JP2019502765A - Non-crosslinked high molecular weight polyimide polymer containing a small amount of bulky diamine - Google Patents

Abstract

  One of the methods described herein relates to producing a membrane comprising a non-crosslinked high molecular weight polyimide polymer containing a small amount of bulky diamine. Also described herein is a hollow fiber polymer membrane comprising a non-crosslinked high molecular weight polyimide polymer with a small amount of bulky diamine. Polyimide polymers include dianhydride monomers, diamino monomers that do not have a carboxylic acid functional group, and optionally a monomer group that includes a diamino monomer that has a carboxylic acid functional group, with 2-10 mole percent of the diamino monomer being bulky It is a diamino compound, and the ratio of the diamino monomer which has a carboxylic acid functional group and the diamino monomer which does not have a carboxylic acid functional group is 0-2: 3. These non-crosslinked high molecular weight polyimide polymers with small amounts of bulky diamines are useful in forming polymer membranes with high permeability and good selectivity that are useful for separating fluid mixtures.

Description

  Non-crosslinked high molecular weight polyimide polymers containing small amounts of bulky diamines are described herein. A method for producing non-crosslinked high molecular weight polyimide polymers using small amounts of bulky diamines is also described herein. These non-crosslinked high molecular weight polyimide polymers are useful for polymer membranes with high performance and good selectivity, which can be used for separation of fluid mixtures.

  Polymer membranes for separating gas mixtures such as methane and carbon dioxide are known. The following documents are incorporated herein by reference in their entirety, for example, U.S. Pat. Nos. 7,247,191, 6,932,859, 6,755,900, and 7,981. No. 8,974, No. 8,066,799, No. 8,337,598, No. 8,394,182 and No. 8,328,906 are produced from such crosslinkable polymers. Crosslinkable polymers and crosslinked hollow fiber membranes are taught. These patents specifically describe crosslinkable polyimide polymers. This crosslinkable polyimide polymer can be produced by monoesterifying the polyimide polymer using a crosslinking agent.

  Crosslinked hollow fiber membranes can be produced by forming fibers from a crosslinkable polyimide polymer and transesterifying the crosslinkable polyimide polymer in the fiber. More specifically, a crosslinkable fiber can be formed from the crosslinkable polyimide polymer, which is then subjected to transesterification conditions to create covalent ester bridges between the crosslinkable polyimide polymers in the fiber. . Crosslinked hollow fiber membranes can be incorporated into the separation module. Other types of separation membranes include flat sheet type separation membranes or flat laminated filters.

  Separation modules that use hollow fiber membranes have a larger surface area than separation modules that use flat sheets or flat laminated filters. Therefore, the hollow fiber separation module has a large separation ability even in the case of a moderately sized module. Module size is important when mounting separation modules on offshore platforms where space and weight are particularly important for separating gas mixtures from hydrocarbon production wells.

  Crosslinked hollow fiber membranes have good selectivity. However, transesterification conditions to create covalent ester crosslinks between crosslinkable polyimide polymers in the fiber cause a significant decrease in permeability. The loss of transmission can be, for example, about 50%, or even as high as about 70% or more. Crosslinking is also a difficult process to implement on a commercial scale.

  Accordingly, there remains a need for a method of producing high molecular weight polyimide polymers that retains its selectivity and permeability. The polymer must also have good strength, flexibility and / or spinnability. Furthermore, it is necessary to produce a separation membrane with improved permeability and selectivity.

A hollow fiber polymer membrane comprising a polyimide polymer membrane material having an average molecular weight of at least 50,000 and made from a polyimide polymer comprising monomer A + B + optionally C
A is a dianhydride of the following formula

Wherein X ₁ and X ₂ are the same or different halogenated alkyl groups, phenyl or halogen,
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are H, alkyl or halogen)
And
B is a cyclic diamino compound having no carboxylic acid functional group,
C is a cyclic diamino compound having a carboxylic acid functional group,
2 to 10 mol% of the diamino monomers B and C are bulky diamino compounds D, and the ratio of C and B is 0 to 2: 3,
The polyimide polymer membrane material comprises less than 30% by weight of crosslinking,
Hollow fiber polymer membranes are described herein.

One of the methods described herein relates to making non-crosslinked high molecular weight polyimide polymers using small amounts of bulky diamines. These non-crosslinked high molecular weight polyimide polymers are useful for polymer membranes with high permeability and good selectivity that are useful for separating fluid mixtures. Another method described herein relates to making membranes from non-crosslinked high molecular weight polyimide polymers containing small amounts of bulky diamines. Still another method is described herein, including for example CO ₂ and CH _4, from a feed stream comprising two or more components, membranes for separating at least one component, such as CO ₂ About using.

  The present disclosure relates to a method of making a film comprising a non-crosslinked high molecular weight polyimide polymer. The method comprises (a) preparing a polyimide polymer from a reaction solution comprising a monomer and at least one solvent, wherein the monomer is a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and optionally, 2-10 mol% of the diamino monomer is a bulky diamino compound containing a diamino monomer having a carboxylic acid functional group, and the ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 -2: 3, and (b) obtaining a film comprising a non-crosslinked polyimide polymer comprising less than 30% by weight of crosslinking.

  In step (a), the monomer is polymerized in a polymerization reaction to yield a polyamide polymer containing amide bonds. An imidization reaction occurs, whereby the amide bond forms an imide bond, resulting in a polyimide polymer. This monomer includes a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and optionally a diamino monomer having a carboxylic acid functionality. Among the diamino monomers, 2 to 10 mol% are bulky diamino compounds. In certain embodiments, 2-5 mol% is a bulky diamino compound. The ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3.

  In some embodiments, step (a) is performed under dehydrating conditions that remove at least a portion of the water formed during the imidization reaction of step (a).

  The method provides a membrane with less than 30 wt% crosslinks that exhibits good permeability and selectivity. In certain embodiments, 2-5 mol% of the diamino monomer is a bulky diamino compound. In certain embodiments, the membrane contains less than 10 wt% crosslinks, and in other embodiments, essentially no crosslinks. In some embodiments, these crosslinks are ester crosslinks.

  In some embodiments, the methods disclosed herein seal defects in a fiber by coating the fiber with a polydimethylsiloxane (PDMS) or cross-linked silicone coating agent. The method further includes the step of:

FIG. 1 shows an exemplary bulky diamine, 2,2′-bis (trifluoromethyl) benzidine (2,2′-bis (trifluoromethyl)-[1,1′-biphenyl] -4,4. '-Diamine and also known as 2CF3) and 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4'-(9-fluorenylidene) dianiline (also known as CF3) .

FIG. 2 shows Comparative Example 12 when tested with a 50/50 vol% CO ₂ / CH ₄ gas mixture at 35 ° C. with a shell side feed at a pressure between 200 and 800 psi. Shows CO ₂ permeability and CO ₂ / CH ₄ selectivity for the fibers.

FIG. 3 shows a test using a 50/50 vol% CO ₂ / CH ₄ gas mixture at 35 ° C. with a shell side feed at a pressure between 200 and 800 psi as described in Example 13. Of CO ₂ permeation and CO ₂ / CH ₄ selectivity for the fibers of Example 13.

FIG. 4 is a CO ₂ permeability for the fiber of Example 13 when tested with a 50/50 vol% CO ₂ / CH ₄ gas mixture at 35 ° C., but with a gas mixture containing 300 ppm heptane. And CO ₂ / CH ₄ selectivity, illustrating the stability against the hydrocarbon impurities described in Example 13.

Figure 5 is the 35 ° C., by the pressure on the shell side feed during 200～800Psi, when tested using a 50/50% by volume of _CO 2 / CH ₄ mixed gas, CO ₂ relates to a fiber of Comparative Example 14 The transmittance is shown.

6, at 35 ° C., by the pressure on the shell side feed during 200～800Psi, when tested using a 50/50% by volume of _CO 2 / CH ₄ mixed gas, CO ₂ relates to a fiber of Comparative Example 14 Shows / CH ₄ selectivity.

  A novel hollow fiber polymer membrane comprising a non-crosslinked polyimide polymer containing a small amount of bulky diamine is disclosed herein. These membranes are surprisingly resistant to plasticization even if they are not cross-linked. The separation membrane needs to exhibit a combination of selectivity and permeability. In forming the membrane, the permeability cannot be reduced to the point where the membrane ceases to function and the selectivity cannot be sacrificed to provide acceptable permeability.

  Preferred polymers that can be used in the hollow fiber membrane of the present invention include polyimide, polyetherimide, polyethersulfone and polysulfone. More preferred polymers that can be used in the membrane material of the present invention include polyimides, polyetherimides, and polysulfones made using analogs of 6FDA. Particularly preferred polyimides that can be used in the present invention include polyimides or polyetherimides made using 6FDA.

Without being bound by theory, it is believed that the incorporation of a small amount of bulky diamine into a high molecular weight polyimide polymer inhibits segmental motion and reduces chain mobility or flexibility. If there is too much segment motion, the free volume required for good transmission is lost. Small amount of bulky diamines, relaxation in glassy polymers, and generally associated increased quasi Tg transition (sub-T _g transition) to the loss of free volume, films resistant to plasticization without being crosslinked It is thought that it is possible to form. In polymer membranes formed with non-crosslinked polyimide polymers that do not contain a small amount of bulky diamines, the membranes show increased permeability and decreased selectivity with increasing CO ₂ pressure, thereby reducing the polyimide The polymer will be much less suitable for the membrane as compared to the polymers disclosed herein. Thus, it is surprising that the polyimide polymers containing small amounts of bulky diamines disclosed herein show good permeability and selectivity even at high CO ₂ pressures, even when not crosslinked. It is to be done.

