Method for the manufacture of an electret fibrous filter
AssigneeVerto Inc.
InventorJan van Turnhout
Life of this patent
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Abstract
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar fiber material wherein a web of the fiber material is continuously fed and stretched. At least one side of the stretched web is homopolarly charged by a plurality of corona charging elements. The charged web material is then fibrillated, collected and processed into a filter.
Claims9
A method for the manufacture of an electrically charged fibrous filter from a high molecular non-polar material, comprising the steps of:
- continuously feeding a film of high molecular isotactic polypropylene material at a rate of 12.2 meters per minute;
- stretching said film in two stages, said first stage of stretching stretches said film at a ratio of 1 :
- 6 at a temperature of approximately 110.degree. C., said second stage of stretching stretches said film at a ratio of 1 :
- 1.5 at a temperature of substantially 130.degree. C.;
- homopolarly charging at least one side of the stretched film with a plurality of corona charging elements, said plurality of corona discharge elements being connected to minus 10 KV, said step of charging including the use of a metal plate connected to an opposite polarity voltage source and a grid whereby said charging corona elements are between said metal plate and said film, said metal plate being connected to a voltage of plus 3 KV, said grid being connected to a voltage of minus 2.3 KV, said corona charging elements being spaced substantially 5 mm from the means for supporting said film during said second stage of stretching;
- fibrillating the charged film into fiber material;
- collecting the fiber material;
- and
- processing the collected fiber material into a filter.
A method for the manufacture of an electrically charged fibrous filter from a high molecular non-polar material, comprising the steps of:
- continuously feeding a film of high molecular isotactic polypropylene material at a rate of 12.2 meters per minute;
- stretching said film in two stages, said first stage of stretching stretches said film at a ratio of 1 :
- 6 at a temperature of approximately 110.degree. C., said second stage of stretching stretches said film at a ratio of 1 :
- 1.5 at a temperature of substantially 130.degree. C;
- homopolarly charging at least one side of the stretched film with a plurality of corona charging elements, said plurality of corona discharge elements being connected to minus 3.2 KV, said step of charging including the use of a metal plate connected to an opposite polarity voltage source whereby said charging corona elements are between said metal plate and said film and said metal plate being connected to a voltage of plus 3 KV, said corona charging elements being spaced substantially 5 mm from the means for supporting said film during said second stage of stretching;
- fibrillating the charged film into fiber material;
- collecting the fiber material;
- and
- processing the collected fiber material into a filter.
Dependencies are inferred from the claim text.