Porous PTFE membrane

Patent metadata

Field	Value
Publication number	US-12318722-B2
Application number	US-201917414908-A
Country	US
Kind code	B2
Filing date	Dec 16, 2019
Priority date	Dec 17, 2018
Publication date	Jun 3, 2025
Grant date	Jun 3, 2025

Abstract

A porous polytetrafluoroethylene (PTFE) membrane including a nonwoven web having a microstructure of substantially only microfibrils fused at crossover points, said membrane having a percent balance of orthogonal dimensions that is within 10%.

First claim

The invention claimed is:

1. A porous polytetrafluoroethylene membrane consisting of polytetrafluoroethylene, the porous polytetrafluoroethylene membrane being a nonwoven web having a microstructure of microfibrils fused at crossover points with less than 100 nodes per 100 μm 2 , said membrane having a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 10% of the tensile peak stress in the cross direction, and wherein the tensile peak stress in the machine direction and the tensile peak stress in the cross direction is up to 130 MPa at room temperature.

2. The membrane of claim 1 having a tensile peak stress in each of the machine direction and the cross direction of at least 5 MPa.

3. The membrane of claim 1 having a pore size value of 0.05 micron to 2 microns.

4. The membrane of claim 1 having an air flow of 0.5 fpm (0.00254 m/sec) to 10 fpm (0.0508 m/sec).

5. The membrane of claim 1 having a bubble point of 10 psi (68.9 KPa) to 60 psi (413.7 KPa).

6. The membrane of claim 1 having an IPA flux to pore size value ratio of 3 to 30 for a pore size of 1 micron or lower.

7. The membrane of claim 1 wherein the microfibrils have an average fiber diameter of 5 nm to 200 nm.

8. The porous polytetrafluoroethylene membrane of claim 1 , wherein the membrane has an IPA flux to pore size value ratio of 3 to 30 for a pore size of 1 micron or lower, and wherein the membrane has a thickness of 1 micron to 30 microns.

9. The porous polytetrafluoroethylene membrane of claim 1 , wherein the membrane has:
a thickness of 1 micron to 30 microns;
an air flow of 0.5 fpm (0.00254 m/sec) to 10 fpm (0.0508 m/sec);

a pore size value of 0.05 micron to 2 microns;
a bubble point of 10 psi (68.9 KPa) to 60 psi (413.7 KPa);

an IPA flux to pore size value ratio of 3 to 30 for a pore size of 1 micron or lower.

10. The porous polytetrafluoroethylene membrane of claim 1 , wherein the membrane has:
a thickness of 1 micron to 30 microns;
an air flow of 0.5 fpm (0.00254 m/sec) to 10 fpm (0.0508 m/sec);
a pore size value of 0.05 micron to 2 microns;
a bubble point of 10 psi (68.9 KPa) to 60 psi (413.7 KPa);

an air permeability to bubble point ratio of up to 0.05 (fpm/psi) (0.037 m/s/MPa); and
wherein as the membrane is made thinner, it increases in strength until it reaches a maximum and then decreases.

11. A fuel cell comprising the porous polytetrafluoroethylene membrane of claim 1 .

12. The membrane of claim 1 , wherein the membrane has a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 5% of the tensile peak stress in the cross direction.

13. A porous polytetrafluoroethylene membrane consisting of polytetrafluoroethylene, the porous polytetrafluoroethylene membrane being a nonwoven web having a microstructure of microfibrils fused at crossover points with less than 100 nodes per 100 μm 2 , the membrane having a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 10% of the tensile peak stress in the cross direction, and wherein the membrane has a thickness of 1 micrometer to 3.8 micrometers.

14. The membrane of claim 13 , wherein the membrane has a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 5% of the tensile peak stress in the cross direction.

15. A fuel cell comprising the membrane of claim 13 .

16. A porous polytetrafluoroethylene membrane consisting of polytetrafluoroethylene, the porous polytetrafluoroethylene membrane being a nonwoven web having a microstructure of microfibrils fused at crossover points with less than 100 nodes per 100 μm 2 , the membrane having a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 10% of the tensile peak stress in the cross direction, and wherein the membrane has a thickness of 7.8 micrometer to 10 micrometers.

17. The membrane of claim 16 , wherein the membrane has a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 5% of the tensile peak stress in the cross direction.

18. A fuel cell comprising the membrane of claim 16 .

19. A porous polytetrafluoroethylene membrane consisting of polytetrafluoroethylene, the porous polytetrafluoroethylene membrane being a nonwoven web having a microstructure of microfibrils fused at crossover points with less than 100 nodes per 100 μm 2 , the membrane having a tensile peak stress in a machine direction and a tensile peak stress in a cross direction, wherein the tensile peak stress in the machine direction is within 5% of the tensile peak stress in the cross direction.

20. A fuel cell comprising the membrane of claim 19 .

Assignees

• Donaldson Co Inc

Inventors

• Suthar Anil
• Brandimarte Richard
• Pannepacker Jr Robert J
• Rajgarhia Stuti S

Classifications

• B01D2325/0281

  Fibril, or microfibril structures · CPC title

• B01D2325/24

  Mechanical properties, e.g. strength · CPC title

• B01D2325/04

  Characteristic thickness · CPC title

• B01D2239/1291

  Other parameters · CPC title

• B01D2239/1233

  Fibre diameter · CPC title