Further disclosed herein is a method for producing a non-crosslinked high molecular weight polyimide polymer film. The method advantageously eliminates the cross-linking step while still providing a membrane with good permeability and selectivity even at high CO ₂ pressures. In certain embodiments, the method can further advantageously omit the monoesterification step. Thus, the method is simplified and has greater advantages for commercialization.

  In certain embodiments, the method may include an esterification step with a monoalcohol or diol. In embodiments that include an esterification step, esterification with a monoalcohol may have certain advantages.

  As described herein, non-crosslinked is meant to include a polyimide polymer that contains less than 30% by weight of cross-linking, or, as specified otherwise, greater than 70% by weight of non-cross-linked groups. In some embodiments, the polyimide polymer comprises less than 20% by weight crosslinking (ie, greater than 80% by weight non-crosslinking groups). In certain embodiments, the polyimide polymer contains less than 10% by weight crosslinks, and in specific embodiments, the polyimide polymer has essentially no crosslinks. In some embodiments, these crosslinks are ester crosslinks. Crosslinking is measured by gel fractionation. In this method, the fiber is first weighed and then placed in tetrahydrofuran (THF) on a roller for 24 hours at room temperature. After removing residual THF, the fiber is weighed again. The percent weight loss correlates with the degree of ester crosslinking. For example, a 90% weight loss indicates 10% by weight crosslinking, and a 70% weight loss indicates 30% by weight crosslinking. Polyimide polymers that have essentially no crosslinks have no measurable crosslinks, as determined by this method, and thus show a weight loss of about 100% when tested according to this method.

  The method described herein can advantageously omit the cross-linking step so that the polyimide polymer need not contain ester groups. Since no ester group is required, the method can further advantageously omit the monoesterification step. Thus, the method is simplified and has greater advantages for commercialization. In other embodiments, the method may include an esterification step with a monoalcohol or diol.

  Monomers for preparing polyimide polymers include dianhydride monomers, diamino monomers that do not have carboxylic acid functional groups, and optionally diamino monomers that have carboxylic acid functional groups, and diamino monomers and carboxylic acids that have carboxylic acid functional groups. The ratio with the diamino monomer having no acid functional group is 0 to 2: 3.

The non-crosslinked high molecular weight polyimide polymer-containing membrane described herein exhibits good permeability and selectivity even at high CO ₂ pressures. Note that this method of making a polyimide polymer membrane does not include the active step of subjecting the polyimide polymer to transesterification conditions to form crosslinks. It should also be noted that this method of making a polyimide polymer membrane may optionally not include the active step of monoesterification. Accordingly, the high molecular weight polyimide polymer membranes and methods disclosed herein have more commercial feasibility.

The membranes described herein have a CO ₂ permeability of at least 20 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and 100 psia pressure. In some embodiments, the membrane has a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and a pressure of 100 psia. In certain embodiments, the membrane has a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and a pressure of 400 psia. Techniques for determining and measuring permeability and selectivity are well known to those skilled in the art. The feed for these measurements is a feed having a CO ₂ / CH ₄ molar ratio of 50/50, and the specific pressure for the measurement is based on the total feed pressure. These techniques are described, for example, in US Pat. Nos. 6,755,900, 6,932,859, 7,247,191, and 8 which are incorporated by reference in their entirety. , 394,182.

As used herein, the term “bulky diamine” refers to about 5 to about 12 diamines. In certain embodiments, the bulky diamine is about 6 to about 12 diamines. In some embodiments, the bulky diamine is about 6 to about 9.5 liters of diamine. Bulky diamine, may also enhance the quasi-Tg _{(sub-T g).} Accordingly, when a bulky diamine is added to the polyimide polymer, the quasi-Tg peak is shifted to a higher side by at least 2 ° C. compared to the same polymer not containing the bulky diamine.

  Bulky diamines include, for example, 2,2′-bis (trifluoromethyl) benzidine (2,2′-bis (trifluoromethyl)-[1,1′-biphenyl] -4,4′-diamine and 2CF 3 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 ′-(9-fluorenylidene) dianiline (also known as CF3), 4,4 ′-( Hexafluoroisopropylidene) dianiline (also known as Fu) and the like, and mixtures thereof. In certain embodiments, the bulky diamine is 2,2′-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine or 4,4 ′-(9 -Fluorenylidene) dianiline (CF3). The bulky diamine is 2-10 mol% of the diamino monomer used to prepare the polyimide polymer, and in certain embodiments, the bulky diamine is a diamino monomer used to prepare the polyimide polymer. Of 2 to 5 mol%.

  The size of the bulky diamine is measured as described below. The molecular structure was constructed by Material Studio 6.1 (Accelrys Software Inc.). Material Studio 6.1, Accelrys, Inc. : San Diego, CA, 2012. Their geometry was optimized using the cvff force field implemented in the “Forcite” module. P. Dauger-Osguthorpe, V.M. A. Roberts, D.C. J. et al. Osguthorpe, J.M. Wolff, M.M. Genest and A.M. T.A. Hagler, structure and energetics of ligands bound to proteins: Collagen hydrofolate reductase-trimethoprim, drug receptor system: E. colidihydrofolate reductase-trimethoprim, trimethoprim, drug receptor system , Funct. Genet. 4, 4, 31-47 (1988). The optimized molecular structure was then exported to the CrystalMaker program (Version 8.7, for Mac OS, Crystal Maker Software Ltd.), from which the physical dimensions of the molecule were determined. CrystalMaker 8.7, CrystalMaker Software Ltd, Yarnton, UK, 2013. The covalent bond radius of the outermost atom (Material Studio 6.1 built-in database) is added to both the length and diameter values. The diamine size then becomes the distance between the axis of the two amine groups in each molecule and the dimension perpendicular to this axis, which can be measured directly by the CrystalMaker program.

  As an example, the size of 2CF3 was measured as 7.3 cm, and the size of CF3 was measured as 6.8 cm.

  Similarly, as used herein, the term “non-crosslinked high molecular weight polyimide polymer” refers to a polyimide polymer having an average molecular weight between about 40,000 and about 400,000. In certain embodiments, the polyimide polymer has an average molecular weight greater than 50,000. For example, the high molecular weight polyimide polymer can have an average molecular weight between about 100,000 and about 300,000.

  As described herein, a “non-crosslinked high molecular weight polyimide polymer” is a polyimide polymer having less than 30% by weight crosslinking, or a polyimide containing more than 70% by weight uncrosslinked groups, as otherwise specified. Refers to a polymer. In some embodiments, the polyimide polymer comprises less than 20% by weight crosslinking (ie, greater than 80% by weight non-crosslinked). In certain embodiments, the polyimide polymer contains less than 10% by weight crosslinks, and in specific embodiments, the polyimide polymer has essentially no crosslinks. When a polyimide polymer is described as having essentially no cross-linking, there is about a 100% weight loss as determined by the gel fractionation method described herein. In certain embodiments, these crosslinks are ester crosslinks.

  In one embodiment, the membrane is a non-crosslinked hollow fiber membrane. Non-crosslinked hollow fiber membranes are manufactured using high molecular weight polyimide polymers containing a small amount of bulky diamine. The method includes spinning a hollow fiber derived from a non-crosslinked polyimide polymer containing a small amount of bulky diamine. The method specifically comprises a dope composition comprising a polyimide polymer containing a small amount of bulky diamine, a volatile component, a spinning solvent, a spinning non-solvent, and optionally an inorganic additive. A method of spinning hollow fibers may be included.

  Non-crosslinked high molecular weight polyimide polymers containing small amounts of bulky diamines disclosed herein can also be cast to form sheets or films. The sheet or film can be cast on a suitable carrier to provide a composite sheet.

Definitions Throughout this specification the following terms are used and have the following meanings unless otherwise indicated.

  As used herein, the term “carboxylic acid functional group” refers to a pendant group that is —COOH.

  The term “diol” refers to a chemical compound containing two hydroxyl groups.

  The term “monoalcohol” refers to a chemical compound containing one hydroxyl group.

  The term “carbodiimide” means a chemical compound containing the functional group N═C═N.

The term “dianhydride” refers to an anhydride group.

Refers to any compound containing two.

  The term “halogenated alkyl” means a straight or branched saturated monovalent hydrocarbon group consisting of 1 to 12 carbon atoms, at least one of which is replaced by a halogen atom (eg, Fluoromethyl, 1-bromo-ethyl, 2-chloro-pentyl, 6-iodo-hexyl, etc.).

  The term “halo” or “halogenated” refers to a functional group containing a halogen atom such as fluorine, chlorine, bromine or iodine.

The term “phenyl” means an aromatic group of 6 carbon atoms having the formula —C ₆ H ₅ .

The term “alkyl” means a straight or branched saturated monovalent hydrocarbon group of 1 to 12 carbon atoms (eg, methyl, ethyl, i-propyl, etc.). The alkyl group has the formula C _n H _{2n + 1} , where n is a non-zero positive integer.

  The term “cyclic diamino compound” means a chemical compound having a ring structure of 3 to 12 carbon atoms, which ring structure is functionalized by two amino groups or substituted amino groups.

  The term “amino” refers to a functional group having the formula —NR′R ″, where R ′ and R ″ are independently H, alkyl, cycloalkyl and aryl.

  The term “cycloalkyl” means a saturated cyclic monovalent hydrocarbon group having a monocyclic ring or multiple condensed rings containing from 3 to 12 carbon atoms. Such cycloalkyl groups include, by way of example, cyclopropyl, cyclohexyl, cyclooctyl, adamantanyl, and the like.

