EP4619145A1

EP4619145A1 - Aliphatic polyamine thin-film composite membranes made via interfacial polymerization

Info

Publication number: EP4619145A1
Application number: EP23805615.4A
Authority: EP
Inventors: Robin DHONDT; Guy Koeckelberghs; Marie LENAERTS; Marloes THIJS; Ivo Vankelecom
Original assignee: Katholieke Universiteit Leuven
Current assignee: Katholieke Universiteit Leuven
Priority date: 2022-11-15
Filing date: 2023-11-15
Publication date: 2025-09-24
Also published as: WO2024105106A1

Abstract

The invention relates to methods of preparing a polyamine-based membranes comprising the steps of polymerizing compound An with compound Bm, wherein An is a molecule with n amine functional groups, and, wherein Bm is a molecule with m aliphatic functional groups selected from a halide, pseudohalide, ammonium, phosphonium, and sulfonium functional group, wherein n > 1, >5, >10, or >20 and wherein m > 2, >5, >10, or >20.

Description

ALIPHATIC POLYAMINE THIN-FILM COMPOSITE MEMBRANES MADE VIA INTERFACIAL POLYMERIZATION.

BACKGROUND OF THE INVENTION

Polymers that are used in commercial membranes have various disadvantages. Next to poor stability in for instance chlorinated and oxidizing solvents, the most widely used polyamides fail to sustain at temperatures higher than 450°C and outside a pH range of 2-12 (Wang et al. (1993) Polymer Bulletin 31, 323-330). The drawbacks of this traditional IFP product have led to the demand for new, solvent-stable membranes with similar performance. Another problem of IFP is the reaction rate. There is It is very important to have a fast, self-inhibited reaction with high yields in order to obtain a cross-linked and dens membrane.

SUMMARY OF THE INVENTION

The present invention relates to thin-film composite (TFC) membranes produced by interfacial polymerization (IP). More particularly, TFC membranes with an aliphatic polyamine top layer. The polyamine TFC membranes are stable in various challenging conditions of extreme pH and chlorine exposure.

The polyamine membrane can be tuned in different ways. It is possible to functionalize and cross-link the membrane. Additionally, a positive or negative charge can be introduced.

Embodiments of the invention are summarized in the following statements

1. A method of preparing a polyamine-based membranes comprising the steps of polymerizing An with Bm, wherein A is a molecule or a part of a molecule with n amine functional groups, and, wherein Bm is a molecule or a part of a molecule with m aliphatic halide functional groups or pseudohalide, ammonium, phosphonium, sulfonium functional groups wherein n ≥ 1≥ ≥5, ≥10, or ≥20 and wherein m ≥ 2, ≥5, ≥10, or ≥20.

Herein An can be a polymer itself with a plurality of amine functional groups. Hence the possibility of A having n ≥ 1, ≥5, ≥10 n amine functional groups.

Within the repeating subunits of such polymer An , a subunit typically comprises 2 or 4 amine functional groups. In specific embodiments all subunits have the same amount of functional groups. In other embodiments only a fraction (eg 1/2, 1/4 1/8) of the subunits have amine functional groups. Herein Bn, can be a polymer itself with a plurality of aliphatic halide functional groups. Hence the possibility of Bm having m ≥ 2, ≥5, ≥10, or ≥20.

Within the repeating subunits of such polymer Bm, a subunit typically comprises 2 or 4 aliphatic halide functional groups. In specific embodiments all subunits have the same amount of functional groups. In other embodiments only a fraction (eg 1/2, 1/4 1/8) of the subunits have aliphatic halide functional groups.

Herewith all combinations of the above n values and above m values are disclosed

2. The method according to statement 1 wherein functional groups are present in one molecule or in different, separate molecules.

3. The method according to statement 1 or 2, wherein the polymerization is performed by interfacial polymerization, phase inversion or solvent evaporation.

4. The method according to any one of statements 1 to 3, wherein n is an aliphatic functional group, and or wherein m is n is an aliphatic functional group.

5. The method according to any one of statement 1 to 4, further comprising the step of during or after said polymerization, treating residual functional groups to alter the membrane structure and performance.

6. The method according to statement 5, wherein said treatment results in the introduction of positive or negative charges.

7. The method according to statement 5 or 6, wherein said treatment is performed with a molecule comprising a functional group selected from the group consisting of an alcohol, phenol, thiol, thiophenol, amine, halide and pseudohalides.

