JP2011258360A - Composite sheet for direct methanol fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite sheet for a direct methanol fuel cell which is excellent in methanol diffusivity and is capable of supplying methanol to an anode over a large area by the diffusion and penetration effect, even if an area of a methanol solution feeding part from a fuel cartridge is comparatively small.SOLUTION: A composite sheet for a direct methanol fuel cell comprises a polyolefin-based resin layer and a water absorptive and diffusive fiber woven fabric layer formed continuously on at least one principal surface of the polyolefin-based resin layer.

Description

The present invention relates to a composite sheet for a direct methanol fuel cell, which has excellent methanol diffusibility and can supply methanol to an anode in a large area by a diffusion permeation effect even when a methanol aqueous solution delivery part from a fuel cartridge has a relatively small area. .

Power consumption and continuous use time are increasing as portable small electronic devices such as mobile phones, personal digital assistants (PDAs), notebook PCs, video cameras, etc. have become multifunctional, and they are installed in portable small electronic devices. There is a strong demand for higher energy density of batteries.

Currently, lithium secondary batteries are mainly used as power sources for portable small electronic devices, but lithium secondary batteries are expected to reach a limit at an energy density of about 600 Wh / L. An early practical application of a fuel cell using a solid polymer electrolyte membrane is expected as a power source to replace the secondary battery.

Among fuel cells, the direct methanol fuel cell (DMFC) can generate electricity by supplying methanol as a fuel or methanol aqueous solution directly into the cell without reforming it into hydrogen. Development is underway. In addition, direct methanol fuel cells are attracting more attention in terms of the high theoretical energy density of methanol, simplification of the system, ease of fuel storage, and the like.
In a direct methanol fuel cell, a method of supplying a methanol aqueous solution using a diffusion auxiliary device such as a pump or a fan is generally used.

However, if diffusion auxiliary devices such as a pump and a fan are used, the overall system is hindered from being miniaturized. Therefore, there is a demand for a fuel supply system that is simplified and miniaturized without using them.

As such a fuel supply system, a method of supplying a methanol aqueous solution with high efficiency by utilizing natural diffusion such as capillary phenomenon has been studied. For example, Patent Document 1 discloses a fuel permeation made of a porous material. A method of introducing methanol to the anode by utilizing a capillary phenomenon by disposing a plate is disclosed. Patent Document 2 discloses a fuel introduction body made of a foam, a fiber bundle, a non-woven fiber or the like, and a foam such as a polyurethane foam is used.

However, in these methods, since the diffusibility of methanol is insufficient, it is necessary to enlarge the contact surface between the liquid flow path from the fuel cartridge and the permeation plate, and there is a problem that it is difficult to reduce the size.

JP 2001-93540 A JP 2003-368866 A

In view of the above situation, the present invention is excellent in methanol diffusibility, and even if the methanol aqueous solution delivery part from the fuel cartridge has a relatively small area, methanol can be supplied to the anode in a large area by the diffusion permeation effect. An object is to provide a composite sheet for a direct methanol fuel cell.

The present invention is a composite sheet for a direct methanol fuel cell having a polyolefin resin layer and a water-absorbing and diffusing fiber woven fabric layer continuously formed on at least one main surface of the polyolefin resin layer.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have found that a sheet used for a direct methanol fuel cell is a water-absorbing and diffusing fiber weave formed continuously on at least one main surface of a polyolefin resin layer and the polyolefin resin layer. By having a fabric layer, it is a composite sheet with extremely high methanol diffusivity while preventing deterioration and deformation due to methanol, so a direct methanol fuel cell that can realize power generation characteristics at a higher current density Has been found, and the present invention has been completed.

The composite sheet for a direct methanol fuel cell of the present invention has a polyolefin resin layer and a water-absorbing and diffusing fiber woven fabric layer continuously formed on at least one main surface of the polyolefin resin layer.
Since the polyolefin-based resin has hydrophobicity, it contributes to the diffusion performance of methanol, and the obtained sheet has high strength.

Examples of the polyolefin resin include an α-olefin homopolymer and a copolymer with a different monomer mainly composed of an α-olefin. Specifically, for example, polyethylene, polypropylene, ethylene and 1 -Copolymers with α-olefins having 4 to 10 carbon atoms such as butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, ethylene-vinyl acetate copolymer Examples thereof include a copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic acid ester copolymer, an ethylene-methacrylic acid ester copolymer, an ethylene-vinyl acetate-methacrylic acid ester copolymer, and an ionomer resin.
Of these, polypropylene is preferred.

