JP5672795B2 - Polymer polymerization method - Google Patents

Description

  The present invention relates to a method for polymerizing a polymer having an ionic group to be a polymer electrolyte material used in a polymer electrolyte fuel cell or the like.

  BACKGROUND ART A fuel cell is a kind of power generation device that extracts electrical energy by electrochemically oxidizing a fuel such as hydrogen or methanol, and has recently attracted attention as a clean energy supply source. In particular, the polymer electrolyte fuel cell has a low standard operating temperature of around 100 ° C. and a high energy density, so that it is a relatively small-scale distributed power generation facility, a mobile power generator such as an automobile or a ship. As a wide range of applications are expected. It is also attracting attention as a power source for small mobile devices and portable devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel metal hydride batteries and lithium ion batteries.

  In polymer electrolyte fuel cells, in addition to conventional polymer electrolyte fuel cells that use hydrogen gas as fuel (hereinafter referred to as PEFC), direct methanol fuel cells that supply methanol directly (hereinafter referred to as DMFC) It is also attracting attention. Since DMFC is liquid and does not use a reformer, it has the advantage that the energy density is high and the usage time of the portable device per filling is long.

  In a fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and a polymer electrolyte membrane serving as a proton conductor between the anode and the cathode are sometimes referred to as a membrane electrode assembly (hereinafter, abbreviated as MEA). ) And a cell in which this MEA is sandwiched between separators is configured as a unit. The polymer electrolyte membrane is mainly composed of a polymer electrolyte material. The polymer electrolyte material is also used as a binder for the electrode catalyst layer.

  The required characteristics of the polymer electrolyte membrane include firstly high proton conductivity. Therefore, an ionic group is introduced into the polymer electrolyte material. In addition, since the polymer electrolyte membrane functions as a barrier that prevents direct reaction between the fuel and oxygen, low permeability of the fuel is required. In particular, in a polymer electrolyte membrane for DMFC that uses an organic solvent such as methanol as fuel, methanol permeation is called methanol crossover (hereinafter sometimes abbreviated as MCO), which means that battery output and energy efficiency are reduced. Cause problems. Other required characteristics include chemical stability to withstand a strong oxidizing atmosphere during fuel cell operation and mechanical strength to withstand repeated thinning and swelling and drying.

  When polymerizing a polymer having an ionic group, which becomes a polymer electrolyte material used in the polymer electrolyte fuel cell or the like, a metal salt is deposited as the reaction proceeds in the desalting polycondensation reaction. This precipitated metal salt may inhibit polymerization or promote thermal decomposition of ionic groups due to a long polymerization reaction. In addition, in order for the polymer electrolyte material to obtain high proton conductivity, the terminal of an ionic group such as a sulfonic acid group must be a proton type, and a metal salt of an ionic group is formed in the presence of an alkali metal salt. However, there is a problem that the terminal of the metal salt of the ionic group tends to aggregate.

  Thus, the polymerization of the polymer electrolyte material according to the prior art is difficult, and there is a problem as an industrially useful polymer electrolyte material for fuel cells.

  For this problem, Patent Document 1 shows a case where crown ethers are present during polymerization of a polymer electrolyte material. However, since this crown ether is used by being included in the monomer structure of copolymerization, it is incorporated into the polymer chain as the polymerization reaction proceeds, and as a scavenger for the metal salt of the ionic group incorporated into the polymer chain as well. Does not function, and the effect of suppressing thermal decomposition of the ionic group due to long-time polymerization does not occur. On the contrary, there is a possibility that the terminal of the metal salt of the ionic group is promoted to aggregate.

  Patent Document 2 describes that crown ether is added as a reaction accelerator during polymerization. However, since the polymerization method in this case is radical polymerization and not desalination polycondensation as in the present invention, polymerization inhibition by the precipitated metal salt, thermal decomposition of the ionic group, and the end of the metal salt of the ionic group It does not suppress aggregation.

JP-A-10-120914 JP 2004-75855 A

  In the present invention, when a monomer containing a metal salt of an ionic group is subjected to desalting polycondensation, polymerization inhibition by the deposited metal salt, thermal decomposition of the ionic group due to a long-time polymerization reaction, and terminal of the metal salt of the ionic group It suppresses the aggregation of.

In order to achieve the above object, the present invention employs the following means. That is, when a monomer containing a metal salt of an ionic group is subjected to desalting polycondensation in the presence of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane and / or dihydroxybenzophenone and an alkali metal salt. And (1) adding a crown ether having a mole number of metal salt of a monomer containing a metal salt of an ionic group, and
(2) A metal salt of a monomer in which the alkali metal contains a metal salt of an ionic group in the number of moles of the hydroxy group of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane and / or dihydroxybenzophenone In the polymer polymerization method, an alkali metal salt is added so that the number of moles is equal to or more than the number of moles added.

  According to the present invention, when a salt containing a metal salt of an ionic group is subjected to desalting polycondensation, polymerization inhibition by the deposited metal salt and thermal decomposition of the ionic group due to a long polymerization reaction and It becomes possible to suppress aggregation of metal salt ends.

