JPWO2006075611A1 - Electrolyte membrane reinforcing material, electrolyte membrane and fuel cell using the same, and method for manufacturing electrolyte membrane reinforcing material - Google Patents

Abstract

The reinforcing material of the present invention includes glass fibers and a coating of phosphosilicate gel formed on the glass fibers. Further, the electrolyte membrane of the present invention includes the reinforcing material of the present invention and the electrolyte membrane reinforced with the reinforcing material. Further, the fuel cell of the present invention includes the electrolyte membrane of the present invention.

Description

  TECHNICAL FIELD The present invention relates to an electrolyte membrane reinforcing material, an electrolyte membrane using the same, a fuel cell, and a method for manufacturing the electrolyte membrane reinforcing material.

  Fuel cells are characterized by high power generation efficiency and low environmental load. Among the fuel cells, a polymer electrolyte fuel cell (PEFC) has a high output, is easy to reduce in size and weight, and can be reduced in cost due to the effect of mass production. Therefore, PEFC is expected as a fuel cell for small-scale on-site type, automobile, and portable.

  At present, what is mainly used as a polymer proton conductive membrane (polymer electrolyte membrane) is a fluorine-based polymer containing a perfluoroalkylene chain as a main skeleton and containing an ion exchange group such as a sulfonic acid group or a carboxylic acid group. It is a polymer film. However, these fluorine-based polymer membranes swell with water content, which causes an increase in size, a decrease in mechanical strength, and the occurrence of creep during long-term operation. Therefore, the fluorine-based polymer film alone has a problem that the handleability during cell formation and the durability after the start of operation are low.

  In order to solve such a problem, attempts have been made to reinforce the polymer membrane with various reinforcing materials, and for example, an electrolyte membrane using glass fiber has been proposed (for example, Japanese Patent Laid-Open No. 10-31815, Japanese Patent Laid-Open No. 3-12815). Open 2004-047450, Unexamined-Japanese-Patent No. 2004-319421).

  However, since the glass fiber itself does not have proton conductivity, there is a problem that the proton conductivity of the electrolyte membrane decreases as the amount of the reinforcing material increases. Therefore, it was difficult to obtain a reinforcing material having high strength while maintaining proton conductivity.

  In view of such circumstances, it is an object of the present invention to provide a reinforcing material capable of forming an electrolyte membrane having high characteristics, an electrolyte membrane and a fuel cell using the same, and a method for manufacturing the reinforcing material. .

  As a result of examination to achieve the above object, the present inventors have found that by forming a coating film of phosphosilicate gel on the surface of the glass fiber, a reinforcing material capable of forming an electrolyte membrane having high properties can be obtained. It was That is, the present inventors have found that the above object can be achieved by using a fiber containing a phosphosilicate-based gel (for example, a glass fiber coated with a phosphosilicate-based gel) as a reinforcing material. The present invention is an invention based on this new finding.

  The electrolyte membrane reinforcing material of the present invention includes glass fibers and a phosphosilicate gel coating formed on the glass fibers.

  The electrolyte membrane of the present invention is an electrolyte membrane including a reinforcing material and an electrolyte reinforced with the reinforcing material, and the reinforcing material is the electrolyte membrane reinforcing material of the present invention.

  That is, the electrolyte membrane of the present invention is an electrolyte membrane containing a reinforcing material and an electrolyte reinforced with the reinforcing material, wherein the reinforcing material is a glass fiber and a phosphosilicate-based gel formed on the glass fiber. And a coating.

The method of the present invention for producing an electrolyte membrane reinforcement comprises a phosphosilicate system from a starting material comprising (i) at least one compound of formula (I) below and a compound containing a phosphoric acid structure. The method includes a step of preparing a sol, and (ii) a step of applying the phosphosilicate sol to the surface of the glass fiber and then performing a heat treatment to form a coating film of the phosphosilicate gel on the surface of the glass fiber.
Si(OR) _m X _4-m ...(I)
[In the formula (I), R represents an alkyl group, X represents a halogen atom, and m represents an integer of 1 or more and 4 or less. ]

  According to another aspect, the present invention provides a reinforcing material for reinforcing an electrolyte membrane, the reinforcing material having proton conductivity. This electrolyte membrane reinforcing material is a fibrous reinforcing material containing a phosphosilicate gel.

  Since the reinforcing material of the present invention has proton conductivity, it is possible to suppress a decrease in proton conductivity due to the reinforcing material. Further, in the reinforcing material of the present invention, since the glass fiber is covered with the coating film of phosphosilicate gel, it is possible to suppress the deterioration of the characteristics due to the elution of the glass fiber component. By using the reinforcing material of the present invention, an electrolyte membrane having high properties such as proton conductivity and durability can be obtained.

  Hereinafter, embodiments of the present invention will be described.

<Electrolyte membrane reinforcing material>
The electrolyte membrane reinforcing material of the present invention includes glass fibers and a phosphosilicate gel coating formed on the glass fibers.

  The phosphosilicate-based gel is a gel obtained by subjecting a starting material containing a compound represented by the above formula (I) to hydrolysis and condensation in a solution in which a compound containing a phosphoric acid structure is dissolved. The phosphosilicate-based gel also includes a gel obtained by heat-treating the sol obtained by the above-mentioned hydrolysis condensation. The starting material may contain a compound in which a part of the substituents of the compound represented by formula (I) is replaced with an organic group, or a metal alkoxide other than silicon alkoxide. By using a silane compound containing an organic group, a phosphosilicate gel containing an organic component can be obtained. Details of the method for producing the phosphosilicate gel will be described later.

  In the reinforcing material of the present invention, the glass fiber is coated with a coating of a phosphosilicate gel having conductivity. Therefore, the electrolyte membrane can be reinforced without significantly reducing the conductivity. Further, by coating the glass fiber with the coating of phosphosilicate gel, it is possible to prevent the metal component of the glass fiber (for example, an alkali metal such as sodium) from eluting.

  The composition of the glass fiber is not particularly limited, and may be, for example, E glass composition, S glass composition, C glass composition, or other composition. The glass fiber used for the reinforcing material may be of one type or may contain a plurality of types of glass fibers. Glass fibers having a C glass composition are preferable because they have high acid resistance. Further, the glass fibers having the E glass composition and the S glass composition are preferable because they can be easily made extremely thin. Further, the glass fiber having the E glass composition is preferable because it is inexpensive.

