Composition having PTFE as main component, mixed powder, material for molding, filtering medium for filter, air filter unit, and a method for manufacturing a porous membrane

Patent metadata

Field	Value
Publication number	US-9707504-B2
Application number	US-201314394946-A
Country	US
Kind code	B2
Filing date	Apr 19, 2013
Priority date	Apr 20, 2012
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A composition, a mixed powder and a material for molding have polytetrafluoroethylene as a main component. Each includes polytetrafluoroethylene that can be fibrillated, a non-hot melt processable component that is not fibrillated, and a hot melt processable component with a melting point of lower than 320° C. that is not fibrillated. The hot melt processable component is contained at equal to or more than 0.1% by weight but less than 20% by weight of a total weight. A filtering medium for an air filter includes a porous membrane made of these components, and an air permeable support. The porous membrane is manufactured, by mixing these components, extruding the mixture, rolling and drawing.

First claim

What is claimed is:

1. A filtering medium for an air filter, the filtering medium comprising:
one or more porous membranes, each porous membrane including polytetrafluoroethylene that can be fibrillated,
a non-hot melt processable component that is not fibrillated, and
a hot melt processable component with a melting point lower than 320° C. that is not fibrillated; and

at least one air permeable support supporting the one or more porous membranes and arranged at least as an outermost layer,
a pressure loss is less than 200 Pa when air is passed through the filtering medium at a flow rate of 5.3 cm/sec,
a PF value is 17 or higher when air containing NaCl particles with a particle diameter of 0.3 μm is passed through the filtering medium at a flow rate of 5.3 cm/sec,
a dust holding capacity of polyalphaolefin particles is 20 g/m 2 or more when air containing polyalphaolefin particles with a count median diameter of 0.25 μm is continuously passed through the filtering medium at a flow rate of 5.3 cm/sec and the pressure loss is increased to 250 Pa,
a membrane thickness of one porous membrane is 30 μm or more, and
the PF value=−log [(Transmittance (%)/100]/Pressure loss (Pa)×1000, with Transmittance=100−Collection efficiency (%).

2. The filtering medium for an air filter according to claim 1 , wherein
collection efficiency of the NaCl particles is 99.97% or more when air including the NaCl particles with a particle diameter of 0.3 μm is passed through the filtering medium at a flow rate of 5.3 cm/second.

3. The filtering medium for an air filter according to claim 1 , wherein
a coefficient of variation obtained by dividing standard deviation of pressure loss distribution by an average value of pressure loss distribution is 5% or less.

4. The filtering medium for an air filter according to claim 1 , wherein
the non-hot melt processable component is low molecular weight polytetrafluoroethylene, a thermosetting resin, or an inorganic filler.

5. The filtering medium for an air filter according to claim 1 , wherein
the hot melt processable component is a fluororesin.

6. The filtering medium for an air filter according to claim 5 , wherein
the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a mixture thereof.

7. The filtering medium for an air filter according to claim 1 , wherein
the filtering medium has a plurality of porous membranes.

8. The filtering medium for an air filter according to claim 7 , wherein
the at least one the air permeable support includes a plurality of air permeable supports, with one of the air permeable supports inserted between two adjacent porous membranes.

9. The filtering medium for an air filter according to claim 1 , wherein
the air permeable support is a non-woven fabric.

10. The filtering medium for an air filter according to claim 9 , wherein
a fiber forming the non-woven fabric is a composite synthetic fiber with a sheath-core structure in which a core component has a higher melting point than a sheath component.

11. An air filter unit including the filtering medium for an air filter according to claim 1 , the air filter unit further comprising:
a frame body holding the filtering medium.

12. A method of manufacturing a porous membrane usable as a filtering medium for a filter to capture fine particles in fluid, the method comprising
mixing
an aqueous dispersion of a hot melt processable component with a melting point lower than 320° C. that is not fibrillated, an aqueous dispersion of polytetrafluoroethylene that can be fibrillated, and
an aqueous dispersion of a non-hot melt processable component that is not fibrillated such that the non-hot melt processable component is contained at equal to or more than 0.1% by weight but less than 20% by weight of a total weight of the total components which form the porous membrane, and performing co-coagulation;

paste-extruding a material obtained from the mixing into a sheet shape extrudate by using a T die;
rolling the extrudate obtained from the extruding into a rolled sheet; and
obtaining a monoaxially drawn product by
drawing the rolled sheet obtained from the rolling 4 or more times but less than 10 times in a length direction of the rolled sheet, at a temperature which is equal to or higher than a melting temperature of the hot melt processable component but equal to or lower than a decomposition temperature of each component forming the porous membrane, to obtain a first resultant product, and
subsequently drawing the first resultant product more than 10 times but less than 25 times in a width direction perpendicular to a length direction of the monoaxially drawn product so that a second resultant product is obtained that is drawn 40 times or more but less than 150 times in elongation area ratio.

Assignees

• Daikin Ind Ltd

Inventors

• Chaen Shinichi
• Kiyotani Hideyuki
• Inui Kunihiko
• Yamanaka Taku
• Bao Li
• Shibuya Yoshiyuki
• Yamamoto Seigo
• Kobayashi Makoto
• Kasai Shunji
• Niinuma Hitoshi

Classifications

• B01D46/543 Primary

  using membranes · CPC title

• B32B27/322

  comprising halogenated polyolefins, e.g. PTFE · CPC title

• C08L83/04

  Polysiloxanes · CPC title

• B01D71/36 Primary

  Polytetrafluoroethylene · CPC title

• B29K2105/0005

  containing compounding ingredients (releasing, lubricating or separating agents B29C33/56, fibers B29K2105/08, B29K2105/12; fillers B29K2105/16, recycled material B29K2105/26) · CPC title