Method for producing particles electrostatically

Patent metadata

Field	Value
Publication number	US-9273428-B2
Application number	US-91994309-A
Country	US
Kind code	B2
Filing date	Feb 26, 2009
Priority date	Feb 29, 2008
Publication date	Mar 1, 2016
Grant date	Mar 1, 2016

Abstract

The invention refers to a method for forming particles or droplets of at least one substance comprising the steps of providing a foamed medium, which foamed medium comprises said substance, and forming particles or droplets of said substance at least partly by electrostatic processing. The use of foamed medium in electrostatic processing enables higher production speeds and increases the evenness of a coating layer formed by electrospinning or electrospraying the particles or droplets on a substrate.

First claim

The invention claimed is:

1. A method for forming particles or droplets of at least one substance comprising the steps of;
i) providing a liquid or solid medium that comprises said substance,
ii) foaming said medium by dispersing gas into said medium in an amount of 50-99% by volume of the total medium,
iii) feeding foamed medium from step ii) to a feed section,
iv) forming particles or droplets of said substance by electrospinning or electrospraying said medium from the feed section, and
v) depositing the particles or droplets on a substrate or collector surface.

2. A method according to claim 1 , wherein the foamed medium in step ii) is provided by dispersing a gas in a liquid or in a solid whereby a dispersion of a gas in a liquid or a gas in a solid is formed, whereafter the at least one substance is incorporated into said dispersion.

3. A method according to claim 1 , wherein the gas is dispersed in the liquid or in the solid in an amount of 75-99% by volume of the total medium.

4. A method according to claim 1 , wherein said liquid is provided by dispersing and/or dissolving said substance in a solvent.

5. A method according to claim 1 , wherein said liquid is a melt of said substance.

6. A method according to claim 1 , wherein said gas is selected from the group consisting of air, carbon dioxide (CO 2 ), steam (H 2 O), nitrogen gas (N 2 ), hydrogen gas (H 2 ) and/or a mixture of any of the said gases.

7. A method according to claim 1 , wherein the particle formation in step iv) is carried out from a free surface of the foamed medium.

8. A method according claim 1 , wherein said substrate is paper or paperboard.

9. A method according to claim 1 , wherein the step iv) of forming particles or droplets of said substance by electrostatic processing is performed in the presence of an alternating current (AC) electric field.

10. A method according to claim 1 , wherein substantially all of said medium is foamed such that the whole medium is an elastic sponge-like composite having bubbles of substantially uniform size and distribution.

11. The method according to claim 1 wherein said medium includes at least one surface active agent and said substance comprises a polymer or blend of polymers and at least one solid particle additive.

12. The method according to claim 1 wherein the feed section comprises a smooth plate and discharge slot, wherein the foamed medium is allowed to move on the plate to the discharge slot.

13. The method according to claim 1 wherein the feed section comprises a variable width slit through which the foamed medium is fed.

14. The method according to claim 1 wherein the feed section comprises a plurality of nozzles.

15. A method for forming a paper or a paper board, comprising the steps of;
i. forming a web of paper or paper board,
ii. providing a liquid or solid medium comprising at least one substance,
iii. foaming said medium by dispersing gas into said medium in an amount of 50-99% by volume of the total medium,
iv. feeding foamed medium from step iii) to a feed section,
v. forming particles or droplets of said substance by electrospinning or electrospraying said medium from the feed section, and
vi. depositing said particles or droplets on said web of paper or paper board.

16. A method for producing a filter comprising a substrate layer and an electrospun fibrous layer, said method comprising the step of electrospinning fibers from a foamed medium from a feed section onto said substrate, wherein the foamed medium is formed by providing a liquid or solid medium comprising a substance, foaming said medium by dispersing a gas into said liquid or solid medium to an amount of 50-99% by volume of the total medium, and feeding the foamed medium to the feed section.

Assignees

• Backfolk Kaj
• Heiskanen Isto
• Harlin Ali
• Stora Enso Oyj

Inventors

• Backfolk Kaj
• Heiskanen Isto
• Harlin Ali

Classifications

• D01D5/0023

  the material being a polymer melt · CPC title

• D21C5/02 Primary

  Working-up waste paper (mechanical part D21B1/08, D21B1/32) · CPC title

• D01D5/0084

  Coating by electro-spinning, i.e. the electro-spun fibres are not removed from the collecting device but remain integral with it, e.g. coating of prostheses · CPC title

• D01D5/0092

  characterised by the electrical field, e.g. combined with a magnetic fields, using biased or alternating fields · CPC title

• B05D1/06

  Applying particulate materials · CPC title