JP4647431B2 - Cross-linked gas separation membrane - Google Patents

Description

  The present invention relates to a gas separation membrane and a method for producing the same, and more particularly to a gas separation membrane that can be used in the fields of exhaust gas treatment and natural gas separation. The gas separation membrane of the present invention is particularly suitable as a carbon dioxide separation membrane.

Against the backdrop of global warming, which has become a global environmental problem in recent years, a technology for reducing carbon dioxide (CO ₂ ), which is one of the causative substances, is urgently needed internationally. One of the reduction technology measures is separation and recovery of CO ₂ from large-scale fixed sources such as steelworks and thermal power plants, and storage processes buried underground or in the ocean. Of these costs, 60 to 70% of this cost is currently separated and recovered from carbon dioxide sources. The carbon dioxide separation and recovery costs are 5,500 yen / t-CO ₂ (absorption method) and 5,000 yen / t-CO ₂ (membrane separation method), and the membrane separation method is cheaper. The adsorption method is a technology that has already been completed, and no further technical improvement is expected. On the other hand, the membrane separation method is expected to be further developed by the technical development described later in this report. Approximately half of the cost of existing membrane separation systems is accounted for by the power costs of vacuum pumps and blower blowers. When combined with such construction costs, it becomes 70-80% of the total cost. In other words, this means that there is room for cost reduction of 70 to 80%. Usually, in the separation of carbon dioxide in the membrane separation method, the supply pressure is as low as about 2 to 5 atm.

Therefore, the present inventor studied to target a gas having a self-pressure as one solution for cost reduction. In other words, by using the self-pressure, a differential pressure is generated across the membrane, so that no power is required. In addition, high permeability (amount of processing gas) is expected due to operation at high temperatures. For example, Future Gen's carbon monoxide shift facility proposed by the United States requires a separation environment at a high temperature (> 150 ° C.) and a high pressure (about 40 atm).
However, polymer separation membranes have a problem that performance is deteriorated by swelling and plasticization with carbon dioxide under high temperature and high pressure. Patent Document 1 discloses a gas separation membrane using a cardo type polymer, but does not take any special measures against the aforementioned problems.
JP-A-10-99666

  The problem to be solved by the present invention is to provide a polymer gas separation membrane that suppresses deformation due to swelling by the gas to be separated while maintaining high efficiency of separation.

The above-described problems of the present invention have been solved by the following gas separation membrane.
Item 1) In the presence of the non-crosslinkable polymer (1) and the polymer (1), the acetylene groups of the crosslinkable polymer (2) having an acetylene group at the molecular terminal are cross-linked by a cross-linking reaction. A gas separation membrane characterized by having a structure.

The preferred embodiments 2) to 6) of the above invention 1) are listed below.
Item 2) The gas separation membrane according to Item 1), wherein the polymer (1) and the polymer (2) are both cardo type polymers having a fluorene ring,
Item 3) The gas separation membrane according to Item 1) or 2), wherein the polymer (1) and the polymer (2) are both polycondensation polymers,
Item 4) The gas separation membrane according to any one of Items 1) to 3), wherein the polymer (1) and the polymer (2) are both polyimide-type polymers,
Item 5) The polymer (1) is 6FDA-FDA and / or 6FDA-TeMPD, and the polymer (2) is 6FDA-FDA-PEPA and / or 6FDA-TeMPD-PEPA, any one of Items 1) to 4) The gas separation membrane described in 1.

Here, the above abbreviations represent the following chemical names. It is shown together with the chemical formula of the repeating chemical structure.
6FDA-FDA: 4,4'-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 '-(9-fluorenylidene) dianiline (FDA) (4,4'-(Hexafluoroisopropylidene) diphthalic anhydride)- 4,4 '-(9-Fluorenylidene) dianiline)

  6FDA-TeMPD: 4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl-1,4-phenylenediamine (TeMPD) (4,4 ′-( Hexafluoroisopropylidene) diphthalic anhydride) -4,4 '-(9-Fluorenylidene) dianiline)

  6FDA-FDA-PEPA: 4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 ′-(9-fluorenylidene) dianiline (FDA) -4- (2-phenylethynyl) phthalic acid Anhydride (PEPA) 4,4 '-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) -4,4'-(9-Fluorenylidene) dianiline (FDA) -4- (2-Phenylethynyl) phthalic anhydride (PEPA)

  6FDA-TeMPD-PEPA: 4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl-1,4-phenylenediamine (TeMPD) -4- (2 -Phenylethynyl) phthalic anhydride (PEPA) (chemical formula omitted)

The above-described problems of the present invention have also been solved by the following method for producing a gas separation membrane.
Item 6) Contains a weight ratio of 4/5 to 19/20 of the non-crosslinkable polymer (1) and a weight ratio of 1/20 to 1/5 of the crosslinkable polymer (2) having an acetylene group at the molecular end. A film-forming step of casting a solution of the mixture to remove the solvent to form a polymer mixture film, and a crosslinking that forms a crosslinked structure by a crosslinking reaction between the acetylene groups by heating the obtained polymer mixture film A process for producing a gas separation membrane.
Preferred embodiments of the invention described in item 6) above are described below.
Item 7) The method for producing a gas separation membrane according to Item 6), wherein the polymer (1) is 6FDA-FDA and / or 6FDA-TeMPD, and the polymer (2) is 6FDA-FDA-PEPA.