The minimum with preferable melting | fusing point (it depends on the endothermic peak temperature of DSC) of the said polyolefin resin is 98 degreeC, and a preferable upper limit is 200 degreeC. If the melting point of the polyolefin resin is lower than 98 ° C., the heat generation of the fuel cell unit itself may cause structural destruction or functional deterioration due to deformation or melting. When the melting point of the polyolefin-based resin exceeds 200 ° C., the processing temperature of the composite sheet becomes high, so that composite processing at a high temperature is required, and the manufacturing apparatus and manufacturing cost may be increased.

The minimum with a preferable number average molecular weight of the said polyolefin resin is 3000, and a preferable upper limit is 60000. By setting the number average molecular weight within the above range, a direct methanol fuel cell composite sheet having excellent methanol diffusion performance can be obtained. In this specification, the number average molecular weight refers to that measured by gel permeation chromatography (GPC).

As the polyolefin resin used in the polyolefin resin layer, a polyolefin resin having the above-described composition may be used alone, or two or more polyolefin resins having the above-described composition may be used in combination. Moreover, when the said polyolefin resin layer is two or more layers, although the said polyolefin resin is good also as a thing of a different composition, in order to suppress the trouble by a deformation | transformation etc., it is preferable to set it as the same composition.

The lower limit of the content of the polyolefin resin in the composite sheet for a direct methanol fuel cell of the present invention is 10% by weight, and the upper limit is 45% by weight. When the content of the polyolefin resin is less than 10% by weight, the diffusion performance of methanol is lowered, or the methanol permeation resistance is insufficient, which may cause a decrease in the output of the fuel cell. On the other hand, if it exceeds 45% by weight, the permeability of methanol in the thickness direction decreases. The minimum with preferable content of the said polyolefin resin is 15 weight%, and a preferable upper limit is 40 weight%. In addition, content of the said polyolefin resin represents content per unit area.
You may add well-known additives, such as antioxidant and a heat stabilizer, to the said polyolefin resin layer in the range which does not impair the essence of this invention.
The water-absorbing and diffusing fibers used in the water-absorbing and diffusing fiber woven fabric layer of the present invention will be described.

Hereinafter, water, methanol, aqueous methanol solution, and these may be referred to as methanol. Moreover, the water absorption of the term “water absorption / diffusion” in the present invention includes not only a limited meaning of absorbing water but also including absorption of methanol and the like.

When a synthetic fiber is used as a water-absorbing and diffusing fiber, the cross-sectional shape of a single yarn is an original fiber and / or a processed yarn of a modified cross-sectional fiber such as W, Z, M, corrugated, porous fiber (porosity 5% ~ 40%) raw yarn and / or processed yarn. In this case, an original yarn and / or processed yarn having a single yarn of 2 dtex or less is used.

The degree of atypical single yarn of the modified cross-section fiber is preferably 1.2 or more and 2.2 or less, and more preferably 1.4 or more and 2.2 or less. If the ratio is 1.2 or more, the balance of water absorption and diffusibility is better than that of the round cross section, and if it exceeds 2.2, the production stability such as spinnability is poor, which is not preferable. The degree of irregularity here refers to calculating the cross-sectional area and circumference (peripheral length) of an atypical fiber single yarn, then finding the radius of a perfect circle with the same cross-sectional area, and from that, the circumference of that perfect circle is calculated. Calculated and calculated by the following formula.
Degree of profile = circumference of atypical fiber / circumference of a perfect circle with the same cross-sectional area as the atypical fiber

In order to increase the water diffusibility by increasing the number of passages of methanol or the like, the degree of profile is 1.4 or more and 2.2 or less, preferably 1.5 or more, and θ _{1 to} θ ₃ is 60 ° or more and 160 as shown in FIG. The filament may have a W-shaped cross section that is at most °, preferably at least 120 ° and at most 150 °. Moreover, the fabric using what used the single thread of this W type | mold cross-section thread to 0.3-2 dtex tends to be excellent in methanol diffusibility. It is presumed that the capillary suction force is increased by the fine capillaries formed when the W cross-section fibers overlap. Here, if the single yarn fineness is smaller than 0.3 dtex, spinning tends to be difficult, and if it exceeds 2 dtex, the methanol diffusibility tends to deteriorate.

