel cell vehicle hose and a stationary fuel cell hose for home use. In addition to this, for example, the above-described cleaning treatment can also be performed on rubber products such as gaskets and various packings used in the fuel cell system. The washed fuel cell rubber product (hose, etc.) thus obtained is excellent in fuel cell use because it is washed more than the conventional washing treatment without impairing rubber properties. Function can be demonstrated.

  Next, examples will be described together with comparative examples.

  First, 100 parts by weight of EPDM (hereinafter abbreviated as “parts”), 100 parts of SRF carbon black, 60 parts of paraffinic oil, 1 part of an antioxidant (aromatic secondary amines), and peroxide crosslinking A rubber compound was prepared by kneading 5 parts of an agent (Park Mill D, manufactured by NOF Corporation) using a Banbury mixer and a roll. This was press vulcanized at 160 ° C. for 45 minutes to produce a test piece having a thickness of 2 mm. The test piece thus obtained is put into a stainless steel autoclave, covered, and then filled with liquefied carbon dioxide, and supercritical (subcritical) at 50 ° C. × 14.7 MPa. In this state, the test piece was washed for 15 minutes. In this manner, the target cleaned test piece was obtained.

[Comparative Example 1]
The washing treatment was not performed. Other than that was carried out similarly to Example 1, and obtained the target test piece.

[Comparative Example 2]
First, 100 parts of acrylonitrile-butadiene rubber (NBR), 60 parts of FEF carbon black, 5 parts of zinc oxide (ZnO), 1 part of stearic acid, and a vulcanization accelerator (Sunceller TT, manufactured by Sanshin Chemical Industry Co., Ltd.) 2 parts, 1 part of vulcanization accelerator (Sunceller CZ, Sanshin Chemical Co., Ltd.), 15 parts of plasticizer and 5 parts of sulfur are kneaded using a Banbury mixer and roll to prepare a rubber compound. did. This was press vulcanized at 160 ° C. for 45 minutes to produce a test piece having a thickness of 2 mm. Then, this test piece was subjected to the same cleaning treatment as in the example, and a target cleaned test piece was obtained.

[Conventional example]
Instead of the above washing treatment, the test piece was washed by immersing in pure water at 80 ° C. for 24 hours. Other than that was carried out similarly to Example 1, and obtained the target wash | cleaned test piece.

  Using the test pieces (rubber products) of the example product and the comparative example product thus obtained, each characteristic was evaluated according to the following criteria. These results are shown in Tables 1 and 2 below.

[Foamed expansion]
The test piece after the cleaning treatment was returned to room temperature and normal pressure, and the surface of the test piece immediately after that was visually observed to evaluate the expansion of the foam. That is, according to surface observation, the case where there was no or almost no foaming or expansion was indicated as ◯, and the case where expansion or many foaming was observed was indicated as x.

[Solution conductivity]
A polypropylene container is filled with 100 ml of 100 ° C. ultrapure water (pure water having a specific conductivity of 1 μS / cm), and two test pieces (28 mm × 28 mm × thickness 2 mm) are placed therein, and 100 ° C. × 168 Heat aging for hours. Thereafter, the conductivity (μS / cm) of the ultrapure water at 25 ° C. was measured using a conductivity meter (HORIBA, Ltd., CONDUCTIVITYMETER D-24).

[Amount of organic carbon in solution (TOC amount)]
A polypropylene container is filled with 100 ml of 100 ° C. ultrapure water (pure water having a specific conductivity of 1 μS / cm), and two test pieces (28 mm × 28 mm × thickness 2 mm) are placed therein, and 100 ° C. × 168 Heat aging for hours. Thereafter, the amount of organic carbon (μg C / l) in the ultrapure water was measured according to JIS K 0102 22.1.

  From the above results, it can be seen that the example products do not cause foam expansion and the solution conductivity and the TOC amount of the solution are kept low. It can also be seen that the values of the solution conductivity and the TOC amount are as low as or lower than those of the conventional example in which high temperature and long time extraction processing with pure water is performed. . Therefore, when the same cleaning treatment as in the example was performed on the fuel cell rubber product such as the fuel cell hose under the same conditions, the cleaning could be performed at a low temperature and in a short time without impairing the rubber physical properties. By the cleaning, extraction of conductive substances and low-molecular-weight organic substances, which are contamination factors, can be hardly caused.

  On the other hand, in Comparative Example 1, since the cleaning process as described above is not performed at all, the solution conductivity and the TOC amount of the solution remain high. In Comparative Example 2, the same cleaning treatment as that in the example was performed, but since the rubber product to be applied was formed of NBR, which is a polar rubber, foam expansion was confirmed.

  The cleaning method of the present invention is applied to rubber products for fuel cells, and is particularly useful for cleaning fuel cell hoses. In addition to this, for example, computer cooling hoses and other general rubber hoses are used. It is also possible to use for washing.

Claims (5)

  A method of cleaning a rubber product for a fuel cell formed of non-polar rubber, wherein the rubber product is cleaned with a supercritical (subcritical) fluid.   The nonpolar rubber is selected from the group consisting of ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR) and brominated butyl rubber (Br-IIR). 2. The method for cleaning a fuel cell rubber product according to claim 1, wherein the cleaning method is at least one.   The method for cleaning a fuel cell rubber product according to claim 1 or 2, wherein the supercritical (subcritical) fluid is carbon dioxide in a supercritical (subcritical) state.   The cleaning with the supercritical (subcritical) fluid is an extraction treatment within 24 hours with a supercritical (subcritical) fluid having an ambient temperature of 32 to 80 ° C. Cleaning method for rubber products for fuel cells.   The method for cleaning a fuel cell rubber product according to any one of claims 1 to 4, wherein the rubber product is a hose for a fuel cell.