  ADVANTAGE OF THE INVENTION According to this invention, the gas separation membrane which suppresses swelling and plasticization of the gas separation membrane by the gas which is going to isolate | separate, for example, a carbon dioxide, and does not cause a performance fall could be provided.

The gas separation membrane of the present invention comprises a non-crosslinkable polymer (1) and a crosslink between the acetylene groups of the crosslinkable polymer (2) having an acetylene group at the molecular end in the presence of the polymer (1). It has a structure crosslinked by reaction.
The above polymer (1) and polymer (2) are dissolved in a common casting solvent, form a self-supporting film that is compatible in a dry state from which the solvent has been removed, and form a network by cross-linking. Any combination can be selected as long as it functions as a gas separation membrane having the above.

  The lower limit of the molecular weight of the polymer (1) and the polymer (2) is determined from the viewpoint of film-forming properties, preferably has a somewhat high molecular weight, and preferably has a number average molecular weight of 10,000 to 100,000, but is not necessarily 1 It is not essential to be over 10,000. The upper limit of the molecular weight of the polymer (1) and the polymer (2) is determined by the solvent solubility, and it is preferable that the polymer (1) and the polymer (2) are uniformly dissolved in a common solvent (may be a mixed solvent) at room temperature. Is preferably 500,000 or less, but this is not an absolute upper limit.

Both the polymer (1) and the polymer (2) may have a main chain composed of silicon or oxygen, but the main chain is preferably an organic polymer containing carbon, nitrogen, and oxygen. Each of the polymer (1) and the polymer (2) may be linear or branched, and may have a hyperbranched structure called a so-called dendrimer. In the polymer (2), acetylene groups are bonded to at least two terminals in the molecule. The hydrogen atom bonded to the carbon atom to which the acetylene group is not bonded to the polymer may be substituted with an organic group, and is preferably substituted. Examples of the substituent include an alkyl group (C1 to C6) or an aryl group (C6 to 10). In the polymer (2), the number of acetylene groups is 2 or more, and in the case of a branched polymer, the number of acetylene groups may be polyfunctional with 3 or more, and this acetylene group may be unsubstituted or substituted. good.
The reaction between substituted acetylene groups will be described later.

  The gas separation membrane of the present invention is preferably composed of a polymer (1) or (2) having a molecular structure with a high free volume fraction. For this purpose, the polymer (1) and / or the polymer (2) preferably contains a bulky group in the molecule, and examples thereof include cardo type polymers into which a fluorene ring is introduced. A gas separation membrane obtained from a combination in which the polymer (1) and / or the polymer (2) is a cardo type polymer having a fluorene ring can be preferably used.

  The polymer (1) and the polymer (2) may be a polyaddition type polymer, but a polycondensation type polymer is preferable in designing a polymer having a large free volume. Polycondensation polymers include aromatic polyimides, aromatic polyamides, aliphatic polyamides, aromatic polycarbonates, aliphatic polycarbonates, aromatic polyesters, aliphatic polyesters, aromatic polysulfones, and aliphatic polysulfones. And aromatic polyimides are preferred.

  As the chemical structure of the structural unit excluding the structural unit of the polymer (1) and the acetylene group of the polymer (2) used in the present invention, the following general formula (1) described in paragraphs 0012 to 0032 of JP-A No. 10-99666 is shown. Examples thereof include polycondensation type polymers having structural units of (5) to (5).

[Wherein Y ₁ , Y ₂ , Y ₃ and Y ₄ represent a divalent organic residue, Y ₅ represents a tetravalent organic residue, and X represents a divalent organic residue, A part of the following structural formula (A)

(Wherein R _{1 to} R ₁₂ are each an alkyl group represented by —H, —C _n H _{2n + 1} (n = 1 to 4), —OC _n H _{2n + 1} (n is 1 to 4). 4 represents an integer of 4.) represents an alkoxyl group, a carboxyl group, a carboxymethyl group, or a halogen, which may be the same or different, and is a divalent organic residue represented by . ]
The polymer (1) and / or (2) used in the present invention is preferably at least one selected from the above polyester structural unit, polycarbonate structural unit, polyether structural unit, polyamide structural unit and polyimide structural unit. It consists of a polymer having a structural unit, more preferably a cardo type polymer.

In the present invention, the polyester structural unit of the general formula (1) is obtained by reacting a diol with a dicarboxylic acid dihalide, preferably a dicarboxylic acid dichloride. Examples of the dicarboxylic acid dichloride used as a raw material for the Y ₁ moiety in the general formula (1) include aromatics such as terephthalic acid dichloride, isophthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, and 2,6-naphthalenedicarboxylic acid dichloride. Aliphatic dicarboxylic acids such as dicarboxylic acid dichloride, oxalic acid dichloride, succinic acid dichloride, glutaric acid dichloride, adipic acid dichloride, pimelic acid dichloride, suberic acid dichloride, fumaric acid dichloride, maleic acid dichloride, 1,4-cyclohexanedicarboxylic acid dichloride Examples thereof include acid dichlorides and mixtures of these dicarboxylic acid dichlorides. Of these, terephthalic acid dichloride, isophthalic acid dichloride, and adipic acid dichloride are preferred because they are easily available industrially.

