JP2007173142A - Fuel container for direct methanol fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel container, not only having little transmission of methanol, but also capable of visually checking a methanol liquid level inside, and also using for a direct methanol type fuel cell capable of injection molding and equipped with thermal resistance, a good handling property and mechanical property enduring internal pressure under methanol existence. <P>SOLUTION: The fuel container of plastic fabricated is formed by injection molding for supplying methanol to a direct methanol fuel cell. The plastic structuring the container has a crystallinity measured by an X-ray diffraction method from 10 to 80%, and also has transparency capable of checking an amount of methanol inside the container. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a container or the like for supplying methanol as a fuel directly to a methanol fuel cell, and more particularly to a fuel container that is standardly installed in equipment using the fuel cell and a fuel container for replenishment.

  A direct methanol fuel cell (DMFC) that uses methanol as a fuel can be operated at low temperatures using a solid polymer membrane as an electrolyte, and since the fuel is liquid, it can be easily transported and stored, and can be downsized. It is rich in mobility. For this reason, it can be applied to portable devices such as notebook computers, camera-integrated VTRs, mobile phones, etc., and not only can the operating time of these devices be extended, but also the charging time of a secondary battery can be reduced. Future development is expected because it is not necessary.

  In a direct methanol fuel cell, a porous fuel electrode and an air electrode including a catalyst electrode are installed on both sides of a solid polymer electrolyte membrane, and methanol and air are supplied thereto, respectively. Methanol reacts with water at the fuel electrode to produce carbon dioxide, protons and electrons, and the protons reach the air electrode through the solid polymer electrolyte membrane, and are supplied from oxygen in the air, the protons and the air electrode. Electrons react to become water.

  When using a methanol fuel cell directly in a portable device, the fuel container for methanol supply is not only small and lightweight, but it is necessary to check the amount of methanol filled. Must-have. In addition, since it is desirable to omit the pump and other devices in the mechanism for supplying liquid fuel, the material of the fuel container needs to be a material that can be molded into a complicated shape that also has the mechanism. . Therefore, a resin that can be molded by an injection molding method, which is a general-purpose molding method, is preferable. In addition, this resin must have the properties of low alcohol permeability and the ability to visually confirm the internal methanol liquid surface, and it is mechanically resistant to heat resistance in the presence of alcohol, good handleability and internal pressure. Physical properties are required.

  In general, a container whose interior is visualized can be obtained by using an amorphous resin, but the methanol permeation resistance is not sufficient. On the other hand, when a general crystalline resin is used, the methanol permeation resistance is excellent, but the inside cannot be visualized. In addition, as a molded product of a crystalline resin having transparency, a molded product of a specific polyacetal resin (Patent Document 1), a molded product of a specific copolymerized polyester resin (Patent Documents 2-7), and a specified A molded product of the thermoplastic polyester resin composition (Patent Document 8) is disclosed. However, these have transparency and semi-transparency that can visualize the inside, but have a drawback that they are not sufficient in terms of permeation resistance to alcohol, heat resistance in the presence of alcohol, mechanical properties, and the like.

JP 2001-288276 A Japanese Patent Laid-Open No. 04-159333 Japanese Patent Laid-Open No. 04-201431 Japanese Patent Laid-Open No. 04-211433 Japanese Patent Laid-Open No. 04-211921 JP 04-348135 A Japanese Patent Laid-Open No. 04-358817 Japanese Patent Laid-Open No. 04-212830

  Therefore, the object of the present invention is not only less permeation of methanol but also visually confirming the methanol liquid level inside, and has heat resistance in the presence of methanol, good handleability, and mechanical properties that can withstand internal pressure. Another object of the present invention is to provide a fuel container for use in an injection moldable direct methanol fuel cell.

  As a result of intensive studies to achieve the above object, the present inventors have found that a specific crystalline resin having a crystallinity and / or crystal orientation in a specific range has not only transparency but also resistance. It is excellent in methanol permeability, can visualize the internal methanol liquid level, satisfies heat resistance, strength and rigidity, and can be injection-molded, and is suitable as a resin for fuel containers of direct methanol fuel cells. As a result, the present invention has been completed.

