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  • C08F8/00—Chemical modification by after-treatment
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  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/20—Manufacture of shaped structures of ion-exchange resins
  • C08J5/22—Films, membranes or diaphragms
  • C08J5/2287—After-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
  • B01D71/80—Block polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J41/00—Anion exchange; Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
  • B01J41/08—Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
  • B01J41/12—Macromolecular compounds
  • B01J41/14—Macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J47/00—Ion-exchange processes in general; Apparatus therefor
  • B01J47/12—Ion-exchange processes in general; Apparatus therefor characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F12/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
  • C08F12/02—Monomers containing only one unsaturated aliphatic radical
  • C08F12/04—Monomers containing only one unsaturated aliphatic radical containing one ring
  • C08F12/06—Hydrocarbons
  • C08F12/08—Styrene
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/18—Introducing halogen atoms or halogen-containing groups
  • C08F8/24—Haloalkylation
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  • C08F8/00—Chemical modification by after-treatment
  • C08F8/44—Preparation of metal salts or ammonium salts
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/20—Manufacture of shaped structures of ion-exchange resins
  • C08J5/22—Films, membranes or diaphragms
  • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
  • C08J5/2218—Synthetic macromolecular compounds
  • C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
  • C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
  • C08L53/025—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes modified
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/16—Membrane materials having positively charged functional groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/42—Ion-exchange membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/28—Polymers of vinyl aromatic compounds
  • B01D71/281—Polystyrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2353/00—Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
  • C08J2353/02—Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers of vinyl aromatic monomers and conjugated dienes

Definitions

• Anion-exchange material based on block polymer of styrene and olefins Field of Art The invention relates to a high-capacity anion-exchange material based on the block copolymer poly(styrene-block-C2-C4-alkylene-stat-C2-C4-alkylene-block-styrene) bearing quaternary 1,1-dimethylpyrrolidinium groups covalently bound to the aromatic nucleus through one of the methyl substituents of the said 1,1-dimethylpyrrolidinium group.
• Background Art Ion-exchange membranes find application on a laboratory as well as industrial scale.
• Ion-exchange membranes are produced either as homogeneous membranes, which are a single-phase system, or as heterogeneous membranes, which are formed by a dispersion of ion-exchange particles in a hydrophobic polymer binder (J. Schauer, L. Bro ⁇ ová, Journal of Membrane Science 250 (2005) 151).
• Anion-exchange (anex) membranes are usually prepared from chloromethylated cross-linked polystyrene, or by grafting styrene or vinylbenzyl chloride onto a porous membrane and subsequent chloromethylation. The chlorine atom from the chloromethyl group is then subjected to a substitution reaction with a trialkylamine to form a quaternary tetraalkylammonium functional group.
• Another method for preparing anex membranes involves quaternization of poly(4-vinylpyridine) (G. Merle, M. Wessling, K. Nijmeijer, J. Membr. Sci.377 (2011) 1).
• Carcinogenic and toxic chloroalkyl ethers or bischloroalkyl ethers are often used for industrial chloromethylation.
• Chloromethylation of the block copolymer poly(styrene-block-ethylene-stat-butylene-block- styrene) (PSEBS) having Mw 30,000 g.mol -1 by a reaction with (chloromethyl)methyl ether catalyzed by ZnCl2 is described in document EP 2157105A1.
• Chloromethylation of PSEBS copolymer using (chloromethyl)methyl ether and subsequent quaternization reaction with trimethylamine is also described in other publications (J. Zhou, J. Guo, D. Chu, R. Chen, J. Power Sources 219 (2012) 272); L. Sun, J. Guo, J. Zhou, Q. Xu, D. Chu, R. Chen, J. Power Sources 202 (2012) 70; J. ⁇ itka, J. Peter, B. Galajdová, L. Pavlovec, Z. Pientka, M. Paidar, J. Hnát, K. Bouzek, Desalination Water Treat. 142 (2019) 90).
• the present invention provides a method for preparing anion-exchange (anex) membranes containing or consisting of a block copolymer poly(styrene-block-C2-C4-alkylene-stat-C2-C4- alkylene-block-styrene), in which the benzene rings of the styrene units bear a quaternary 1,1- dimethylpyrrolidinium group covalently attached via one of its methyls (formula I), said method comprising the following steps: – subjecting poly(styrene-block-C2-C4-alkylene-stat-C2-C4-alkylene-block-styrene) to chloromethylation on the benzene rings in the styrene units to form a chloromethylated poly(styrene-block-C2-C4-alkylene-stat-C2-C4-alkylene-block-styrene); – casting the chloromethylated poly
• the block copolymer poly(styrene-block-C2-C4-alkylene-stat-C2- C4-alkylene-block-styrene) used as a starting copolymer for the chloromethylation has a number average molar mass of 10,000 to 1,000,000 g.mol -1 and a weight percent of styrene in the range of 10 to 70%.