  The term “aliphatic” refers to a non-aromatic organic compound in which the carbon atoms are joined together in a straight or branched chain. Aliphatics include paraffinic (eg alkyl) compounds, olefinic (eg alkenyl) compounds and alkynyl compounds.

  The term “antilyotropic salt” refers to a salt that interacts with solvent molecules other than polymer molecules.

  The term “amide” means a functional group having a carbonyl group (C═O) linked to a nitrogen atom or a compound containing this functional group.

  The term “ester” means a functional group having a carbonyl group (C═O) linked to an alkoxy group.

The term “alkoxy” refers to an alkyl group linked to oxygen, such as, for example, methoxy (—OCH ₃ ) or ethoxy (—OCH ₂ CH ₃ ).

  The term “aryl” is an unsaturated aromatic carbocyclic group of 6 to 20 carbon atoms having a single ring (eg, phenyl) or multiple condensed (fused) rings (eg, naphthyl or anthryl). Refers to the group. Exemplary aryl includes phenyl, naphthyl, and the like.

The term “alkenyl” refers to a linear or branched unsaturated monovalent hydrocarbon group having from 2 to 12 carbon atoms and containing at least one, for example 1-3 double bonds. This term is exemplified by groups such as ethenyl (—CH═CH ₂ ), 2-propenyl (—CH ₂ —CH═CH ₂ ), and the like.

The term “alkynyl” refers to a linear or branched monovalent hydrocarbon group having 2 to 12 carbon atoms and containing at least one, for example, 1 to 3, triple bonds. This term is exemplified by groups such as ethynyl (—C≡CH), 2-propynyl (—CH ₂ —C≡CH), n-butynyl (—CH ₂ —CH ₂ —C≡CH), and the like.

  As used herein, the term “reduce” means to decrement or diminished.

  As used herein, the term “molecular weight” or “average molecular weight” means the weight average molecular weight as measured by gel permeation chromatography (GPC) using polystyrene as a standard. This method is described in ASTM D5296-05.

  “Draw ratio” means the ratio of winding speed to extrusion speed.

  “Glass transition temperature” (Tg) is the temperature at which a polymer transitions from hard and glassy to soft and rubbery.

The term “quasi-T _g ” (sub-T _g ) refers to what is also referred to as T _β , which is the β-relaxation temperature at which segment motion of the polymer is detected.

The term “permeability” or P refers to the pressure and thickness normalized flux of a given component, such as CO ₂ . The permeability can be measured, for example, by Barrrers.

The standard unit for measuring gas permeability through a supported gas separation membrane is Barrer, which is defined as follows:

(In the formula, flux (flow velocity) is a unit of cm ³ / cm ² × second, and is a volume of a permeated gas per second at standard temperature and pressure, cm is a film thickness, cm ² is the area of the film, cm.Hg is the pressure (or driving force).

  The term “permeance” refers to the ratio of permeability to membrane thickness.

The term “selectivity” refers to the ratio of the permeability of two components through the membrane (ie, P _A / P _B , where A and B are the two components).

The selectivity of the supported gas separation membrane in the separation of a fluid mixture of two components is the ratio of the velocity of the component that passes easily and the velocity of the component that does not easily pass. Defined. Selectivity can be obtained directly by contacting the supported gas separation membrane with a known gas mixture and analyzing the permeate. Alternatively, the first-order approximation of selectivity can be obtained by calculating the ratio of the passage speeds of two components that are individually determined on the same gas separation membrane. The passing speed can be expressed in Barrer units. As an example of selectivity, O ₂ / N ₂ = 10 indicates that the target film can pass oxygen gas at a rate ten times the rate of nitrogen.

The productivity (permeability) of a gas separation membrane is measured with a GPU defined as follows:

The membranes disclosed herein have a CO ₂ permeability of at least 20 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and a pressure of 100 psia. In some embodiments, the membrane has a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and a pressure of 100 psia. In some embodiments, the membrane has a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 at 35 ° C. and a pressure of 400 psia.

Permeability, permeability and selectivity are measured by techniques well known to those skilled in the art, for example, as described in US Pat. No. 7,247,191, the entire contents of which are incorporated by reference. As described herein, permeability and selectivity are measured at 35 ° C. and 100 psia pressure. The feed for these measurements is a feed having a CO ₂ / CH ₄ molar ratio of 50/50, and the specific pressure for the measurement is based on the total feed pressure.

  Permeability and selectivity are measured at 35 ° C. and 100 psia pressure as standard values for comparison herein, while permeability and selectivity are measured at higher pressures, such as 200sia or 400 psia. Note that you can also. When permeability and selectivity are measured at 200 psia or 400 psia, it is expected that these measurements demonstrate poorer performance than when measured at 100 psia. Thus, if the standard values for permeability and selectivity are met when measured at a pressure of 200 psia or 400 psia, the standard values of permeability and selectivity are met when measured at a pressure of 100 psia. Be expected. For example, if a membrane shows good permeability and selectivity when measured at 35 ° C. and a pressure of 200 psia, the membrane also has good permeability and selectivity when measured at 35 ° C. and a pressure of 100 psia. Is expected to show.

The term “PDMC” refers to a propanediol monoester polymer. One form of PDMC having a DAM: DABA ratio of 3: 2 is the following structure:

Have

Method for producing a film of a non-crosslinked polyimide polymer having a small amount of bulky diamine The method for producing a non-crosslinked polyimide polymer described herein comprises preparing a polyimide polymer from a reaction solution comprising a monomer and at least one solvent. Wherein the monomer comprises a dianhydride monomer, a diamino monomer having no carboxylic acid functional group, and optionally a diamino monomer having a carboxylic acid functional group, wherein 2 to 10 mol% of the diamino monomer is bulky diamino And a step wherein the ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3. The step of treating the polyimide polymer with a diol in esterification conditions to form a non-crosslinked monoesterified polyimide polymer is not required, and thus monomers with carboxylic acid functionality are optional. Therefore, the ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3. Next, a membrane comprising uncrosslinked polyimide polymer is obtained from the polyimide polymer, which membrane comprises less than 30% by weight of crosslinking. In some embodiments, these crosslinks may be ester crosslinks.

  In some embodiments, a film comprising a non-crosslinked polyimide polymer that incorporates a small amount of bulky diamine may contain defects in the film. These defects can be sealed by coating the hollow fiber with polydimethylsiloxane (PDMS) or a cross-linked silicone coating agent. In these embodiments, the method can further include encapsulating the polyimide polymer with polydimethylsiloxane (PDMS) or a cross-linked silicone coating. This sealing step may include a dip coating with a layer of polydimethylsiloxane or a cross-linked silicone coating agent that functions to plug any defects that may be formed in the method. This is a conventional method for sealing defects. This post-treatment step is described in US Pat. No. 8,337,598, which is incorporated by reference in its entirety.

Polymerization Reaction and Imidization Reaction In step (a), the monomer is polymerized in a polymerization reaction to yield a polyamide polymer containing amide bonds. An imidization reaction occurs, whereby the amide bond forms an imide bond, resulting in a polyimide polymer. This monomer includes a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and optionally a diamino monomer having a carboxylic acid functionality. The ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3. In some embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is from 1:16 to 2: 3. In other embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is 0 to 1:16. Thus, in an embodiment where no diamino monomer having a carboxylic acid functional group is present, the ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is zero.

  Among the diamino monomers, 2 to 10 mol% are bulky diamino compounds. In certain embodiments, 2-5 mol% of the diamino monomer is a bulky diamino compound. A small amount of bulky diamine allows the formation of a high molecular weight polyimide polymer.

  Step (a) includes preparing a polyimide polymer from a reaction solution comprising a monomer and at least one solvent. The monomer and at least one solvent are mixed such that the monomer dissolves in the solvent to form a reaction solution. This monomer is then polymerized by the formation of an amide bond, resulting in a polyamide polymer. The polyamide polymer is then subjected to imidization conditions, which converts the amide bond to an imide ring, resulting in a polyimide polymer.

  This monomer includes a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and optionally a diamino monomer having a carboxylic acid functionality. The ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3. In some embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is from 1:16 to 2: 3. In other embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is 0 to 1:16. Among the diamino monomers, 2 to 10 mol% are bulky diamino compounds. In certain embodiments, 2-5 mol% of the diamino monomer is a bulky diamino compound.

  In certain embodiments, the monomer comprises a dianhydride monomer, a diamino monomer having no carboxylic acid functional group, no diamino monomer having a carboxylic acid functional group, and 2-10 mol% bulky diamino compound It is. In other embodiments, the monomer consists essentially of a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and essentially free of a diamino monomer having a carboxylic acid functionality. Is a bulky diamino compound.

  The imidization reaction of step (a) can be performed under dehydrating conditions. Water is produced as a byproduct during the imidization reaction. Such dehydration conditions remove at least a portion of this by-product water from the reaction solution. Since water generated during the imidation reaction may decompose the imide ring of the polyimide polymer during the subsequent monoesterification reaction, it is desirable to remove the water in step (a). This imidized residual water can also cause chain breakage of the polyimide polymer. Polyimide polymers can be prepared by “one pot” synthesis.

Monomer The monomer may comprise between about 15 and about 25% by weight of the reaction solution. This monomer includes a dianhydride monomer, a diamino monomer having no carboxylic acid functionality, and optionally a diamino monomer having a carboxylic acid functionality. The ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3. In some embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is from 1:16 to 2: 3. In other embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is 0 to 1:16. Of the diamino monomers, about 2 to about 10 mol% are bulky diamino compounds. In one embodiment, about 2 to about 5 mole percent of the diamino monomer is a bulky diamino compound.