It is a figure which shows the structure of the electrolyte polymer which does not add crown ether and was added. It is a figure which shows the radial distribution function and coordination number of the sulfur atoms in a sulfonic acid group. It is the figure which showed the change by the superposition | polymerization time of the weight average molecular weight of the polymer obtained in Example 1, and a sulfonic acid group density. FIG. 4 is a graph showing changes in the weight average molecular weight and sulfonic acid group density of the polymer obtained in Comparative Example 1 with polymerization time. It is the figure which showed the change by the polymerization time of the weight average molecular weight of the polymer obtained in Example 2, and a sulfonic acid group density. FIG. 6 is a graph showing changes in the weight average molecular weight and sulfonic acid group density of the polymer obtained in Comparative Example 2 with polymerization time. FIG. 4 is a graph showing changes in the weight average molecular weight and sulfonic acid group density of the polymer obtained in Comparative Example 3 with polymerization time.

  Hereinafter, preferred embodiments of the present invention will be described.

  The polymerization method of the present invention is applied when a salt containing a metal salt of an ionic group is subjected to desalting polycondensation. The ionic group mentioned here is not particularly limited as long as it is an atomic group having a negative charge, but is preferably one having proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group are preferably used.

  In the present invention, it is essential that the ionic group and the metal cation constitute a metal salt of the ionic group, and the metal cation that forms the salt is not particularly limited in its valence, etc. Can be used. Specific examples of preferred metal cations include Li, Na, K, Rh, Mg, Ca, Sr, Ti, Al, Fe, Pt, Rh, Ru, Ir, and Pd. Among these, Na and K which are inexpensive and do not adversely affect the solubility and can be easily proton-substituted are more preferably used.

  Two or more kinds of these ionic groups can be contained in the polymer electrolyte membrane, and may be preferable by combining them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least a sulfonic acid group, a sulfonimide group, and a sulfuric acid group from the viewpoint of high proton conductivity, and most preferable to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance.

  The amount of sulfonic acid groups in the polymer electrolyte membrane can be expressed as a value of sulfonic acid group density (mmol / g). The sulfonic acid group density of the polymer electrolyte membrane in the present invention is preferably 0.1 to 5.0 mmol / g, more preferably 0.5 to 5.0 in terms of proton conductivity, fuel crossover and mechanical strength. 3.0 mmol / g, and most preferably 0.8 to 2.0 mmol / g from the point of fuel crossover. When the sulfonic acid group density is lower than 0.1 mmol / g, sufficient proton generation characteristics may not be obtained due to low proton conductivity. When the sulfonic acid group density is higher than 5.0 mmol / g, it may be used as an electrolyte membrane for a fuel cell. In addition, sufficient water resistance and mechanical strength when containing water may not be obtained.

  Here, the sulfonic acid group density is the number of moles of sulfonic acid groups introduced per gram of the dried polymer electrolyte membrane, and the larger the value, the greater the amount of sulfonic acid groups. The sulfonic acid group density can be determined by elemental analysis or neutralization titration. Among these, it is preferable to calculate from the S / C ratio using an elemental analysis method for ease of measurement. However, when a sulfur source other than a sulfonic acid group is included, the ion exchange capacity is obtained by a neutralization titration method. You can also The polyelectrolyte material of the present invention includes an embodiment that is a complex composed of a monomer having an ionic group and other components, and in this case as well, the sulfonic acid group density is obtained on the basis of the total amount of the complex. To do.

  The polymer having an ionic group used in the present invention may contain other components such as an inactive polymer or an organic or inorganic compound that does not have conductivity or ionic conductivity, as long as the object of the present invention is not impaired. It may be contained.

  The metal cations bound to these ionic groups are bound by a cyclic metal scavenger described later, acting as a protective group for a kind of ionic groups, and presuming that thermal decomposition due to prolonged polymerization is suppressed. Yes. In addition, by adding a cyclic metal scavenger that interacts strongly with the metal cation bound to the ionic group, the added molecules are trapped between the ionic group / metal cation / ionic group to suppress aggregation. I made the hypothesis.

  As a basis for this, the results calculated by computational science are shown below.

  In order to verify the hypothesis of the aggregation suppression, the inventors examined the microstructure of the polymer electrolyte membrane to which crown ether, which is one of the cyclic metal scavengers, was added by molecular simulation. Molecular simulations are reliable for detailed structures and motions at the atomic level, which are difficult to experiment with models of liquids, polymers, proteins, etc., due to dramatic improvements in speed and development of methodologies in recent years. It is a technique that is becoming successful in obtaining knowledge.

The inventors first performed molecular orbital calculations at the B3LYP / 6-31G (d, p) level to evaluate the interaction energy between K ⁺ and crown ether (18-Crown-6). The molecular orbital method is to evaluate the electronic state of a molecule by numerically solving the Schrodinger equation. As a result of the calculation, it was found that the interaction energy between K ⁺ and crown ether was 77 kcal / mol, which was very strong as compared with the hydrogen bond (about 5 kcal / mol). This result means that crown ether can be suitably used as a K ⁺ scavenger.

