JP2010015960A - Electrolyte film for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer membrane having excellent proton conductivity and excellent mechanical strength as an electrolyte film suitable for fuel cell. <P>SOLUTION: The electrolyte film for fuel cell includes a sulfonic group-containing aromatic polyurea resin manufactured from a raw material component including (a) a polyisocyanate; (b) an aromatic ring-containing polyamine having an amine value of 30-120, represented by the formula (1); and (c) a sulfonating agent. In the formula, R<SP>1</SP>represents a polyalkylene polyether, polyalkylene polyester or polyalkylene, A represents an oxygen atom or imino group, and m represents an integer of 1-3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane for a fuel cell. Specifically, the present invention relates to an ion conductive polymer membrane for a fuel cell made of a polyurea resin having a sulfonic acid group.

In view of recent environmental issues, the spread and development of clean energy has become a major issue worldwide. From the viewpoint of low pollution and high efficiency, fuel cells are attracting attention as one of them. A fuel cell is one that converts chemical energy of fuel into electrical energy and extracts it by electrochemically oxidizing a fuel such as hydrogen or methanol using oxygen or air. There are various types of fuel cells, such as alkaline type, phosphoric acid type, molten carbonate type, solid electrolyte type, and solid polymer type, depending on the type of electrolyte, but they can operate at low temperatures and are easy to handle. In addition, solid polymer forms with high output density are attracting attention as energy sources for electric vehicles and homes. A proton conductive membrane is used as the electrolyte membrane of these polymer electrolyte fuel cells. As such proton conductive polymer electrolyte membranes, super strong acid group-containing fluorine-based polymers and hydrocarbon-based polymers are known. By making these polymer electrolyte membranes as thin as possible, the internal resistance in the fuel cell can be reduced, so that the polymer electrolyte membrane can be operated at a high current, and thus the fuel cell can be miniaturized. However, the electrolyte membrane made of the super strong acid group-containing fluoropolymer has a limitation in thinning because the strength of the membrane, particularly the tear strength, is weak. In addition, an electrolyte membrane made of a hydrocarbon polymer is relatively inexpensive, but has a problem with conductivity and strength, particularly tear strength. Recently, a polyamide film having a sulfonic acid group (see Patent Document 1) and a polyimide film having a sulfonic acid group (see Patent Document 2) have also been proposed. However, even these electrolyte membranes still have problems in strength, particularly tear strength, and cannot be made thinner than conventional electrolyte membranes.
JP 2002-280019 A JP 2002-358978 A

  An object of the present invention is to provide a polymer membrane having excellent proton conductivity and tear strength as an electrolyte membrane suitable for a fuel cell.

式中、Ｒ^１はポリアルキレン、ポリアルキレンポリエーテル又はポリアルキレンポリエステルを表し、Ａは酸素原子またはイミノ基を表す。またｍは１〜３の整数を表す。The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention provides a polyisocyanate (a), an aromatic ring-containing polyamine (b) having an amine number of 30 to 120 represented by the general formula (1) [in the following, an aromatic ring-containing polyamine (b) or simply (b) And a sulfonic acid group-containing aromatic polyurea resin produced from a raw material component containing a sulfonating agent (c).

In the formula, R ¹ represents a polyalkylene, a polyalkylene polyether, or a polyalkylene polyester, and A represents an oxygen atom or an imino group. M represents an integer of 1 to 3.

  The electrolyte membrane for a fuel cell of the present invention is superior in mechanical strength than the conventional one, and can form an electrolyte membrane with a thinner film thickness than the conventional one, thus showing excellent proton conductivity and contributing to the miniaturization of the fuel cell. To do.

  As the polyisocyanate (a) which is a raw material component of the sulfonic acid group-containing aromatic polyurea resin in the present invention, ordinary ones can be used, and aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates and araliphatics. A polyisocyanate is mentioned.

  Aromatic polyisocyanates include 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (hereinafter abbreviated as TDI), 4,4'- and And / or 2,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, and derivatives thereof.

  Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate and hexamethylene diisocyanate; examples of the alicyclic polyisocyanate include isophorone diisocyanate (hereinafter abbreviated as IPDI), 4,4-dicyclohexylmethane diisocyanate, and methylcyclohexylene diisocyanate; Examples of the aliphatic polyisocyanate include m- and / or p-xylylene diisocyanate and α, α, α ′, α′-tetramethylxylylene diisocyanate.

  Of the polyisocyanates (a), preferred are aromatic polyisocyanates, and more preferred are MDI and derivatives thereof.