• the starting copolymer is a poly(styrene-block-ethylene-stat- butylene-block-styrene) copolymer (PSEBS).
• Chloromethylation can preferably be carried out by the process described in the patent document CZ305138, i.e.
• the starting block copolymer poly(styrene-block-C2-C4- alkylene-stat-C2-C4-alkylene-block-styrene) into a reaction with dimethoxymethane, with a reagent selected from the group PCl3, SOCl2 and SiCl4, and with a ZnCl2 catalyst, at a temperature within the range of 10°C to 65°C, for at least 2 hours, in some embodiments for 2 to 24 h, in other embodiments for 24 hours to 1 month.
• water and/or C1-C4 alcohol is used as a suitable solvent for the reaction step of the chloromethylated membrane with 1-methylpyrrolidine.
• the reaction of the membrane with 1-methylpyrrolidine is carried out at a temperature within the range of 20°C to 65°C, more preferably for at least 24 hours to 48 hours.
• the preparation procedure can be illustrated by the following reaction scheme, which, however, does not limit the scope of protection: Afterwards, an anion exchange step can be performed, i.e. the chloride anion can be exchanged for another anion.
• the present invention further provides an anion-exchange membrane containing or consisting of a block copolymer poly(styrene-block-C2-C4-alkylene-stat-C2-C4-alkylene-block-styrene), in which the benzene rings of the styrene units carry quaternary 1,1-dimethylpyrrolidinium group covalently attached to the benzene ring via one of the methyls.
• the membrane is obtainable by the method according to the invention.
• the block copolymer can be represented schematically by formula I: Formula (I)
• the membranes of the invention are highly ion-conductive, have good mechanical properties even in the dry state, and are usable, for example, in applications for ion-exchange materials, such as solid electrolytes, ion-exchange membranes, ion-exchange binders and catalyst carriers.
• High ionic conductivity refers to a conductivity of at least 50 mS.cm -1 in the hydroxide cycle at a temperature of 25 °C.
• the content of styrene units is in the range of 10 to 70 wt.%, more preferably 20 to 40 wt.%, and the content of alkylene units of each type is in the range of 10 to 50 wt.%, based on the weight of the starting poly(styrene-block-C2-C4-alkylene-stat-C2-C4-alkylene-block- styrene) without the bound 1,1-dimethylpyrrolidinium groups.
• the alkylene is butylene and ethylene.
• the content of 1,1-dimethylpyrrolidinium groups is in the range of 0.8 to 3.2 mmol.g- 1 , more preferably 0.9 to 1.9 mmol.g -1 , based on the weight of unswollen block copolymer with the bound 1,1-dimethylpyrrolidinium groups and with a chloride counterion, according to formula I.
• the chloride counterion is a counterion that is formed during the preparation reaction and is used here as a reference counterion.
• Membranes with other counterions can be prepared by the anion exchange step, and the content of 1,1-dimethylpyrrolidinium groups can be converted (re-calculated) to the content relative to the copolymer with the reference counterion.
• the membranes obtainable by the method according to the present invention can be preferably used for the preparation of homogeneous or microheterogeneous membranes, impregnation of electrodes in electrochemical devices or as catalyst carriers.
• Examples of carrying out the Invention Example 1 5 g of PSEBS block copolymer with a styrene content of 29 wt.%, i.e.1.45 g (0.0139 mol), was dissolved in 95 g of chloroform, and 10 g (0.131 mol) of dimethoxymethane, 1.8 g (0.0132 mol) of ZnCl2 and 2 g (0.0146 mol) of PCl3 were added.
• ZnCl2 was dispersed by stirring for 1 h and the mixture was then heated at 60 °C for 24 h. Then the reaction mixture was diluted with 100 g of chloroform and precipitated into 2 L of ethanol. The precipitated polymer was filtered off, washed with 2 L of ethanol and dried at room temperature. Chlorine content 4.56 wt.%. Degree of chloromethylation 49%. The product was soluble in toluene and chlorinated solvents.
• Example 2 5 g of block copolymer PSEBS with a styrene content of 29 wt. %, i.e.