  Next, the present inventors investigated the fine structure of the electrolyte polymer to which crown ether was added using a molecular dynamics method. The molecular dynamics method is a method of finding the locus of each molecule by solving the equation of motion of the molecular collective system for every constituent molecule.

  In this calculation, a molecular dynamics calculation of 1 nanosecond was performed using the polymer model shown in the structural formula (1).

  As the composition of the system, four molecules of the polymer represented by the structural formula (1) are arranged in the system, and 410 molecules of NMP molecules are arranged so that the concentration of the polymer solution is 20 wt% (model without crown ether addition). . Furthermore, a model in which 24 molecules of crown ether (18-crown-6) were arranged so as to be equimolar with the sulfonic acid group in the polymer was also created separately (crown ether addition model).

As a calculation condition, the temperature is set to the Nose-Hoover method [M. Tuckerman, B.M. J. et al. Berne and G. J. et al. Martyna, J.M. Chem. Phys. 97, 1990 (1992). ], And the pressure is controlled to 25 ° C., and the pressure is changed to the Parrino-Rahman method using an oblique cell [M. Parrinello and A.M. Rahman, J .; Appl. Phys. , 52, 7182 (1981). ] To 1 atm. The calculation of the vdW interaction and the electrostatic interaction in the real space is made with a cutoff radius rc = 10 angstroms, and the electrostatic interaction in the reverse space is made with α = 0.21 angstrom ⁻¹ and | n | ² _max = 50. Calculations were made using the Ewald method.

For the potential parameters used in the molecular dynamics calculation, the polymer bond length and bond angle equilibrium positions, dihedral force field parameters, charge, and K ⁺ vdW parameters were optimized by molecular orbital calculations. Further, the vdW parameters ^{SO 3-} portion literature [W. R. Cannon, B.D. M.M. Pettitt, J.A. A. McCammon, J.M. Phys. Chem. 98, 6225 (1994). ] Parameters were used. For other parameters, the general-purpose parameter AMBER [W. D. Cornell, P.A. Cieplak, C.I. I. Bayly, I.D. R. Gould, K.M. M.M. Merz Jr, D.M. M.M. Ferguson, D.M. C. Spellmeyer, T.M. Fox, J. et al. W. Caldwell and P.M. A. Kollman, J .; Am. Chem. Soc. 117, 5179 (1995). ], DREIDING [S. L. Mayo, B.M. D. Olafson, W.M. A. Goddard III, J. et al. Phys. Chem. 94, 8897 (1990). ] Was used.

The structure of the crown ether non-added / added model obtained by molecular dynamics calculation is shown in FIG. As shown in FIG. 1, the sulfonic acid group is strongly aggregated via K ⁺ in the product not added with crown ether, and the crown ether is inserted between the sulfonic acid group / K ⁺ / sulfonic acid group in the product added with crown ether. I understood.

In order to quantitatively estimate the aggregation suppression effect of the sulfonic acid group, the radial distribution function and coordination number between sulfur atoms in the sulfonic acid group were calculated. Here, the radial distribution function g (r) is obtained by multiplying the average number of particles <n _ij (r)> by a normalization constant as shown in Equation (1). Here, the average number of particles <n _ij (r)> is an average value of the number of particles existing in a region having a distance r ± Δr around a certain particle i. The coordination number is obtained by integrating the average number of atoms <n (r)> up to a certain distance.

  The calculation results are shown in FIG. From FIG. 2, it was found that the coordination number of the product without added crown ether was about 0.8 at the position of the first peak of the radial distribution function. This indicates that another sulfonic acid group is present at a high probability of about 80% in the first coordination sphere of the sulfonic acid group. On the other hand, it was found that the crown ether-added product has a coordination number between sulfonic acid groups of about 0.2, which is much smaller than that of the crown ether-free product.

  The results of the above molecular simulation show that by adding a cyclic metal scavenger that strongly interacts with the metal cation bound to the ionic group, the added molecule is interrupted between the ionic group / metal cation / ionic group. This suggests the hypothesis of suppressing aggregation. Moreover, from the viewpoint of suppressing aggregation of ionic groups, it is preferable to add an aggregation inhibitor such that the coordination number of sulfonic acid groups is 0.4 or less in the first coordination sphere.

  Thus, it is considered that a cyclic metal scavenger such as crown ether binds to a metal salt of an ionic group and acts like a kind of protective group to suppress thermal decomposition.

  In addition, as other effects, the cyclic metal scavenger acts on the terminal of the monomer containing the metal salt of the ionic group at the time of polymerization, thereby suppressing aggregation of ionic groups and solubility in a solvent. It is speculated that a higher molecular weight polymer can be obtained because the reaction can be carried out in a more uniform system by improving.

  The aggregation suppression effect of the metal salt of the ionic group is maintained even after it is formed on the electrolyte membrane, and the polymer obtained by this polymerization method has a uniform composition and no aggregates are found. An electrolyte membrane is obtained.

