Filter medium and structure

• US 20070039300A1
• Filed: 11/01/2006
• Published: 02/22/2007
• Est. Priority Date: 11/05/2004
• Status: Active Grant

• Current Assignee: Donaldson Company Incorporated
• Original Assignee: Donaldson Company Incorporated
• Inventors: Dema, Keh, Olson, Linda, Kahlbaugh, Brad
• Granted Patent: US 7,309,372 B2
• Time in Patent Office: Days
• US Class Current: 55/527
• CPC Class Codes: B01D 2275/10 Multiple layers
• CPC Class Codes: B01D 39/2024 otherwise bonded, e.g. by resins
• CPC Class Codes: B01D 39/2089 otherwise bonded, e.g. by resins
• CPC Class Codes: B01D 46/10 Particle separators, e.g. dust precipitators, using filter plates, sheets or pads having plane surfaces
• CPC Class Codes: B01D 46/2411 Filter cartridges
• CPC Class Codes: B01D 46/521 using folded, pleated material
• CPC Class Codes: B01D 46/71 with pressurised gas, e.g. pulsed air

Abstract

Thermoplastic bicomponent binder fiber can be combined with other media, fibers and other filtration components to form a thermally bonded filtration media. The filtration media can be used in filter units. Such filter units can be placed in the stream of a mobile fluid and can remove a particulate load from the mobile stream. The unique combination of media fiber, bicomponent binder fiber and other filtration additives and components provide a filtration media having unique properties in filtration applications.

Claims

1. A filtration medium comprising a thermally bonded sheet comprising:

(a) about 10 to 90% of a thermoplastic binder fiber having a fiber diameter of 5 to 50 micrometers and a fiber length of about 0.1 to 5 centimeters; and

(b) about 10 to 90 wt % of a media fiber having a diameter about 1 to 50 micrometers and an aspect ratio of about 10 to 10,000;

wherein the media has a thickness of about 0.1 to 2 millimeters, a solidity of about 2 to 25%, a basis weight of about 2 to 200 g-m<sup>−

2</sup>, a pore size of about 0.2 to 100 micrometers and a permeability of about 2 to 200 ft-min−

1.

2. The medium of claim 1 wherein the binder fiber of the sheet additionally comprises a bicomponent binder fiber.

3. The medium of claim 1 wherein the binder fiber of the sheet comprises a homopolymer thermoplastic binder fiber.

5. The medium of claim 1 wherein the media comprises about 50 to 80 wt % of a glass fiber.

6. The medium of claim 5 wherein the glass fiber is selected from a fiber having an average fiber diameter of about 0.1 to 1 micrometer, a fiber having a fiber diameter of about 0.3 to 2 micrometers;

a fiber having a diameter of about 0.5 to 5 micrometers, a fiber having a diameter of about 0.75 to 7 micrometers, a fiber having a diameter of about 1 to 10 micrometers, a fiber having a diameter of about 10 to 50 micrometers and any combinations of such fibers thereof.

7. The medium of claim 6 wherein the glass fiber comprises two of the fibers.

8. The medium of claim 1 wherein the thermoplastic binder fiber comprises a thermoplastic polyester fiber.

9. The medium of claim 8 wherein the thermoplastic polyester fiber is selected from a fiber having an average fiber diameter of about 7 micrometers, a fiber having an average fiber diameter of about 10 to 15 micrometers, a fiber having an average fiber diameter of about 15 to 18 micrometers, a fiber having an average fiber diameter of about 19 to 25 micrometers and any combination thereof.

10. The medium of claim 9 wherein the polyester fiber is a combination of two of the fibers.

11. The medium of claim 1 wherein the filtration medium comprises:

(a) about 10 to 90 wt % of a thermoplastic polyester binder fiber having a fiber length of about 0.1 to 15 centimeters; and

(b) about 10 to 90 wt % of a glass media fiber having a fiber diameter of about 0.1 to 50 micrometers and an aspect ratio of about 10 to 10,000.

13. The medium of claim 1 wherein the thermally bonded sheet additionally comprises about 0.1 to 35 wt % of a binder resin.

14. The medium of claim 1 wherein the medium comprises two or more layers of the thermally bonded sheet.

15. The medium of claim 1 wherein the medium comprises about 0.01 to 10 wt % of a surface tension modifying composition.

16. The medium of claim 15 wherein the surface tension modifying composition is a fluoro-organic surfactant.

17. A method of filtering a gaseous stream, the method comprising the steps of:

(a) passing a stream through a filter unit, the filter unit comprising a thermally bonded sheet of claim 1;

and

(b) retaining any particulate entrained in the stream within the filter.

4. The medium of claim 4 wherein the media comprises about 20 to 80 wt % of a secondary fiber.

12. The medium of claim 12 wherein the glass fiber is selected from a fiber having an average fiber diameter of about 0.01 micrometer, a fiber having an average fiber diameter of about 0.3 to 2 micrometers, a fiber having a fiber diameter of about 0.5 to 5 micrometers, a fiber having a fiber diameter of about 0.75 to 7 micrometers, a fiber having a fiber diameter of about 1 to 10 micrometers, a fiber having a fiber diameter of about 10 to 50 micrometers and combinations thereof;

and wherein the polyester fiber is selected from a fiber having an average fiber diameter of less than about 7 micrometers, a fiber diameter of about 10 to 15 micrometers, a fiber having a fiber diameter of about 15 to 18 micrometers, a fiber having a fiber diameter of about 19 to 25 micrometers and any combination thereof.