  The diamino monomer may comprise a cyclic diamino compound and a diamino aromatic. As described herein, about 2 to about 10 mole percent of the diamino monomer is a bulky diamino compound. Diamino monomers containing carboxylic acid functional groups are optional and thus may be absent, i.e. absent.

  For example, the monomer may include dianhydride monomer A, diamino monomer B having no carboxylic acid functional group, and optionally diamino monomer C having a carboxylic acid functional group. The ratio of the diamino monomer having no acid functional group is 0 to 2: 3, and 2 to 10 mol% of the diamino monomers B and C is the bulky diamino compound D. In certain embodiments, the monomer comprises dianhydride monomer A, diamino monomer B having no carboxylic acid functionality and no diamino monomer C having a carboxylic acid functionality.

The dianhydride monomer A is a dianhydride of formula (I):

(Wherein X ₁ and X ₂ are independently halogenated alkyl, phenyl, or halogen, and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently H , Alkyl, or halogen.)
It may be.

  When the monomer includes monomers A, B and optionally C, the ratio of C to B is 0 to 2: 3. In certain embodiments, the ratio of C to B is 0 to 1: 8. In certain embodiments, the ratio of C to B is about 2: 3. In some embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is from 1:16 to 2: 3. In other embodiments, the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is 0 to 1:16. Of the diamino monomers, about 2 to about 10 mol% are bulky diamino compounds. In one embodiment, about 2 to about 5 mole percent of the diamino monomer is a bulky diamino compound.

Monomer A may be 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), also known as 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane. It has been. 6FDA has the following formula:

Have Since 6FDA limits the possible rotations, inclusion of 6FDA in the monomer provides stability to the polyimide polymer.

Monomers with limited possible rotation, such as 6FDA, are desirable because they improve the selectivity of membranes produced according to the methods disclosed herein. Monomers with bulky side chains, such as (CF ₃ ) _{2 in} 6FDA, also inhibit chain packing, which improves the permeability of molecules to the membrane. Both selectivity and permeability are important for efficient and productive separation. Furthermore, references to these structural property relationships can be found in Koros and Fleming, Journal of Membrane Science, 83, 1-80 (1993), which is incorporated herein by reference in its entirety. .

Monomer B, which is a cyclic diamino compound having no carboxylic acid functional group, may be a diamino aromatic compound having two or more aromatic rings, and the amino groups are present on the same or different aromatic rings. Yes. For example, monomer B is 4,4′-isopropylidenedianiline, 3,3′-hexafluoroisopropylidenedianiline, 4,4′-hexafluoroisopropylidenedianiline, 4,4′-oxydianiline, 3 , 3′-oxydianiline, 4,4′-diaminodiphenyl, diaminotoluene, diaminobenzotrifluoride, dimethyldiaminobenzene, trimethyldiaminobenzene or tetramethyldiaminobenzene. Monomer B may also be 2,4,6-trimethyl-m-phenylenediamine (DAM), which has the following formula:

Represented by

Monomer C which is a cyclic diamino compound having a carboxylic acid functional group is optional. Therefore, monomer C may not be present. If present, monomer C may be diaminobenzoic acid. It has the following formula:

Represented by More specifically, when present, monomer C may be 3,5 diaminobenzoic acid (DABA).

  Bulky diamino compound D is about 5 to about 12 diamines. In some embodiments, the bulky diamine is from about 6 to about 12 diamines, and in certain embodiments, the bulky diamine is from about 6 to about 9.5 diamines. Examples of the bulky diamino compound D include 2,2′-bis (trifluoromethyl) benzidine (2,2′-bis (trifluoromethyl)-[1,1′-biphenyl] -4,4′-diamine. And also known as 2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 '-(9-fluorenylidene) dianiline (also known as CF3), 4,4' -(Hexafluoroisopropylidene) dianiline (also known as Fu) and the like, and mixtures thereof. In certain embodiments, the bulky diamine is 2,2′-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 ′-(9 -Fluorenylidene) dianiline (CF3), or a mixture thereof. FIG. 1 shows typical bulky diamines 2CF3 and CF3.

  The bulky diamine is 2-10 mol% of the diamino monomer used to prepare the polyimide polymer, and in certain embodiments, the bulky diamine is a diamino monomer used to prepare the polyimide polymer. Of 2 to 5 mol%.

  In one embodiment of the method described herein, the monomer comprises A, B, C and D, where A is 6FDA, B is DAM, C is DABA, D is 2, 2'-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine or 4,4 '-(9-fluorenylidene) dianiline (CF3). In this embodiment, the 6FDA content of the monomer mixture is about 50% by weight, and the remaining about 50% by weight of the monomer mixture is DAM, DABA and 2CF3, 5- (trifluoromethyl) -1,3-phenylenediamine. Alternatively, it is composed of CF3. As described above, 2 to 10 mol% of the monomer mixture of DAM and DABA is composed of bulky diamino compound D (2CF3, 5- (trifluoromethyl) -1,3-phenylenediamine or CF3). In certain embodiments, 2-5 mol% of the monomer mixture of DAM and DABA is composed of bulky diamino compound D (2CF3, 5- (trifluoromethyl) -1,3-phenylenediamine or CF3). The

  In one example, the 6FDA content of the monomer mixture may be about 50% by weight, with the remaining about 50% by weight being about 35-40 mol% DABA, about 55-60 mol% DAM, and about 2-5 It may be mol% 2CF3, 5- (trifluoromethyl) -1,3-phenylenediamine or CF3.

  Whatever monomer is used, according to some embodiments of the methods described herein, the monomers can be purified prior to step (a). Monomers can be purified by techniques known in the art, such as sublimation or recrystallization.

Solvent The monomer is dissolved in at least one solvent that creates a reaction solution and promotes polymerization. The obtained polyamide polymer remains in the reaction solution for imidization. The at least one solvent may comprise between about 75 and about 95% by weight of the reaction solution. The at least one solvent may be at least one high boiling organic solvent. The solvent may be a mixture of organic solvents. Exemplary high boiling organic solvents are listed in Table 1 along with their normal boiling points.

Thus, the solvent of the reaction solution can be any one of the organic solvents listed above, or a mixture thereof. High boiling solvents are desirable because they can prevent excessive solvent evaporation, which would significantly change the concentration in the reaction solution and in subsequent steps.

Dehydration conditions When dehydration conditions are utilized during step (a) to remove water, the concentration of water in the reaction solution can be maintained between about 0 wt% and about 0.26 wt%.

  The dehydrating conditions can be the presence of a chemical dehydrating agent and / or a mechanical dehydrating agent. The dehydration conditions can be present only in the chemical dehydrating agent, can be present only in the mechanical dehydrating agent, or can be in the presence of a combination of chemical and mechanical dehydrating agents.

  If a chemical dehydrating agent is utilized, the chemical dehydrating agent does not interfere with the imidization reaction of step (a). For example, the chemical dehydrating agent does not decrease the rate of the imidization reaction and does not decrease the yield of the polyimide polymer.

Polymerization conditions In the polymerization reaction of step (a), the monomers in the reaction solution are polymerized to form a polyamide polymer containing a small amount of bulky diamine. The polymerization can be carried out at room temperature with stirring or otherwise stirring the reaction solution. The solvent concentration during the polymerization is between about 75 to about 95% by weight of the reaction solution.

Imidization conditions In the imidization reaction of step (a), the amide bond of the polyamide polymer forms an imide ring, resulting in a polyimide polymer. The imidization reaction in step (a) is performed for a long time of about 12 to 36 hours. Such a long time ensures that the imidization reaction proceeds and is complete, which is important with respect to the yield of the polyimide polymer. The imidization reaction can be performed at a temperature between about 160 ° C and about 200 ° C. The solvent concentration during imidization is between about 75 to about 95% by weight of the reaction solution.

  A polyimide polymer incorporating a small amount of bulky diamine has a high molecular weight.

Optional Monoesterification Reaction If a diamino monomer having a carboxylic acid functionality is present, after polymerization, the polyimide polymer can optionally be monoesterified to yield a monoesterified polyimide polymer. More specifically, the carboxylic acid functionality (—COOH) of the polyimide polymer can react with the hydroxyl functionality (—OH) of a monoalcohol or diol to convert the —COOH group to an ester.

  In certain embodiments, the polyimide polymer is esterified with a monoalcohol. Esterification with monoalcohols rather than diols produces monoesterified polyimide polymers with less exposure of hydroxyl groups. Therefore, the monoesterified polyimide polymer is less hydrophilic than the monoesterified polyimide polymer formed with the diol and can be easily spun.

  In other embodiments, the polyimide polymer can be esterified with a diol. When monoesterifying with a diol, only one of the —OH groups of the diol molecule reacts with the —COOH group to produce water as a by-product. Use dehydration conditions to at least partially remove by-product water so that the average molecular weight of the monoesterified polyimide polymer is at least partially maintained, fully maintained, or even increased be able to.

  Optional monoesterification can further comprise treating the polyimide polymer with a monoalcohol or diol in the presence of an acid catalyst to promote the monoesterification reaction. If the acid catalyst is present in an amount less than that normally used in conventional monoesterification reactions that do not remove water, the monoesterified polyimide polymer will retain some of its molecular weight or be completely Or even increase.

  In some embodiments, the polymerization is also performed under dehydrating conditions that remove at least a portion of the water formed during the imidization reaction.

  After the imidization reaction of step (a) is completed, the reaction solution contains a polyimide polymer, at least one solvent, and any unreacted monomers. If monoesterification is utilized, monoalcohol or diol can be added directly to the reaction solution to form a monoesterification reaction solution. Thus, both imidization and monoesterification reactions can be carried out in one reaction vessel or “one pot”. Alternatively, the polyimide polymer can be isolated and then mixed with a monoalcohol or diol to form a monoesterification reaction solution so that the imidization reaction and monoesterification reaction can be performed in separate reaction vessels. .