  Next, desalting polycondensation will be described. As a method of polymerizing using a monomer having an ionic group, a monomer having an ionic group in a repeating unit may be used, and if necessary, an appropriate protecting group may be introduced to perform a deprotecting group after polymerization. . Such a method is described, for example, in Journal of Membrane Science, 197, 2002, p.231-242. The present invention is a method limited to the desalting polycondensation among the above polymerization methods, and is most effective when applied in the presence of an alkali metal salt.

  Preferred polymerization conditions for the polymerization method are shown below.

  In the desalting polycondensation, a polymer can be obtained by reacting the monomer mixture in the presence of a basic compound. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Solvents that can be used include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphontriamide and the like. However, it is not limited to these, and any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction may be used. These organic solvents may be used alone or as a mixture of two or more.

  Examples of the alkali metal salt include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like, and those that can convert an aromatic diol into an active phenoxide structure can be used. It can use without being limited to.

  From the viewpoint of reactivity, when monomers containing a metal salt of an ionic group are polymerized in the presence of an alkali metal salt, they form a salt with the same metal, that is, the ionization tendency is the same, or The alkali metal salt is preferably formed using a metal having a higher ionization tendency. When a metal having a high ionization tendency is used for the alkali metal salt, the metal salt of the ionic group of the monomer is replaced with the metal of the alkali metal salt, and the alkali metal salt is reduced from the charged amount, and the polymerization is increased. It tended to be difficult.

  As a specific example, when a monomer having a sodium salt of a sulfonic acid group is polymerized in the presence of potassium carbonate, the amount of potassium carbonate is less than the charged amount because the terminal of the sulfonic acid group is replaced with potassium. . In addition, it is known that sodium carbonate produced by replacement is generally inferior in polymerization activity as compared with potassium carbonate, and the degree of polymerization may be difficult to increase.

  As a countermeasure, it is preferable to add the alkali metal salt in an amount corresponding to the number of moles of the metal salt of the ionic group of the monomer, and by doing so, the molecular weight can be increased without inferior polymerization activity.

  A combination of monovalent alkali metal and halogen is preferably used as the inorganic salt to be eliminated, that is, the reaction terminal of the monomer. Specifically, Li, Na, K, Rb and F, Cl, Br, I and the like. In consideration of the low cost and the cyclic metal scavenger, Na, K, F, and Cl are particularly preferably used. The detached inorganic salt may bind to a basic compound or a decomposition product of the basic compound. The decomposition product of the basic compound may also be hindered in the polymerization reaction. Similarly, the cyclic metal compound has an effect of suppressing the hindrance.

  In polycondensation, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water-absorbing agent such as molecular sieve can also be used.

  Azeotropic agents used to remove reaction water or water introduced during the reaction generally do not substantially interfere with polymerization, co-distill with water and boil between about 25 ° C and about 250 ° C. Any inert compound. Common azeotropic agents include benzene, toluene, xylene, chlorobenzene, methylene chloride, dichlorobenzene, trichlorobenzene and the like. Of course, it is beneficial to select an azeotropic agent whose boiling point is lower than that of the dipolar solvent used. An azeotropic agent is commonly used, but it is not always necessary when high reaction temperatures are used, such as temperatures above 200 ° C., especially when the inert gas is continuously sparged into the reaction mixture. In general, it is desirable to carry out the reaction in an inert atmosphere and in the absence of oxygen.

  When the condensation reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult.

  After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, by adding the reaction solution to a solvent having low polymer solubility and high by-product inorganic salt solubility, the inorganic salt is removed, the polymer is precipitated as a solid, and the polymer is obtained by filtering the precipitate. You can also. The recovered polymer is optionally washed with water, alcohol or other solvent and dried. Once the desired molecular weight is obtained, halide or phenoxide end groups can optionally be reacted by introducing a phenoxide or halide end-capping agent that forms a stable end group.

  In addition, a polymer purification method that does not use water has been proposed, and solid-liquid separation is performed by filter filtration or centrifugation. For example, in the centrifugation, the precipitated impurities are settled, and the supernatant containing the polymer is separated to be purified. However, it contains more salts, monomers, and oligomers than when purified by precipitation in water in a solvent, and complete separation of the polymer is difficult. However, by adding a cyclic metal scavenger, metal cations and ionic groups can be removed. The monomer or oligomer it has can be solubilized in an organic solvent and can be removed by acid treatment or water washing without precipitation after being formed into a film.

  In the case where a crystalline monomer is used in the present invention, a protecting group may be introduced in order to improve the film forming property. Since this protecting group needs to be introduced without deprotecting from the viewpoint of processability, it is necessary to carry out polymerization and purification in consideration of the conditions under which the protecting group can exist stably. Since the protecting group substituted on the aromatic ring undergoes a deprotection reaction under acidic conditions, it is necessary to keep the system neutral or alkaline.

  The deprotection reaction can be performed in the presence of water and acid under non-uniform or uniform conditions, but from the viewpoint of mechanical strength and solvent resistance, a method of acid treatment after molding into a film or the like Is more preferable. Specifically, it is possible to deprotect the molded membrane by immersing it in an aqueous hydrochloric acid solution, and the acid concentration and the aqueous solution temperature can be appropriately selected.