8. Use of a membrane obtained by the method according to any one from statements 1-3 in strong acidic conditions below pH 2 or below pH 1 or in strong caustic conditions above pH 12 or above pH 13, or strong oxidizing conditions corresponding to IM NaOCI) at room temperature or elevated temperature above 100 °C, above 150 °C or above 200 °C.

DETAILED DESCRIPTION

Figure 1: synthesis of membrane and filtration properties

Figure 2: quaternization and crosslinking of membrane and filtration properties Figure 3: structural integrity

To solve the stability shortcomings of commercial membranes, a more robust polymer has been developed. An aliphatic polyamine membrane is chosen because of its amine bond which is more robust than amide bonds. The amine bonds are resistant to hydrolysis and are more pH resistant. The polymer is made by a reaction of an aliphatic (oligo) amine, e.g. trans-cyclohexane diamine, and an aliphatic oligohalide via a nucleophilic substitution, e.g. 1,2,4, 5-tetrakis (bromomethyl) benzene, l,4-di(bromomethyl)benzene, 1,2-dibromoethane, 1,6-dibromohexane, 1,2-diaminoethane, 1,2-dibromoethane or 1,6-dibromohexane.

One aspect of the invention relates to methods of preparing a polyamine-based membranes comprising the steps of polymerizing compound An with compound Bm. Herein An is a molecule with n amine functional groups, and, Bm is a molecule with m aliphatic functional groups selected from a halide, pseudohalide, ammonium, phosphonium, and sulfonium functional group.

Herein n ≥ 1, ≥5, ≥10, or ≥20 and m ≥ 2, ≥5, ≥10, or ≥20.

Typically the m functional group is a halide.

Examples of the amine functional group of An are substituents such as -NH₂, -CH₂- NH₂, -(CH₂)₂-NH₂, -(CH₂)₃-NH₂, or -(CH₂)₄-NH_Z.

Examples of the aliphatic functional group are substituents such -CH₂-halide, - (CH₂)₂-halide, -(CH₂)₃-halide, or -(CH_z)₄-halide. Equally such C1-C4 alkyl chains can have a pseudohalide, ammonium, phosphonium, or sulfonium functional group instead of the halide group.

In specific embodiments n is between 2 and 5 and m is between 2 and 5, more specifically is 2 or 4, and m is 2 or 4.

These lower n and m values are typical for An and Bm molecules with a molecular weight below 500, below 1000 or below 2000

Typical molecules as use in the examples contain one six-membered aliphatic or six- membered aromatic ring.

Examples are 1,2-cyclohexane diamine (CHDA), l,2,4,5-tetra(bromomethyl)benzene and l,4-di(bromomethyl)benzene (TBMB).

Apart from the above small molecular weight compounds, An and/or Bm themselves can be polymers of repeating subunits with n and m functional group. These polymers are used in the formation of membranes in the currently claimed methods

Hence for such polymers An and Bm as a whole m and n have higher values, e.g ≥10, ≥20, ≥50. Examples of such n and m values are independently between 10 and 50, 10 and 100, 10 and 150, 10 and 200, 25 and 50, 25 and 100, 25 and 150, 25 and 200, 50 and 100, 50 and 150, 50 and 200, 100 and 150, 100 and 200, 150 and 200.

Referring to the subunits in such An polymer and Bm polymer, each repeating subunit typically has n or m values of 2 or 4.

The polymerization of An with Bm can be performed by interfacial polymerization, phase inversion or solvent evaporation, typically by interfacial polymerization. After or during polymerization residual functional groups can be treated to alter the membrane structure and performance, for example by quaternization or crosslinking. Quaternization can be performed with methyliodide or benzylbromide.

Crosslinking can be performed with 1,6-dibromohexane.

Membranes obtained by the methods of the present invention can be used in harsh physicochemical conditions such as

- strong acidic conditions below pH 2 or below pH 1,

- strong caustic conditions above pH 12 or above pH 13,

- strong oxidizing conditions corresponding to IM NaOCI.

Moreover filtration in these conditions can occur at room temperature or at a temperature above 100 °C, above 150 °C or above 200 °C.