In the general formula (1) representing the aromatic ring-containing polyamine (b) which is one of the raw material components, the polyalkylene polyether in the group represented by R ¹ includes ethylene oxide, propylene oxide and / or tetrahydrofuran. Examples thereof include residues obtained by removing hydroxyl groups from polyalkylene ether glycols such as polypropylene ether glycol and tetramethylene ether glycol obtained by ring-opening polymerization.

Examples of the polyalkylene polyester in the group represented by R ¹ include aliphatic polyester glycols such as polyethylene adipate and polypropylene adipate obtained by condensing an aliphatic glycol with a dicarboxylic acid and extending the chain, and the opening of ε-caprolactone. Examples thereof include a residue obtained by removing a hydroxyl group from polyester glycol or the like obtained by ring polymerization. Examples of the polyalkylene in the group represented by R ¹ include a residue obtained by removing a terminal hydroxyl group from polybutadiene glycol.

  Of A in the general formula (1), an oxygen atom is preferable. m is an integer of 1 to 3, and preferably 1.

  The aromatic ring-containing polyamine (b) has an amine value of 30 to 120, preferably 40 to 90. If the amine value is less than 30, the mechanical strength is insufficient, and if it exceeds 120, the tensile strength decreases.

  Specific examples of the aromatic ring-containing polyamine (b) include polyethylene glycol bis (4-aminobenzoate), polyethylene glycol bis (2-aminobenzoate), polyethylene glycol bis (3-aminobenzoate), polytetramethylene glycol bis (4 -Aminobenzoate), polytetramethylene glycol bis (2-aminobenzoate), polypropylene glycol bis (4-aminobenzoate), polypropylene glycol bis (2-aminobenzoate), poly (oxyethylene-oxypropylene) glycol bis (4- Aminobenzoate), polyoxybutylene glycol bis (4-aminobenzoate), polytetramethylene glycol bis (3,5-diaminobenzoate), polypropylene ether Glycerol tris (4-aminobenzoate), polypropylene ether pentaerythritol tetrakis (4-aminobenzoate), polyoxyethylene bis (4-aminobenzamide), polyoxypropylene bis (4-aminobenzamide), polyoxypropylene bis (3 5-diaminobenzamide), polyoxypropylene ether glycerol tris (4-aminobenzamide), and the like. Among these, polytetramethylene glycol bis (4-aminobenzoate) is preferable, and “Elastomer 1000” (manufactured by Ihara Chemical Co., Ltd.) is a commercially available product.

  The sulfonating agent (c) in the present invention is a compound capable of introducing a sulfonic acid group into the polyurea resin. For example, chlorosulfonic acid (c1), sultone (c2), aminosulfonic acid (c3) and sulfonic acid Examples thereof include group-containing polyamine (c4), which will be described in detail in the production method described later.

  Examples of the method for producing a sulfonic acid group-containing aromatic polyurea resin in the present invention include the following production method (1) and production method (2).

Production method (1):
A method in which an aromatic polyurea resin is produced by a one-shot method or a prepolymer method using a polyisocyanate (a), an aromatic ring-containing polyamine (b), and, if necessary, a chain extender, and then a sulfonic acid group is introduced.

Examples of the production method (1) include the following three production methods.
(1-1) A method in which an aromatic ring in an aromatic polyurea resin is sulfonated with chlorosulfonic acid (c1).
(1-2) A method of sulfonating active hydrogen atoms in an aromatic polyurea resin with sultone (c2).
(1-3) A method in which an active hydrogen atom in an aromatic polyurea resin and aminosulfonic acid (c3) are jointed with diisocyanate to introduce a sulfonic acid group at the terminal.

Production method (2):
A method of producing a prepolymer using a polyisocyanate (a) and an aromatic ring-containing polyamine (b), and introducing a sulfonic acid group using the sulfonic acid group-containing polyamine (c4) as a chain extender.

  Among the above production methods, (1-1) and (1-3) among the production methods (1) are preferable from the viewpoint of sulfonic acid group equivalent (molecular weight per sulfonic acid group, hereinafter abbreviated as EW). ) And production method (2), and more preferred is production method (2) from the viewpoint of the tear strength of the film.

  In the production method (1), the one-shot method is prepared by dissolving the aromatic ring-containing polyamine (b) in an organic solvent in advance, adding the polyisocyanate (a), and reacting at room temperature to 80 ° C. for 1 to 10 hours. Can be done. If necessary, a urethanization catalyst may be used. As the catalyst, an organic tin compound, a tertiary amine or the like can be used. Examples of the organic solvent include organic solvents that are substantially non-reactive with isocyanate groups, such as dimethylformamide (hereinafter abbreviated as DMF), dimethylacetamide, tetrahydrofuran (hereinafter abbreviated as THF), dioxane, N- Examples include methyl pyrrolidone, toluene, and alkyl acetate.