  The weight ratio of the acidic aqueous solution required for the polymer is preferably 1 to 100 times, but a larger amount of water can be used. The acid catalyst is preferably used at a concentration of 0.1 to 50% by weight of water present. Suitable acid catalysts include strong mineral acids such as hydrochloric acid, nitric acid, fluorosulfonic acid, sulfuric acid, and strong organic acids such as p-toluenesulfonic acid, trifluoromethane sulfonic acid, and the like. Depending on the film thickness of the polymer and the like, the amount of acid catalyst and excess water, reaction pressure, and the like can be appropriately selected.

  For example, if it is a film with a thickness of 50 μm, it can be easily deprotected by immersing it in an acidic aqueous solution as exemplified by a 6N hydrochloric acid aqueous solution and heating at 95 ° C. for 1 to 48 hours. It is. Further, even when immersed in a 1N aqueous hydrochloric acid solution at 25 ° C. for 24 hours, most of the protecting groups can be deprotected. However, the deprotection conditions are not limited to these, and the deprotection may be performed with an acid gas, an organic acid, or the like, or may be deprotected by heat treatment.

  The molecular weight of the polymer used as the polymer electrolyte material of the present invention thus obtained is 10000 to 5 million, preferably 10,000 to 500,000 in terms of polystyrene-converted weight average molecular weight. If it is less than 10,000, the mechanical strength may be insufficient, such as cracking in the molded film. On the other hand, if it exceeds 5 million, there may be problems such as insufficient solubility, high solution viscosity, and poor processability. In addition, since the polymer electrolyte material obtained by the present invention is insoluble in a solvent, it may be difficult to measure the molecular weight.

  The sulfonic acid group in the polymer used as the polymer electrolyte material of the present invention may be introduced by block copolymerization or random copolymerization. It can be appropriately selected depending on the chemical structure of the polymer used and the high crystallinity. Random copolymerization is more preferable when fuel barrier properties and low water content are required, and block copolymerization is more preferably used when proton conductivity and high water content are required.

  The cyclic metal scavenger will be described.

  The cyclic metal scavenger is not particularly limited as long as the cyclic metal scavenger has a cyclic structure and forms a chelate complex with a metal cation or a structure that includes a metal cation. For example, porphyrin, phthalocyanine, corrole, chlorin, cyclodextrin, crown ethers, thiacrown ethers in which O of crown ether is replaced with S, NH, etc., azacrown ethers, etc. are preferably used. From the viewpoint of cost, crown ethers are preferable, and among them, 12-Crown-4 (1,4,7,10-Tetraoxacyclododecane), 15-Crown-5 (1,4,7,10,13-Pentaoxacyclopentadecane), 18 -Crown-6 (1,4,7,10,13,16-Hexaoxacyclooctadecane) is preferably used.

  The amount of these additives is appropriately determined experimentally and is not particularly limited. One type may be used alone, or two or more types may be mixed and used.

  As described above, the cyclic metal scavenger is removed after the completion of the polymerization reaction, and it is desired that the cyclic metal scavenger easily acts on the ionic group. Have no polymerizable or reactive groups. Moreover, it is preferable that self is not high molecular weight or does not have a steric hindrance group. These are appropriately determined experimentally.

  As to which stage of polymerization the cyclic metal scavenger is added, when it is added at the monomer stage, the cyclic metal scavenger tends to act on the monomer unit having an ionic group, and it is cyclic until the acid treatment step to remove it. Since the metal scavenger acts, the effect of suppressing the aggregation of metal salts of ionic groups is great, and the addition amount of the cyclic metal scavenger is small, which is preferable.

  The polymer obtained by the polymerization method of the present invention can be applied to various uses. For example, it can be applied to medical applications such as extracorporeal circulation columns and artificial skin, applications for filtration, ion exchange resin applications, various structural materials, and electrochemical applications. It is also suitable as an artificial muscle. Among these, it can be preferably used for various electrochemical applications. Examples of the electrochemical application include a fuel cell, a redox flow battery, a water electrolysis device, a chloroalkali electrolysis device, and the like. Among these, a fuel cell is most preferable, and is suitable as a binder for an electrolyte membrane and a catalyst layer.

  Furthermore, the application of the polymer electrolyte fuel cell using the polymer electrolyte molded body obtained by the present invention is not particularly limited, but a power supply source of a mobile body is preferable. In particular, mobile devices such as mobile phones, personal computers, PDAs, televisions, radios, music players, game machines, headsets, DVD players, human-type and animal-type robots for industrial use, home appliances such as cordless vacuum cleaners, and toys , Electric bicycles, motorcycles, automobiles, buses, trucks and other vehicles and ships, power supplies for mobiles such as railways, stationary primary generators such as stationary generators, or alternatives to these It is preferably used as a hybrid power source.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these examples are for understanding this invention better, and this invention is not limited to these.

