Asymmetric membranes and related methods

Patent metadata

Field	Value
Publication number	US-10010835-B2
Application number	US-201514645972-A
Country	US
Kind code	B2
Filing date	Mar 12, 2015
Priority date	Mar 13, 2014
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

Microporous polymer membranes and related methods of fabrication are provided. An asymmetric microporous membrane embodiment includes, but is not limited to, a thermoplastic polymer substrate defining a plurality of micropores, the thermoplastic polymer including one or more of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and a combination thereof; and a polymethylpentene (PMP) polymer skin positioned on the thermoplastic polymer substrate, wherein when the thermoplastic polymer substrate includes PMP, the PMP polymer skin has a crystallinity that differs from a crystallinity of the PMP in the polymer substrate.

First claim

What is claimed is:

1. A method of making an asymmetric microporous membrane comprising:
providing a polymethylpentene (PMP) polymer skin resin and a substrate resin, the substrate resin including one or more of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and a combination thereof;
co-extruding the PMP polymer skin resin and the substrate resin to form a membrane precursor; and
stretching the membrane precursor to form an asymmetric microporous membrane having a PMP polymer skin on a thermoplastic polymer substrate; and
wherein co-extruding the PMP polymer skin resin and the substrate resin to form a membrane precursor includes co-extruding the PMP polymer skin resin and the substrate resin through a co-extrusion die to form the membrane precursor.

2. The method of claim 1 , wherein providing a polymethylpentene (PMP) polymer skin resin and a substrate resin includes providing the PMP polymer skin resin and the substrate resin exclusive of any oils for subsequent removal to form pores or any pore-forming particulate to facilitate pore formation.

3. The method of claim 1 , wherein the substrate resin includes polymethylpentene (PMP).

4. The method of claim 3 , wherein PMP polymer skin has a crystallinity that is less than a crystallinity of the PMP of the substrate resin.

5. The method of claim 4 , wherein the crystallinity of the PMP polymer skin resin is less than about 40%, and wherein the crystallinity of the PMP of the substrate resin is greater than about 40%.

6. The method of claim 4 , wherein the crystallinity of the PMP of the substrate resin is greater than about 60%.

7. The method of claim 1 , wherein the PMP polymer skin has a thickness of less than about 2 microns.

8. The method of claim 1 , wherein the thermoplastic polymer substrate has a thickness of less than about 150 microns.

9. The method of claim 1 , wherein the asymmetric microporous membrane is a non-homogeneous membrane.

10. The method of claim 1 , further including annealing the membrane precursor.

11. The method of claim 10 , wherein annealing the membrane precursor includes annealing the membrane precursor prior to stretching the membrane precursor.

12. A method of making a multi-layered membrane comprising the method of making an asymmetric microporous membrane of claim 1 , wherein the PMP polymer skin comprises an outer layer and/or an inner layer of the multi-layered membrane.

13. A method of making an asymmetric microporous hollow fiber membrane comprising:
providing a polymethylpentene (PMP) polymer skin resin and a substrate resin, the substrate resin including one or more of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and a combination thereof, wherein when the substrate resin includes PMP, the PMP polymer skin resin has a crystallinity that differs from a crystallinity of the PMP of the substrate resin;
co-extruding the PMP polymer skin resin and the substrate resin to form a hollow fiber membrane precursor; and
stretching the hollow fiber membrane precursor to form an asymmetric microporous hollow fiber membrane having a PMP polymer skin on a thermoplastic polymer substrate; and
wherein co-extruding the PMP polymer skin resin and the substrate resin to form a hollow fiber membrane precursor includes co-extruding the PMP polymer skin resin and the substrate resin through a co-extrusion die to form the hollow fiber membrane precursor.

14. The method of claim 13 , wherein providing a polymethylpentene (PMP) polymer skin resin and a substrate resin includes providing the PMP polymer skin resin and the substrate resin exclusive of any oils for subsequent removal to form pores or any pore-forming particulate to facilitate pore formation.

15. A method of making a multi-layered hollow fiber membrane comprising the asymmetric microporous hollow fiber membrane of claim 13 , wherein the PMP polymer skin comprises an outer layer and/or an inner layer of the multi-layered hollow fiber membrane.

Assignees

• 3M Innovative Properties Co

Inventors

• Cho Kwantai
• Delozier J Clifton

Classifications

• B01D71/26

  Polyalkenes · CPC title

• B29L2031/755

  Membranes, diaphragms · CPC title

• B29C47/065

  Operations & Transport · mapped topic

• B29C47/0057

  Operations & Transport · mapped topic

• B01D69/088 Primary

  Co-extrusion; Co-spinning · CPC title