Alcohols When utilized, monoalcohols useful in the methods described herein include propanol, butanol, pentanol, and the like.

  When utilized, the length of the diol is an important consideration. If the diol is too long or too short, the diol can reduce the permeability and / or selectivity of the membrane formed from the monoesterified polyimide polymer.

  Diols useful in the methods described herein include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, benzenedimethanol, 1,3 -Butanediol and mixtures thereof are included. In one embodiment of the method described herein, the diol is selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, benzenedimethanol, and mixtures thereof. In another embodiment, the diol is selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, and mixtures thereof. In yet another embodiment, the diol is selected from the group consisting of ethylene glycol, 1,3-propanediol, and mixtures thereof. In yet another embodiment, the diol is 1,3-propanediol.

Dehydration conditions Similar to the dehydration conditions of optional step (a), the dehydration conditions of the optional monoesterification step can be provided by the use of chemical dehydrating agents and / or mechanical dehydrating agents. Thus, the dehydrating conditions can be a chemical dehydrating agent alone, a mechanical dehydrating agent alone, or a combination of a chemical dehydrating agent and a mechanical dehydrating agent. Whether the dehydration condition is chemical or mechanical, the monoesterification reaction solution maintains the concentration of water in the monoesterification reaction solution between about 0 wt% and about 0.08 wt%. It is desirable to remove the water produced therein.

  When a chemical dehydrating agent is utilized, the chemical dehydrating agent does not interfere with the monoesterification reaction. For example, the chemical dehydrating agent does not reduce the rate of monoesterification reaction and does not reduce the yield of monoesterified polyimide polymer. The chemical dehydrating agent can be an azeotropic chemical dehydrating agent or can be a carbodiimide. When carbodiimide is used as a chemical dehydrating agent, it can be used in a stoichiometric amount of between about 1 and about 4 times based on the number of moles of water removed. The azeotropic chemical dehydrating agent forms an azeotrope with the by-product water, which can be removed by boiling from the monoesterification reaction solution. Such azeotropic chemical dehydrating agents are well known to those skilled in the art and include ODCB, benzene, toluene, and mixtures thereof.

  When an azeotropic chemical dehydrating agent is used as the chemical dehydrating agent, it can be used in relatively large amounts, for example, between about 1 ml to about 4 ml per gram of polyimide polymer. Such a large amount of azeotropic chemical dehydrating agent ensures that the water produced by the monoesterification reaction is removed from the monoesterification reaction solution.

  The chemical dehydrating agent can be periodically added to the monoesterification reaction solution. For example, ODCB can be added periodically. According to one embodiment of the method described herein, the chemical dehydrating agent is added to the monoesterification reaction solution in three separate batches.

  As in step (a), the mechanical dehydrating agent is a physical system designed to remove water. An exemplary mechanical dehydrating agent is a Dean-Stark trap. Dean-Stark traps are well known to those skilled in the art. Any mechanical system that prevents water distilled from the monoesterification reaction solution from returning to the monoesterification reaction solution is suitable.

  When dehydration conditions are utilized in step (a), the dehydration conditions for monoesterification can be the same as the dehydration conditions for step (a). In fact, this simplifies the overall method described herein, so it is desirable to have the same dehydration conditions. In conventional polymerization / imidization / monoesterification reaction methods, the polyimide polymer precipitates from the reaction solution. However, if the same dehydration conditions are utilized during monoesterification, this extra precipitation step is eliminated. Furthermore, the same dehydration conditions from the imidization reaction of step (a) can be used for the monoesterification reaction.

Acid Catalysts Acid catalysts useful in monoesterification reactions are well known to those skilled in the art. The acid catalyst activates the carboxyl functionality of the polyimide polymer so that the polyimide polymer reacts with the hydroxyl group of the monoalcohol or diol. Exemplary acid catalysts include para-toluenesulfonic acid, sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, and mixtures thereof. If the dehydration conditions utilized include carbodiimide, an acid catalyst may not be necessary because the carboxyl functionality of the polyimide polymer is activated by carbodiimide.

  The amount of acid catalyst present during the optional monoesterification reaction under dehydrating conditions also affects the average molecular weight of the monoesterified polyimide polymer. More specifically, when the amount of acid catalyst used is less than the conventional amount and dehydration conditions exist, there is little or no molecular weight reduction or no molecular weight reduction. Even an increase occurs.

  Between about 0 milligrams and about 2.5 milligrams of acid catalyst per gram of polyimide polymer can be added to the monoesterification reaction solution without undergoing undesirable molecular weight reduction. In other examples, less than about 5.0 milligrams of acid catalyst per gram of polyimide polymer can be added to the monoesterification reaction solution without incurring undesirable molecular weight reduction.

Optional Monoesterification Conditions When utilized, the monoesterification reaction solution is heated at a relatively high temperature for an extended period of time with or without a catalyst. Generally, the monoesterification reaction solution is heated at a temperature between about 120 ° C. and about 140 ° C. for about 12-30 hours.

Film containing non-crosslinked polyimide polymer A polyimide polymer containing a small amount of bulky diamine maintains a relatively high average molecular weight, is mechanically strong and flexible, and can be spun easily and quickly. A small amount of bulky diamine allows the formation of a high molecular weight polyimide polymer. Even in the absence of crosslinking, fiber membranes made with small amounts of bulky diamines show good permeability and selectivity even at high CO ₂ pressures. Therefore, a polyimide polymer containing a small amount of bulky diamine is suitable for a separation membrane even in the absence of crosslinking. The small amount of bulky diamine, segmental motion is minimized, thus quasi T _g is improved. Membranes containing non-crosslinked polyimide polymers with small amounts of bulky diamines are surprisingly resistant to plasticization even if not crosslinked.

  Polyimide polymers produced as described herein can have an average molecular weight between about 40,000 and about 400,000. In some embodiments, the polyimide polymer has an average molecular weight of at least 50,000. In one embodiment, the polyimide polymer has an average molecular weight between about 100,000 and about 300,000. In one embodiment, the polyimide polymer has an average molecular weight between about 100,000 and about 300,000. The weight average molecular weight described herein is measured using gel permeation chromatography (GPC). The polyimide polymer may also have a polydispersity index between about 2 and about 4.

  The method for producing the polymer membrane described herein does not include the active step of subjecting the polyimide polymer to transesterification conditions to form a crosslinked membrane. The polymer film manufacturing method described herein may optionally omit the active step of treating the polyimide polymer with a diol in the presence of dehydration conditions and esterification conditions. The polymer membrane disclosed herein comprises a non-crosslinked polyimide polymer with a small amount of bulky diamine, and the membrane contains less than 30% by weight of crosslinking. In some embodiments, the membrane comprises less than 20 wt% crosslinks, or less than 10 wt% crosslinks. In certain embodiments, the membrane is essentially free of crosslinks. In some embodiments, these crosslinks can be ester crosslinks.

  In one embodiment, the non-crosslinked membrane is a non-crosslinked hollow fiber membrane. The non-crosslinked hollow fiber membrane is produced by a method including a step of spinning the non-crosslinked hollow fiber from the non-crosslinked polyimide polymer.

  In some embodiments, a polyimide polymer incorporating a small amount of bulky diamine may not be spun into a hollow fiber without defects and may contain defects in the fiber coating. These defects can be sealed by coating the hollow fiber with polydimethylsiloxane (PDMS) or a cross-linked silicone coating agent. Accordingly, the methods described herein may optionally include a dip coating with a layer of polydimethylsiloxane or a cross-linked silicone coating agent that fills any defects that may form in the method. It works like this. This is a conventional method for sealing defects. In these embodiments, the method further comprises sealing the defect by coating the hollow fiber with polydimethylsiloxane (PDMS) or a cross-linked silicone coating agent.

  Membranes made from non-crosslinked high molecular weight polyimide polymers containing small amounts of bulky diamines can take any form known in the art, such as hollow fiber, tubular, and other membrane shapes. Other film shapes include spiral bent films, pleated films, flat sheet films and polygonal films. Non-crosslinked high molecular weight polyimide polymers containing small amounts of bulky diamines disclosed herein can also be cast to form sheets or films. These sheets or films can be cast on a suitable carrier to provide a composite sheet. Sheets and films can be cast on sheets of other polymers. The polymer carrier can be a porous low cost polymer. Thus, the porous polymer should be used as a carrier for a less porous sheet or film formed from a non-crosslinked high molecular weight polyimide polymer containing a small amount of bulky diamine as disclosed herein. Can do.

  In the method of forming a non-crosslinked hollow fiber membrane, the non-crosslinked hollow fiber is spun from a non-crosslinked polyimide polymer. The polyimide polymer can be spun into a monoesterified hollow fiber at a high winding speed. In order to produce such a hollow fiber, a polyimide polymer can be blended with the spinning dope, whereby the hollow fiber is spun into a hollow fiber by a spinning method such as a wet quench / dry jet spinning method. Wet quench / dry jet spinning methods are discussed in detail below, but it should be understood that other types of spinning methods (eg, wet spinning) can be used to form hollow fibers.

Since non-crosslinked polyimide polymers contain a small amount of bulky diamine, non-crosslinked hollow fibers formed from such polymers show good selectivity and permeability even at high CO ₂ pressures. Non-crosslinked membranes show good selectivity for the separation of CO ₂ and CH ₄ even at high pressure. For example, hollow fibers spun from PDMC containing CF3 of 5 mol%, in 35 ° C. and 100 psia, pure gas selectivity between or between about 25 to about 50 from about 25 to about 65 _(CO 2 / CH ₄ ). Note that for fibers with small defects, a post-treatment with PDMS is utilized. For fibers without defects, no post treatment is required to obtain a selectivity of 25 or greater.