[Measuring method]
(1) Weight average molecular weight The weight average molecular weight of the polymer was measured by GPC. Tosoh's HLC-8022GPC is used as an integrated device of an ultraviolet detector and a differential refractometer, and Tosoh's TSK gel SuperHM-H (inner diameter 6.0 mm, length 15 cm) is used as the GPC column. N-methyl-2 -Measured with a pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol / L of lithium bromide) at a flow rate of 0.2 mL / min, and the weight average molecular weight was determined in terms of standard polystyrene.
(2) Sulfonic acid group density 0.1 g of the prepared electrolyte membrane was weighed and dried under reduced pressure at 80 ° C. for 12 hours or more in a vacuum dryer, and then the weight was measured. The electrolyte membrane was immersed in a 30% potassium chloride solution for 2 hours, washed with pure water, and then dried again at 80 ° C. for 12 hours or more in a vacuum dryer. 10 wt% sulfuric acid (weighed) was placed in a sample bottle containing the electrolyte membrane and immersed at 60 ° C. for 2 hours. A solution obtained by diluting a 10 wt% sulfuric acid solution 10 times with pure water was used as a sample, and the amount of potassium was measured with a capillary electrophoresis apparatus manufactured by Otsuka Electronics. From the measured concentration, the sulfonic acid group density was calculated according to the following formula.

Potassium weight in acid treatment solution (g) = 10wt% sulfuric acid weight (g) x potassium concentration in acid treatment solution (ppm) / 10 ⁶
Sulfonic acid group density (mmol / g) = {Potassium weight in acid treatment solution (g) x 1000} / {39 x Electrolyte membrane weight (g)}
Synthesis Example 1: Synthesis of a monomer (disodium 3,3′-disulfonate-4,4′-difluorobenzophenone) containing a metal salt of an ionic group Fuming 109.1 g of 4,4′-difluorobenzophenone (Aldrich reagent) The reaction was carried out at 100 ° C. for 10 hours in 150 mL of sulfuric acid (50% SO ₃ ) (Wako Pure Chemical Reagent). Thereafter, the mixture was poured little by little into a large amount of water, neutralized with NaOH, and 200 g of sodium chloride was added to precipitate the composite. The resulting precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone represented by the above general formula (G2). The purity was 99.3%.

Synthesis Example 2: Synthesis of monomer (2,2-bis (4-hydroxyphenyl) -1,3-dioxolane) (K-DHBP) containing a hydrolyzable solubility-imparting group, equipped with a stirrer, a thermometer, and a distillation tube In a 500 ml flask, 49.5 g of 4,4'-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate and 0.50 g of p-toluenesulfonic acid monohydrate are charged and dissolved. Thereafter, the mixture was stirred while maintaining at 78 to 82 ° C. for 2 hours. Further, the internal temperature was gradually raised to 120 ° C. and heated until the distillation of methyl formate, methanol, and trimethyl orthoformate completely stopped. After cooling this reaction liquid to room temperature, the reaction liquid was diluted with ethyl acetate, the organic layer was washed with 100 ml of 5% aqueous potassium carbonate solution and separated, and then the solvent was distilled off. Crystals were precipitated by adding 80 ml of dichloromethane to the residue, filtered and dried to obtain 52.0 g of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane.

[Example 1]
In a 4000 mL reaction vessel equipped with a Dean-Stark trap, a stirrer, a nitrogen introduction tube, and a dropping funnel were added 138 g of potassium carbonate (Aldrich reagent, 1 mol), 103.3 g (0.4 mol) of K-DHBP obtained in Synthesis Example 2, Dihydroxybenzophenone 21.4 g (Wako Pure Chemicals Reagent, 0.1 mol), 4,4′-difluorobenzophenone 43.6 g (Aldrich Reagent, 0.2 mol), and the metal salt of the ionic group obtained in Synthesis Example 1 126.7 g (0.3 mol) of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone which is a monomer to be contained, and 158.4 g of 18-Crown-6 as a cyclic metal scavenger (Wako Pure Chemical Industries, Ltd. 6 mol), and after substitution with nitrogen, 1250 mL of N-methylpyrrolidone (NMP), toluene 5 0mL and the mixture was dehydrated at 160 ° C. under reflux, heated and then toluene is removed, and 7 hours polymerization at 205 ° C., to obtain a polymer stock solution A.

  The polymerization stock solution A was set in an inverter / compact high-speed cooling centrifuge model 6930 manufactured by Kubota Seisakusho, an angle rotor RA-800, and solid-liquid separation was performed at 25 ° C. for 30 minutes with a centrifugal force of 20000 G. Since the cake and the supernatant liquid (coating liquid) could be separated cleanly, the supernatant liquid was recovered. Only the supernatant was pressure filtered through a 5 μm polytetrafluoroethylene (PTFE) filter and transferred to a separable flask. Next, it distilled under reduced pressure at 80 degreeC, stirring, NMP was removed until the viscosity of the supernatant liquid became 10 Pa.s, and the coating liquid A was obtained.

  Next, a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray Industries, Inc.) was used as a substrate, and the coating liquid A was cast by a slit die and dried at 150 ° C. for 15 minutes.