• Example 3 The chloromethylated polymer prepared according to Example 2 was dissolved into a 5% solution in tetrahydrofuran, cast onto a Teflon pad and covered with a petri dish to slow down the solvent evaporation. Under these conditions, the solvent was evaporated at laboratory temperature after 48 h. The thus prepared membrane weighing about 1 g was embedded in 100 ml of a 35% ethanol solution of 1-methylpyrrolidine in a reaction vessel. The vessel was tightly closed and heated at 60 °C for 24 h. Then the membrane was removed and immersed in 0.5 L of 1M HCl for 1 h.
• Example 4 The chloromethylated polymer prepared according to Example 2 was dissolved into a 5% solution in tetrahydrofuran, cast onto a Teflon pad and covered with a petri dish to slow down the evaporation of the solvent. Under these conditions, the solvent was evaporated at laboratory temperature after 48 h.
• the thus prepared membrane weighing about 1 g was embedded in 100 ml of a 10% ethanol solution of 1-methylpyrrolidine in a reaction vessel.
• the vessel was tightly closed and left at a laboratory temperature of 25°C for 48 h.
• the membrane was then removed and immersed in 0.5 L of 1M HCl for 1 h.
• the membrane was again removed, washed with demineralized water and dried at laboratory temperature.
• Conversion to the OH ⁇ phase was performed by immersing the membrane in 1 L of 1M NaOH for 1 h and then washing with distilled water.
• the ionic conductivity in the OH ⁇ phase of the membrane at 30 °C is 30.2 mS.cm -1 .
• Example 5 Determination of chlorine content
• the membrane is first cast, and only on the finished membrane, the reaction of the chloromethyl group with 1-methylpyrrolidine is performed to form a charged 1,1-dimethylpyrrolidinium functional group.
• the reaction is almost quantitative.
• the reaction in the solvent is important because it allows the membrane to swell, which ensures that the reagent reaches all the chloromethyl groups.
• an elemental analysis of the membranes converted from the Cl- phase to the OH- phase was performed.
• the conversion to the OH- phase was carried out according to the procedure described in J Appl Electrochem (2012) 42:545–554, section 2.3 “pretreatment of the membrane”.
• the membrane is immersed for 24 hours in demineralized water, then it is immersed in 0.1M NaOH for 2 hours, then it is immersed in 0.1M HCl overnight, then it is immersed in 0.1M NaOH for 4 hours and finally is immersed in demineralized water for 24 hours. After each immersion step, the membrane was washed with demineralized water.
• the amount of HCl and NaOH relative to the theoretical content of charged functional groups in the membrane is in the range of 10 to 100.
• the chloromethylated membrane before reaction with 1-methylpyrrolidine had a chlorine content of 5.09 ⁇ 0.01 %.
• the chlorine content was 2.45 ⁇ 0 %. After conversion to the OH- phase, the chlorine content was 0.11 ⁇ 0 %.
• Another chloromethylated membrane before reaction with 1-methylpyrrolidine had a chlorine content of 2.61 ⁇ 0.02 %, i.e. it was a membrane with a lower content of chloromethyl groups.
• the chlorine content was 2.28 ⁇ 0.02 %. After conversion to the OH- phase, the chlorine content was 0.11 ⁇ 0 %.
• Example 6 Determination of ion exchange capacity The ion exchange capacity was evaluated by spectrophotometric determination of the molar amount of nitrate ions exchanged by a membrane sample of known weight.
• the membrane samples were immersed in 0.1 mol.dm ⁇ 3 NaOH for 4 hours, then in 0.1 mol.dm ⁇ 3 HCl for 12 hours, and then in 0.1 mol.dm ⁇ 3 NaOH for 4 hours. After each immersion step, the membrane was washed with demineralized water. The membrane samples were subsequently placed in 1 L of 1 mol.dm ⁇ 3 KNO3 solution for 24 hours. Five samples with dimensions of 1 ⁇ 1 cm 2 were measured for each membrane. Each of the samples was then thoroughly rinsed with demineralized water and transferred to 0.1 L of 0.1 mol.dm ⁇ 3 NaCl solution for a period of 24 hours.
• Industrial Applicability Anex membranes (and ion-exchange membranes in general) are used in both laboratory and industrial scale. The most important applications include mainly electrochemical desalination of sea and brackish waters, separation of electrolytes from non-electrolytes, purification of pharmaceutical preparations, use as solid electrolytes and use in other electrochemical processes such as electrodialysis, electrolysis and fuel cells.

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