In the present invention, the polycarbonate structural unit of the general formula (2) is obtained by reacting a diol with a phosgene dimer. Examples of the phosgene dimer used as a raw material for the Y ₂ moiety in the general formula (2) include trichloromethyl chloroformate.

In the present invention, the polyether structural unit of the general formula (3) is obtained by reacting a diol with a halogenated diphenylsulfone. As the halogenated diphenylsulfone used as a raw material for the Y ₃ moiety in the general formula (3), the following structural formula (B)

(Wherein R ₁₃ and R ₁₄ are H or an electron-withdrawing group, and R ₁₅ is a halogen). Here, the electron-withdrawing groups R ₁₃ and R ₁₄ are preferably halogen such as F, Cl, Br or NO ₂ , and the substituent R ₁₅ may be any of F, C1, or Br. This compound B may be used alone or in combination of two or more. Representative examples of such compounds include 4,4′-dichlorodiphenyl sulfone, 3,3 ′, 4,4′-tetrachlorodiphenyl sulfone, 4,4′-dichloro-3,3′-dinini. Examples thereof include dichlorodiphenyl sulfones such as trodiphenyl sulfone and mixtures thereof.

  In the above general formulas (1) to (3), as a raw material of the X portion, the following structural formula (A1)

[However, in the formula, R _{1 to} R ₁₂ are the same as in the structural formula (A). The diol having a fluorene skeleton represented by the above formula is used alone or in combination with a diol having the fluorene skeleton and other diols.

  As the diols having this fluorene skeleton, bisphenol fluorenes are used. Specifically, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene. 9,9-bis (3,5-dimethyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-ethyl-4-hydroxyphenyl) fluorene, 9,9-bis (3,5-diethyl-4) -Hydroxyphenyl) fluorene, 9,9-bis (3-bromo-4-hydroxyphenyl) fluorene, 9,9-bis (3,5-dibromo-4-hydroxyphenyl) fluorene, 9,9-bis (4- Hydroxyphenyl) fluorene-4-carboxylic acid and the like, and mixtures thereof. Other diols include aromatic diols such as bisphenol A, bisphenol F, bisphenol S, p-xylylene glycol, and naphthalenediol, and aliphatic diols such as ethylene glycol, diethylene glycol, and butanediol. It is done. Further, alkali metal salts such as sodium and potassium can also be used.

  In the case of the general formulas (1) to (3), the component molar ratio between the diol having a fluorene skeleton and the other diols is desirably 10/90 or more. When this component molar ratio is 10/90 or more, excellent solvent solubility and thermal stability can be obtained for the precursor cardo type polymer.

In the present invention, the polyamide structural unit of the general formula (4) is obtained by reacting a diamine with a dicarboxylic acid dihalide, preferably a dicarboxylic acid dichloride. Examples of the dicarboxylic acid dichloride used as a raw material for the Y ₄ moiety in the general formula (4) include aromatics such as terephthalic acid dichloride, isophthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, and 2,6-naphthalenedicarboxylic acid dichloride. Aliphatic dicarboxylic acids such as dicarboxylic acid dichloride, oxalic acid dichloride, succinic acid dichloride, glutaric acid dichloride, adipic acid dichloride, pimelic acid dichloride, suberic acid dichloride, fumaric acid dichloride, maleic acid dichloride, 1,4-cyclohexanedicarboxylic acid dichloride Examples thereof include acid dichlorides and mixtures of these dicarboxylic acid dichlorides. Of these, terephthalic acid dichloride, isophthalic acid dichloride, and adipic acid dichloride are preferred because they are easily available industrially.

In this invention, the polyimide structural unit of General formula (5) can be preferably used as a structural unit of a polymer (1) and a polymer (2), and is obtained by making diamine and tetracarboxylic dianhydride react. Examples of the tetracarboxylic dianhydride used as a raw material for the Y ₅ moiety in the general formula (5) include pyromellitic anhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, bis (3 , 4-dicarboxyphenyl) sulfone dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ′ , 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride and the like, and mixtures thereof.

  In the above general formulas (4) and (5), as a raw material of the X portion, the following structural formula (A2)

[Wherein, R _{1 to} R ₁₂ are the same as those in the structural formula (A)] alone, or a diamine having the fluorene skeleton and other diamines having the fluorene skeleton. Use in combination. Diamines having no fluorene ring can also be used alone.