  Next, the dried film is peeled off from PET and immersed in pure water at 25 ° C. for 10 minutes to wash residual salt, residual monomer, residual potassium carbonate, residual NMP, residual 18-crown-6, etc., and then 10 weight at 60 ° C. It was immersed in 30% sulfuric acid for 30 minutes, and hydrolysis of the hydrolyzable solubilizing group and proton exchange of the metal salt of the sulfonic acid group were performed.

  Next, this membrane was washed with pure water until the washing solution became neutral, and dried at 60 ° C. for 30 minutes to obtain an electrolyte membrane A having a thickness of 15 μm.

  As shown in FIG. 3, the finally obtained electrolyte membrane A had a weight average molecular weight of 184,000 and a sulfonic acid group density of 2.2 mmol / g. In addition, the polymerization liquid at the polymerization elapsed time 0 hour, 0.5 hour, 1.5 hour, 2.5 hour, 3.5 hour, 7.0 hour was sampled from the reaction kettle, Similarly, it processed into the electrolyte membrane, the sulfonic acid group density and the weight average molecular weight were measured, and it plotted in FIG.

  When polymerization is carried out by adding 18-Crown-6 as a cyclic metal scavenger, the molecular weight and sulfonic acid group density are not significantly changed from about 3 hours of polymerization time, and thermal decomposition of the sulfonic acid group occurs for a long time of polymerization. I understand that it is not.

[Comparative Example 1]
The same preparation as in Example 1 except that 18-crown-6 was not added and the amount of NMP was increased to 1950 g. Dehydration was carried out at 160 ° C. while refluxing, and the toluene was removed by heating, followed by polymerization at 205 ° C. for 7 hours. Then, a polymerization stock solution B was obtained. Further, the membrane formation / acid treatment was performed in the same manner as in Example 1 to obtain an electrolyte membrane B. As shown in FIG. 4, the finally obtained electrolyte membrane B had a weight average molecular weight of 79,000 and a sulfonic acid group density of 1.1 mmol / g.

  Also, polymerization elapsed time 0 hour, 1.0 hour, 1.5 hour, 2.0 hour, 2.5 hour, 3.0 hour, 3.0 hour, 3.5 hour, 4.0 hour , 4.5 hours, 5.5 hours, 6.5 hours and 7.5 hours of the polymerization solution was sampled from the reaction kettle and processed into an electrolyte membrane to measure the sulfonic acid group density and weight average molecular weight. And plotted in FIG.

  Compared to Example 1, the molecular weight and the sulfonic acid group density were significantly reduced from about 3 hours of polymerization time, and it is considered that the unit containing the sulfonic acid group was decomposed by the long polymerization time.

[Example 2]
Stirrer, nitrogen inlet tube and dropping funnel are added to a 4000 mL reaction vessel equipped with a Dean-Stark trap and 138.2 g of potassium carbonate (Aldrich reagent, 1. 0 mol) was added. Furthermore, 103.3 g (0.4 mol) of K-DHBP obtained in Synthesis Example 2, 21.4 g of dihydroxybenzophenone (Wako Pure Chemical Reagent, 0.1 mol), and a metal salt of the ionic group obtained in Synthesis Example 1 Disodium 3,3′-disulfonate-4,4′-difluorobenzophenone 21.2 g (0.5 mol) as a monomer to be contained, and 264 g of 18-Crown-6 as a cyclic metal scavenger (Wako Pure Chemical, 1.0 mol) After nitrogen substitution, 1540 mL of N-methylpyrrolidone (NMP) and 550 mL of toluene were added, dehydrated at 160 ° C. while refluxing, heated to remove toluene, and polymerized at 205 ° C. for 7 hours. Obtained.

  The polymerization stock solution C was set in an inverter compact high-speed cooling centrifuge model 6930 manufactured by Kubota Seisakusho, an angle rotor RA-800, and solid-liquid separation was performed at 25 ° C. for 30 minutes with a centrifugal force of 20000 G. Since the cake and the supernatant liquid (coating liquid) could be separated cleanly, the supernatant liquid was recovered. Only the supernatant was pressure filtered through a 5 μm polytetrafluoroethylene (PTFE) filter and transferred to a separable flask. Next, it distilled under reduced pressure at 80 degreeC, stirring, NMP was removed until the viscosity of the supernatant liquid became 10 Pa.s, and the coating liquid C was obtained.

  Next, a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray Industries, Inc.) was used as a substrate, and the coating liquid C was cast by a slit die and dried at 150 ° C. for 15 minutes.

  Next, the dried film is peeled off from PET and immersed in pure water at 25 ° C. for 10 minutes to wash residual salt, residual monomer, residual potassium carbonate, residual NMP, residual 18-crown-6, etc., and then 10 weight at 60 ° C. It was immersed in 30% sulfuric acid for 30 minutes, and hydrolysis of the hydrolyzable solubilizing group and proton exchange of the metal salt of sulfonic acid group were performed.

  Next, this membrane was washed with pure water until the washing solution became neutral, and dried at 60 ° C. for 30 minutes to obtain an electrolyte membrane C having a thickness of 15 μm.

