Highly-selective polyimide membranes with increased permeance, said membranes consisting of block copolyimides

1. A block copolyimide, comprising the blocks (A) and (B) having the following structures (Ia) and (Ib)

wherein

R1 comprises either or both of the functional groups R 1 a or R 1 b

R2 comprises at least one of the functional groups R 2 a, R 2 b or R 2 c

R3 comprises at least one of the functional groups R 3 a, R 3 b or R 3 c

and R4 comprises at least one of the following functional groups R 4 a, R 4 b or R 4 c

wherein at least one of the radicals X 1 to X 4 , are equal to CH 3 or a C 2 to C 4 alkyl radical and the functional groups R 1 to R 4 are selected such that the blocks A and B have a differing composition,

wherein block lengths n and m of blocks (A) and (B) are each from 5 to 1000, and

wherein the block copolyimide is soluble in an aprotic dipolar solvent.

2. The block copolyimide according to claim 1 ,

wherein

the block lengths n and m of blocks (A) and (B) are each from 5 to 150,

and/or

the molecular weight M n of the block copolyimide is, based on polystyrene standards, in the range from 10,000 to 200,000 g/mol,

and/or

the molecular weight M w of the block copolyimide is in the range from 10,000 to 500,000 g/mol,

and/or

the polydispersity index is in the range from 1 to 10.

3. The block copolyimide according to claim 1 ,

wherein the block (B) in isolated form is soluble in an aprotic dipolar solvent.

4. The block copolyimide according to claim 1 ,

wherein

R 1 consists in total to an extent >50 mol %, of groups R 1 a and R 1 b and also any further tetravalent, aromatic, functional groups,

and/or

R 2 consists in total to an extent >50 mol %, of groups R e a, R 2 b and/or R 2 c and any further divalent, aromatic, functional groups,

and/or

R 3 consists in total to an extent >50 mol %, of groups R 3 a, R 3 b and/or R 3 c and also any further tetravalent, aromatic, functional groups,

and/or

R 4 consists in total to an extent >50 mol %, of groups R 4 a, R 4 b and/or R 4 c and any further divalent, aromatic, functional groups.

5. The block copolyimide according to claim 4 ,

wherein

R 1 consists of 0 to 100 mol % R 1 a and 0 to 100 mol % R 1 b, wherein the mole percentages of the functional groups R 1 a and R 1 b are in each case chosen within the recited ranges such that they total 100 mol % of functional groups R 1 ,

and/or

R 2 consists of 0 to 100 mol % R 2 a and/or 0 to 100 mol % R 2 b and/or 0 to 100 mol % R 2 c, wherein the mole percentages of the functional groups R 2 a, R 2 b and R 2 c are in each case chosen within the recited ranges such that they total 100 mol % of functional groups R 2 ,

and/or

R 3 consists of 0 to 100 mol % R 3 a and/or 0 to 100 mol % R 3 b and/or 0 to 100 mol % R 3 c, wherein the mole percentages of the functional groups R 3 a, R 3 b and R 3 c are in each case chosen within the recited ranges such that they total 100 mol % of functional groups R 3

and/or

R 4 consists of 0 to 100 mol % R 4 a and 0 to 100 mol % R 4 b and 0 to 100 mol % R 4 c, wherein the mole percentages of the functional groups R 4 a, R 4 b and R 4 c are in each case chosen within the recited ranges such that they total 100 mol % of functional groups R 4 .

6. The block copolyimide according to claim 1 ,

wherein:

block (A) consists of:

100 mol % R 1 b, 64 mol % R 2 a, 16 mol % R 2 b and 20 mol % R 2 c,

or

40 mol % R 1 a, 60 mol % R 1 b, 80 mol % R 2 a and 20 mol % R 2 b, and block (B) consists of

40 to 60 mol % R 3 a, 0 to 10 mol % R a b, 60 to 30 mol % R 3 c, 90 to 100 mol % R 4 a, 0 to 10 mol % R 0 b and 0 to 10 mol % R 0 c,

or

50 mol % R 3 a, 50 mol % R 1 c and 100 mol % R 4 a,

wherein the recited mole percentages relate to the functional groups R 1 , R 2 , R 3 and R 4 such that the amounts of the various units are each selected such that the sum total is 100 mol % for each of these groups.

7. A process for preparing a block copolyimide according to claim 1 ,

comprising the following steps:

a. preparing an oligoimide having terminal anhydrides from at least one dianhydride of formula (II)

and at least one diamine of formula (III)

H 2 N—R 4 —NH 2   (III)

wherein R 3 and R 4 are each as defined in claim 1 , and

b. reacting the oligo/polyimide of step a) with at least one dianhydride of formula (IV)

and at least one diisocyanate (V)

OCN—R 2 —NCO  (V)

wherein R 1 and R 2 are each as defined in claim 1 , to form a block copolyimide.

8. The process according to claim 7 , wherein

step a) comprises the following subsidiary steps:

a1) preparing an oligoamide acid from at least one diamine of formula (III) and at least one dicarboxylic anhydride of formula (II) in an aprotic dipolar solvent, wherein the dicarboxylic anhydride is present in molar excess,

a2) imidating the oligoamide acid,

a3) precipitating the oligoimide of step a2)

a4) washing, and

a5) drying, and/or conditioning.

9. The process according to claim 8 ,

wherein

the imidating in step a2) is effected thermally or chemically, wherein chemical imidizing is effected by adding a base and a water-withdrawing agent.

10. The process according to claim 9 ,

wherein

the base comprises tertiary organic amines and/or basic salts.

11. The process according to claim 7 ,

wherein the step b) comprises the following subsidiary steps:

b1) preparing a solution of the oligoimide of step a) in an aprotic dipolar solvent together with PMDA and/or with BTDA and with a basic catalyst, and

b2) adding at least one diisocyanate selected from the group consisting of 2,4-TDI, 2,6-TDI and 4,4′-MDI to form a block copolymer.

12. A process for preparing a block copolyimide according to claim 1 , comprising the following steps:

(i) preparing an oligoimide having terminal anhydrides from at least one dianhydride of formula (IV)

and at least one diisocyanate of formula (V)

OCN—R 2 —NCO  (V)

wherein R 1 and R 2 are each as defined in claim 1 , and

(ii) preparing a polyimide/polyamide acid block copolymer by reacting block (A) as obtained from step (i) with at least one dianhydride of formula (II)

and at least one diamine of formula (III)

H 2 N—R 4 —NH 2   (III),

wherein R 3 and R 4 are each as defined in claim 1 ,

and/or a block (B) having terminal amino groups, prepared from at least one dianhydride of formula (II) and at least one diamine of formula (III),

and

(iii) chemically imidating the polyimide/polyamide acid copolymer formed in step iii).

13. An asymmetrically integral hollow fiber membrane or asymmetrically integral flat sheet membrane prepared from a block copolyimide according to claim 1 .

14. A hollow fiber membrane module comprising an asymmetrically integral hollow fiber membrane according to claim 13 .

15. A process for separation of gases, comprising separating a gas mixture with

an asymmetrically integral hollow fiber membrane or asymmetrically integral flat sheet membrane according to claim 13 .

16. A device for separation of gases, comprising an asymmetrically integral hollow fiber membrane or asymmetrically integral flat sheet membrane according to claim 13 .

17. An asymmetrically integral hollow fiber membrane or asymmetrically integral flat sheet membrane, prepared from a solution obtained by the process according to claim 7 .

18. The process according to claim 7 , wherein step b) is carried out using a tertiary organic amine or a basic salt as catalyst.

19. The block copolyimide according to claim 1 , wherein R4 comprises at least one R 4 c functional group.