  Table 1 shows a general composition range of the E glass composition. In addition, the E glass composition may include one or more kinds of trace components other than the components shown in Table 1 below. The content of one trace component is usually less than 0.2% by mass (the same is true for the glass compositions in Tables 2 and 3 below).

  Table 2 shows the general composition range and the preferable composition range of the C glass composition. The C glass composition may contain one or more kinds of trace components other than the components shown in Table 2 below.

  Table 3 shows the general composition range of the S glass composition. The S glass composition may include one or more kinds of trace components other than the components shown in Table 3 below.

  In the reinforcing material of the present invention, the glass fiber may form a cloth-like sheet (hereinafter, also referred to as “glass fiber sheet”). For example, the glass fibers may form a woven fabric or a non-woven fabric. According to this structure, a sheet-shaped reinforcing material is obtained.

  When the glass fibers compose the glass fiber sheet, the glass fibers composing the sheet may be bonded together by a coating. The entangled portion of the fibers is fixed and reinforced with the coating of phosphosilicate gel, whereby a reinforcing material having high strength can be obtained. The reinforcing material may be a plurality of single fibers that do not form a glass fiber sheet.

When the reinforcing material of the present invention is in the form of a sheet, its porosity is usually in the range of 60% by volume to 98% by volume, preferably in the range of 80% by volume to 98% by volume, more preferably 85% by volume. % To 95% by volume (for example, 90% to 95% by volume). The porosity of the reinforcing material can be controlled by the size of glass fiber, the amount of glass fiber per unit volume, the amount of coating film, and the like. When the porosity exceeds 98% by volume, the strength is significantly reduced. On the other hand, when the porosity is less than 60% by volume, the flexibility is lowered, and the electrolyte membrane is likely to be damaged during assembly or pressurization. The porosity V (volume %) is calculated by the following formula.
V (volume %)=[1-W/t×{(1-cB)/ρG+cB/ρB}]×100
t: Thickness of the sheet when pressed at a pressure of 20 kPa W: Mass per unit area of the sheet ρG: Density of glass fiber (about 2.5×10 ³ kg/m ³ )
ρB: Density of coating of phosphosilicate gel cB: Mass ratio of coating of phosphosilicate gel to the mass of the sheet

  The density ρB of the coating of the phosphosilicate gel was measured by preparing a mass of the phosphosilicate gel under the same conditions as the coating. The mass ratio cB of the phosphosilicate gel coating film was calculated by measuring the mass of the sheet before the film formation and the mass of the sheet after the film formation.

  When the reinforcing material of the present invention is in the form of a sheet, its thickness is, for example, 100 μm or less, preferably 50 μm or less. Note that this thickness is a value obtained by measuring the thickness of the sheet pressed with a pressure of 20 kPa with a dial gauge.

When the reinforcing material of the present invention is in the form of a sheet, its basis weight (mass per unit area) is, for example, in the range of ² g/m ^{2 to} 50 g/m ² , and in one example, 3 g/m ^{2 to} 25 g/m. It is in the range of ² .

  Further, the glass fiber may be a short fiber that does not form a cloth-like sheet. In this case, the glass fibers are dispersed in the electrolyte.

  The average diameter and the average fiber length of the glass fiber are selected according to conditions such as desired strength, shape of the reinforcing material, and glass composition. An example of the average diameter of the glass fiber may be in the range of 0.1 μm to 20 μm. Moreover, an example of the average length of the glass fibers may be in the range of 0.5 mm to 20 mm.

  The phosphosilicate-based gel (phosphosilicate glass) coating can be formed by, for example, a sol-gel method. The amount of the phosphosilicate gel coating is, for example, in the range of 1% by mass to 90% by mass (for example, in the range of 2% by mass to 30% by mass) of the entire reinforcing material. The method for producing the phosphosilicate gel coating will be described later.

  The surface of the coating of the phosphosilicate gel may be treated with a silane coupling agent. The treatment with the silane coupling agent increases the binding force between the reinforcing material and the electrolyte. When the reinforcing material and the electrolyte have different thermal expansion coefficients, if the reinforcing material and the electrolyte are weakly bonded, the reinforcing material and the electrolyte may be separated due to temperature change. As a result, water clusters in the electrolyte membrane may be divided or deformed, and the proton conductivity may be reduced. Such a decrease in proton conductivity can be suppressed by increasing the bonding force between the reinforcing material and the electrolyte by using the silane coupling agent. Examples of silane coupling agents include aminosilane, methacrylsilane, epoxysilane, vinylsilane, mercaptosilane, isocyanatesilane, and fluorosilane.

  The coating may be a phosphosilicate gel containing no organic component or a phosphosilicate gel containing an organic component. These phosphosilicate gels will be described later.

<Electrolyte membrane>
The electrolyte membrane (proton conductive membrane) of the present invention includes the reinforcing material of the present invention and an electrolyte reinforced with the reinforcing material.

  What is called a solid electrolyte can be applied to the electrolyte, and for example, a polymer electrolyte, an inorganic-organic composite electrolyte, or an inorganic electrolyte can be applied.

  The electrolyte may be a polyelectrolyte. The polymer electrolyte is not particularly limited, but for example, has perfluoroalkylene as a main skeleton, has a perfluorovinyl ether side chain, and has an ion exchange group such as a sulfonic acid group or a carboxylic acid group at the end of a part of the side chain. A fluorine-based polymer having the same can be used. As the fluorine-based polymer, for example, Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Chemical Industry Co., Ltd., or Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd. may be used. Good.

  The proportion of the reinforcing material in the entire electrolyte membrane may be, for example, in the range of 2% by volume to 40% by volume. The thickness of the electrolyte membrane may be, for example, 100 μm or less, preferably 50 μm or less.

<Fuel cell>
The fuel cell of the present invention comprises the electrolyte membrane of the present invention. The parts other than the electrolyte membrane are not particularly limited, and any material and structure can be applied. A preferable example of the fuel cell of the present invention is a fuel cell obtained by replacing the electrolyte membrane of a known polymer electrolyte fuel cell with the electrolyte membrane of the present invention. In this case, the material and structure of a known polymer electrolyte fuel cell can be applied to the portion other than the electrolyte membrane, and it can be manufactured by a known method.