  Bisaniline fluorenes are used as diamines having a fluorene skeleton, specifically 9,9-bis (4-aminophenyl) fluorene and 9,9-bis (3-methyl-4-aminophenyl) fluorene. 9,9-bis (3,5-dimethyl-4-aminophenyl) fluorene, 9,9-bis (3-ethyl-4-aminophenyl) fluorene, 9,9-bis (3,5-diethyl-4) -Aminophenyl) fluorene, 9,9-bis (3-bromo-4-aminophenyl) fluorene, 9,9-bis (3,5-dibromo-4-aminophenyl) fluorene, 9,9-bis (4- Aminophenyl) fluorene-4-carboxylic acid, methyl 9,9-bis (4-aminophenyl) fluorene-4-carboxylate, and the like, and mixtures thereof.

Other diamines include aromatic diamines such as 2,7-diaminofluorene, naphthalenediamine, 2,8-diaminodibenzofuran, 4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, hexa Examples include aliphatic diamines such as methylene diamine and isopropyl diamine.
Examples of diamines having no fluorene ring include 2,3,5,6-tetramethyl-1,4-phenylenediamine.

  In the general formulas (4) and (5), the component molar ratio between the diamine having a fluorene skeleton and the other diamines is preferably 10/90 or more. When this component molar ratio is 10/90 or more, excellent solvent solubility and thermal stability can be obtained for the precursor cardo type polymer.

  In the present invention, as the cardo type polymer having cardo type structural units represented by the general formulas (1) to (5), a polyester structural unit, a polycarbonate structural unit, a polyether structural unit, a polyamide structural unit, or a polyimide, respectively. In addition to a polymer composed of polyester, polycarbonate, polyether, polyamide, or polyimide having any one of the structural units, it may be a copolymer having two or more of these cardo-type structural units, May be a mixture of two or more polymers selected from these polymers and copolymers.

The crosslinkable polymer (2) used in the present invention has an acetylene group at the molecular end. The acetylene group may be unsubstituted or substituted acetylene group. The substituted acetylene group refers to a structure in which a hydrogen atom bonded to a terminal acetylene carbon is substituted with a substituent. The terminal hydrogen atom is preferably substituted with an alkyl group or a phenyl group, and more preferably substituted with a phenyl group.
In order to introduce a (substituted) acetylene group to the molecular terminal, a (substituted) acetylene compound having a functional group can be used. For example, 4- (2-phenylethynyl) phthalic anhydride (PEPA) can be used to synthesize a polyimide having a (substituted) acetylene group introduced at the terminal. Polyester having a (substituted) acetylene group introduced at the terminal can be synthesized using propargyl alcohol or phenylpropargyl alcohol. Polyamide having a substituted acetylene group introduced at the terminal can be synthesized using propargylamine.

(Mixing ratio of both polymers)
The mixing ratio of the polymer (1) and the polymer (2) is not particularly limited, but it is generally preferable that the non-crosslinkable polymer (1) is in excess of the crosslinkable polymer (2). If the ratio of the crosslinkable polymer (2) is low, sufficient crosslinking cannot be obtained, and swelling / plasticization of the gas separation membrane cannot be suppressed. Conversely, if there is too much crosslinking polymer (2), the flexibility of the separation membrane Tend to be lost. In general, the mixture is preferably a mixture of the weight ratio of 4/5 to 19/20 of the non-crosslinked polymer (1) and 1/20 to 1/5 of the crosslinkable polymer (2) having an acetylene group at the molecular end. .

  The shape of the separation membrane main body used in the present invention is not particularly limited as long as it is a shape generally used for gas separation, and examples thereof include a flat membrane shape and a hollow fiber membrane shape. A well-known method can be adopted as the film forming method. For example, when forming a flat membrane-like separation membrane body, the raw material polymer is dissolved in a suitable organic solvent, and if necessary, lithium chloride or the like is optionally added for the purpose of improving solution stability. Add to prepare the stock solution. A crosslinking catalyst may be added. Next, this film-forming stock solution is cast or coated on a smooth glass plate, polytetrafluoroethylene plate, mirror-finished stainless steel plate, or stainless steel belt, and then heated to evaporate a part of the solvent. If necessary, heating is performed to advance the cross-linking reaction to achieve networking of the gas separation membrane.

  In order to form a hollow fiber membrane-shaped separation membrane body, the membrane-forming stock solution is extruded into the coagulation liquid from the peripheral annular port of a double-pipe structure hollow fiber spinning nozzle and simultaneously from the central circular port. Is mixed with the solvent of the film-forming stock solution, but for cardo-type polymers, an insoluble solvent is extruded into the coagulation solution, air-dried at room temperature, vacuum-dried, and then allowed to proceed with a crosslinking reaction at an appropriate temperature. Form a network.

A typical crosslinking reaction of the polymer (2) used in the present invention is cyclization dimerization of an acetylene group (alkyne) bonded to a molecular terminal and formation of arene by cyclization trimerization. This cyclization dimerization and cyclization trimerization proceed with a transition metal catalyst even at a relatively low temperature (room temperature to 150 ° C.), and the latter trimerization produces substituted benzenes. As a metal catalyst for promoting the cyclization dimerization and cyclization trimerization, a nickel catalyst and a cobalt catalyst have been known for a long time, but a high-valent metal of group 5 exhibits an excellent catalytic action. Recently, niobium or tantalum halides can be preferably used, and TaCl ₅ and NbCl ₅ can be exemplified. In the production method of the present invention, TaCl ₅ or NbCl ₅ is preferably used as a cross-linking reaction catalyst between acetylene groups at a relatively low temperature. The amount used can be arbitrarily added as long as it is an effective amount for accelerating the crosslinking reaction. The range of 0.01 to 2% by weight relative to the total dry weight of polymer (1) and polymer (2) is common.
In addition, cyclic | annular trimerization advances even if there is no said transition metal catalyst in comparatively high temperature (above 150 degreeC-400 degreeC, for example, 350 degreeC).

