METHOD FOR PRODUCING AROMATIC POLYETHERSULFONES CONTAINING ISOHEXIDE

Abstract

The present invention relates to a method for producing a block copolymer of the poly-ethersulfone type containing a biosourced diol, to a block copolymer that can be obtained by said method, and to the use of said block copolymer for producing membranes.

Claims

1. A process for the preparation of a block copolymer of aromatic polyether type comprising the following successive stages: a) preparation of a first polymer block having the repeat unit: ##STR00015## with a number-average molar mass M.sub.n of between 1000 and 30 000 g/mol and where n is an integer greater than 1, X is Cl or F and Y is CO or SO.sub.2, the preparation of said first block consisting of the reaction between a 1,4:3,6-dianhydrohexitol and an excess of a halogenated bisaromatic compound chosen from 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-difluorodiphenyl ketone and 4,4′-dichlorodiphenyl ketone in the presence of a base in an organic solvent, b) preparation of a second polymer block having the repeat unit: ##STR00016## with a number-average molar mass Mn of between 1000 and 30 000 g/mol and where m is an integer of greater than 1 and R originates from an aromatic or aliphatic diol, the preparation of this second block consisting of the reaction between an aromatic or aliphatic diol in excess or in a stoichiometric amount with 4,4′-dichlorodiphenyl sulfone or 4,4′-difluorodiphenyl sulfone in the presence of a base in an organic solvent and optionally a cosolvent, c) reaction between the first block and the second block according to block copolymerization in two successive stages or block copolymerization in two distinct stages.

2. The process as claimed in claim 1, wherein the organic solvent of the stage of preparation of the first polymer block is a polar aprotic solvent.

3. The process as claimed in claim 1, wherein the 1,4:3,6-dianhydrohexitol used in the stage of preparation of the first polymer block is isosorbide.

4. The process as claimed in claim 1, wherein the proportion of monomers is between 10% and 50% by weight with respect to the sum of the weight of the solvent and of the weight of the monomers.

5. The process as claimed in claim 1, wherein the stage of preparation of the first polymer block is carried out at a temperature of between 160° C. and 250° C.

6. The process as claimed in claim 1, wherein the preparation of the first polymer block and the preparation of the second polymer block are carried out in the same reaction medium.

7. The process as claimed in claim 1, wherein the stage of preparation of the second block is carried out with a 1,4:3,6-dianhydrohexitol/bisphenol A molar ratio of between 1/99 and 99/1.

8. The process as claimed in claim 1, wherein the organic solvent of the stage of preparation of the second polymer block is a polar aprotic solvent.

9. The process as claimed in claim 1, wherein the polar aprotic solvent/cosolvent molar ratio is between 0.1 and 10.

10. The process as claimed in claim 1, wherein the stage of preparation of the second polymer block is carried out at a temperature of between 90° C. and 150° C.

11. The process as claimed in 1, wherein the stage of reaction between the first block and the second block is carried out at a temperature of between 150° C. and 200° C.

12. A block copolymer of aromatic polyether type comprising the repeat units of the formula I: ##STR00017## in which: A is ##STR00018## where Y is CO or SO.sub.2 and n is an integer greater than 1, B is ##STR00019## where R originates from an aliphatic or aromatic diol and m is an integer greater than 1, n′ and m′ are each independently of each other an integer greater than 1, the molar ratio n′/m′ is between 1/99 and 99/1, and p is an integer greater than 1.

13. The block copolymer as claimed in claim 12, in which the average molecular weight is greater than 30 000 g/mol.

14. The use of a block copolymer capable of being obtained by the process as claimed in claim 1 or of the copolymer as claimed in claim 12 for the manufacture of membranes.

Description

FIGURES

[0099] FIG. 1. Photograph of a membrane obtained with the block copolymer according to the invention example 1

[0100] FIG. 2. Differential scanning calorimetry carried out at 10° C./min from 20° C. to 300° C.