<Method of manufacturing electrolyte membrane reinforcing material>
Hereinafter, an example of the method of the present invention for producing a reinforcing material for an electrolyte membrane will be described. According to this method, the reinforcing material of the present invention can be obtained.

First, a phosphosilicate sol is prepared from a starting material containing at least one compound represented by the following formula (I) (hereinafter sometimes referred to as compound (A)) and a compound having a phosphoric acid structure. (Step (i)).
Si(OR) _m X _4-m ...(I)
[In the formula (I), R represents an alkyl group, X represents a halogen atom, and m represents an integer of 1 or more and 4 or less. ]

  R in the formula (I) is an alkyl group having 5 or less carbon atoms, such as a methyl group or an ethyl group. X is a halogen atom such as chlorine, fluorine or bromine. The compound of formula (I) is a compound that becomes a sol by hydrolysis and condensation, and is typically tetraalkoxysilane.

  Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

In this specification, the phosphate structure includes structures such as “PO ₄ ”and “PO ₃ ”. Usually, a compound containing “PO ₄ (phosphate ion: PO ₄ ³⁻ )” as a phosphate structure is used. That is, phosphoric acid (P ₂ O ₅ .nH ₂ O) is usually used as a compound having a phosphoric acid structure (hereinafter, may be referred to as “phosphoric acid compound”). For example, orthophosphoric acid (H ₃ PO ₄ ) Is used. Further, metaphosphoric acid (HPO ₃ ) or pyrophosphoric acid (H ₄ P ₂ O ₇ ) may be used as the phosphoric acid compound.

  The phosphosilicate sol may be formed by a method of causing hydrolysis condensation in a solution containing the compound (A) and a phosphoric acid compound, or after partially hydrolyzing and condensing the compound (A), You may form by the method of adding a phosphoric acid compound and further hydrolyzing and condensing. Hydrolytic condensation can be performed by a method used in a known sol-gel method, for example, a method of reacting in a solution containing water, an acid catalyst, and optionally an alcohol. As described below, in addition to the compound (A), a compound in which a part of the substituents of the chemical formula (I) is the organic group Z may be hydrolyzed and condensed.

  Next, the phosphosilicate sol is applied to the surface of the glass fiber and then heat-treated to form a phosphosilicate gel film on the surface of the glass fiber (step (ii)).

  The glass fiber described above can be used as the glass fiber. As described above, this glass fiber may form a cloth-like sheet (glass fiber sheet).

  The coating is formed by, for example, dropping a predetermined amount of phosphosilicate sol on a flat plate, immersing glass fibers (for example, a glass fiber sheet) in the sol under normal pressure or reduced pressure, and drying and heat-treating in that state. You may. In this method, the amount of the coating film can be controlled by the concentration of the sol and the dropping amount. Further, the coating film may be formed by immersing glass fiber in a phosphosilicate sol, then pulling it up, and drying and heat treatment. In this method, the amount of the coating can be controlled by the concentration of the sol and the pulling rate of the glass fiber.

  The amount of the coating film may be controlled by the amount of sol with which the glass fiber is impregnated, or may be controlled by repeating step (ii) a plurality of times.

  The sol is preferably dried at a temperature of 20°C to 70°C. The heat treatment after drying is preferably performed at a temperature of 100° C. or higher, and may be performed in the range of 100° C. to 350° C., for example.

In addition to the compound (A), the material of the phosphosilicate sol may further include a compound in which some of the substituents of the formula (I) are other substituents. A film of a phosphosilicate-based gel containing an organic component can be formed by adding a compound in which a part (for example, one) of the four substituents of the formula (I) is an organic group. In this case, the starting material contains at least one compound represented by the following formula (II) in addition to the compound (A).
Si(OR ² ) _s X ² _t Z _4-st ...(II)
[In the formula (I), R ² represents an alkyl group, X ² represents a halogen atom, and Z represents an alkoxy group or an organic group other than a halogen atom. 0≦s≦3, 0≦t≦3, 1≦s+t≦3. ]

The alkyl group or halogen atom described for R and X in formula (I) can be applied to R ² and X ² , respectively. Examples of the organic group Z include organic groups containing an epoxy group, an amino group, an acryl group, and the like, and specifically, a γ-glycidoxypropyl group or the like can be used.

  A phosphosilicate gel containing an organic component is obtained by hydrolytically condensing the compound (A) and at least one compound represented by the chemical formula (II) in a solution in which a compound containing a phosphoric acid structure is dissolved. Can be formed.

  However, the proton conductivity of a phosphosilicate-based gel that does not substantially contain an organic component (such as an alkyl chain) is about 10 times the proton conductivity of a phosphosilicate-based gel that contains an organic component. Therefore, from the viewpoint of conductivity, it is preferable to use the compound of formula (I) and phosphoric acid to prepare a phosphosilicate sol substantially free of organic components. On the other hand, a coating film of a phosphosilicate-based gel containing an organic component has higher toughness than a phosphosilicate-based gel containing only an inorganic component, and is therefore preferable in that a reinforcing material having a higher tensile strength can be obtained.

  The starting material for the phosphosilicate gel may include other metal alkoxide such as alkoxyaluminum. However, the amount (molar amount) of the other metal alkoxide is smaller than the total amount (molar amount) of the compound represented by the chemical formula (I) and the compound represented by the chemical formula (II).

<Method for producing electrolyte membrane>
When the reinforcing material is a glass fiber sheet, an electrolyte membrane is obtained by disposing an electrolyte in the voids of the glass fiber sheet. For example, the glass fiber sheet may be impregnated with an electrolyte solution, dispersion or sol and then dried. In addition, you may heat-process after drying as needed.

  When the reinforcing material is a glass fiber sheet and the electrolyte is a polymer electrolyte, for example, the glass fiber sheet may be dipped in a solution or dispersion of the polymer electrolyte and then dried. For example, first, a dispersion liquid of a fluoropolymer electrolyte (polymer electrolyte) is prepared, and a glass fiber sheet is impregnated with a solution obtained by diluting the dispersion liquid with isopropyl alcohol. Then, the glass fiber sheet impregnated with the electrolyte solution is dried and heat-treated to obtain an electrolyte membrane.