The water-absorbing and diffusing fiber is preferably a synthetic fiber. Synthetic fibers do not absorb water by the fiber matrix, but can have water absorption and diffusivity due to physical factors, that is, retention of methanol and the like by crimping, capillarity between single fibers, surface area increasing effect by atypical cross section, etc. Because. As the synthetic fiber, fibers made of a polyester polymer having fiber-forming properties such as homopolymers such as polyethylene terephthalate, polybutylene terephthalate and polytrimethylene terephthalate, and polyester copolymers with these polymers are preferably used. However, the present invention is not limited to this. The fiber material is required to be not melted at the heating temperature in the step of compounding the polyolefin resin since it is compounded with the polyolefin resin in the melt compounding step. Further, it is required that the water-absorbing and diffusing fiber woven fabric layer is not completely melted at the heating temperature in the heat setting process or the hot pressing process. This is because if the fiber is melted at the above temperature, the fiber cross-sectional shape contributing to the water absorption diffusivity cannot be maintained. In addition, it is necessary not to dissolve in methanol or the like under use conditions in a fuel cell at 80 ° C. or lower. Examples of such water-absorbing and diffusing fibers that are commercially available are polyester fibers manufactured by Asahi Kasei Fibers Co., Ltd., Technofine (registered trademark), and CEOα (Seo Alpha) (registered trademark) manufactured by Toray Industries, Inc. Etc.

Furthermore, when a synthetic fiber raw yarn is crimped to give a crimp, a synthetic fiber with improved retention of methanol or the like can be obtained. In this case, however, the low crimp, that is, the crimp elongation rate is preferably 15% or less. This is because, when the crimp is high, the space for holding methanol or the like increases, but conversely, the diffusibility of methanol or the like decreases. Thus, if the shape of the synthetic fiber and the yarn processing conditions are appropriately selected, the balance between water absorption and diffusibility is excellent. Furthermore, it is more preferable to use a cellulose composite yarn composed of cellulose fiber and synthetic fiber as the water-absorbing and diffusing fiber because the affinity with methanol and the like is increased.

In addition to the above, the fiber substrate itself is a fiber having water absorption, such as recycled cellulose fiber such as viscose rayon and cupra rayon, and natural fibers such as cotton, hemp and wool in the form of spun yarn, long fiber yarn and processed yarn. Can be used. Fibers that can absorb water by these fiber substrates themselves are preferable because vapor-like methanol and the like can also absorb and diffuse water. Among them, cotton yarns and regenerated cellulose long fiber yarns having a single fiber length having a high twist coefficient value that are relatively long and densely spun can obtain high water absorption and diffusibility. Among the regenerated cellulose long fibers, those having a single yarn exceeding 10 dtex are not preferable because swelling is remarkable and the surface area of the fiber is reduced, and the diffusibility is poor.
The total fineness of the fibers constituting the water-absorbing and diffusing fiber woven fabric layer of the present invention is 20 to 100 dtex, preferably 30 to 90 dtex.

Moreover, although the said fiber can also be used with a non-twisted yarn, in order to improve the convergence property of a fiber, it is more preferable that the twisting process, the interlace process, the false twisting process, etc. are performed. In the case of twisting, 10 to 1500 T / m is preferable, and 100 to 800 T / m is particularly preferable.

By twisting the yarn in the above range, the convergence of the water-absorbing diffusible fiber is improved, the methanol diffusibility in the fiber length direction is improved, and an appropriate retention property of methanol or the like can be secured.

As the woven fabric structure of the water-absorbing and diffusing fiber woven fabric layer of the present invention, a known woven structure such as plain weave, tatami mat, twill weave, satin weave can be applied. Which woven structure is adopted can be appropriately determined depending on the desired diffusion directionality, required physical properties, and the like, but since a high-density and thin woven fabric can be easily obtained, a plain woven structure is particularly preferable.

The raw machine after weaving can be subjected to a relaxation process and a heat setting process after impurities such as fiber oil are removed by scouring. Furthermore, it is preferable to go through a hot pressing step in addition to a normal tentering heat setting step. The water-absorbing and diffusing property of the water-absorbing and diffusing fiber woven fabric can be further improved by hot pressing.

Since the variation in the size of the gap formed between the fibers of the water-absorbing and diffusing fiber woven fabric layer can be reduced, not only the unevenness of impregnation is less likely to occur when the polyolefin resin is melted and impregnated, but also the impregnation. The variation in depth in the thickness direction is also reduced, and the unevenness at the interface of the polyolefin resin layer is reduced. As a result, the methanol diffusibility of the obtained direct methanol fuel cell composite sheet is greatly improved.