  The prepolymer in the prepolymer method of the production method (1) is a polyisocyanate (a) and an aromatic ring-containing polyamine (b), and the isocyanate group / amino group equivalent ratio is usually 2.01 to 2.5, preferably Is produced by reacting at a ratio of 2.02 to 2.1. The production of the prepolymer is usually carried out by a reaction at 20 ° C. to 80 ° C., preferably 20 ° C. to 60 ° C., and the reaction time is usually 2 to 10 hours. The prepolymer can be produced in the presence or absence of the organic solvent substantially nonreactive with isocyanate groups. The prepolymer usually has a free isocyanate group content of 1 to 10% by weight.

  As a chain extender in the prepolymer method, an amine value of a compound containing two amino groups or hydroxyl groups in the molecule, for example, an aromatic ring-containing polyamine represented by the same formula as the general formula (1) is used. Of 200-300 {for example, polytetramethylene glycol bis (4-aminobenzoate) having an amine value of 200-300}, 3,3′-dichloro-4,4′-diaminodiphenylmethane (hereinafter abbreviated as MOCA) ), Trimethylene-bis (4-aminobenzoate), 4,4′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter abbreviated as BAPP), bis [4 -(4-aminophenoxy) phenyl] sulfone, 1,3-bis (4-aminophenoxy) benzene and 9,9'-bi (4-aminophenyl) fluorene, and the like. Of the chain extenders, polytetramethylene glycol bis (4-aminobenzoate) having an amine value of 200 to 300, MOCA and BAPP are preferable from the viewpoint of tear strength.

  In the chain extension reaction, the isocyanate group / amino group equivalent ratio of the prepolymer is usually 0.8 to 1.3, preferably 0.9 to 1.2, and the reaction temperature is usually 20 ° C to 80 ° C, preferably 20 ° C. The reaction is carried out at ˜60 ° C., and the reaction time is usually 2 to 10 hours.

  The sulfonation reaction of the production method (1-1) can be performed by gradually dropping chlorosulfonic acid (c1) into an organic solvent solution of polyurea resin at 0 to 50 ° C. The number of moles of chlorosulfonic acid (c1) charged is preferably 0.5 to 2 with respect to the number of moles 1 of the aromatic ring in the polyurea resin.

  In the sulfonation reaction of the production method (1-2), sodium hydride or the like is added to an organic solvent solution of a polyurea resin, and the active hydrogen atom is replaced with sodium at −10 to 10 ° C., and then sultone (c2) and Sulfonation is carried out by reacting at -5 to 70 ° C for 1 to 5 hours to obtain a sulfonated sodium salt, and a sulfonic acid can be obtained by adding an acid (such as hydrochloric acid). Examples of active hydrogen atoms in the polyurea resin include active hydrogen atoms such as urea groups and urethane groups. Examples of sultone (c2) include 1,3-propane sultone.

The aminosulfonic acid (c3) that can be used in the sulfonation reaction of the production method (1-3) is an aminoalkylenesulfonic acid having 1 to 6 carbon atoms of an alkylene group, such as aminomethylenesulfonic acid (hereinafter abbreviated as AMS). ), Aminoethylenesulfonic acid (taurine), aminopropylenesulfonic acid and the like, and AMS is preferred. These are preferably neutralized with a tertiary amine before use to form a salt. Examples of the tertiary amine include 1,8-diazabicyclo [5.4.0] undecene-7 (hereinafter abbreviated as DBU) and 1,5-diazabicyclo [4.3.0] nonene-7. Moreover, as a diisocyanate, the diisocyanate of what was illustrated as said polyisocyanate (a) is mentioned, An aliphatic or alicyclic diisocyanate is preferable. In the sulfonation reaction, aminosulfonic acid salt and diisocyanate are added to an organic solvent solution of polyurea resin and reacted at 50 to 130 ° C. for 1 to 10 hours, and an acid (hydrochloric acid or the like) is further added to obtain sulfonic acid. it can. The number of equivalents of active hydrogen atoms in the polyurea resin / number of equivalents of NCO group of diisocyanate / number of equivalents of NH ₂ group of aminosulfonic acid is preferably 1 / 0.5 to 1 / 0.5 to 1. If necessary, a urethanization catalyst may be used. As the catalyst, an organic tin compound, a tertiary amine or the like can be used.