  When the reinforcing material is not a glass fiber sheet but an aggregate of single fibers, a solution, dispersion or sol of electrolyte and a plurality of single fibers are mixed and dried to obtain an electrolyte membrane reinforced with single fibers. be able to. At this time, if necessary, heat treatment may be performed after drying. For example, an electrolyte membrane is obtained by mixing a solution or dispersion containing a polymer electrolyte with a plurality of single fibers, rolling the mixed solution into a film, and drying (heat treatment if necessary).

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, glass fibers having the C glass composition shown in Table 4 were used, but other glass fibers described above may be used.

[Example 1]
Glass short fibers having the C glass composition shown in Table 4 and having an average diameter of 0.7 μm and an average length of about 3 mm were prepared. The glass fiber was put into a pulper for disentangling the fiber, and sufficiently dissociated and dispersed in an aqueous solution adjusted to pH 2.5 with sulfuric acid. In this way, a glass fiber dispersion liquid was prepared.

A glass fiber nonwoven fabric (1) was prepared from this glass fiber dispersion using a wet papermaking machine. The nonwoven fabric (1) had a thickness of 90 μm and a basis weight of 14 g/m ² . The non-woven fabric (1) had a porosity of about 95% by volume.

  Next, a coating of phosphosilicate gel was formed on the glass fiber of the nonwoven fabric (1) by the following method. First, tetraethoxysilane, orthophosphoric acid, ethanol, and pure water were mixed at a molar ratio of about 1:1:5:3 and stirred for 2 hours to obtain a phosphosilicate sol. An appropriate amount of this sol was poured into a polyolefin tray, and the glass fiber nonwoven fabric (1) was immersed in the sol. Then, the nonwoven fabric was pulled up from the sol, dried and heat-treated. In this way, a glass fiber non-woven fabric (2) on which a phosphosilicate gel coating film was formed was obtained.

  The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 94.8% by volume.

  Next, a proton conductive membrane was produced using the nonwoven fabric (2). First, a non-woven fabric (2) was impregnated with a solution obtained by diluting a dispersion liquid of a fluoropolymer electrolyte (Nafion DE2020: manufactured by DuPont) with isopropyl alcohol, and naturally dried for 12 hours or more. Then, after heat-treating at 120 degreeC for 1 hour, it pressed at 120 degreeC and 10 MPa with the hot press apparatus. Thus, a proton conductive membrane was obtained. The concentration and impregnation amount of the electrolyte dispersion liquid were adjusted so that the thickness of the film after hot pressing was 80 μm.

[Examples 2 to 4]
A coated glass fiber nonwoven fabric (2) was formed in the same manner as in Example 1 except that the volume of the phosphosilicate gel coating formed on the glass fiber was changed. The volume of the phosphosilicate gel coating was about 10% in Example 2, about 40% in Example 3, and about 60% in Example 4 with respect to the volume of the glass fiber.

  The volume of the coating was controlled by changing the amount of the phosphosilicate sol with which the glass fiber nonwoven fabric (1) was impregnated.

  The porosity of the formed nonwoven fabric (2) was about 94.5% in Example 2, about 93% in Example 3, and about 92% in Example 4. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Example 1.

[Example 5]
On the glass fiber of the glass fiber non-woven fabric (1) described in Example 1, a coating film of phosphosilicate gel containing an organic component was formed by the following method. First, tetraethoxysilane, γ-glycidoxypropyltrimethoxysilane, orthophosphoric acid, ethanol, and pure water are mixed at a molar ratio of about 0.25:0.75:1:5:3, and 2 After stirring for a time, a phosphosilicate sol containing an organic component was obtained. An appropriate amount of this sol was poured into a polyolefin tray, and the glass fiber nonwoven fabric (1) was immersed in the sol. Then, the sol was dried at 20 to 70° C. while the nonwoven fabric (1) was kept in the tray, then transferred from the tray to a smooth glass plate and heat-treated at 120 to 200° C. In this way, a glass fiber non-woven fabric (2) on which a phosphosilicate gel coating containing an organic component was formed was obtained.

  The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 94.8% by volume. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Example 1.

[Examples 6 to 9]
A glass fiber nonwoven fabric (2) having a coating of a phosphosilicate gel containing an organic component was formed in the same manner as in Example 5 except that the volume of the coating formed on the glass fiber was changed. .. The volume of the coating of the phosphosilicate gel containing the organic component was about 10% in Example 6, about 40% in Example 7, about 60% in Example 8 and the volume in Example 9 with respect to the volume of the glass fiber. It was set to about 200%.

  The volume of the coating was changed by adjusting the volume of the sol.

  The non-woven fabric (2) obtained had a porosity of about 94.5% in Example 6, about 93% in Example 7, about 92% in Example 8 and about 85% in Example 9. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Example 1.

[Example 10]
Glass short fibers having the C glass composition shown in Table 4 and having an average diameter of 0.7 μm and an average length of about 3 mm were prepared. The glass fiber was put into a pulper for disentangling the fiber, and sufficiently dissociated and dispersed in an aqueous solution adjusted to pH 2.5 with sulfuric acid. In this way, a glass fiber dispersion liquid was prepared.

A glass fiber sheet was formed from this glass fiber dispersion using a wet papermaking apparatus, and further pressed before drying to prepare a glass fiber nonwoven fabric (1). The glass fiber nonwoven fabric (1) had a thickness of 90 μm and a basis weight of 30 g/m ² . The porosity of this glass fiber nonwoven fabric was about 87% by volume.

  Next, a phosphosilicate film containing an organic component was formed on the glass fiber of the glass fiber nonwoven fabric (1) by the following method. First, tetraethoxysilane, orthophosphoric acid, ethanol, and pure water were mixed at a molar ratio of about 1:1:5:3 and stirred for 2 hours to obtain a phosphosilicate sol. An appropriate amount of this sol was poured into a polyolefin tray to impregnate the sol with the glass fiber nonwoven fabric (1). Then, the nonwoven fabric was pulled up from the sol, dried and heat-treated. In this way, a glass fiber non-woven fabric (2) on which a phosphosilicate gel coating containing an organic component was formed was obtained. The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 86% by volume. Using this nonwoven fabric (2), a proton conductive membrane was formed in the same procedure as in Example 1.

[Comparative Example 1]
The electrolyte dispersion liquid used in Example 1 was put in a glass petri dish having a good flatness on the bottom surface, naturally dried for 12 hours or more, and then heat-treated at 120° C. for 1 hour to form a film. This membrane-shaped electrolyte was pressed at 120° C. and 10 MPa with a hot press machine to obtain a proton conductive membrane. The concentration of the electrolyte dispersion was the same as in Example 1, and the amount of the liquid was adjusted so that the thickness of the film after hot pressing was 80 μm.