Reproducibility via interfacial polymerization is obtained by increasing the degree of polymerization and reaction rate. Slower reactions result in looser and thicker films characterized by a lower rejection (Zhu et al. (2020) Sep. Purif. Technol. 239, 116528; Wang eta/. (2019) RscAdv. 9, 2042-2054). The reason is that the monomer in the aqueous phase has more time to diffuse deeper into the organic phase, which results in a thicker reaction zone. To obtain the desired polymerization degree the precise membrane formation must be considered, and is achieved by the formation of a cross-linked polymer network. This is typically obtained by a polycondensation of An and Bm monomers. The formation of the network polymer depends on the Pn, the degree of polymerization, which is most affected by f, the mean number of functional groups, and p, the conversion. A network is formed if Pn reaches infinity, this implies that f and p must be high. After the network formation, unreacted functional groups can still react with each other, which further tightens the network. The reaction is performed fast, to avoid that the monomer in one phase can diffuse in the other phase further away from the interface. Two different circumstances occur, one close to the interface, where the monomer concentration reaches its maximum, and one further away from the interface, where the monomer concentration is lower. Because of the lower concentration, a fully cross-linked network polymer can never be formed. As a result, a very tick film, which is very loose on top and denser at the support layer is obtained. The solution to make a reproducible, thin and dense top layer is achieved by increasing the mean number of functional groups f.

Membrane separation technology has gained an important place in the chemical industry. It can be applied in the separation of a range of components of varying molecular weights in gas or liquid phases, including but not limited to nanofiltration, desalination, and water treatment. It has several advantages to offer compared to the traditional separation processes, such as distillation, adsorption, absorption or solvent extraction. The benefits include continuous operation, lower energy consumption, the possibility of integration with other separation processes, mild conditions and thus more environment friendly, easy but linear up-scaling, the feasibility of making tailor-made membranes and less requirement of additives (Basic Principles of Membrane Technology, Second Edition, M. Mulder, Kluwer Academic Press, Dordrecht. 564p).

In membrane separations, the aim is to retain one (or more) component(s) of a mixture, while other components can freely permeate through the membrane under a driving force that can be a pressure, concentration or potential gradient. Membranes are used in many applications, for example as inorganic semiconductors, biosensors, heparinized surfaces, facilitated transport membranes utilizing crown ethers and other carriers, targeted drug delivery systems including membrane-bound antigens, catalyst containing membranes, treated surfaces, sharpened resolution chromatographic packing materials, narrow-band optical absorbers, and in various water treatments which involve removal of a solute or contaminant for example dialysis, electrolysis, microfiltration, ultrafiltration and reverse osmosis (Membrane technology and applications, R. Baker, John Wiley & Sons, 2004, 538p).

Although membrane separation processes are widely applied in the filtration of mild aqueous fluids, they have not been (widely) used under highly challenging pH or oxidizing conditions. Their relatively poor performance and/or stability in these conditions decreases their applicability in more aggressive feeds, despite an enormous potential economical market. For example, chemical and pharmaceutical syntheses or textile dyeing are frequently performed in organic solvents containing products with high added value, like acids and bases or catalysts, which would be recoverable via membrane technology. The recovery of metal salts from acid mine leachates, treatment of harsh waste streams from chemical and pharmaceutical industries and purification of chlorinated water streams in desalination are other examples in which ultra-stable membranes could serve a purpose.

Many membranes for aqueous applications are thin film composite (TFC) membranes made by interfacial polymerization (IFP). The IFP technique is well known (Petersen, (1993) J. Membr. Sei, 83, 81-150 and several procedures (e.g. US3,744,642, US4,277,244, (JS4,950,404) are illustrative of the fundamental method for preparing TFC membranes. One of the earliest patents to describe membranes of the type used in the present invention, US3,744,642 discloses the process of reaching a broad group of aliphatic or carbocyclic primary diamines with aliphatic or carbocyclic diacyl halides on a porous support membrane to form TFC membranes.

In IFP, an aqueous solution of a reactive monomer (often an amine (e.g. a diamine)) is first deposited in the pores of a porous support membrane (e.g. a polysulfone ultrafiltration membrane)- this step is also referred to as support membrane impregnation. Then, the porous support membrane, loaded with the first monomer, is immersed in a water-immiscible (organic) solvent solution containing a second reactive monomer (e.g. a tri- or diacid chloride). The two monomers react at the interface of the two immiscible solvents until a thin film presents a diffusion barrier and the reaction is completed to form a highly cross-linked thin film layer that remains attached to the support membrane. Since membranes synthesized via this technique usually have a very thin top layer, high solvent permeances are expected. High flux is often associated with thin membranes, while high selectivity should not be affected by membrane thickness (Koops et al. (1994) J. Appl. Polymer Sei. 53, 1639-1651). Since the first successes reached within this field by Loeb and Sourirajan, extensive research has been performed starting from their reverse osmosis membranes disclosed in US3,133,132. A subsequent breakthrough was achieved by Cadotte. Inspired by the work of Morgan, who was the first to describe "interfacial polymerization", Cadotte produced extremely thin films using the knowledge about interfacial polymerization, as claimed in US4,277,344.