  The production method (2) is a method in which a prepolymer obtained in the same manner as the production method of the prepolymer in the production method (1) is reacted with a sulfonic acid group-containing polyamine (c4) as a chain extender. . Examples of the sulfonic acid group-containing polyamine (c4) include 2,2'-benzidine disulfonic acid (hereinafter abbreviated as BDS). These are preferably neutralized with a tertiary amine before use to form a salt. Examples of the tertiary amine include DBU and 1,5-diazabicyclo [4.3.0] nonene-7. In the chain extension reaction, the isocyanate group / amino group equivalent ratio of the prepolymer is usually 0.8 to 1.3, preferably 0.9 to 1.2, and the reaction temperature is usually 20 ° C to 80 ° C, preferably 20 ° C. The reaction is performed at -60 ° C, and the reaction time is usually 2 to 10 hours, and an acid (hydrochloric acid or the like) can be added to obtain sulfonic acid.

  The sulfonic acid group equivalent (molecular weight per sulfonic acid group, hereinafter abbreviated as EW) of the sulfonic acid group-containing aromatic polyurea resin in the present invention is preferably 300 to 1300, more preferably 400 to 1200. When the EW is within this range, it becomes easy to achieve both the strength of the membrane and the proton conductivity. EW is determined from elemental analysis of sulfur in the sulfonic acid group-containing aromatic polyurea resin.

  The electrolyte membrane of the present invention is obtained by further molding a powdery resin obtained by washing and purifying, if necessary, the sulfonic acid group-containing polyurea resin obtained as described above. Washing is performed with ion-exchanged water, methanol, acetone or the like, and purification is performed by dissolving in DMF, putting in a large amount of methanol, filtering and drying. Molding into a sheet can be obtained by dissolving the powdered resin in a solvent (for example, DMF), bar coating or spin coating, drying at 30 to 80 ° C., and then peeling off the sheet.

  The electrolyte membrane of the present invention is excellent in physical strength, particularly tensile strength, of the sulfonic acid group-containing polyurea resin that is a constituent component thereof, so that the film thickness can be reduced, and the film thickness is usually 3 to 50 microns, Preferably it is 5-40 microns.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

Method for measuring sulfonic acid group equivalent (EW):
The sulfur atom content in the sample was measured by elemental analysis (combustion method) and calculated in terms of sulfonic acid groups.
Proton conductivity measurement method:
A platinum wire (diameter: 0.2 mm) was pressed against the surface of the strip-shaped electrolyte membrane at an interval of 5 mm to form an electrode, and the resistance when alternating current (1 kHz) was applied was measured with an impedance analyzer. The proton conductivity was determined by 1 / (R × T × D) from the electrode interval and the slope of resistance (R), the thickness (t) of the electrolyte membrane, and the width (D) of the electrolyte membrane. The measurement was performed at 80 ° C. and a humidity of 95%.
Tensile strength measurement method:
It measured at room temperature with the autograph (Shimadzu "AG-X type").

Example 1
In a 500 cc three-necked flask equipped with a stirrer, a nitrogen introducing tube, and a dropping funnel, 136.8 g of THF, 12.6 g of “Elastomer 1000” (Ihara Chemical Industry Co., Ltd., amine number 89) and MDI (Mitsui Chemical Polyurethane ( 2.6 g) was added, and a polyurea resin was synthesized by reacting at 60 ° C. for 3 hours in a nitrogen stream (all reactions in the following examples and comparative examples were also in a nitrogen stream). To this solution, 4.6 g of chlorosulfonic acid was added dropwise and reacted at room temperature for 3 hours. This solution was put in a Teflon petri dish and dried under reduced pressure at 60 ° C. to obtain a film. This membrane was washed with ion-exchanged water until the washing solution became neutral, and dried at 60 ° C. under reduced pressure to obtain an electrolyte membrane. The EW was 1132, the proton conductivity was 2.8 × 10 ⁻⁵ S / cm, and the tensile strength was 31 MPa. When calculated from EW, two sulfonic acid groups are introduced per four aromatic rings.

Example 2
To a 500 cc three-necked flask equipped with a stirrer and a nitrogen introduction tube, 12.6 g of the “elastomer 1000” and 5.1 g of MDI were added and reacted at 40 ° C. for 1 hour to synthesize a prepolymer. 10 g of DMF was added to this prepolymer to form a uniform solution (hereinafter abbreviated as Solution A). After 2.7 g of MOCA was added to this solution A and reacted at room temperature for 1 hour, 174 g of DMF was further added to obtain a uniform molten iron. To this homogeneous solution, 6.9 g of chlorosulfonic acid was added dropwise and reacted at room temperature for 3 hours. The obtained solution was put into a Teflon petri dish and dried under reduced pressure at 60 ° C. to obtain a film. This membrane was washed with ion-exchanged water until the washing solution became neutral, and dried at 60 ° C. under reduced pressure to obtain an electrolyte membrane. The EW was 507, the proton conductivity was 1.5 × 10 ⁻³ S / cm, and the tensile strength was 22 MPa. As calculated from EW, 6 sulfonic acid groups are introduced per 8 aromatic rings.