EXAMPLES

Example 1

[0101] Preparation of a block copolymer according to the invention in which the 1,4:3,6-dianhydrohexitol/bisphenol A ratio is 50/50.

[0102] 0.7313 g (5 mmol, 1 eq.) of isosorbide, 1.5606 g (5.38 mmol, 1.076 eq.) of 4,4′-dichlorodiphenyl sulfone (DCDPS) and 1.3961 g (10 mmol, 2 eq.) of K.sub.2CO.sub.3 are dissolved in 5.31 g of DMS 0 in a three-necked flask equipped with a swan neck, a stirrer and a nitrogen inlet. A reflux condenser is fitted in order to condense the DMSO. The round-bottomed flask is heated with an oil bath at 210° C. for 7 h 30. The temperature is subsequently brought back to 120° C.

[0103] Subsequently, 1.1533 g (5 mmol, 1 eq.) of bisphenol A (BPA), 1.4509 g (5 mmol, 1 eq.) of 4,4′-dichlorodiphenyl sulfone (DCDPS) and 1.3963 g (10 mmol, 2 eq.) of K.sub.2CO.sub.3 (99%) in 12.71 g of NMP and 8.47 g of toluene are added. A Dean-Stark apparatus is fitted in order to form the water-toluene azeotrope. The medium is left at 120° C. for 15 h, then at 160° C. for 3 h 30 and finally at 180° C. for 4 h.

[0104] The reaction medium is poured into water, bringing about the precipitation of the polymer, which is subsequently filtered off and then dried at 80° C. for 16 h. The polymer is subsequently dissolved in 20 ml of DMSO and reprecipitated from a large volume of water, filtered off and dried under vacuum at 40° C. for 16 h.

Counterexample 2

[0105] This example is a polyethersulfone purchased from Acros Organics 178910050 in the form of transparent granules. The product has not undergone any treatment. This product is a polyethersulfone which is devoid of isosorbide but containing bisphenol A.

Counterexample 3

[0106] This comparative example corresponds to example No. 5 of the patent WO2014/072473 of Solvay Specialty Polymers, USA, carried out in DMSO as reaction solvent. It is a polyethersulfone homopolymer starting from isosorbide.

Counterexample 4

[0107] This comparative example corresponds to example No. 5 of the patent WO2016/032179 of Samyang Corporation, carried out in DMSO as reaction solvent without chlorobenzene as cosolvent. It is a statistical copolymer of polyethersulfone based on isosorbide and on bisphenol A with the isosorbide/bisphenol A molar ratio of 50/50.

Counterexample 5

[0108] This example corresponds to a mixture of counterexample 2 with counterexample 3 dissolved in DMSO at 20% by weight and then precipitated from water. The mixture is subsequently dried at 80° C. for 16 h.

[0109] The characterizations applied to the examples are described below: [0110] Nuclear Magnetic Resonance (NMR). The 100 MHz .sup.13C spectra were produced on a BrUker Ascend™ 400 in a 5 mm glass tube in d.sub.6-DMSO. [0111] Differential scanning calorimetry (DSC) (FIG. 2) The differential scanning calorimetry analysis was carried out on a DSC-Q5000 SA, TA Instruments, USA, with a flow rate of 50 ml/min in nitrogen at 10° C./min or 20° C./min from 20° C. to 300° C. and in a drilled aluminum crucible. [0112] Size-Exclusion Chromatography (SEC): The analysis of the molar masses was carried out by size-exclusion chromatography with an Agilent PLgel 5 μm column in DMF/LiBr at 50° C. for 35 min with a flow rate of 0.5 ml/min and in PS calibration.

TABLE-US-00001 TABLE 1 Analyses Ability to Examples M.sub.n.sup.1 (g/mol) PI Tg.sup.1 (° C.) form films Example 1 80 000 1.6 200 Yes Counterexample 2 90 000 1.6 190 Yes Counterexample 3 34 000 1.2 200 No Counterexample 4 30 000 1.1 150 No .sup.1DSC: Heating/cooling/heating cycle from 20° C. to 300° C. at 20° C./min, drilled aluminum crucible

[0113] .sup.13C NMR proves a level of incorporation of 56% of isosorbide with respect to the total level of diols incorporated.