The thin film layer can be from several tens of nanometers to a few micrometers thick. The thin film is selective between molecules, and this selective layer can be optimized for solute rejection and solvent flux by controlling the coating conditions, the characteristics and concentrations of the reactive monomers, the choice of the support membrane or the use of additives (e.g. acid-acceptors, surfactants ... ). The (micro-)porous support can be selectively chosen for porosity, strength and solvent resistance. There is a myriad of supports or substrates for membranes. Specific physical and chemical characteristics to be considered when selecting a suitable substrate include porosity, surface porosity, pore size distribution of surface and bulk, permeability, solvent resistance, hydrophilicity, flexibility, mechanical integrity and charges. Pore size distribution and overall surface porosity of the surface pores are of great importance when preparing a support for IFP.

An example of interfacial polymerization used to prepare TFC membranes are "Nylons", which belong to a class of polymers referred to as polyamides. One such polyamide is made, for example, by reacting a triacyl chloride, such as trimesoylchloride, with a diamine, such as m- phenylenediamine. The reaction can be carried out at an interface by dissolving the diamine in water and bringing a hexane solution of the triacyl chloride on top of the water phase. The diamine reacts with the triacyl chloride at the interface between these two immiscible solvents, forming a polyamide film at or near the interface which is less permeable to the reactants. Thus, once the film forms, the reaction slows down drastically, leaving a very thin film. In fact, if the film is removed from the interface by mechanical means, fresh film forms almost instantly at the interface, because the reactants are so highly reactive.

Among the products of interfacial polymerization are polyamides, polyureas, polyurethanes, polysulfonamides, polyesters (US 4,917,800), polyacrylates, or 13- alkanolamines (US20170065937). Factors affecting the making of continuous, thin interfacial films include temperature, the nature of the solvents and co-solvents (including ionic liquids: Marien et al. (2016) ChemSusChem 9, 1101-111), and the concentration and the reactivity of monomers and additives.

EXAMPLES

Example 1: Membranes from 1,2-cyclohexanediamine (CHDA) with 1, 2,4,5- tetra(bromomethyl)benzene (TBMB)

1,2-cyclohexanediamine (CHDA) and potassiumphosphate (K3PO4) were dissolved in water, (the aqueous phase), and l,2,4,5-tetra(bromomethyl)benzene (TBMB) was dissolved in methylisobutylketon (MIBK) (the organic phase) (Figure 1 top part). A polyimide support was immersed in the aqueous amine solution for 5 minutes. Afterwards, the support was removed from the solution, residual amine solution was removed with a wiper and the top of the support was contacted with the organic phase. The two phases were kept in contact for 30 minutes, whereafter the organic solution was removed. The membrane was rinsed with clean MIBK, left to dry in the air for 1 min and placed in a beaker with distilled water.

The performance of the membranes was determined using a dead-end high- throughput filtration set-up. A feed solution of 35pM Rose Bengal (RB 1017 g/mol) or Methyl Orange (MO, 327 g/mol) in water is used and stirred at 340 ppm to minimize concentration polarization. Three coupons were cut from the membrane and tested to check the reproducibility and determine the standard deviation. The pressure applied on the membranes were kept at 10 bar. The permeance (P, L/m^zhbar) was calculated using the following equation

P = V / (Δt*/1*ΔP) [equation 1] With V the permeate volume, At the permeate collection time, A the effective membrane area and AP the applied pressure. The rejection (R, %) was determined using the following equation

R = (1 -(cp/c/)) + 100 [equation 2]

With c_P the permeate solute concentration and cr the feed solute concentration. The solute concentration in the feed and permeate were determined via UV-Vis spectroscopy.

A significant portion of MO, and all of RB were retained, (figure 1, bottom part)

Example 2. Quaternisation and crosslinking of membranes.

Membranes as prepared in Example 1, were treated with methyl iodide (Mel) for quaternation or with 1,6-dibromohexane (BrC₆Hi_ZBr) for crosslinking (figure 2 top panel). This was done by pouring a solution of these compounds on top of the membrane. The treatment was performed for both reagents of 10 minutes and 1 hour.