  That is, the present invention relates to a plastic fuel container formed by injection molding for directly supplying methanol to a methanol fuel cell, wherein the plastic constituting the container has a crystallinity measured by an X-ray diffraction method. The fuel container for direct methanol fuel cells is characterized by being a plastic having transparency in which the amount of methanol inside the container can be visually recognized. In the present invention, the plastic is a polyacetal resin having a degree of crystal orientation measured by X-ray diffraction of 80% or more and a crystallinity of 50 to 80%, crystallinity measured by X-ray diffraction Is a polybutylene terephthalate resin containing 5 to 20 mol% of a comonomer component, or a crystallinity measured by an X-ray diffraction method is 10 to 30%, and a polyethylene terephthalate resin The polybutylene terephthalate resin is preferably contained in an amount of 5 to 30% by weight.

  The fuel container of the direct methanol fuel cell according to the present invention is excellent in alcohol permeation resistance, heat resistance in the presence of alcohol, and handleability despite the fact that injection molding is possible. Furthermore, since it has mechanical properties that can withstand internal pressure, it can be easily downsized and is suitable as a fuel container for a portable fuel cell.

  Below, the fuel container for direct methanol fuel cells of this invention is explained in full detail. The fuel container of the present invention is made of a plastic having a crystallinity of 10 to 80% measured by an X-ray diffraction method and having transparency capable of confirming the amount of methanol inside the container. In addition, since the fuel container is premised on versatility, it is necessary that this plastic be versatile as well as injection moldable.

  Various plastics are known as general-purpose plastics. In the present invention, in particular, the amount of methanol inside can be visualized. (A) The degree of crystal orientation by X-ray diffraction method is 80% or more and the degree of crystallinity is 50 to 50%. An acetal resin that is 80%, (B) a polybutylene terephthalate resin having a crystallinity of 10 to 30% by X-ray diffraction method and containing 5 to 20 mol% of a comonomer component, and (C) X-ray diffraction It is preferable to use any resin selected from polybutylene terephthalate resins having a crystallinity of 10 to 30% by the method and containing 5 to 30% by weight of polyethylene terephthalate resin.

  The polyacetal resin used in the fuel container of the present invention is mainly composed of trioxane and formalin, and includes all resins whose basic molecular structure is composed of repeating units of oxymethylene units. Examples of such polyacetal resins include homopolymers composed solely of oxymethylene units, polyacetal resins mainly composed of oxymethylene units, ethylene oxide, 1,3-dioxolane, diethylene glycol formal, or 1,4- A polyacetal resin such as a copolymer containing a comonomer component such as butanediol formal, or a block polymer into which a block component has been introduced can be mentioned.

  As the polyacetal resin used in the present invention, a branched / crosslinked polyacetal resin having a branched / crosslinked structure (hereinafter abbreviated as a crosslinked polyacetal resin (A)) is particularly preferable. As a component that forms a branched / crosslinked structure, known polyfunctional glycidyl compounds, polyfunctional alcohol compounds, polyfunctional ester compounds, polyfunctional isocyanate compounds, polyfunctional acid anhydride compounds, polyfunctional alkoxysilane compounds Examples thereof include compounds. These are used for a reaction during polymerization of a polyacetal resin or a reaction during extrusion in an extruder to form a branched / crosslinked structure within and / or between molecules of the polyacetal resin. The above-mentioned crosslinked polyacetal resin (A) can be produced by a known method. Cross-linked polyacetal resin, unlike linear polyacetal resin, does not require any contrivance such as extremely reducing the thickness of the product and has a high degree of design freedom, so it is suitable for obtaining a fuel container that can visualize the internal methanol liquid level. is there.