  When forming a separation membrane by the solvent casting method, a crosslinking reaction catalyst is added to a solution of a mixture of the polymer (1) and the polymer (2) and cast. Prior to complete removal of the solvent, it can be stripped and stretched. Usually, after removing the solvent and drying, heating is performed as necessary to advance the crosslinking reaction between the acetylene groups. In addition, it is convenient to add the crosslinking reaction catalyst to the casting solution in advance, but the solvent that swells the obtained membrane after casting the polymer mixture solution without the addition of the crosslinking catalyst. It is also possible to supply a crosslinking reaction catalyst dissolved in the membrane into the membrane to advance the crosslinking reaction.

The heating temperature necessary for causing the crosslinking reaction varies depending on whether or not the transition metal catalyst is used and the combination of the polymer (1) and the polymer (2), but is usually 40 to 300 ° C, preferably 50 to 250 ° C.
The optimum heating temperature and heating time can be determined by preliminary experiments. When the heating temperature is lower than the optimum temperature, the crosslinking reaction does not proceed sufficiently, and the mechanical strength is reduced due to plasticization of the separation membrane. When the heating temperature is higher than the optimum temperature, the separation membrane is cured. It progresses to lose flexibility and is sometimes accompanied by coloring.
The heating time depends on the heating temperature, but in many cases is 0.5 to 10 hours.
A gas separation membrane crosslinked by appropriately selected heating conditions is insoluble in many organic solvents.

(Other additives)
In the gas separation membrane of the present invention, known polymer fillers and additives such as inorganic materials, oligomers, plasticizers, and pigments can be appropriately added to the separation functional layer as necessary.

(Film thickness, protective plate)
The thickness of the separation functional layer of the gas separation membrane according to the present invention is 10 nm to 1.0 μm, preferably 20 to 500 nm, more preferably 20 to 300 nm, and still more preferably 50 to 150 nm.
When the gas separation membrane of the present invention is used, a reinforcing plate can be used at least on the permeation side of the gas separation membrane. Reinforcing plates may be used on both the gas supply side and the gas permeation side of the gas separation membrane. The structure of the reinforcing plate is not particularly limited as long as the polymer separation membrane can be mechanically reinforced. The material preferably has holes that do not absorb or adsorb the separation target gas such as carbon dioxide and allow the mixed gas to pass through without resistance. Examples of such a material include polysulfone, polystyrene, nylon, polyvinylidene fluoride, and polyetherimide porous plates.
The reinforcing plate may be a composite material (FRP) reinforced with fibers or the like in order to improve its mechanical strength.

(Operation conditions of separation membrane)
When the gas separation membrane of the present invention is used for separation of carbon dioxide, it can be used at high temperature and high pressure. The temperature is 150 ° C or higher, preferably 150 ° C to 300 ° C, and the pressure is 10 atm or higher, preferably 40 to 100 atm. In addition, it is 1 atmosphere (1 atm) = 1.013 * 10 < ⁵ > Pa.

Example 1
6FDA-FDA and 6FDA-TeMPD were synthesized as examples of the polymer (1) used in the gas separation membrane of the present invention, and 6FDA-FDA-PEPA was synthesized as an example of the polymer (2).
1) Reagents used The following reagents were used in the experiment.
(1) Monomer 4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) used was purchased from Aldrich. Further, 4- (2-phenylethynyl) phthalic anhydride (PEPA) having a terminal acetylene structure was purchased from Wako Pure Chemical Industries, Ltd.
As a diamine monomer having a cardo ring, 4,4 ′-(9-fluorenylidene) dianiline (FDA) was a reagent of Aldrich. The reagent of Tokyo Chemical Industry Co., Ltd. was used for 2,3,5,6-tetramethyl-1,4-phenylenediamine (TeMPD), which is a diamine monomer having no cardo ring.

(2) Polymer All the polymers used in this study were synthesized by the polymerization method described in “2) Polymerization” which will be described later.
(3) Solvent / Catalyst N, N-dimethylacetamide (DMAc), which is a polymerization solvent for polyimide, was used after dehydrating a special grade reagent manufactured by Pure Chemical Co., Ltd. with Molecular Sieve 4A (manufactured by Pure Chemical Co., Ltd.).
Pyridine and acetic anhydride (both are special grade reagents manufactured by Junsei Chemical Co., Ltd.), which are imidation catalysts, were used after dehydration with Molecular Sieve 4A (produced by Junsei Chemical Co., Ltd.).
For purification of polyimide, a reagent grade N, N-dimethylformamide (DMF) manufactured by Junsei Chemical Co., Ltd. was used after dehydration with Molecular Sieve 4A (manufactured by Junsei Chemical Co., Ltd.). Pure reagent grade 1 methanol was used as it was. Further, dichloromethane (DCM) and tetrahydrofuran (THF) were used as film forming solvents for all polymers. DCM and THF were used after dehydrating a special reagent manufactured by Pure Chemical Co., Ltd. with Molecular Sieve 4A (manufactured by Pure Chemical Co., Ltd.).