[Comparative example 2]
A proton conductive membrane was formed in the same manner as in Example 1 except that the glass fiber nonwoven fabric (1) described in Example 1 was used as a reinforcing material as it was without forming a film. The concentration and impregnation amount of the electrolyte dispersion liquid were adjusted so that the thickness of the film after hot pressing was 80 μm.

[Evaluation of reinforcing material and proton conductive membrane]
The following measurements were performed on the reinforcing materials and the proton conductive membranes produced in Examples 1 to 10 and Comparative Examples 1 and 2 described above. In addition, the reinforcing material of Examples 1-10 is a glass fiber nonwoven fabric (2) provided with a coating, and the reinforcing material of Comparative Example 2 is a glass fiber nonwoven fabric (1) not provided with a coating.

[Thickness of reinforcing material]
The thickness of the reinforcing material was measured using a thickness gauge while the reinforcing material was pressed at a pressure of about 20 kPa.

[Proton Conductive Membrane Thickness]
It measured using the micrometer.

[Measurement of tensile strength of reinforcing material and proton conductive membrane]
Each of the reinforcing material and the electrolyte membrane was cut into a width of 20 mm and a length of 80 mm to prepare a test piece. The test piece was chucked at a chuck interval of 30 mm and pulled at a speed of 10 mm/min to measure the load (N) at break. This measured value was divided by the measured values of the sample thickness and width to calculate the tensile strength (MPa).

[Proton conductivity]
Using an impedance analyzer, the proton conductivity (S/m) in the thickness direction of the proton conductive membrane was measured.

  Table 5 shows the above measurement results.

  As is clear from Table 5, the reinforcing materials of Examples 1 to 10 had higher tensile strength than the reinforcing material of Comparative Example 2. In addition, the proton conductive membranes of Examples 1 to 10 had equivalent proton conductivity and higher tensile strength than the proton conductive membranes of Comparative Examples.

  INDUSTRIAL APPLICABILITY The present invention can be applied to an electrolyte membrane reinforcing material used for a fuel cell, and an electrolyte membrane and a fuel cell using the same. Further, the present invention can be applied to a method for manufacturing an electrolyte membrane reinforcing material.

[0002]
[0007]
As a result of examination to achieve the above object, the present inventors have found that by forming a coating film of phosphosilicate gel on the surface of the glass fiber, a reinforcing material capable of forming an electrolyte membrane having high properties can be obtained. It was That is, the present inventors have found that the above object can be achieved by using a fiber containing a phosphosilicate gel (for example, a glass fiber coated with a phosphosilicate gel) as a reinforcing material. The present invention is an invention based on this new finding.
[0008]
The electrolyte membrane reinforcing material of the present invention is an electrolyte membrane reinforcing material comprising a glass fiber and a coating of phosphosilicate-based gel formed on the glass fiber, wherein the coating is a phosphosilicate-based gel containing an organic component. is there.
[0009]
The electrolyte membrane of the present invention is an electrolyte membrane including a reinforcing material and an electrolyte reinforced with the reinforcing material, and the reinforcing material is the electrolyte membrane reinforcing material of the present invention.
[0010]
That is, the electrolyte membrane of the present invention is an electrolyte membrane containing a reinforcing material and an electrolyte reinforced with the reinforcing material, wherein the reinforcing material is a glass fiber and a phosphosilicate-based gel formed on the glass fiber. And a coating, and the coating is a phosphosilicate gel containing an organic component.
[0011]
The method of the present invention for producing an electrolyte membrane reinforcement comprises a phosphosilicate system from a starting material comprising (i) at least one compound of formula (I) below and a compound containing a phosphoric acid structure. A step of preparing a sol; and (ii) applying the phosphosilicate sol to the surface of the glass fiber and then heat treating it to form a phosphosilicate gel coating on the surface of the glass fiber, The starting material comprises at least one compound of formula (II) below.
Si(OR) _{mX4 -m} ...(I)
[In the formula (I), R represents an alkyl group, X represents a halogen atom, and m represents an integer of 1 or more and 4 or less. ]
^{_{Si (OR 2) s X 2}} t Z 4-s-t ··· (II)
[In Formula (II), R ² represents an alkyl group, X ² represents a halogen atom, and Z represents an organic group other than an alkoxy group and a halogen atom. 0≦s≦3, 0≦t≦3, 1≦s+t≦3. ]
[0012]
According to another aspect, the present invention provides a reinforcing material for reinforcing an electrolyte membrane, the reinforcing material having proton conductivity. This electrolyte membrane reinforcing material is a fibrous reinforcing material containing a phosphosilicate gel.
[0013]
Since the reinforcing material of the present invention has proton conductivity, it is possible to suppress a decrease in proton conductivity due to the reinforcing material. Further, in the reinforcing material of the present invention, since the glass fiber is covered with the coating film of phosphosilicate gel, it is possible to suppress the deterioration of characteristics due to the elution of the glass fiber component. By using the reinforcing material of the present invention, properties such as proton conductivity and durability are improved.

[0007]
, Isocyanate silane, and fluorosilane.
[0035]
The coating is a phosphosilicate gel containing an organic component. This phosphosilicate gel will be described later.
[0036]
<Electrolyte membrane>
The electrolyte membrane (proton conductive membrane) of the present invention includes the reinforcing material of the present invention and an electrolyte reinforced with the reinforcing material.
[0037]
What is called a solid electrolyte can be applied to the electrolyte, and for example, a polymer electrolyte, an inorganic-organic composite electrolyte, or an inorganic electrolyte can be applied.
[0038]
The electrolyte may be a polyelectrolyte. The polymer electrolyte is not particularly limited, but for example, has perfluoroalkylene as a main skeleton, has a perfluorovinyl ether side chain, and has an ion exchange group such as a sulfonic acid group or a carboxylic acid group at the end of a part of the side chain A fluorine-based polymer having the same can be used. As the fluorine-based polymer, for example, Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Kogyo Co., Ltd., or Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd. may be used. Good.
[0039]
The proportion of the reinforcing material in the entire electrolyte membrane may be, for example, in the range of 2% by volume to 40% by volume. The thickness of the electrolyte membrane may be, for example, 100 μm or less, preferably 50 μm or less.
[0040]
<Fuel cell>
The fuel cell of the present invention comprises the electrolyte membrane of the present invention. The parts other than the electrolyte membrane are not particularly limited, and any material and structure can be applied. A preferable example of the fuel cell of the present invention is a fuel cell obtained by replacing the electrolyte membrane of a known polymer electrolyte fuel cell with the electrolyte membrane of the present invention. In this case, the material and structure of a known polymer electrolyte fuel cell can be applied to the portion other than the electrolyte membrane, and it can be manufactured by a known method.
[0041]
<Method of manufacturing electrolyte membrane reinforcing material>
Hereinafter, an example of the method of the present invention for producing a reinforcing material for an electrolyte membrane will be described. This