  The crosslinked polyacetal resin (A) used in the present invention needs to have a crystal orientation of 80% or more by X-ray diffraction method and a crystallinity of 50 to 80%. The X-ray diffraction method used in the present invention is measured using wide-angle X-ray diffraction (transmission mode). The degree of crystal orientation can be obtained from the ratio (percentage) of the cross-linked polyacetal resin (A) in the two-dimensional scattering pattern to the total azimuth angle of the peak intensity (half-value width) of the azimuth angle on the (100) diffraction plane. The degree can be obtained from the average value of the ratio (percentage) of the X-ray diffraction intensity of the (100) diffraction surface to the total of the X-ray diffraction intensity and the amorphous halo intensity of the (100) diffraction surface. Furthermore, it is necessary to control the transparency of the molded product which is the fuel container of the present invention so that the amount of methanol inside can be confirmed. From this viewpoint, the total light transmittance (JIS K7105) of the crosslinked polyacetal resin (A) used in the present invention is preferably 70% or more.

  The polybutylene terephthalate resin (B) used in the fuel container of the present invention is a polybutylene terephthalate resin containing 5 to 20 mol% of a comonomer component, which is terephthalic acid or an ester-forming derivative thereof and 1,4-butanediol. And a comonomer component other than these are used as the third monomer raw material. As the third monomer raw material which is such a comonomer component, known carboxylic acids and derivatives thereof, hydroxycarboxylic acids and derivatives thereof, phenols and derivatives thereof, aliphatic alcohols and derivatives thereof, alicyclic alcohols and derivatives thereof And amines and derivatives thereof, hydroxyamines and derivatives thereof, amides and derivatives thereof, isocyanates and derivatives thereof, isocyanurates and derivatives thereof, and the like. In the present invention, these third raw materials can be used alone or in combination of two or more.

  Said polybutylene terephthalate resin (B) can be suitably manufactured by well-known methods, such as interfacial polycondensation using a condensation reaction or transesterification, melt polymerization, or solution polymerization. Moreover, the polymerization degree of resin can further be raised by heat-processing the obtained resin under reduced pressure or presence of inert gas, and carrying out solid phase polymerization.

  The polybutylene terephthalate resin (B) used for the fuel container of the present invention needs to have a crystallinity of 10 to 30% by X-ray diffraction. The X-ray diffraction method used here is measured using wide-angle X-ray diffraction (transmission mode) as in the case of the polyacetal resin, and the crystallinity is the (100) diffraction plane of the polybutylene terephthalate resin. It can be determined from the average value of the ratio (percentage) of the X-ray diffraction intensity of the (100) diffraction surface to the total of the X-ray diffraction intensity and the amorphous halo intensity. Furthermore, in the present invention, when the fuel container for a direct methanol fuel cell is used, it is necessary to control the transparency so that the amount of methanol inside can be confirmed. From this viewpoint, the total light transmittance (JIS K7105) is 70. % Or more is preferable.

  The polybutylene terephthalate resin (C) containing 5 to 30% by weight of polyethylene terephthalate resin used in the present invention is the above-described polybutylene terephthalate resin (B) or the comonomer component used in the resin (B) of 0 to It is a resin in which 5 to 30% by weight of polyethylene terephthalate resin is blended with respect to polybutylene terephthalate resin used by reducing to 5 mol%. These resin mixed compositions are easily prepared by known equipment and methods that have been conventionally used as a method for preparing resin mixed compositions.

  The above-mentioned polybutylene terephthalate resin (C) containing 5 to 30% by weight of the polyethylene terephthalate resin used in the present invention needs to have a crystallinity of 10 to 30% by the X-ray diffraction method. The X-ray diffraction method used here is the same as in the case of the acetal resin, and the crystallinity when measured using wide-angle X-ray diffraction (transmission mode) is X of the (100) diffraction plane of the polybutylene terephthalate resin. It can be determined from the average value of the ratio (percentage) of the X-ray diffraction intensity of the (100) diffraction surface with respect to the total of the line diffraction intensity and the amorphous halo intensity. Furthermore, in the present invention, when the fuel container for a direct methanol fuel cell is used, it is necessary to control the transparency so that the amount of methanol inside can be confirmed. From this viewpoint, the total light transmittance (JIS K7105) is 70. % Or more is preferable.

