Filter Medium, Process for Producing the Same, Method of Use Thereof, and Filter Unit

• US 20080307971A1
• Filed: 04/26/2006
• Published: 12/18/2008
• Est. Priority Date: 04/26/2005
• Status: Abandoned Application

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Mori, Masaaki, Horie, Yuri, Kawano, Eizo
• Application Number:
  US11/919,294
• Publication Number:
  US 20080307971A1
• Time in Patent Office: Days
• US Class Current: 95/287
• CPC Class Codes: B01D 2239/0478 on a layer of the filter
• CPC Class Codes: B01D 2239/0631 Electro-spun
• CPC Class Codes: B01D 2239/065 More than one layer present in the filtering material apparatus incorporating such gas filtering material B01D2275/10
• CPC Class Codes: B01D 2239/083 Binders between layers of the filter
• CPC Class Codes: B01D 2239/10 Filtering material manufacturing
• CPC Class Codes: B01D 2239/1233 Fibre diameter
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: D01D 5/0038 the fibre formed by solvent evaporation, i.e. dry electro-spinning
• CPC Class Codes: D01F 6/18 from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide
• CPC Class Codes: D04H 1/4282 Addition polymers
• CPC Class Codes: D04H 1/4326 Condensation or reaction polymers
• CPC Class Codes: D04H 1/43828 sheath-core
• CPC Class Codes: D04H 1/43838 Ultrafine fibres, e.g. microfibres
• CPC Class Codes: D04H 13/00 Other non-woven fabrics

Abstract

The present invention provides a filter medium reducing an increase in pressure drop while in use even in an environment where ultrafine particles form a large proportion of the particles to be collected. The filter medium includes a porous polytetrafluoroethylene (PTFE) membrane, an air-permeable supporting member and a web layer made of polymeric fibers formed by electrospinning (charge induction spinning, electrostatic spinning). The filter medium of the present invention may include an air-permeable adhesive layer adjacent to the web layer.

Claims

1. A filter medium comprising a porous polytetrafluoroethylene membrane, an air-permeable supporting member and a web layer made of polymeric fibers and formed by electrospinning.

2. The filter medium according to claim 1, wherein the polymeric fibers have an average fiber diameter in a range from 10 nm to 5 μ

m inclusive.

3. The filter medium according to claim 2, wherein the polymeric fibers have the average fiber diameter of no more than 1 μ

m.

4. The filter medium according to claim 2, wherein the polymeric fibers have the average fiber diameter of no less than 200 nm.

5. The filter medium according to claim 2, wherein the polymeric fibers have the average fiber diameter of no less than 400 nm.

6. The filter medium according to claim 1 further comprising an air-permeable adhesive layer,

wherein the air-permeable adhesive layer is disposed adjacent to the web layer.

7. A filter unit comprising the filter medium according to claim 1 and a supporting frame for supporting the filter medium.

8. A method of manufacturing the filter medium according to claim 1, comprising:

forming a web layer made of polymeric fibers by depositing the polymeric fibers by electrospinning on a principal surface of a laminate including a porous polytetrafluoroethylene membrane and an air-permeable supporting member.

9. The method of manufacturing the filter medium according to claim 8,

wherein the laminate includes an air-permeable adhesive layer disposed on the principal surface of the laminate, and

the web layer is formed on the air-permeable adhesive layer.

10. A method of using the filter medium according to claim 1, comprising:

disposing the web layer upstream relative to gas flow to be filtered from the porous polytetrafluoroethylene membrane.