[0114] With SEC, a single Gaussian curve of 80 000 g/mol in polystyrene calibration is observed. The molar mass Mn of the block copolymer according to the invention, example 1, is higher than that of the isosorbide-based homopolymer, counterexample 3, and than that of the 50/50 isosorbide/bisphenol A statistical copolymer, counterexample 4, respectively 34 000 and 30 000 g/mol. The DSC analysis (FIG. 2) shows that the block copolymer according to the invention, example 1, has a single Tg at 192° C. The mixture of the isosorbide-based homopolymer, counterexample 3 (C3 in FIG. 2), and commercial PES, counterexample 2 (C2 in FIG. 2), exhibits two Tg values at 183° C. and 208° C. (counterexample 5; C4 in FIG. 2). These two analyses are in agreement with the block nature of the polymer of the invention and refute the hypothesis of the formation of two homopolymers, one based on isosorbide and the other based on bisphenol A.

[0115] Particularly advantageously, the copolymer according to the invention exhibits an average molecular weight comparable to that of the market reference. It is a high weight, in particular in the sense that it is greater than 50 000 g/mol, and thus makes said copolymer capable of being used for the manufacture of membranes.

[0116] Preparation of a Membrane

[0117] A membrane can be prepared from a 20% by weight solution of the polymer in NMP poured onto a glass sheet. The solvent is subsequently evaporated using the following thermal cycle: 70° C. for 2 h, 120° C. for 1 h, 150° C. for 1 h and 200° C. for 1 h. After curing, a transparent brown membrane is obtained for example 1 (FIG. 1). A membrane is also obtained with counterexample 2.

[0118] The copolymer of the invention is film-forming, unlike counterexamples 3 and 4 of the literature.

[0119] The characterizations applied to the two membranes are described below:

[0120] Contact Angle

[0121] The contact angle was measured with water and diiodomethane according to the Owens, Wendt, Rabel and Kaelble model.

[0122] Dynamic Sorption

[0123] The water uptake measurement was carried out with a Dynamic Vapor Sorption device (DVS Q-5000 SA, TA Instruments) at atmospheric pressure and at the isotherm of 21° C. with a sorption/desorption cycle from 0% to 90% humidity.

[0124] Permeability

[0125] The experiments are carried out at ambient temperature. The handling operation consists in inserting the film to be studied into the permeation cell. After a high-vacuum desorption of 16 h, the permeation experiment consists in imposing a pressure (3 bar) of a chosen gas in the upstream compartment of the cell and in measuring the pressure rise in the downstream compartment of the cell. The permeability is calculated from the slope of the straight pressure line as a function of time under stationary conditions, corrected if necessary for the static vacuum.

TABLE-US-00002 TABLE 2 Analyses obtained on the membranes Hydrophilicity properties Contact angle H.sub.2O 50% Sorption (°) (g of water/g sample) Example 1 89.03 0.89% Counterexample 2 89.20 0.39% Permeability properties P(He) P(CO.sub.2) P(O.sub.2) Selectivity Selectivity (Barrer) (Barrer) (Barrer) He/CO.sub.2 CO.sub.2/O.sub.2 Counterexample 2 12.4 6.1 2.65 2.03 2.30 Example 1 8.3 2.93 0.5 2.83 5.86

[0126] In short, from these analyses, the selectivity for certain gases is improved. For example, in a particularly advantageous and discriminating manner, the CO.sub.2/O.sub.2 selectivity changes from 2.30 for counterexample 2 to 5.86 for example 1. More significantly still, and more advantageously still, the hydrophilic nature is much more important for the product according to the invention: the water absorption is more than 2 times greater than that observed for the commercial product. This property is particularly advantageous for a membrane, the ability of which to rapidly hydrate will condition its yield and its efficiency.