The upper limit of the total thickness of the composite sheet for a direct methanol fuel cell of the present invention is preferably 0.3 mm, and more preferably 0.2 mm. When the total thickness exceeds 0.3 mm, methanol diffusibility is lowered. A preferred lower limit is 0.01 mm. If the total thickness is less than 0.01 mm, unevenness in methanol diffusion tends to occur. A more preferable lower limit is 0.05 mm, and a more preferable upper limit is 0.17 mm.

As a specific structure of the composite sheet for a direct methanol fuel cell according to the present invention, the polyolefin-based resin layer (A) and the water-absorbing and diffusing fiber woven fabric layer (B) are (A) / (B) or (B) / It may be a two-layer structure laminated as shown in (A), or 3 laminated as shown in (A) / (B) / (A) or (B) / (A) / (B). It may be a layer structure or a four-layer structure of (A) / (B) / (A) / (B). Especially, it is preferable to make the surface by the side of a fuel supply into a water absorptive diffusible fiber woven fabric layer (B).

The composite sheet for a direct methanol fuel cell of the present invention is preferably formed by integrally laminating a sheet made of a water diffusible fiber woven fabric and a sheet made of a polyolefin resin by heat fusion. The direct methanol fuel cell composite sheet obtained by such a method has a structure in which the water-absorbing and diffusing fiber woven fabric layer and the polyolefin resin layer are integrated at the joint, resulting in greatly improved methanol diffusion performance. Can be improved. In particular, the laminated interface is preferably a structure in which a porous polyolefin resin is impregnated between fibers constituting the water-absorbing and diffusing fiber woven fabric.

The basis weight of the sheet made of the water-absorbing and diffusing fiber woven fabric is not particularly limited, but a preferable lower limit is 30 g / m ² and a preferable upper limit is 85 g / m ² . When the basis weight of the sheet made of the water-absorbing and diffusing fiber woven fabric is less than 30 g / m ² , unevenness may occur when supplying methanol, and when it exceeds 85 g / m ² , sufficient methanol diffusion effect cannot be obtained. Sometimes.

Although it does not specifically limit as thickness of the sheet | seat which consists of the said water absorptive diffusible fiber woven fabric, A preferable minimum is 0.05 mm and a preferable upper limit is 0.18 mm. When the thickness of the sheet comprising the water-absorbing and diffusing fiber woven fabric is less than 0.05 mm or exceeds 0.18 mm, a sufficient methanol diffusion effect may not be obtained.

The basis weight of the sheet made of the polyolefin resin is not particularly limited, but a preferred lower limit is 5 g / m ² and a preferred upper limit is 45 g / m ² . If the basis weight of the polyolefin resin sheet is less than 5 g / m ² , unevenness may occur during methanol supply, and if it exceeds 45 g / m ² , methanol permeation may be inhibited.

Although it does not specifically limit as thickness of the sheet | seat which consists of said polyolefin resin, A preferable minimum is 0.05 mm and a preferable upper limit is 0.75 mm. When the thickness of the sheet made of the polyolefin resin is less than 0.05 mm or exceeds 0.75 mm, a sufficient methanol diffusion effect may not be obtained.

Examples of the form of the polyolefin resin sheet include spunbond nonwoven fabric sheets, wet papermaking nonwoven fabric sheets, wet-spun nonwoven fabric sheets, nonwoven fabric sheets such as melt blown nonwoven fabric sheets, porous sheets obtained by film stretching, and foamed porous sheets. .

Further, the sheet made of the polyolefin resin is made of the water-absorbing and diffusing fiber woven fabric by integrally combining the sheet made of the water-absorbing and diffusing fiber woven fabric and the sheet made of the polyolefin resin by heat fusion. Can be easily fused and fixed with high adhesion without blocking the holes.

The processing temperature at the time of heat-sealing is performed at a temperature higher than the melting point of the polyolefin-based resin, but the processing can be performed at a temperature lower than the melting point of the polyolefin-based resin.

The method for producing the direct methanol fuel cell composite sheet of the present invention is not particularly limited. For example, as described above, a sheet made of a water-absorbing and diffusing fiber woven fabric and a sheet made of a polyolefin resin are heat-sealed. The method of laminating integrally is mentioned.

Specifically, for example, a sheet made of a water-absorbing and diffusing fiber woven fabric and a sheet made of polyolefin resin are passed through a pair of heated rollers, and a predetermined nipping pressure is applied while applying a nipping pressure. A method of passing at a speed is mentioned.