In summary, non-crosslinked hollow fiber membranes exhibit the same or similar selectivity and permeability as crosslinked hollow fiber membranes made from polyimide polymers with bulky diamines, even at high CO ₂ pressures, and the pressure is increased. In this case, the non-crosslinked hollow fiber membrane produced from the monoesterified polyimide polymer having no bulky diamine exhibits considerably better selectivity and permeability stability.

Formation of hollow fibers from a spinning dope A spinning dope is a homogeneous one-phase solution that contains a non-crosslinked polyimide polymer, a volatile component, optional inorganic additives, a spinning solvent, and a spinning non-solvent. it can.

  Polymer concentration is an important issue. Sufficient polymer must be present to form strong fibers and membranes that can withstand high pressures. However, too much polymer increases the resistance of the membrane structure and adversely affects membrane performance. In one embodiment of the method described herein, the polyimide polymer is present in the spin dope in an amount between about 20 wt% and about 50 wt%. In another embodiment, the polyimide polymer is present in the spin dope in an amount between about 25 wt% and about 45 wt%. In yet another embodiment, the polyimide polymer is present in the spin dope in an amount between about 30 wt% and about 40 wt%.

  The volatile component can be an organic solvent having a specific room temperature vapor pressure and a specific boiling point. Such an organic solvent helps to form a dense film separation layer of the hollow fiber. The organic solvent evaporates effectively and efficiently during the dry jet step of the wet quench / dry jet spinning process, and the solvent evaporation outside the initial fiber produces more polymer chains at higher concentrations. It is believed that this helps to maintain the wet state, thereby promoting vitrification and formation of a dense film. The specific room temperature vapor pressure of the organic solvent can be greater than about 0.05 bar. Alternatively, the specific room temperature vapor pressure can be greater than about 0.1 bar. As another alternative, the specific room temperature vapor pressure can be greater than about 0.2 bar. The specific boiling point of the organic solvent can be between about 30 ° C and about 100 ° C. Alternatively, the specific boiling point can be between about 40 ° C and about 90 ° C. As another alternative, the specific boiling point can be between about 50 ° C and about 70 ° C.

  Exemplary organic solvents include tetrahydrofuran (THF) and acetone. In one embodiment of the method described herein, the volatile component is present in the spin dope in an amount between about 5 wt% and about 25 wt%. In another embodiment, the volatile component is present in the spinning dope in an amount between about 5 wt% and about 20 wt%. In yet another embodiment, the volatile component is present in the spin dope in an amount between about 10 wt% and about 15 wt%.

  Optional inorganic additives enhance phase separation, increase the porosity of the substructure, and increase the viscosity of the spinning dope. Optional inorganic additives reduce the time required for phase separation of the monoesterified polyimide polymer.

The optional inorganic additive can be an antilyotropic salt. As defined herein, the term “antilyotropic salt” refers to a salt that interacts with solvent molecules other than polymer molecules. Ekiner O. M.M. Et al., Journal of Membrane Science 53 (1990) 259-273. Exemplary antilyotropic salts include LiNO ₃ , LiClO ₄ , MgCl ₂ , ZnCl ₂ and NaI.

The concentration of inorganic additives is also an important issue. Inorganic additives can reduce the time required for phase separation, but if the porosity spreads over the non-vitrified coating layer of the hollow fiber, excess inorganic additive (eg LiNO ₃ ) is deficient. It is thought to cause formation. In one embodiment of the method described herein, the concentration of the antilyotropic salt in the spinning dope is between about 0 and about 10% by weight. In another embodiment, the concentration of antilyotropic salt in the spinning dope is between about 2 and about 8% by weight. In yet another embodiment, the concentration of the antilyotropic salt in the spinning dope is between about 4 and about 7% by weight.

  The spinning solvent can be a high-boiling organic solvent. Exemplary high boiling organic solvents are listed in Table 1 above, along with their normal boiling points. High boiling organic solvents with high affinity for water can enhance the phase separation of the hollow fibers during the wet quench step of the spinning process. NMP is a particularly desirable spinning solvent because it dissolves many of the polymers used for spinning, is relatively mild compared to other spinning solvents, and has a high affinity for water. The concentration of the spinning solvent can depend on many factors, including the molecular weight of the polyimide polymer, the polydispersity index of the polyimide polymer, and other components of the spinning dope and should be determined by the precipitation method discussed below. Can do. The concentration of the spinning solvent can be, for example, between about 25 and about 35% by weight.

  The non-spinning solvent can be an alcohol such as an aliphatic alcohol or water. In one embodiment of the method described herein, the spinning non-solvent is a lower boiling aliphatic alcohol, such as methanol or ethanol. The normal boiling points of methanol and ethanol are 64.7 ° C and 78.4 ° C, respectively. Some spinning non-solvents (eg, ethanol) may function as an additional volatile component. The concentration of the spinning non-solvent depends directly on the concentration of the spinning solvent and can also be determined by the precipitation method discussed below. The concentration of the spinning non-solvent can be, for example, between about 15 and about 25% by weight.

  The concentration of spinning solvent and non-spinning solvent can be determined by repeated precipitation, where the concentration of spinning solvent and non-spinning solvent is determined by the polyimide polymer, volatile constituents and optional inorganic additions. Depends on the concentration of each thing. Such a precipitation method ensures that the spinning dope is a homogeneous one-phase solution, but is still in close proximity to the precipitation point, which reduces phase separation during the wet quench step.

  According to the precipitation method, the concentration of non-crosslinked polyimide polymer, volatile constituents and optional inorganic additives are set. Next, initial concentrations of spinning solvent and spinning non-solvent are selected. Components at these concentrations are mixed in small sample vials. First, a volatile component, a spinning solvent, and a spinning non-solvent are mixed to form a solution. Next, optional inorganic additives are added to the solution. After the optional inorganic additive is dissolved in this solution, the polyimide polymer is added to this solution to obtain a spun dope sample. The polymer can be added in batches to facilitate dispersion of the polymer throughout the solution. If the polymer precipitates, the spinning solvent concentration is increased somewhere between about 0% to about 5% by weight to reach the final spinning solvent concentration. The spinning non-solvent concentration is similarly reduced to reach the final spinning non-solvent concentration. If the polymer does not precipitate, repeat the precipitation test, changing the concentration of spinning solvent and / or spinning non-solvent. Repeat until a final concentration is achieved that achieves a homogeneous one-phase spin dope close to the settling point.

  Large amounts of spinning dope can be prepared depending on their final concentration. Since the precipitation point can change as the polymer structure and / or average molecular weight changes, it is advantageous to perform the precipitation process with a small amount of spin dope sample before spinning any batch of spin dope. It is.

Dry Jet / Wet Quench Spinning Method to Form Hollow Fibers A number of advantages can be recognized when dry jet / wet quench spinning method is used to spin non-crosslinked high molecular weight polyimide polymers into hollow fibers. First, the hollow fiber can be spun at a higher winding speed. Second, the dry jet step can increase chain entanglement, which can be hypothesized that a coating is formed on the hollow fiber. Third, the high molecular weight polymer can increase the viscosity of the dope, which allows the spinning dope to be spun at an elevated dope temperature. Such an increased dope temperature is required for film formation by evaporation.

  Dry jet / wet quench spinning methods are well known in the art. In general, in the dry jet / wet quench spinning method, a spinning dope containing a polymer is extruded from a spinneret orifice into a filament, which is separated from the coagulation bath by a gas layer or a non-coagulated liquid. The filament passes through a gas layer, such as air, or a non-coagulated liquid, such as toluene or heptane, and is then directed to a coagulation bath. The conveyance to the filament through the gas layer is generally called a dry jet method. The coagulation bath can be either an aqueous system such as pure water or a non-aqueous system such as methanol. The conveyance of the filament through the coagulation bath is generally called a wet quench method. After the filament exits the coagulation bath, the filament can be washed. If the coagulation bath contains any acid, cleaning is particularly important and can be carried out with water alone or with a combination of alkaline solution and water. The filament is dried and wound on a rotating drum. The filaments can be air dried on a drum, or the drum can be heated to promote drying.

  According to one embodiment of the method for producing the non-crosslinked hollow fiber membrane described herein, the polyimide polymer is extruded from the spinneret orifice to obtain a hollow fiber. This hollow fiber is carried from a gas layer of air and a coagulation bath of deionized water. The fiber leaves the deionized water bath and is wound on a take-up drum.

  The take-up drum can be partially placed in a container of deionized water at room temperature to keep the fibers moist. The fibers are left on the take-up drum for about 10 minutes to about 20 minutes, then cut into yarn and left in another deionized water bath for about 2 days to about 3 days. The This deionized water bath helps remove the solvent from the fiber. The fiber can then be dehydrated by fluid exchange with non-solvents that reduce surface tension, such as ethanol and hexane. Finally, the fibers can be air dried and / or oven dried.

  According to the method described herein, the spinneret orifice can have a smaller dimension than that used in conventional spinning methods. Smaller spinneret dimensions allow hollow fibers to be spun under normal conditions (ie, less than 300 microns) into fibers useful for producing membranes that can be used under high pressure conditions. Fiber with a diameter of Smaller spinneret dimensions also improve mixing in the spinneret and shear during extrusion. In addition, smaller spinneret dimensions increase the extrusion rate, resulting in a lower draw ratio (ie, the take-up rate divided by the extrusion rate). A too high stretch ratio can cause high orientation / elongation stress, which can be detrimental during subsequent processing, so a low stretch ratio is desirable.