[0008]
According to the above method, the reinforcing material of the present invention can be obtained.
[0042]
First, a phosphosilicate sol is prepared from a starting material containing at least one compound represented by the following formula (I) (hereinafter sometimes referred to as compound (A)) and a compound having a phosphoric acid structure. (Step (i)).
Si(OR) _{mX4 -m} ...(I)
[In the formula (I), R represents an alkyl group, X represents a halogen atom, and m represents an integer of 1 or more and 4 or less. ]
[0043]
R in the formula (I) is an alkyl group having 5 or less carbon atoms, such as a methyl group or an ethyl group. X is a halogen atom such as chlorine, fluorine or bromine. The compound of formula (I) is a compound that becomes a sol by hydrolysis and condensation, and is typically tetraalkoxysilane.
[0044]
Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.
[0045]
In this specification, the phosphate structure includes structures such as “PO ₄ ”and “PO ₃ ”. Usually, a compound containing “PO ₄ (phosphate ion: PO ₄ ³⁻ )” as a phosphate structure is used. That is, phosphoric acid (P ₂ O ₅ .nH ₂ O) is usually used as the compound having a phosphoric acid structure (hereinafter, may be referred to as “phosphoric acid compound”), and for example, orthophosphoric acid (H ₃ PO _{4 ).} ) Is used. Further, metaphosphoric acid (HPO ₃ ) or pyrophosphoric acid (H ₄ P ₂ O ₇ ) may be used as the phosphoric acid compound.
[0046]
The phosphosilicate sol may be formed by a method of causing hydrolysis and condensation in a solution containing the compound (A) and a phosphoric acid compound, or after partially hydrolyzing and condensing the compound (A), You may form by the method of adding a phosphoric acid compound and further hydrolyzing and condensing. Hydrolytic condensation can be performed by a method used in a known sol-gel method, for example, a method of reacting in a solution containing water, an acid catalyst, and optionally an alcohol. As will be described later, in addition to the compound (A), a compound in which a part of the substituents of the chemical formula (I) is the organic group Z is hydrolytically condensed.
[0047]
Next, the phosphosilicate sol is applied to the surface of the glass fiber and then heat-treated to form a phosphosilicate gel coating on the surface of the glass fiber (step (ii)).
[0048]
The glass fiber described above can be used as the glass fiber. As mentioned above, this

[0009]
The lath fibers may form a cloth-like sheet (glass fiber sheet).
[0049]
The coating is formed, for example, by dropping a predetermined amount of phosphosilicate sol on a flat plate, immersing the glass fiber (eg, glass fiber sheet) in the sol under normal pressure or reduced pressure, and drying and heat-treating in that state. You may. In this method, the amount of the coating film can be controlled by the concentration of the sol and the dropping amount. Alternatively, the coating may be formed by immersing glass fiber in a phosphosilicate sol, then pulling it up, and drying and heat treatment. In this method, the amount of the coating can be controlled by the concentration of the sol and the pulling rate of the glass fiber.
[0050]
The amount of the coating film may be controlled by the amount of the sol with which the glass fiber is impregnated, or may be controlled by repeating the step (ii) a plurality of times.
[0051]
The sol is preferably dried at a temperature of 20°C to 70°C. The heat treatment after drying is preferably performed at a temperature of 100° C. or higher, and may be performed in the range of 100° C. to 350° C., for example.
[0052]
The material of the phosphosilicate sol further contains, in addition to the compound (A), a compound in which some of the substituents of the formula (I) are other substituents. A film of a phosphosilicate-based gel containing an organic component can be formed by adding a compound in which a part (for example, one) of the four substituents of the formula (I) is an organic group. In this case, the starting material contains at least one compound represented by the following formula (II) in addition to the compound (A).
^{_{Si (OR 2) s X 2}} t Z 4-s-t ··· (II)
[In Formula (II), R ² represents an alkyl group, X ² represents a halogen atom, and Z represents an organic group other than an alkoxy group and a halogen atom. 0≦s≦3, 0≦t≦3, 1≦s+t≦3. ]
[0053]
The alkyl group or halogen atom described for R and X in formula (I) can be applied to R ² and X ² , respectively. Examples of the organic group Z include organic groups containing an epoxy group, an amino group, an acryl group, and the like, and specifically, a γ-glycidoxypropyl group or the like can be used.
[0054]
In a solution in which a compound containing a phosphoric acid structure is dissolved, the compound (A) and at least one compound represented by the chemical formula (II) are hydrolyzed and condensed to contain an organic component.

［００６２］
［参考例１］
表４に示したＣガラス組成を有し、平均直径０．７μｍで平均長さ約３ｍｍのガラス短繊維を用意した。このガラス繊維を、繊維を解きほぐすためのパルパーに投入し、硫酸でｐＨ２．５に調整した水溶液中で充分に解離、分散させた。このようにして、ガラス繊維分散液を作製した。
［００６３］
このガラス繊維分散液から、湿式抄紙装置を用いて、ガラス繊維の不織布（１）を作製した。不織布（１）は、厚さが９０μｍであり、目付量は１４ｇ／ｍ^２であった。不織布（１）の空隙率は、約９５体積％であった。
［００６４］
次に、不織布（１）のガラス繊維上に、ホスホシリケート系ゲルの被膜を以下の方法で形成した。まず、テトラエトキシシラン、オルトリン酸、エタノール、および純水を、モル比でおよそ１：１：５：３の割合で混合し、２時間撹拌して、ホスホシリケート系ゾルを得た。このゾルをポリオレフィン製トレイに適量注ぎ、ゾル中にガラス繊維不織布（１）を浸漬した。その後、不織布をゾルから引き上げて乾燥および熱処理した。このよう[0011]
A degrading film is obtained.
【Example】
[0060]
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, glass fibers having the C glass composition shown in Table 4 were used, but other glass fibers described above may be used.
[0061]
[Table 4]