According to the present invention, a direct methanol type that is excellent in methanol diffusibility and can supply methanol in a large area to the anode by the diffusion permeation effect even if the methanol aqueous solution delivery part from the fuel cartridge has a relatively small area. A composite sheet for a fuel cell can be provided.

In addition to efficient diffusion supply of high-concentration methanol aqueous solution, it can be made thin, and by using natural diffusion using fibers, diffusion auxiliary equipment such as pumps and fans can be used. Therefore, it can be suitably used for a small direct methanol fuel cell.

The cross-sectional shape of a single yarn constituting a typical water-absorbing and diffusing fiber is shown.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
(Preparation of water diffusible fiber woven fabric sheet 1)

For both warp and weft yarns, we used a polyester multifilament yarn 56dtex, 30 filaments (manufactured by Asahi Kasei Fibers Co., Ltd., Technofine (registered trademark)) with a W-shaped cross section for a plain weave structure. In the scouring / relaxing process of the woven raw machine, the oil agent is removed in a bath at 40 to 98 ° C., and after setting the width by dry heat, the hot press machine is used to perform a hot press set at 190 ° C. for 30 seconds, and warp Finishing to 54 / 2.54 cm and weft 54 / 2.54 cm, a water-absorbing and diffusing woven fabric sheet 1 (thickness 0.11 mm, basis weight 48 g / m ² ) was obtained.

Here, the sheet thickness was measured using a digital thickness meter (manufactured by Mitutoyo Corporation, measuring part φ20 mm). For the sheet basis weight, the weight of a 25 mm × 200 mm test piece was measured and converted to a weight per 1 m ² . Hereinafter, each sheet thickness and each sheet basis weight were measured similarly.
(Preparation of water diffusible fiber woven fabric sheet 2)

The water-absorbing and diffusing fiber woven fabric sheet 2 (thickness 0.11 mm, basis weight 52 g / gram) is the same as the water-absorbing and diffusing fiber woven fabric sheet 1 except for finishing to 54 warps / 2.54 cm and 80 wefts / 2.54 cm. m ² ) was obtained.
(Preparation of water diffusible fiber woven fabric sheet 3)

The water-absorbing and diffusing fiber woven fabric sheet 3 (thickness 0.15 mm, basis weight 65 g / gram) is the same as the water-absorbing and diffusing fiber woven fabric sheet 1 except that the warp yarns are 108 / 2.54 cm and the wefts are 108 / 2.54 cm. m ² ) was obtained.
Example 1

A nonwoven fabric sheet (melting point: 164 ° C., circular fiber cross section, fiber diameter: 0.8 to 8 μm, basis weight: 30 g / m ²⁾ on the main surface opposite to the methanol supply surface of the water-absorbing and diffusing fiber woven fabric sheet 1 , 0.30 mm thick), and heat-sealed by heating at 150 ° C. for 3 seconds using a hot press machine. A composite sheet having a total thickness of 0.11 mm and a polypropylene content of 38% by weight was obtained.
(Example 2)

Non-woven sheet made of homopolypropylene (melting point 164 ° C., circular fiber cross section, fiber diameter 0.8-8 μm, basis weight 30 g / m ² , thickness 0) .30 mm) was placed and heated at 150 ° C. for 3 seconds using a hot press machine, and heat-sealed. A composite sheet having a total thickness of 0.11 mm and a polypropylene content of 38% by weight was obtained.
(Example 3)

A non-woven sheet made of homopolypropylene (melting point: 164 ° C., circular fiber cross section, fiber diameter: 0.8 to 8 μm, basis weight: 20 g / m ²⁾ on the main surface opposite to the methanol supply surface of the water-absorbing and diffusing fiber woven fabric sheet ² , Thickness 0.19 mm) was placed and heated at 150 ° C. for 3 seconds using a hot press machine to be heat-sealed. A composite sheet having a total thickness of 0.11 mm and a polypropylene content of 28% by weight was obtained.
Example 4

On the main surface opposite to the methanol supply surface of the water-absorbing and diffusing fiber woven fabric sheet 3, a non-woven sheet made of high-density polyethylene (melting point 129 ° C., circular fiber cross section, fiber diameter 0.8-8 μm, basis weight 20 g / m ² and a thickness of 0.19 mm), and heat-sealed by heating at 135 ° C. for 3 seconds using a hot press machine. A composite sheet having a total thickness of 0.15 mm and a high-density polyethylene content of 23.5% by weight was obtained.
(Example 5)