  The ring diameter of the spinneret orifice may be about half the size of a conventional spinneret orifice. For example, the ring diameter can be between about 600 microns and about 1300 microns and the outer diameter of the piercing needle can be between about 300 microns and about 700 microns.

  The draw ratio can be less than 150. Alternatively, the draw ratio can be less than 100. As another alternative, the stretch ratio can be less than 50. As yet another alternative, the draw ratio can be less than 10.

  The distance between the extrusion point from the spinneret and the surface of the deionized water bath is referred to herein as the “air gap height”. The air gap height must be greater than 0 cm. The air gap height can be between about 1 cm and about 5 cm. Alternatively, the air gap height can be between about 1 cm and about 10 cm. As another alternative, the air gap height can be between about 1 cm and about 20 cm. A larger air gap height is advantageous for film formation.

  Similarly, a relatively high spinning dope temperature (ie, the temperature of the spinning dope immediately before extrusion from the spinneret) is advantageous for film formation. The spinning dope temperature can be higher than 40 ° C. Alternatively, the spinning dope temperature can be greater than 50 ° C. As yet another alternative, the spinning dope temperature can be greater than 60 ° C.

  As described above, according to one embodiment, the coagulation bath contains deionized water. A sufficiently high coagulation bath temperature ensures proper phase separation in the coagulation bath. If phase separation is inappropriate, the fibers are ground in the first guide roll after extrusion. The coagulation bath temperature can be between about 10 ° C and about 70 ° C. Alternatively, the coagulation bath temperature can be between about 25 ° C and about 60 ° C. As another alternative, the coagulation bath temperature can be between about 40 ° C and about 50 ° C.

  The winding speed (i.e., the speed at which the hollow fiber is wound on the winding drum) can be significantly faster than the winding speed used in spinning the low molecular weight polymer. This is because the high molecular weight polymers described herein can withstand the greater stresses associated with higher winding speeds. If smaller diameter fibers are required, the winding speed can be increased at a fixed extrusion speed. Winding speeds between about 20 m / min and about 150 m / min (eg, between about 20 m / min and about 70 m / min) can be achieved by the methods described herein.

  The surface velocity of the air surrounding the spinneret can be greater than 50 ft / min. Alternatively, the surface velocity of the air surrounding the spinneret can be greater than 80 ft / min. As another alternative, the face velocity of the air surrounding the spinneret can be greater than 100 ft / min.

Method Using Membrane The mixture containing the gas to be separated can be enriched by passing the gas mixture through the membrane disclosed herein. Such gas mixtures to be concentrated can be derived from hydrocarbon wells, such as petroleum wells or gas wells, including offshore wells. The separated liquid mixture can also be concentrated by passing the liquid mixture through the membrane disclosed herein.

For example, using a membrane comprising a non-crosslinked polyimide polymer, multiple gases can be separated by:
(A) selected from the group consisting of air, a mixture of methane and nitrogen, a mixture of methane and hydrogen, a mixture of methane and hydrogen sulfide, a refinery stream, a mixture of carbon dioxide and methane, and synthesis gas. Preparing a feed stream to be performed,
The feed stream comprises a gas component selected from the group consisting of nitrogen, oxygen, hydrogen, hydrogen sulfide and carbon dioxide;
(B) maintaining a pressure differential between the upstream side of the membrane and the downstream side of the membrane;
(C) contacting the upstream side of the membrane with the feed stream at a pressure between about 20 psia and about 4000 psia;
(D) separating the permeate stream downstream of the membrane with a higher molar fraction of the faster permeate component of the feed stream; and (e) the faster permeate composition of the feed stream. Separating a retentate stream having a lower mole fraction of components.

  The feed stream can be concentrated in the gas component at a temperature between about 25 ° C and 200 ° C. In one embodiment, the feed flow is measured at a temperature of 35 ° C. The feed stream can be present at a pressure of about 50 psia to about 4000 psia. As another alternative, the feed stream can be present at a pressure from about 100 psia to about 1000 psia, or from about 100 psia to about 200 psia. In one embodiment, the feed flow is measured at a pressure of 100 psia or 200 psia. The temperature of the feed stream can be that temperature produced from a hydrocarbon well (eg, a petroleum or gas well including offshore well). These conditions can be varied using routine experimentation depending on the feed flow. The downstream side of the membrane can be maintained as a vacuum.

  Various gas mixtures can be purified using the membranes disclosed herein. For example, applications include concentrating air with nitrogen and oxygen, removing carbon dioxide from a methane stream, removing hydrogen sulfide from a methane stream, removing nitrogen or hydrogen from a methane stream, or carbon monoxide from a syngas stream. including. Membranes can also be used in the separation of hydrogen from refinery streams and other process streams, for example from dehydrogenation reaction effluents in the catalytic dehydrogenation of paraffin. In general, the membrane can be used in any separation method using a gas mixture including, for example, hydrogen, nitrogen, methane, hydrogen sulfide, carbon dioxide, carbon monoxide, helium and oxygen.

  If further purification is required, the product in the permeate stream can be passed through an additional membrane and / or the product can be purified by distillation using techniques well known to those skilled in the art. Typically, membrane systems can consist of a number of modules connected in various configurations. See, for example, Prasad et al., J. Pat. Membrane Sci. 94, 225-248 (1994). The modules connected in series are used to refine the feed, permeate and residual streams in order to improve the separation and purification of the feed, permeate and residual streams and to optimize the performance of the membrane system. It offers many design possibilities.

  The membranes disclosed herein are such as those disclosed in US Pat. Nos. 6,932,859 and 7,247,191, which are incorporated herein by reference in their entirety. Can be used in separation systems.

  Membranes made from non-crosslinked high molecular weight polyimide polymers can take any form known in the art, for example, hollow fibers, tubular shapes, and other membrane shapes. Other film shapes include spiral bent films, pleated films, flat sheet films and polygonal films.

  The hollow fibers described herein are used in bundled arrangements potted at either end to form tube sheets and are attached to a pressurized container so that the inside of these tubes The outside of these tubes can be isolated.

  The following examples are presented as specific illustrations and are not intended to be limiting.

(Example 1)
In 60 wt% NMP, vacuum dried monomer (16.62 grams DAM, 12.24 grams DABA, and 1.77 grams CF3 diamine) was dissolved. To this was added 89.37 grams of 6FDA dianhydride dissolved in 40% by weight NMP to give a mole of 5.5 (6FDA-DAM): 0.5 (6FDA-CF3): 4 (6FDA-DABA). A ratio was obtained.

  This mixture was polycondensed at room temperature under a nitrogen purge for 24 hours to obtain a polyamide polymer.

(Example 2)
To the polyamide in NMP of Example 1, 21.0 ml β-picoline as catalyst was added along with 186.3 ml acetic anhydride. This polymer was imidized at room temperature under a nitrogen purge for 24 hours to obtain a polyimide polymer. The polyimide was washed with methanol and filtered. The polyimide was then dried at room temperature for 8 hours and then at 210 ° C. for 24 hours.

(Example 3)
30-40% by weight of the polymer of Example 2, 25-35% by weight of NMP, 15-25% by weight of ethanol as spinning non-solvent, 10-15% by weight of THF as volatile constituents, and viscosity enhancing salt As a spinning dope containing 2 to 8% by weight of LiNO ₃ . Next, using this spinning dope, hollow fibers without defects are spun at 50 to 70 ° C., an air gap of 1 to 5 cm, and a winding speed of 20 to 70 m / min.

(Example 4)
The fiber of Example 3 is tested using a 50/50 vol% CO ₂ / CH ₄ gas mixture at 200 psi and 35 ° C. with shell side feed. The CO ₂ permeability is over 80 GPU and the CO ₂ / CH ₄ selectivity is over 20.

(Example 5)
In 60 wt% NMP, vacuum dried monomer (16.62 grams DAM, 12.24 grams DABA, and 1.77 grams CF3 diamine) was dissolved. To this was added 89.37 grams of 6FDA dianhydride dissolved in 40% by weight NMP to give a mole of 5.5 (6FDA-DAM): 0.5 (6FDA-CF3): 4 (6FDA-DABA). A ratio was obtained.

  This mixture was polycondensed at room temperature under a nitrogen purge for 24 hours to obtain a polyamide polymer.

(Example 6)
To the polyamide in NMP of Example 5, 21.0 ml β-picoline as catalyst was added along with 186.3 ml acetic anhydride. This polymer was imidized at room temperature under a nitrogen purge for 24 hours to obtain a polyimide polymer. The polyimide was washed with methanol and filtered. The polyimide was then dried at room temperature for 8 hours and then at 210 ° C. for 24 hours.

(Example 7)
60 grams of the polyimide polymer obtained in Example 6 and 390 grams of NMP were mixed and heated to about 100 ° C. 150 ml of toluene was added as a dehydrating agent and the mixture was heated to about 130 ° C. Next, 0.3 grams of p-toluenesulfonic acid (p-TSA) was added as a catalyst. Then 202 ml of 1,3-propanediol was slowly added and the polymer was esterified at about 130 ° C. under a nitrogen purge for 24 hours. The mixture was then cooled to about 50 ° C. and the polymer was precipitated in 50/50 vol% methanol / water. The monoesterified polymer was then washed with methanol / water, filtered and dried at room temperature for 12 hours and at 70 ° C. for 24 hours.

(Example 8)
32% by weight of the monoesterified polymer of Example 7, 32% by weight of NMP, 15.8% by weight of ethanol as spinning non-solvent, 13.7% by weight of THF as volatile constituents and 6 as viscosity-enhancing salt A spin dope containing 5 wt% LiNO ₃ was prepared.

(Example 9)
Using the spinning dope of Example 8, hollow fibers were spun under the same conditions as in Example 6, but with an air gap of 5 cm.

