Liquid filtration media
AssigneeE. I. Du Pont de Nemours and Company
InventorsGuanghui Chen, Henricus Jacobus Cornelis Gommeren, Lawrence Mark Knorr
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Abstract
A liquid filter with a composite medium that has a nanoweb adjacent to and optionally bonded to a microporous membrane. The membrane is characterized by an LRV value of 3.7 at a rated particle size, and the nanoweb has a fractional filtration efficiency of greater than 0.1 at the rated particle size of the membrane. The nanoweb also has a thickness efficiency ratio of greater than 0.0002 at that efficiency. The nanoweb acts to provide depth filtration to the membrane, prefilters particles and extends the lifetime of the membrane.
Claims27
A filter system for filtering particles from liquid comprising at least one nanoweb layer of polymeric nanofibers upstream of, and in fluid contact with, a microfiltration membrane, wherein the nanoweb layer has a filtration efficiency rating of at least 10% to 30% for a particle size at which the membrane is rated with an LRV of 3.7 or greater, and a thickness efficiency ratio of greater than about 0.0002, and wherein the pressure drop across the nanoweb is less than or equal to 60% of that across the filter system for a given fluid flow rate.
A filter system for filtering particles from liquid comprising at least one nanoweb layer of polymeric nanofibers upstream of, and in fluid contact with, a microfiltration membrane, wherein the nanoweb layer has;
- a mean flow pore size of less than or about five times that of the membrane,
- a bubble point pore size of less than or about 7.5 times than that of the membrane, and
- a thickness less than or equal to about twice the thickness of the membrane wherein the nanoweb layer has a filtration efficiency rating of 10%-30%.
A method for filtering particles from a liquid comprising the steps of passing the liquid through a nanoweb layer, followed by a membrane layer in fluid contact with the nanoweb layer, in which the nanoweb layer has a filtration efficiency rating of at least 10% for a particle size at which the membrane is rated with an LRV of 3.7 or greater, and a thickness efficiency ratio of greater than about 0.0002, and wherein the pressure drop across the nanoweb is less than or equal to 60% of that across the composite liquid filtration medium for a given fluid flow rate, and the nanoweb layer is positioned upstream of the microfiltration membrane wherein the nanoweb layer has a filtration efficiency rating of 10%-30%.
A method for filtering particles from a liquid comprising the steps of passing the liquid through a nanoweb layer, followed by a membrane layer, wherein the nanoweb layer has;
- a mean flow pore size of less than or about fives times that of the membrane,
- a bubble point pore size of less than or about 7.5 times than that of the membrane, and
- a thickness less than or equal to about twice the thickness of the membrane, and the nanoweb layer is positioned upstream of the microfiltration membrane wherein the nanoweb layer has a filtration efficiency rating of 10%-30%.
Dependencies are inferred from the claim text.