Example 3
6.48 g of BDS neutralized with DBU was added to the solution A obtained in the same manner as in Example 2, and reacted at room temperature for 3 hours. To this solution, 208 g of DMF was further added to obtain a uniform solution. This solution was put in a Teflon petri dish and dried under reduced pressure at 60 ° C. to obtain a film. This membrane was immersed in a 10% aqueous hydrochloric acid solution at room temperature for 10 hours, washed with ion exchange water until the washing solution became neutral, and dried under reduced pressure at 60 ° C. to obtain an electrolyte membrane. The EW was 1007, the proton conductivity was 8.7 × 10 ⁻⁵ S / cm, and the tensile strength was 35 MPa.

Example 4
To solution A obtained in the same manner as in Example 2, 8.8 g of IPDI and 10.4 g of AMS neutralized with DBU were added and reacted at 50 ° C. for 5 hours. To this solution, 322 g of DMF was further added to obtain a uniform solution. This solution was put in a Teflon petri dish and dried under reduced pressure at 60 ° C. to obtain a film. This membrane was immersed in a 10% aqueous hydrochloric acid solution at room temperature for 10 hours, washed with ion exchange water until the washing solution became neutral, and dried under reduced pressure at 60 ° C. to obtain an electrolyte membrane. The EW was 528, the proton conductivity was 4.2 × 10 ⁻⁴ S / cm, and the tensile strength was 25 MPa.

Comparative Example 1
A 500 cc three-necked flask equipped with a stirrer, a nitrogen introducing tube and a dropping funnel was charged with 180 ml of dimethylacetamide, 10 g of 2,5-diaminobenzenesulfonic acid, 4.7 g of lithium chloride and 12.6 g of pyridine, and dissolved at 100 ° C. . Then, it cooled to -5 degreeC, the solution which melt | dissolved 10.8 g of terephthalic acid chloride in 60 ml of dimethylacetamide was added gradually, and it was made to react at room temperature for 15 hours. The product was precipitated in methanol, filtered, washed, and dried under reduced pressure at 60 ° C. to obtain a comparative electrolyte membrane (polyamide resin electrolyte membrane). The EW was 337, the proton conductivity was 4.4 × 10 ⁻⁶ S / cm, and the tensile strength was 17 MPa.

  The electrolyte membrane for fuel cells of the present invention can be used as an electrolyte membrane for fuel cells for various applications, for example, fuel cells for automobiles, mobile communication bodies, and households.

Claims (5)

A sulfonic acid group-containing aromatic produced from a raw material component comprising a polyisocyanate (a), an aromatic ring-containing polyamine (b) having an amine number of 30 to 120 represented by the general formula (1) and a sulfonating agent (c) An electrolyte membrane for a fuel cell comprising a polyurea resin.

(In the formula, R ¹ represents a polyalkylene polyether, polyalkylene polyester or polyalkylene, A represents an oxygen atom or an imino group, and m represents an integer of 1 to 3).   2. The fuel cell electrolyte according to claim 1, wherein the sulfonic acid group-containing aromatic polyurea resin is a sulfonic acid group-containing aromatic polyurea resin obtained by sulfonating an aromatic ring in the polyurea resin with chlorosulfonic acid (c1). film.   The sulfonic acid group-containing aromatic polyurea resin is obtained by joining the active hydrogen atom in the polyurea resin and aminosulfonic acid (c3) with diisocyanate to introduce a sulfonic acid group at the terminal. 2. The fuel cell electrolyte membrane according to claim 1, which is a resin.   The sulfonic acid group-containing aromatic polyurea resin is obtained by extending a chain by adding a sulfonic acid group-containing polyamine (c4) as a chain extender to the urethane prepolymer produced from the polyisocyanate and the aromatic ring-containing polyamine. The electrolyte membrane for a fuel cell according to claim 1, which is a sulfonic acid group-containing aromatic polyurea resin.   The electrolyte membrane for a fuel cell according to any one of claims 1 to 4, wherein the sulfonic acid group equivalent (molecular weight per sulfonic acid group) of the sulfonic acid group-containing aromatic polyurea resin is 300 to 1300.