A non-woven sheet made of homopolypropylene (melting point: 164 ° C., circular fiber cross section, fiber diameter: 0.8 to 8 μm, basis weight: 10 g / m ²⁾ , A thickness of 0.10 mm) was placed, and heat fusion was performed by heating at 150 ° C. for 3 seconds using a hot press machine. A composite sheet having a total thickness of 0.11 mm and a polypropylene content of 17% by weight was obtained.
(Comparative Example 1)

A nonwoven fabric sheet (melting point: 164 ° C., circular fiber cross section, fiber diameter: 0.8 to 8 μm, basis weight: 5 g / m ² on the main surface opposite to the methanol supply surface of the water-absorbing and diffusing fiber woven fabric sheet ^2. , Thickness 0.07 mm) was placed, and heat fusion was performed by heating at 150 ° C. for 3 seconds using a hot press machine. A composite sheet having a total thickness of 0.11 mm and a polypropylene content of 9% by weight was obtained.
(Comparative Example 2)

A nonwoven fabric sheet (melting point: 164 ° C., circular fiber cross section, fiber diameter: 0.8 to 8 μm, basis weight: 45 g / m ^{2) formed} on the main surface opposite to the methanol supply surface of the water-absorbing and diffusing fiber woven fabric sheet ² , 0.34 mm thick), and heat-sealed by heating at 150 ° C. for 3 seconds using a hot press machine. A composite sheet having a total thickness of 0.12 mm and a polypropylene content of 46% by weight was obtained.
(Comparative Example 3)
A water-absorbing and diffusing fiber woven fabric sheet 3 was used.
(Comparative Example 4)
A water-absorbing and diffusing fiber woven fabric sheet 2 was used.
(Comparative Example 5)
A water-absorbing and diffusing fiber woven fabric sheet 1 was used.
(Comparative Example 6)
A nonwoven fabric sheet made of homopolypropylene (melting point 164 ° C., circular fiber cross section, fiber diameter 0.8-8 μm, basis weight 10 g / m ² , thickness 0.10 mm, one layer) was used.
(Evaluation)
(Methanol permeation diffusivity test)

About the sheet | seat obtained by the Example and the comparative example, a sheet | seat is mounted in the circular frame shape of inner diameter 76mm, outer diameter 86mm, and height 20mm, and a micropipette is taken from 5 mm above the 1st layer (methanol IN side) surface. 10 μL of a special grade methanol reagent colored with a small amount of blue ink was dropped. After the dropping, the sheet was visually observed, and the blue portion was judged to be due to methanol penetration and evaluated according to the following criteria.
(Methanol permeability)
○: When the blue part shape on the drop side (front) and the opposite side (back) is oval or circular, and the blue part area on the back is equal to or greater than the table. Unevenness: The blue part shape on the front and back is mosaic. When the blue area on the back is small (methanol permeation resistance)
The amount of methanol reagent dropped was set to 50 μL, and when the dropping was completed within 20 seconds, the state of formation of droplets on the opposite side (back) of the dropping was observed and evaluated according to the following criteria. The test was performed in a constant temperature and humidity environment of 40 ° C. and 90% RH.
○: No generation of droplets ×: Generation of droplets When droplets are generated, methanol permeation resistance is insufficient, which may cause a decrease in fuel cell output due to excessive methanol supply. It was judged.

According to the present invention, a direct methanol type that is excellent in methanol diffusibility and can supply methanol in a large area to the anode by the diffusion permeation effect even if the methanol aqueous solution delivery part from the fuel cartridge has a relatively small area. A composite sheet for a fuel cell can be provided.

In addition to efficient diffusion supply of high-concentration methanol aqueous solution, it can be made thin, and by using natural diffusion using fibers, diffusion auxiliary equipment such as pumps and fans can be used. Therefore, it can be suitably used for a small direct methanol fuel cell.

Claims (4)

A composite sheet for a direct methanol fuel cell, comprising a polyolefin-based resin layer and a water-absorbing and diffusing fiber woven fabric layer continuously formed on at least one main surface of the polyolefin-based resin layer. 2. The composite sheet for a direct methanol fuel cell according to claim 1, wherein a sheet made of a water-absorbing and diffusing fiber woven fabric and a sheet made of a polyolefin resin are integrally laminated by heat fusion. The composite sheet for a direct methanol fuel cell according to claim 1 or 2, wherein the content of the polyolefin resin is 10 to 45% by weight. 4. The direct methanol fuel cell composite sheet according to claim 1, wherein the polyolefin resin is polypropylene.

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