  In addition, the above-mentioned crosslinked polyacetal resin (A), polybutylene terephthalate resin (B), and polybutylene terephthalate resin (C) containing 5 to 30% by weight of polyethylene terephthalate resin used in the fuel container of the present invention include As long as the effect of the present invention is not impaired, a general additive for the thermoplastic resin, for example, a stabilizer such as an antioxidant or an antioxidant, a colorant such as a dye or a pigment, a lubricant, Add one or more nucleating agents, release agents, antistatic agents, surfactants, organic polymer materials, inorganic or organic fibrous, powdery, plate-like fillers, etc. Can do.

  The fuel container for a direct methanol fuel cell of the present invention can be molded using a known injection molding machine. The molding conditions are preferably a mold temperature of 10 to 100 ° C., an injection pressure of 20 to 500 MPa, an injection speed of 5 to 1000 mm / s, and a screw rotation speed of 30 to 600 rpm. If the resin temperature in the cylinder is in a temperature range where plasticization is possible, the molding cycle, plasticization time, etc. can be arbitrarily set.

  Under any condition, when the finally molded container is composed of the crosslinked polyacetal resin (A), the degree of crystal orientation by the X-ray diffraction method is 80% or more and the degree of crystallinity is 50. When it is composed of a polybutylene terephthalate resin containing 5 to 20 mol% of the comonomer component (B), crystallization by X-ray diffraction method is possible. In the case of polybutylene terephthalate resin containing 5 to 30% by weight of (C) polyethylene terephthalate resin, the degree of methanol is 10 to 30%, and can be confirmed by the X-ray diffraction method. It is necessary to satisfy characteristics such as a crystallinity of 10 to 30% and confirmation of the amount of methanol inside.

  By using a plastic that satisfies these characteristics, not only is it resistant to alcohol permeation, heat resistance in the presence of alcohol, and handleability, but it is also possible to check the methanol liquid level inside, The fuel container of the direct methanol fuel cell of the present invention having mechanical properties that can withstand the above can be produced.

Since the fuel container of the present invention can be easily reduced in size and weight, it is suitable as a fuel container for a direct methanol fuel cell (DMFC) using methanol as a fuel or a replenishment container, and this is used as a fuel container or the like. As a result, it is possible to easily realize the application of a direct methanol fuel cell to various electric / electronic devices such as a notebook computer, a camera-integrated VTR, and a mobile phone, which is extremely significant in the industry.
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, this invention is not limited by these.

  Cross-linked polyacetal resin A (cross-linked polyacetal resin polymerized using trioxane, 1,3-dioxolane and polyfunctional glycidyl compound as a raw material), cross-linked polyacetal resin A2 (trioxane, 1,3-dioxolane polymerization reaction product as polyfunctional isocyanate) Cross-linked polyacetal resin reacted with the compound in an extruder), polybutylene terephthalate resin B1 (polybutylene terephthalate resin containing 8 mol% of comonomer component), polybutylene terephthalate resin B2 (polybutylene terephthalate containing 12 mol% of comonomer component) Resin), polybutylene terephthalate resin C1 (containing 10% by weight of polyethylene terephthalate resin), and polybutylene terephthalate resin C2 (15% by weight of polyethylene terephthalate resin) ), Using an injection molding machine, adjusting the molding conditions, 20 (mm) × 20 (mm) × 20 (mm) box-shaped part (model part of fuel container composed of five surfaces, thickness Was injection molded. Next, the crystallinity, crystal orientation, methanol permeation resistance, transparency, and mechanical properties were evaluated. The results are shown in Table 1 (crosslinked polyacetal resin) and Table 2 (polybutylene terephthalate resin). The evaluation conditions are as follows.