  As shown in FIG. 5, the finally obtained electrolyte membrane C had a weight average molecular weight of 242,000 and a sulfonic acid group density of 3.0 mmol / g. In addition, the polymerization liquid at the polymerization elapsed time 0 hour, 0.5 hour, 1.5 hour, 2.5 hour, 3.5 hour, 7.0 hour was sampled from the reaction kettle, Similarly, it processed into the electrolyte membrane, the sulfonic acid group density and the weight average molecular weight were measured, and it plotted in FIG.

  When polymerization is carried out by adding 18-Crown-6 as a cyclic metal scavenger, the molecular weight and sulfonic acid group density are not significantly changed from the polymerization time around 2 hours, and thermal decomposition of the sulfonic acid group occurs for a long time of polymerization. I understand that it is not.

[Comparative Example 2]
18-Crown-6 was not added and the amount of NMP was increased to 2800 g. The same preparation as in Example 2 was carried out, dehydrated at 160 ° C. while refluxing, heated to remove toluene, and polymerized at 205 ° C. for 7 hours. As a result, a polymerization stock solution D was obtained. Further, the membrane formation / acid treatment was performed in the same manner as in Example 2 to obtain an electrolyte membrane D. As shown in FIG. 6, the finally obtained electrolyte membrane D had a weight average molecular weight of 43,000 and a sulfonic acid group density of 0.42 mmol / g.

  In addition, polymerization elapsed time 0 hour, 0.5 hour, 1.5 hour, 2.5 hour, 3.5 hour, 3.5 hour, 4.5 hour, 5.5 hour, 7.0 hour The polymerization solution was sampled from the reaction kettle, processed into an electrolyte membrane, the sulfonic acid group density and the weight average molecular weight were measured, and plotted in FIG.

  Compared to Example 2, it can be seen that the molecular weight did not increase before the start of temperature increase, and the molecular weight and sulfonic acid group density decreased after the temperature increase. Since no cyclic metal scavenger is added, the liquid sampled at every elapsed polymerization time shows precipitation that seems to be monomers and oligomers, and the polymerization reaction may not proceed.

  Moreover, from the results of Example 1, Comparative Example 1, Example 2, and Comparative Example 2, it can be seen that the higher the sulfonic acid group density, the more effective the present invention.

[Comparative Example 3]
The charge was the same as in Example 2 except that the amount of potassium carbonate was 69.1 g (Aldrich reagent, 0.5 mol) which was the reaction equivalent of the diol monomer, and after dehydrating at 160 ° C. while refluxing, the temperature was raised. Toluene was removed and polymerization was carried out at 205 ° C. for 7 hours to obtain a polymerization stock solution E. Further, the membrane formation / acid treatment was performed in the same manner as in Example 2 to obtain an electrolyte membrane E. As shown in FIG. 7, the finally obtained electrolyte membrane E had a weight average molecular weight of 63,000 and a sulfonic acid group density of 1.52 mmol / g.

  Also, polymerization elapsed time 0 hour, 1.0 hour, 1.5 hour, 2.0 hour, 2.5 hour, 3.0 hour, 3.0 hour, 3.5 hour, 4.0 hour , 4.5 hours, 5.5 hours, 6.5 hours and 7.5 hours of the polymerization solution was sampled from the reaction kettle and processed into an electrolyte membrane to measure the sulfonic acid group density and weight average molecular weight. And plotted in FIG.

  Compared with Example 2, it can be seen that the molecular weight does not increase before the start of temperature increase, and the molecular weight does not increase after the temperature increase. In Comparative Example 3 in which the amount of potassium carbonate is the reaction equivalent of the diol monomer, the terminal sodium of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone, which is a monomer containing a metal salt of an ionic group, Since the replacement with potassium was not considered, it is considered that the sodium carbonate produced by the exchange was inferior in polymerization activity and could not be made high in molecular weight.

  The membrane electrode assembly of the present invention is suitable for a fuel cell using hydrogen or methanol as fuel. The use of the fuel cell of the present invention is not particularly limited, but is such as electric bicycles, motorcycles, vehicles such as automobiles, buses, trucks, mobiles such as ships, railways, mobile phones, personal computers, PDAs, video cameras, digital cameras. Mobile devices such as cordless vacuum cleaners, toys, robot power supply sources, stationary primary generators such as stationary generators, alternatives to secondary batteries, or hybrid power sources with these or solar cells, or charging It is preferably used for use.

Claims (2)

When a monomer containing a metal salt of an ionic group is subjected to desalting polycondensation in the presence of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane and / or dihydroxybenzophenone and an alkali metal salt, (1) adding a crown ether having a molar number of metal salt or more of a monomer containing a metal salt of an ionic group;
(2) A metal salt of a monomer in which the alkali metal contains a metal salt of an ionic group in the number of moles of the hydroxy group of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane and / or dihydroxybenzophenone A polymer polymerization method comprising adding an alkali metal salt so that the number of moles is equal to or more than the number of moles added.   The metal ionization tendency of the alkali metal salt and the metal ionization tendency of the monomer containing the ionic group metal salt are the same, or the metal ionization tendency of the alkali metal salt metal containing the ionic group metal salt The polymer polymerization method according to claim 1, which has a higher ionization tendency.