Method for the manufacture of an electret fibrous filter
AssigneeMinnesota Mining and Manufacturing Company
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] film of the fiber material is continuously fed and stretched. At least one side of the stretched [web] film is homopolarly charged by a plurality of corona charging elements. The charged [web] film material is then fibrillated, collected and processed into a filter.
Claims48
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;
- and collecting the fiber material [;
- and processing the collected fiber material into a filter] to form 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;
- and collecting the fiber material [;
- and processing the collected fiber material into a filter] to form a filter .
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- heating said film stretching said film along the longitudinal axis thereof as defined by the path of movement of said film;
- homopolarly electrically charging at least one side of said film;
- fibrillating the charged film into fiber material;
- and
- collecting the fiber material to form a filter.
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- heating said film
- stretching said film;
- homopolarly electrically charging at least one side of said film;
- fibrillating the charged film into fiber material substantially in the longitudinal direction thereof as defined by the path of feeding of the film;
- and
- collecting the fiber material to form a filter.
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- heating said film;
- stretching said film;
- homopolarly electrically charging at least one side of said film;
- fibrillating the charged film into fiber material;
- and
- collecting the fiber material on a roller and simultaneously taking one or more layers lying on top of the other together from said roller to form a filter.
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- heating said film;
- stretching said film;
- homopolarly electrically charging at least one surface of said film using a corona device spaced from the surface of said film whereby the electric charge is sprayed onto the surface of said film;
- fibrillating the charged material into fiber material;
- and
- collecting the fiber material to form a filter.
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- stretching said film in two stages along the longitudinal axis thereof as defined by the path of movement of said film, and including the step of applying heat to both said two stages;
- homopolarly charging said film in said second stage;
- fibrillating the charged film into fiber material substantially along said longitudinal axis;
- and
- collecting the fiber material to form a filter.
A method for the manufacture of an electrically charged fibrous filter from a highly molecular non-polar material, comprising the steps of:
- continuously feeding a film of said material;
- stretching said film along the longitudinal axis thereof as defined by the path of movement of said film and including the step of applying heat to said film;
- homopolarly charging the stretched film on both surfaces thereof by spraying one surface with a charge of one polarity and spraying the other surface of said film with an equal charge of the opposite polarity;
- fibrillating the charged film into fiber material substantially along said longitudinal axis;
- and
- collecting the fiber material to form a filter.
Dependencies are inferred from the claim text.