(1) Evaluation of degree of crystallinity and degree of crystal orientation Using the obtained molded product, crystallinity is evaluated by wide-angle X-ray diffraction (transmission mode), and the degree of crystallinity and degree of crystal orientation (polyacetal) Resin material only) was measured. The degree of crystallinity is the average value of the ratio (percentage) of the X-ray diffraction intensity of each (100) diffraction surface to the total of the X-ray diffraction intensity and amorphous halo intensity of the (100) diffraction surface of the polyacetal resin or polybutylene terephthalate resin. I asked for it. The degree of crystal orientation was determined from the ratio (percentage) of the peak intensity (half width) of the azimuth angle of the (100) diffraction plane of the polyacetal resin in the two-dimensional scattering pattern to the total azimuth angle.

(2) Evaluation of resistance to methanol permeation Using a pressure-resistant sealed container made of glass, the obtained molded product was immersed in methanol at 20 ° C. for 25 weeks and at 60 ° C. for 3 weeks, and then the surface was wiped off. The methanol permeation resistance was evaluated by measuring the weight increase rate of the molded product. Evaluation was performed according to the following criteria.
○: The weight increase rate of the molded product is very small.
(Triangle | delta): The weight increase rate of a molded article is small.
X: The weight increase rate of a molded article is remarkably many.

(3) Evaluation of transparency Methanol was poured into the obtained molded product, transparency was evaluated visually, and the degree of transparency was evaluated according to the following criteria. Furthermore, the total light transmittance (JIS K7105) for each surface of the molded product was measured, and the average value was calculated.
○: The liquid level and the inside of the liquid can be clearly confirmed.
(Triangle | delta): The liquid level of methanol can be seen clearly and the inside of a liquid can be confirmed a little.
X: It is difficult or impossible to confirm the liquid level of methanol.

(4) Evaluation of mechanical properties The obtained molded product was freely dropped onto an iron plate from a height of 3 m, impact fracture evaluation was performed, and cracks and cracks were evaluated.

Comparative Examples 1-6
Polyacetal resin A1, polybutylene terephthalate resin B1 and polybutylene terephthalate resin C1 used in Examples 1, 3, and 5 were used, and molding conditions (A1 was injection pressure / injection speed, B1 and C1 were mold temperatures, Cylinder temperature) is adjusted to form box-shaped parts with different crystallinity and crystal orientation, and then the methanol permeability resistance, transparency, and mechanical properties are evaluated in the same manner as in the examples. Implemented. The results are shown in Table 1 (crosslinked polyacetal resin) and Table 2 (polybutylene terephthalate resin).

Comparative Examples 7 and 8
Box shape with different crystallinity and crystal orientation using polyacetal resin a (linear polyacetal resin made from formaldehyde) and polybutylene terephthalate resin b (polybutylene terephthalate resin containing no comonomer component) The parts were molded, and subsequently, methanol permeation resistance, transparency, and mechanical properties were evaluated in the same manner as in the examples. The results are shown in Table 1 (polyacetal resin) and Table 2 (polybutylene terephthalate resin).

Claims (4)

  A plastic fuel container formed by injection molding for directly supplying methanol to a methanol fuel cell, wherein the plastic constituting the container has a crystallinity of 10 to 80% measured by an X-ray diffraction method A fuel container for a direct methanol fuel cell, characterized by being a transparent plastic that can visually recognize the amount of methanol inside the container.   2. The fuel for a direct methanol fuel cell according to claim 1, wherein the plastic is a crosslinked polyacetal resin having a degree of crystal orientation measured by an X-ray diffraction method of 80% or more and a degree of crystallinity of 50 to 80%. container.   2. The direct methanol according to claim 1, wherein the plastic is a polybutylene terephthalate resin having a crystallinity measured by an X-ray diffraction method of 10 to 30% and a comonomer component of 5 to 20 mol%. Fuel container for fuel cells. The direct methanol fuel according to claim 1, wherein the plastic is a polybutylene terephthalate resin containing 5 to 30% by weight of a polyethylene terephthalate resin, and the crystallinity measured by X-ray diffraction method is 10 to 30%. Battery container for batteries.