(Example 10)
The fiber of Example 9 was tested at 200 psi and 35 ° C. using a 50/50 vol% CO ₂ / CH ₄ gas mixture with shell side feed. The CO ₂ permeability was about 95 GPU and the CO ₂ / CH ₄ selectivity was 28.

(Example 11)
The fiber of Example 9 was coated with a 2 wt% polydimethylsiloxane (PDMS) solution for 30 minutes and then vacuum dried at 200 ° C. for 2 hours. These fibers were tested under the same conditions as in Example 10. The CO ₂ permeability was about 90 GPU and the CO ₂ / CH ₄ selectivity was 43.

(Comparative Example 12)
The fiber of Example 9 was crosslinked at 200 ° C. under vacuum, then coated with a 2 wt% polydimethylsiloxane (PDMS) solution for 30 minutes, and then vacuum dried at 200 ° C. for 2 hours. . Then, these fibers, the pressure on the shell side feed between 200～800Psi, was tested using a 50/50 volume% of _CO 2 / CH ₄ mixed gas at 35 ° C.. FIG. 2 shows that the CO ₂ permeability remained in the range of about 82-92 GPU and the CO ₂ / CH ₄ selectivity was in the range of 38-48.

(Example 13)
The fibers of Example 11, the shell-side feed pressure between 200～800Psi, at 35 ° C., was tested with 50/50% by volume of _CO 2 / CH ₄ mixed gas. FIG. 3 shows that the CO ₂ permeability remained in the range of about 100-115 GPU and the CO ₂ / CH ₄ selectivity was in the range of 38-42. It is surprisingly resistant to it. The fiber of Example 13 is also the same 50/50 vol% CO ₂ / CH ₄ gas mixture at 35 ° C., but tested using a gas mixture containing 300 ppm heptane to determine hydrocarbon impurities. It showed the stability against. FIG. 4 shows the CO ₂ permeability and CO ₂ / CH ₄ selectivity for these feeds.

(Comparative Example 14)
Hollow fibers were produced as described herein using 6FDA, DAM and DABA with a ratio of 6FDA-DAM: 6FDA-DABA of 3: 2.

These fibers were tested at 35 ° C. with a 50/50 vol% CO ₂ / CH ₄ gas mixture with a shell side feed at a pressure between 200 and 800 psi. FIG. 5 shows that the CO ₂ permeability improved significantly as the pressure increased up to 800 psi. FIG. 6 shows that the CO ₂ / CH ₄ selectivity decreased significantly as the pressure increased up to 800 psi.

  As shown in FIGS. 5 and 6, in polymer membranes formed with non-crosslinked polyimide polymers that do not contain a small amount of bulky diamine, these membranes show improved permeability and reduced selectivity, This makes this polyimide polymer much less suitable for membranes than the polymers disclosed herein.

Although the method described herein has been described in connection with certain specific embodiments thereof, it may be practiced without departing from the spirit and scope of the method as defined in the appended claims. It will be appreciated by those skilled in the art that additions, deletions, modifications and substitutions may be made which are not explicitly described.

Claims (36)

A method for producing a film comprising a non-crosslinked high molecular weight polyimide polymer comprising:
(A) preparing a polyimide polymer from a reaction solution comprising a monomer and at least one solvent, wherein the monomer is a dianhydride monomer, a diamino monomer having no carboxylic acid functional group, and optionally a carboxylic acid functional group 2 to 10 mol% of the diamino monomer is a bulky diamino compound, and the ratio of the diamino monomer having a carboxylic acid functional group to the diamino monomer having no carboxylic acid functional group is 0 to 2: 3 And (b) obtaining a film comprising a non-crosslinked polyimide polymer comprising less than 30% by weight of crosslinking.   The method of claim 1, comprising no step of treating the polyimide polymer with a diol under esterification conditions.   The process according to claim 1, wherein the membrane obtained in step (b) comprises less than 10% by weight of crosslinking.   The method of claim 1 wherein the membrane obtained in step (b) is essentially free of cross-linking.   The method of claim 1 wherein less than 30 wt% of the crosslinks are ester crosslinks. The monomer is
(A) A dianhydride monomer A wherein A is a dianhydride of formula (I):

(X ₁ and X ₂ are independently alkyl halide, phenyl or halogen;
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently H, alkyl or halogen),
(B) a diamino monomer B having no carboxylic acid functional group, and (c) a diamino monomer C optionally having a carboxylic acid functional group.
Including
2-10 mol% of the diamino monomer is a bulky diamino compound D.
The method of claim 1.   A is 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), B is 2,4,6-trimethyl-m-phenylenediamine (DAM), and C is 3,5 The method according to claim 6, which is diaminobenzoic acid (DABA) and the ratio of C to B is from 1:16 to 2: 3.   The bulky diamino compound D is 2,2′-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 ′-(9-fluorenylidene) dianiline ( The method of claim 7, which is CF3), or a mixture thereof.   The method according to claim 1, wherein 2 to 5 mol% of the diamino monomer is a bulky diamino compound D.   The bulky diamino compound D is 2,2′-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 ′-(9-fluorenylidene) dianiline ( 2. The method of claim 1, comprising CF3), or a mixture thereof.   The monomer includes a dianhydride monomer, a diamino monomer having no carboxylic acid functional group, no diamino monomer having a carboxylic acid functional group, and 2 to 10 mol% of the diamino monomer being a bulky diamino compound. Item 2. The method according to Item 1.   The method of claim 1, wherein the monomer consists essentially of a dianhydride monomer and a diamino monomer having no carboxylic acid functional group, and 2 to 10 mol% of the diamino monomer is a bulky diamino compound.   The process according to claim 1, wherein the ratio of diamino monomer having a carboxylic acid functional group to diamino monomer having no carboxylic acid functional group is from 1:16 to 2: 3.   The method of claim 1, wherein the polyimide polymer has an average molecular weight of 100,000 to 300,000 as measured by gel permeation chromatography. The method of claim 1, wherein the membrane of step (b) exhibits a CO ₂ permeability of at least 20 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 100 psia. The method of claim 1, wherein the membrane of step (b) exhibits a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 100 psia. The method of claim 1, wherein the membrane of step (b) exhibits a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 400 psia.   The method of claim 1, wherein the membrane is a non-crosslinked hollow fiber membrane and the method further comprises spinning hollow fibers from a polyimide polymer.   The method of claim 1, further comprising coating a film comprising non-crosslinked polyimide polymer with polydimethylsiloxane.   14. The method of claim 13, further comprising treating the polyimide polymer with monoalcohol under esterification conditions after preparing the polyimide polymer in step (a). A hollow fiber polymer membrane comprising a polyimide polymer membrane material having an average molecular weight of at least 50,000 and formed from a polyimide polymer comprising monomer A + B + optionally C.
A is a dianhydride of the following formula

Wherein X ₁ and X ₂ are the same or different halogenated alkyl groups, phenyl or halogen,
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are H, alkyl or halogen)
And
B is a cyclic diamino compound having no carboxylic acid functional group,
C is a cyclic diamino compound having a carboxylic acid functional group,
2 to 10 mol% of the diamino monomers B and C are bulky diamino compounds D, and the ratio of C and B is 0 to 2: 3,
The polyimide polymer film material comprises less than 30% by weight of crosslinking,
The hollow fiber polymer membrane.   The membrane according to claim 21, wherein the ratio of C to B is from 1:16 to 2: 3.   The membrane according to claim 21, wherein the ratio of C to B is from 0 to 1:16.   The film of claim 21, wherein the polyimide polymer does not include diamino monomer C having a carboxylic acid functional group.   The membrane of claim 21 wherein the polyimide polymer membrane material comprises less than 10 wt% crosslinks.   The membrane of claim 21, wherein the polyimide polymer membrane material is essentially free of crosslinks.   The membrane of claim 21 wherein less than 30 wt% of the crosslinks are ester crosslinks.   A is 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), B is 2,4,6-trimethyl-m-phenylenediamine (DAM), and C is 3,5 The membrane according to claim 21, which is diaminobenzoic acid (DABA).   The bulky diamino compound D is 2,2′-bis (trifluoromethyl) benzidine (2CF3), 5- (trifluoromethyl) -1,3-phenylenediamine, 4,4 ′-(9-fluorenylidene) dianiline ( The film according to claim 21, which is CF3) or a mixture thereof.   The membrane of claim 21, wherein the polyimide polymer has an average molecular weight of 100,000 to 300,000 as measured by gel permeation chromatography.   The film according to claim 21, wherein 2 to 5 mol% of the diamino monomer is a bulky diamino compound D.   The dianhydride monomer A is 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and the diamino monomer B having no carboxylic acid functional group is 2,4,6-trimethyl-m-phenylenediamine (DAM), the diamino monomer C having a carboxylic acid functional group is 3,5-diaminobenzoic acid (DABA), and the bulky diamino compound D is 2,2′-bis (trifluoromethyl) benzidine (2CF3). The film of claim 21, wherein the film is 5- (trifluoromethyl) -1,3-phenylenediamine or 4,4 ′-(9-fluorenylidene) dianiline (CF 3).   The film according to claim 32, wherein 2 to 5 mol% of the diamino monomer is a bulky diamino compound D. The membrane of claim 21, wherein the membrane exhibits a CO ₂ permeability of at least 20 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 100 psia. The membrane of claim 21, wherein the membrane exhibits a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 100 psia. The membrane of claim 21, wherein the membrane exhibits a CO ₂ permeability of at least 40 GPU and a CO ₂ / CH ₄ selectivity greater than 20 as measured at 35 ° C. and a pressure of 400 psia.