Afterwards a filtration of RB and MO was performed as described in example 1. Retention of both compounds did not significantly upon treatment with methyl iodide (Mel) or 1,6-dibromohexane (BrC«Hi₂Br). Figure (2 middle and bottom panel))

Example 3: stability of membranes from 1,2-cyclohexane diamine with l,2,4,5-tetra(bromomethyl)benzene.

Membranes prepared from via interfacial polymerization 1,2-cyclohexane diamine with 1,2,4, 5 tetra (bromomethyl) benzene, and were treated with IM HCI, IM NaOH, NaOCI room temperature and at 40 °C for 1 h and 24 h, respectively.

FTIR of the membranes does not change significantly after treatment with acid, alkali or oxidizing reagents (figure).

Example 4: Membranes from 1,2-cyclohexane diamine (CHDA) with 1,4- di(bromomethyl)benzene (TBMB)

An emulsion of CHDA and TBMB was made in dimethylformamide and was stirred for 2 hour at 80°C. Afterwards it was poured on a glass plate and heated to 80 °C to evaporate most of the DMF resulting in a viscous solution. After 30 minutes water was added and a precipitated film was observed.

Claims

1. A method of preparing a polyamine-based membranes comprising the steps of polymerizing compound An with compound Bm, wherein An is a molecule with n amine functional groups, and, wherein Bm is a molecule with m aliphatic functional groups selected from a halide, pseudohalide, ammonium, phosphonium, and sulfonium functional group. wherein n ≥ 1, ≥5, ≥10, or ≥20 and wherein m ≥ 2, ≥5, ≥10, or ≥20.

2. The method according to claim 1, wherein the m functional group is a halide.

3. The method according to claim 1 or 2, wherein the amine functional group of An is -NH₂, -CH2-NH2, -(CHz)₂-NH₂, -(CH₂)₃-NH₂, or -(CH₂)4-NH₂.

4. The method according to any one of claims 1 to 3, wherein the aliphatic functional group is -CHz-halide, -(CHz)z-halide, -(CHz)₃-halide, or -(CH₂)4- halide.

5. The method according to any one of claims 1 to 4, wherein n is between 2 and 5 and m is between 2 and 5.

6. The method according to any one of claims 1 to 5, wherein n is 2 or 4, and m is 2 or 4.

7. The method according to any one of claims 1 to 6, wherein An and/or Bm contain one six-membered aliphatic or six-membered aromatic ring.

8. The method according to any one of claims 1 to 7, wherein An and/or Bm are compounds with a molecular weight below 500, below 1000 or below 2000.

9. The method according to any one of claims 1 to 8, wherein An is 1,2- cyclohexane diamine (CHDA) and/or Bm is 1,2, 4, 5- tetra( bromomethyl) benzene or l,4-di(bromomethyl)benzene (TBMB).

10. The method according to any one of claims 1 to 4, wherein An is a polymer of repeating subunits.

11. The method according to any one of claims 1 to 4, wherein Bm is a polymer of repeating subunits.

12. The method according to claim 10 or 11, wherein in said polymer An or Bm , n or m is ≥10 or is ≥20 .

13. The method according to claim 10 or 11, wherein in each repeating subunit n or n or m is 2 or 4.

14. The method according to any one of claims 1 to 13, wherein the polymerization is performed by interfacial polymerization, phase inversion or solvent evaporation.

15. The method according to any one of claims 1 to 14, wherein the polymerization is performed by interfacial polymerization.

16. The method according to any one of claim 1 to 15, further comprising the step of during or after said polymerization, treating residual functional groups to alter the membrane structure and performance.

17. The method according to claim 16, wherein said treatment is a quaternization or crosslinking.

18. The method according to claim 16, wherein the quaternization is performed with methyliodide or benzylbromide.

19. The method according to claim 17, wherein the crosslinking is performed with 1,6-dibromohexane.

20. Use of a membrane obtained by the method according to any one of claims 1 to 18 for filtration in one or more of :

- strong acidic conditions below pH 2 or below pH 1,

- strong caustic conditions above pH 12 or above pH 13,

- strong oxidizing conditions corresponding to IM NaOCI. Use of the membrane according to claim 20, wherein the use is at room temperature or at a temperature above 100 °C, above 150 °C or above 200 °C.