2) Polymerization (1) Synthesis of non-crosslinkable polyimide 6FDA-FDA with a cardo ring and 6FDA-TeMPD without a cardo ring both synthesized a polyamic acid intermediate by low-temperature solution condensation polymerization, Polyimide was synthesized using chemical imidization reaction.
Diamine (FDA or TeMPD) was dissolved in DMAc at room temperature. After 30 minutes, 6 FDA equimolar to the diamine component was added to this solution and allowed to react at room temperature for 12 hours. At this time, the total monomer concentration in DMAc was about 20 wt%.
Then, acetic anhydride (5 moles per mole of monomer) and pyridine (7 moles per mole of monomer) were added and reacted at room temperature. All were performed under nitrogen atmosphere. After 5 hours, the reaction solution was poured into a large amount of methanol. The high molecular weight product precipitated as a solid component in methanol. The solid product was collected by filtration and dried. The dissolution reprecipitation purification, which was redissolved in DMF and poured into methanol, was repeated until no impurities were detected by FT-IR, ¹ H-NMR, and ¹³ C-NMR. At the same time, the structure of the solid product was confirmed to be the expected 6FDA-FDA and 6FDA-TeMPD.

(2) Synthesis of a crosslinkable polyimide having a substituted acetylene group at the end 6FDA-FDA-PEPA having a terminal acetylene group was synthesized by chemical imidation after synthesizing a polyamic acid intermediate by low-temperature solution condensation polymerization. Polyimide was synthesized. Diamine (FDA) was dissolved in DMAc at room temperature. After 30 minutes, a diamine component and an arbitrary proportion of terminal acetylene anhydride PEPA were added to this solution and allowed to react at room temperature for 3 hours. (Hereafter, 6FDA-FDA-PEPA (9: 2) for each ratio, the same shall apply hereinafter as (8: 4), (7: 6), (5:10)). 6FDA was added so that it might be equimolar with a component, and it was made to react at room temperature for 12 hours as it was. At this time, the total monomer concentration in DMAc was about 30 wt%.
Then, acetic anhydride (5 moles per mole of monomer) and pyridine (7 moles per mole of monomer) were added and reacted at room temperature. All were performed under nitrogen atmosphere. After 5 hours, the reaction solution was poured into a large amount of methanol. The high molecular weight product precipitated as a solid component in methanol. It was repeated until no impurities were detected by FT-IR, ¹ H-NMR, and ¹³ C-NMR by dissolution reprecipitation purification using a combination of DMF and methanol. At the same time, it was confirmed that the structure of the solid product was the expected 6FDA-FDA-PEPA.

3) Characterization (1) Molecular weight measurement Molecular weight measurement was performed using HLC-8220GPC (detector RI-8220, column TSKgel SuperHMH) manufactured by Tosoh Corporation by gel permeation chromatography. The collection was performed at a column temperature of 40.0 ° C. and a flow rate of 0.200 ml / min with a collection time of 50 minutes. The molecular weight was determined using polystyrene as a standard sample and THF as a solvent.

(Comparative Examples 1 and 2)
(2) Preparation of uncrosslinked film (film formation)
Film formation of 6FDA-FDA and 6FDA-TeMPD was performed by a solvent casting method using DCM as a solvent. First, a DCM solvent was added to the purified polyimide so as to have a solution concentration of 3 to 5 wt%, and dissolved for 1 day or more. Next, the polyimide solution was filtered using a fine filter paper to remove dust and the like. The solution is allowed to stand for more than 1 day, defoamed, cast on a flat dish made of polytetrafluoroethylene, covered so that dust does not enter, and the solvent is evaporated for about 2 to 3 days. Obtained. The obtained polyimide film was peeled off with pure water and then vacuum-dried at room temperature for 1 week or longer to remove the residual solvent.

(Examples 1-4)
(3) Preparation of Crosslinked Film A film membrane obtained by the solvent casting method was heated to produce a crosslinked separation membrane.
A film containing non-crosslinkable 6FDA-FDA or 6FDA-TeMPD as a main component and added with 1/10 by weight of crosslinkable 6FDA-FDA-PEPA was prepared from a DCM solution by a solvent casting method.
As the crosslinking reaction catalyst, tantalum pentachloride (manufactured by Aldrich) was used.
Prepare a DCM solution (1) of 6FDA-FDA-PEPA (9: 2), a DCM solution (2) of 6FDA-FDA, and a DCM solution (3) of 6FDA-TeMPD. (1), (2) and (1) ) And (3) were mixed. The concentration of the solution was 3 to 5 wt%. Any mixing ratio was prepared such that the non-crosslinkable polymer 6FDA-FDA or 6FDA-TeMPD and the crosslinkable polymer 6FDA-FDA-PEPA (9: 2) were 9: 1. (Hereinafter referred to as 6FDA-FDA-6FDA-FDA-PEPA (9: 1), 6FDA-TeMPD-6FDA-FDA-PEPA (9: 1).)