[0062]
[Reference Example 1]
Glass short fibers having the C glass composition shown in Table 4 and having an average diameter of 0.7 μm and an average length of about 3 mm were prepared. The glass fiber was put into a pulper for disentangling the fiber, and sufficiently dissociated and dispersed in an aqueous solution adjusted to pH 2.5 with sulfuric acid. In this way, a glass fiber dispersion liquid was prepared.
[0063]
A glass fiber nonwoven fabric (1) was prepared from this glass fiber dispersion using a wet papermaking machine. The nonwoven fabric (1) had a thickness of 90 μm and a basis weight of 14 g/m ² . The non-woven fabric (1) had a porosity of about 95% by volume.
[0064]
Next, a coating of phosphosilicate gel was formed on the glass fiber of the nonwoven fabric (1) by the following method. First, tetraethoxysilane, orthophosphoric acid, ethanol, and pure water were mixed at a molar ratio of about 1:1:5:3 and stirred for 2 hours to obtain a phosphosilicate sol. An appropriate amount of this sol was poured into a polyolefin tray, and the glass fiber nonwoven fabric (1) was immersed in the sol. Then, the nonwoven fabric was pulled up from the sol, dried and heat-treated. like this

[0012]
Thus, a glass fiber non-woven fabric (2) having a phosphosilicate gel coating formed thereon was obtained.
[0065]
The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 94.8% by volume.
[0066]
Next, a proton conductive membrane was produced using the nonwoven fabric (2). First, a non-woven fabric (2) was impregnated with a liquid obtained by diluting a dispersion liquid of a fluoropolymer electrolyte (Nafion DE2020: manufactured by DuPont) with isopropyl alcohol, and naturally dried for 12 hours or more. Then, after heat-treating at 120 degreeC for 1 hour, it pressed at 120 degreeC and 10 MPa with the hot press apparatus. Thus, a proton conductive membrane was obtained. The concentration and impregnation amount of the electrolyte dispersion liquid were adjusted so that the thickness of the film after hot pressing was 80 μm.
[0067]
[Reference Examples 2 to 4]
A coated glass fiber nonwoven fabric (2) was formed in the same manner as in Reference Example 1 except that the volume of the phosphosilicate gel coating formed on the glass fiber was changed. The volume of the phosphosilicate gel coating was about 10% in Reference Example 2, about 40% in Reference Example 3, and about 60% in Reference Example 4 with respect to the volume of the glass fiber.
[0068]
The volume of the coating was controlled by changing the amount of the phosphosilicate sol with which the glass fiber nonwoven fabric (1) was impregnated.
[0069]
The porosity of the formed nonwoven fabric (2) was about 94.5% in Reference Example 2, about 93% in Reference Example 3, and about 92% in Reference Example 4. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Reference Example 1.
[0070]
[Example 5]
On the glass fiber of the glass fiber nonwoven fabric (1) described in Reference Example 1, a coating film of phosphosilicate gel containing an organic component was formed by the following method. First, tetraethoxysilane, γ-glycidoxypropyltrimethoxysilane, orthophosphoric acid, ethanol, and pure water are mixed at a molar ratio of about 0.25:0.75:1:5:3, and 2 After stirring for a time, a phosphosilicate sol containing an organic component was obtained. An appropriate amount of this sol was poured into a polyolefin tray, and the glass fiber nonwoven fabric (1) was immersed in the sol. Thereafter, the sol was dried at 20 to 70° C. while the nonwoven fabric (1) was kept in the tray, then transferred from the tray to a smooth glass plate and heat treated at 120 to 200° C. In this way, the phosphosilicate-based gel containing organic components

[0013]
A glass fiber nonwoven fabric (2) having a coating film was obtained.
[0071]
The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 94.8% by volume. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Reference Example 1.
[0072]
[Examples 6 to 9]
A glass fiber nonwoven fabric (2) having a coating of a phosphosilicate gel containing an organic component was formed in the same manner as in Example 5 except that the volume of the coating formed on the glass fiber was changed. .. The volume of the coating of the phosphosilicate gel containing the organic component was about 10% in Example 6, about 40% in Example 7, about 60% in Example 8 and the volume in Example 9 with respect to the volume of the glass fiber. It was set to about 200%.
[0073]
The volume of the coating was changed by adjusting the volume of the sol.
[0074]
The porosity of the obtained nonwoven fabric (2) was about 94.5% in Example 6, about 93% in Example 7, about 92% in Example 8 and about 85% in Example 9. Using these nonwoven fabrics (2), a proton conductive membrane was formed in the same procedure as in Reference Example 1.
[0075]
[Example 10]
Glass short fibers having the C glass composition shown in Table 4 and having an average diameter of 0.7 μm and an average length of about 3 mm were prepared. The glass fiber was put into a pulper for disentangling the fiber, and sufficiently dissociated and dispersed in an aqueous solution adjusted to pH 2.5 with sulfuric acid. In this way, a glass fiber dispersion liquid was prepared.
[0076]
A glass fiber sheet was formed from this glass fiber dispersion using a wet papermaking machine, and further pressed before drying to prepare a glass fiber nonwoven fabric (1). The glass fiber nonwoven fabric (1) had a thickness of 90 μm and a basis weight of 30 g/m ² . The porosity of this glass fiber nonwoven fabric was about 87% by volume.
[0077]
Next, a phosphosilicate film containing an organic component was formed on the glass fiber of the glass fiber nonwoven fabric (1) by the following method. First, tetraethoxysilane, orthophosphoric acid, ethanol, and pure water were mixed at a molar ratio of about 1:1:5:3 and stirred for 2 hours to obtain a phosphosilicate sol. An appropriate amount of this sol was poured into a polyolefin tray to impregnate the sol with the glass fiber nonwoven fabric (1). After that, pull the nonwoven fabric out of the sol to dry and heat it.

