Separation membranes and process for preparing the same

• US 4,948,400 A
• Filed: 06/28/1989
• Issued: 08/14/1990
• Est. Priority Date: 06/30/1988
• Status: Expired due to Term

• Current Assignee: Nippon Steel Chemical Company Limited (Nippon Steel Corporation)
• Original Assignee: Nippon Steel Chemical Company Limited (Nippon Steel Corporation)
• Inventors: Yamada, Yasuharu, Furukawa, Nobuyuki, Furukawa, Masaya
• Primary Examiner(s): Spitzer, Robert
• Application Number:
  US07/372,995
• Time in Patent Office: 412 Days
• Field of Search: 55/16, 55/158, 210/500.39, 528/310, 528/332, 528/335, 528/340
• US Class Current: 96/10
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: B01D 71/701 Polydimethylsiloxane
• CPC Class Codes: B01D 71/80 Block polymers
• CPC Class Codes: C08G 73/106 containing silicon
• CPC Class Codes: C08G 77/455 containing polyamide, polyesteramide or polyimide sequences

Abstract

Polyimide-based separation membranes of this invention are made from polyimides having repeating units of the general formulas (A) and (B) ##STR1## wherein Ar₁ and Ar₃ are tetravalent aromatic radicals containing at least one aromatic ring, Ar₂ is a divalent aromatic radical containing at least one aromatic ring, R₁ and R₂ are organic radicals, R₃ to R₆ are monovalent hydrocarbon radicals, and n is an integer from 1 to 50 at a mole ratio (A)/(B) of 5/95 to 95/5, have high gas permeation coefficients, high mechanical strength, and excellent heat resistance, and are useful for separation and concentration of mixed gases.

Claims

1. Polyimide-based separation membranes made from polyimides having repeating units of the general formulas (A) and (B) ##STR12## wherein Ar₁ and Ar₃ are tetravalent aromatic radicals containing at least one aromatic ring, Ar₂ is a divalent aromatic radical containig at least one aromatic ring, R₁ and R₂ are divalent organic radicals, R₃ to R₆ are monovalent hydrocarbon radicals, and n is an integer from 1 to 50 with the mole ratio of (A) to (B) falling in the range of 5/95 to 95/5.

2. Separation membranes according to claim 1 wherein Ar₁ and Ar₃ in the repeating units (A) and (B) are ##STR13## or radicals of the general formula ##STR14## wherein X is a single bond, --O--, --CO--, --SO₂ --, or --C(CF₃)₂ --.

3. Separation membranes according to claim 1 wherein Ar₂ in the repeating unit of the general formula (A) is ##STR15## wherein R₇ and R₈ are monovalent hydrocarbon radicals and p and q are integer from 0 to 4, or a radical of the general formula ##STR16## wherein Y is a single bond, --C(CF₃)₂ --, --O--, --C(CH₃)₂ --, --SO₂ --, --CH₂ --, ##STR17##

4. Separation membranes according to claim 1 wherein R₁ and R₂ in the repeating unit of the general formula (B) are --(CH₂)_m --, ##STR18## wherein m is an integer from 1 to 3.

5. Separation membranes according to claim 1 wherein R₃, R₄, R₅, and R₆ in the repeating unit of the general formula (B) are methyl or phenyl.

6. Separation membranes according to claim 1 wherein n in the repeating unit of the general formula (B) is from 1 to 30.

7. Separation membranes according to claim 1 wherein the polyimides have a microphase separated structure.

8. A process for the preparation of separation membranes which comprises forming polyimide precursors by the reaction of aromatic tetracarboxylic acid dianhydrides, aromatic diamines, and diaminosiloxanes of the general formula (C) ##STR19## wherein R₁ and R₂ are divalent organic radicals, R₃ to R₆ are monovalent hydrocarbon radicals, and n is an integer from 1 to 50, making said precursors into a membrane, and imidizing said membrane.

10. A process for the preparation of separation membranes according to claim 8 or 9 wherein R₁ and R₂ are --(CH₂)_m --, ##STR21## wherein m is an integer from 1 to 3.

11. A process for the preparation of separation membranes according to claim 8 or 9 wherein R₃, R₄, R₅, and R₆ are methyl or phenyl.

9. A process for the preparation of separation membranes which comprises dissolving polyimides having the repeating units of the general formulas (A) and (B) ##STR20## wherein Ar₁ and Ar₃ are tetravalent aromatic radicals containing at least one aromatic ring, Ar₂ is a divalent aromatic radical containing at least one aromatic ring, R₁ and R₂ are divalent organic radicals, R₃ to R₆ are monovalent hydrocarbon radicals, and n is an integer from 1 to 50, at a mole ratio (A)/(B) of 5/95 to 95/5 in a solvent, making said solution into a membrane, and removing said solvent.