Mixed solution concentration X (%), the concentration C _A of both the polymer solution prior to mixing, C _B (wt%) mixed with the weight W _A of both solutions, from W _B (g), was calculated by the following equation.

The networking of 6FDA-TeMPD as a main component was performed by heating the film obtained by the solvent casting method to 250 ° C. stepwise.
The 6FDA-FDA-6FDA-FDA-PEPA (9: 1) or 6FDA-TeMPD-6FDA-FDA-PEPA (9: 1) networked membranes were both strong enough to withstand the measurement.

(4) Solvent solubility The solvent solubility of the prepared free-standing membrane was examined using several types of solvents. Six types of solvents, DCM, DMAc, DMF, N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP), THF, and methanol were used.
The networked (6FDA-TeMPD)-(6FDA-FDA-PEPA) (9: 1) membrane was well dissolved in DCM, dissolved in DMAc, DMF, NMP and THF, but insoluble in methanol. .

4) Gas permeation measurement (1) Low-temperature low-pressure gas permeation measurement Low-temperature low-pressure gas permeation measurement is a gas permeation measurement device described in Nakagaki Masayuki's "Membrane Experiment Method" Kitami Shobo, pages 217-219 (1984). It was performed using. The measurement was performed for five gas species of hydrogen, oxygen, nitrogen, carbon dioxide, and methane at a supply gas pressure of about 76 cmHg (1 atm) and a measurement temperature of 35 ° C. All these gases were high purity gas cylinders. This apparatus is welded with Pyrex (registered trademark) glass except for a part on the high pressure side, and a vacuum cock having a particularly good quality is used. Moreover, the stainless steel permeation cell on which the membrane is mounted is also used with less vacuum leakage, and the low pressure side is glass welded to the measurement line. Since the high pressure side is connected by a ball joint, membrane exchange can be easily performed. The vacuum pump was an oil rotary vacuum pump, and the ultimate vacuum was 10 ⁻³ Torr.

The gas permeability with respect to the polyimide 6FDA-FDA membrane having a cardo ring was in the order of hydrogen> carbon dioxide>oxygen>nitrogen> methane from the gas having high permeability. In the case of nitrogen and methane with respect to carbon dioxide, the gas selectivity of (CO ₂ / N ₂ ) is about 27, and the gas selectivity of (CO ₂ / CH ₄ ) is about 37, so that selective carbon dioxide separation is achieved. It became clear that it was a membrane. From these results, when evaluating the position of gas separation performance and gas permeation performance of nitrogen with respect to carbon dioxide, it becomes clear that the model polymer 6FDA-FDA in this study is located in the vicinity of the Upper Bound in 2000. It became clear that it was an excellent membrane separation material.

(2) High-temperature and high-pressure gas permeation measurement High-temperature and high-pressure gas permeation measurement is performed according to T. Nakagawa, T. Nishimura, and A. Higuchi, J. Membr. Sci., 206, 149-163 (2002). The measurement was performed using a quantity measuring device. The measurement was performed for carbon dioxide at 6 supply pressures of 1 atm, 10 atm, 15 atm, 20 atm, 30 atm, and 40 atm. The measurement temperature was 35 ° C and 150 ° C. The stainless steel gas permeable cell of this device is a modification of the reverse osmosis device, and the supply gas side is entirely piped with stainless steel metal. Although the gas permeation side is made of Pyrex (registered trademark) glass, a safety device is provided by using a common joint with a flexible joint in order to cope with a high-pressure gas inflow due to a film breakage. This is a mechanism in which when the high-pressure gas flows in, the flexible joint bends and disengages at the same time. In order to keep the gas permeable cell at a constant temperature, the periphery of the cell was covered with a mantle heater, and the cell temperature was adjusted using a temperature controller. The pressure on the supply side was determined using MKS Baratron 740B (1,000 psi), and the pressure on the permeate side was determined using MKS Baratron 626A (1,000 Torr). Details of the measurement followed the above-mentioned document.