[0014]
Processed. In this way, a glass fiber non-woven fabric (2) on which a phosphosilicate gel coating containing an organic component was formed was obtained. The volume of the phosphosilicate gel coating was about 5% of the volume of the glass fiber. The porosity of the glass fiber nonwoven fabric (2) was about 86% by volume. Using this non-woven fabric (2), a proton conductive membrane was formed in the same procedure as in Reference Example 1.
[0078]
[Comparative Example 1]
The electrolyte dispersion liquid used in Reference Example 1 was placed in a glass petri dish having a good flatness on the bottom surface, naturally dried for 12 hours or more, and then heat-treated at 120° C. for 1 hour to form a film. This membrane-shaped electrolyte was pressed at 120° C. and 10 MPa with a hot press machine to obtain a proton conductive membrane. The concentration of the electrolyte dispersion was the same as in Reference Example 1, and the amount of the liquid was adjusted so that the thickness of the film after hot pressing was 80 μm.
[0079]
[Comparative example 2]
A proton conductive membrane was formed in the same manner as in Reference Example 1, except that the glass fiber nonwoven fabric (1) described in Reference Example 1 was used as a reinforcing material as it was without forming a coating film. The concentration and impregnation amount of the electrolyte dispersion liquid were adjusted so that the thickness of the film after hot pressing was 80 μm.
[0080]
[Evaluation of reinforcing material and proton conductive membrane]
The following measurements were performed on the reinforcing materials and the proton conductive membranes produced in Reference Examples 1 to 4, Examples 5 to 10 and Comparative Examples 1 and 2 described above. The reinforcing materials of Reference Examples 1 to 4 and Examples 5 to 10 were glass fiber nonwoven fabrics (2) having a coating film, and the reinforcing materials of Comparative Example 2 were glass fiber nonwoven fabric (1) having no coating film. ..
[0081]
[Thickness of reinforcing material]
The thickness of the reinforcing material was measured using a thickness gauge while the reinforcing material was pressed at a pressure of about 20 kPa.
[0082]
[Proton Conductive Membrane Thickness]
It measured using the micrometer.
[0083]
[Measurement of tensile strength of reinforcing material and proton conductive membrane]
Each of the reinforcing material and the electrolyte membrane is cut into a width of 20 mm and a length of 80 mm to obtain a test piece.

［００８７］
表５から明らかなように、参考例１〜４および実施例５〜１０の補強材は、比較例２の補強材に比べて、引張強度が高かった。また、参考例１〜４および実施例５〜１０のプロトン伝導性膜は、比較例のプロトン伝導性膜と比べて、プロトン伝導度が同等であり引張強度が高かった。
【産業上の利用可能性】
［００８８］
本発明は、燃料電池に用いられる電解質膜の補強材、ならびにそれを用いた電解質膜および燃料電池に適用できる。また、本発明は、電解質膜補強材の製造方法に適用できる。[0015]
It was made. The test piece was chucked at a chuck interval of 30 mm and pulled at a speed of 10 mm/min to measure the load (N) at break. This measured value was divided by the measured values of the sample thickness and width to calculate the tensile strength (MPa).
[0084]
[Proton conductivity]
Using an impedance analyzer, the proton conductivity (S/m) in the thickness direction of the proton conductive membrane was measured.
[0085]
Table 5 shows the above measurement results.
[0086]
[Table 5]

[0087]
As is clear from Table 5, the reinforcing materials of Reference Examples 1 to 4 and Examples 5 to 10 had higher tensile strength than the reinforcing material of Comparative Example 2. In addition, the proton conductive membranes of Reference Examples 1 to 4 and Examples 5 to 10 had equivalent proton conductivity and higher tensile strength than the proton conductive membranes of Comparative Examples.
[Industrial availability]
[0088]
INDUSTRIAL APPLICABILITY The present invention can be applied to an electrolyte membrane reinforcing material used for a fuel cell, and an electrolyte membrane and a fuel cell using the same. Further, the present invention can be applied to a method for manufacturing an electrolyte membrane reinforcing material.

Claims (15)

  An electrolyte membrane reinforcing material comprising glass fibers and a phosphosilicate gel coating formed on the glass fibers.   The electrolyte membrane reinforcing material according to claim 1, wherein the glass fiber constitutes a cloth-like sheet.   The electrolyte membrane reinforcing material according to claim 2, wherein the glass fibers forming the sheet are bonded to each other by the coating film.   The electrolyte membrane reinforcing material according to claim 2, wherein the porosity is in the range of 60% by volume to 98% by volume.   The electrolyte membrane reinforcing material according to claim 1, wherein the surface of the coating film is treated with a silane coupling agent.   The electrolyte membrane reinforcing material according to claim 1, wherein the coating film is a phosphosilicate gel containing no organic component. An electrolyte membrane comprising a reinforcing material and an electrolyte reinforced with the reinforcing material,
An electrolyte membrane in which the reinforcing material includes glass fibers and a phosphosilicate-based gel coating formed on the glass fibers.   The electrolyte membrane according to claim 7, wherein the glass fiber constitutes a cloth-like sheet.   The electrolyte membrane according to claim 8, wherein the glass fibers forming the sheet are bonded to each other by the coating film.   The electrolyte membrane according to claim 8, wherein the void ratio of the reinforcing material is in the range of 60% by volume to 98% by volume.   The electrolyte membrane according to claim 7, wherein the electrolyte is a polymer electrolyte.   A fuel cell using the electrolyte membrane according to claim 7. (I) a step of preparing a phosphosilicate sol from a starting material containing at least one compound represented by the following formula (I) and a compound having a phosphoric acid structure,
(Ii) A method for producing an electrolyte membrane reinforcing material, which comprises a step of applying the phosphosilicate sol on the surface of glass fiber and then heat treating it to form a coating film of phosphosilicate gel on the surface of the glass fiber.
Si(OR) _m X _4-m ...(I)
[In the formula (I), R represents an alkyl group, X represents a halogen atom, and m represents an integer of 1 or more and 4 or less. ]   The method for producing an electrolyte membrane reinforcing material according to claim 13, wherein the glass fiber constitutes a cloth-like sheet. The method for producing an electrolyte membrane reinforcing material according to claim 13, wherein the starting material contains at least one compound represented by the following formula (II).
Si(OR ² ) _s X ² _t Z _4-st ...(II)
[In the formula (I), R ² represents an alkyl group, X ² represents a halogen atom, and Z represents an alkoxy group or an organic group other than a halogen atom. 0≦s≦3, 0≦t≦3, 1≦s+t≦3. ]