(A) Change in CO ₂ permeability over time of networked 6FDA-FDA-6FDA-FDA-PEPA (9: 1) membrane (A1) Change over time in carbon dioxide permeability at 35 ° C. and 10 atm was observed. The initial transmittance was about 1 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). Almost no change in transmittance with time was observed in the time range of 12 hours.
(A2) The time change of the carbon dioxide permeability at 35 ° C. and 40 atm was observed. The initial transmittance was about 2 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). In the time range extending over 12 hours, the transmission increased by about 25%.
(B) Change in CO ₂ permeability over time of networked 6FDA-TeMPD-6FDA-FDA-PEPA (9: 1) membrane (B1) Change over time in carbon dioxide permeability at 35 ° C. and 10 atm was observed. The initial transmittance was about 4 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). No change in transmittance over time was observed in the time range extending over 12 hours.
(B2) The time change of the carbon dioxide gas permeability at 35 ° C. and 40 atm was observed to be about 4 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). No change in transmittance over time was observed in the time range extending over 12 hours.
(B3) Changes in carbon dioxide gas permeability over time at 150 ° C. and 10 atm were observed. The initial transmittance was 2.7 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). No change in transmittance over time was observed in the time range extending over 12 hours.
(B4) The change with time of the carbon dioxide permeability at 150 ° C. and 40 atm was observed. The initial transmittance was about 2 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). No change in transmittance over time was observed in the time range extending over 12 hours.
(C: Comparison) Change over time of CO ₂ permeability of 6FDA-TeMPD film not networked (C1) The change over time in the permeability of carbon dioxide gas at 35 ° C. and 10 atm was observed. The initial transmittance was about 7 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). No change in transmittance over time was observed in the time range extending over 12 hours.
(C2) The time change of the carbon dioxide permeability at 35 ° C. and 40 atm was observed. The initial transmittance was about 12 × 10 ⁻⁸ (cm ³ (STP) cm) / (cm ² s cmHg). The transmission increased by about 66% over a time range of 12 hours.

As can be seen from the above results, in the 6FDA-TeMPD film that is not networked, the CO ₂ permeability time change increased by 66% in the time range of 12 hours at 35 ° C. and 40 atm (C2).
With the networked 6FDA-FDA-6FDA-FDA-PEPA (9: 1) membrane, the CO ₂ permeability time variation increased only 25% over a 12 hour time range at 35 ° C. and 40 atmospheres (A2 ).
In the networked 6FDA-TeMPD-6FDA-FDA-PEPA (9: 1) membrane, no change in CO ₂ permeability over time was observed over a 12 hour time range at 35 ° C. and 40 atmospheres (B2). Furthermore, in the networked 6FDA-TeMPD-6FDA-FDA-PEPA (9: 1) membrane, the permeability of carbon dioxide at 40 atmospheres was not observed in the time range of 12 hours even at a high temperature of 150 ° C. (B4).
The polymer separation membrane formed with a network has the ability to separate carbon dioxide gas and the like with high efficiency, and can maintain a long time range even at high temperature and high pressure. This is because plasticization by carbon dioxide gas could be suppressed by forming a network in the polymer separation membrane.

Claims (7)

Non-crosslinkable polymer (1), and
In the presence of the polymer (1), the crosslinkable polymer (2) having an acetylene group at the molecular end has a structure crosslinked by a crosslinking reaction between the acetylene groups.
Carbon dioxide separation membrane. The carbon dioxide separation membrane according to claim 1, wherein both the polymer (1) and the polymer (2) are cardo type polymers having a fluorene ring. The carbon dioxide separation membrane according to claim 1 or 2, wherein the polymer (1) and the polymer (2) are both polycondensation polymers. The carbon dioxide separation membrane according to any one of claims 1 to 3, wherein the polymer (1) and the polymer (2) are both polyimide-type polymers. Polymer (1) is 6FDA-FDA (4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 ′-(9-fluorenylidene) dianiline (FDA)) and / or 6FDA-TeMPD ( 4,4′-hexafluoroisopropylidenediphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl-1,4-phenylenediamine (TeMPD)),
Polymer (2) is 6FDA-FDA-PEPA (4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 ′-(9-fluorenylidene) dianiline (FDA) -4- (2- Phenylethynyl) phthalic anhydride (PEPA)) and / or 6FDA-TeMPD-PEPA (4,4′-hexafluoroisopropylidenediphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl- The carbon dioxide separation membrane according to any one of claims 1 to 4, which is 1,4-phenylenediamine (TeMPD) -4- (2-phenylethynyl) phthalic anhydride (PEPA)). Solution of a mixture containing a weight ratio of 4/5 to 19/20 of the non-crosslinkable polymer (1) and a weight ratio of 1/20 to 1/5 of the crosslinkable polymer (2) having an acetylene group at the molecular end Forming a polymer mixture film by casting and removing the solvent, and
A heating step of the obtained polymer mixture film to form a crosslinked structure by a crosslinking reaction between the acetylene groups,
A method for producing a carbon dioxide separation membrane. The polymer (1) is 6FDA-FDA (4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 ′-(9-fluorenylidene) dianiline (FDA)) and / or 6FDA-TeMPD ( 4,4′-hexafluoroisopropylidenediphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl-1,4-phenylenediamine (TeMPD)) ,
Polymer (2) is 6FDA-FDA-PEPA (4,4′-hexafluoroisopropylidene diphthalic dianhydride (6FDA) -4,4 ′-(9-fluorenylidene) dianiline (FDA) -4- (2- Phenylethynyl) phthalic anhydride (PEPA)) and / or 6FDA-TeMPD-PEPA (4,4′-hexafluoroisopropylidenediphthalic dianhydride (6FDA) -2,3,5,6-tetramethyl- It is 1,4-phenylenediamine (TeMPD) -4- (2-phenylethynyl) phthalic anhydride (PEPA)) .
A method for producing a carbon dioxide separation membrane.