Method for producing a filter medium, and a filter medium

Patent metadata

Field	Value
Publication number	US-11241645-B2
Application number	US-202016878058-A
Country	US
Kind code	B2
Filing date	May 19, 2020
Priority date	Aug 19, 2015
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

In a method for producing a filter medium, at least one substrate layer of a nonwoven comprising cellulose fibers and/or synthetic polymer fibers is provided and a fiber layer of polymer fibers is deposited on the at least one substrate layer. Prior to depositing the fiber layer, a solvent is applied to the at least one substrate layer, wherein a material of the substrate layer and/or a material of the fiber layer is soluble in the solvent. A filter medium produced by the method has material-fused connections at crossing points of the polymer fibers and/or cellulose fibers of the substrate layer with the polymer fibers of the fiber layer.

First claim

What is claimed is:

1. A filter medium comprising:
at least one substrate layer of nonwoven substrate fibers comprising polymer fibers and/or cellulose fibers;
a nanofiber layer of electrospun polymer nanofibers, electrospun directly onto the substrate fibers of the at least one substrate layer, wherein at least 90% of the electrospun polymer nanofibers in the nanofiber layer are nanofibers having a fiber diameter of less than 500 nm;
wherein because the nanofiber layer is electrospun, the electrospun polymer nanofibers of the nanofiber layer have diameters that vary only minimally, varying less than with electroblown fibers;
wherein individual electrospun polymer nanofibers of the nanofiber layer have first crossing points defined as where individual electrospun polymer nanofibers cross over and contact each other;
wherein respective individual electrospun polymer nanofibers of the nanofiber layer have substrate crossing points where individual electrospun polymer nanofibers cross over and contact the nonwoven substrate fibers;
wherein at the substrate crossing points, the respective individual electrospun polymer nanofibers form first material-fused connections to the nonwoven substrate fibers, the first material-fused connections formed by a solvent which is applied onto the at least one substrate layer before the electrospun polymer nanofibers are applied;
wherein a material of the at least one substrate layer and/or a material of the nanofiber layer of electrospun polymer nanofibers is soluble in the solvent to form the first material-fused connections without binding agents or thermal fusing;
wherein the first material-fused connections are formed at first crossing points of respective individual electrospun polymer nanofibers as flat fused areas of partially dissolved and/or dissolved electrospun polymer nanofibers and nonwoven substrate fibers formed within a crossing area of the respective first crossing points;
wherein at first crossing points which do not coincide with substrate crossing points, the individual electrospun polymer nanofibers form second material-fused connections, the second material-fused connections formed of partially dissolved electrospun polymer nanofibers, such that an original unfused fiber contour of the electrospun polymer nanofibers is recognizable after fusing at the second material-fused connections;
wherein the second material-fused connections are formed by the solvent alone, without binding agents or thermal fusing.

2. The filter medium according to claim 1 , wherein
the filter medium does not have flat fused areas at the second material-fused connections.

3. The filter medium according to claim 1 , wherein
the flat fused areas are closed flat structures; and
wherein in an area of each closed flat structure, a fiber contour of the respective electrospun polymer nanofibers is not recognizable.

4. The filter medium according to claim 1 , wherein
fewer than 80% of the first crossing points have the respective flat fused areas of the partially dissolved and/or dissolved electrospun polymer nanofibers and substrate fibers.

5. The filter medium according to claim 1 , wherein
fewer than 60% of the first crossing points have the respective flat fused areas of the partially dissolved and/or dissolved electrospun polymer nanofibers and substrate fibers.

6. The filter medium according to claim 1 , wherein an average fiber diameter of the electrospun polymer nanofibers is less than 200 nm.

7. The filter medium according to claim 1 , wherein the solvent is an acid or a base.

8. The filter medium according to claim 7 , wherein the acid is a diluted acid or a concentrated acid.

9. The filter medium according to claim 7 , wherein the base is a diluted base or a concentrated base.

10. The filter medium according to claim 7 , wherein the solvent comprises a plastic compound.

Assignees

• Mann & Hummel Gmbh

Inventors

• Neumann Jens
• Kreiner Anton
• Weindl Markus
• Zisslsberger Christian

Classifications

• B01D2239/0681

  The layers being joined by gluing · CPC title

• B32B7/12

  using interposed adhesives or interposed materials with bonding properties · CPC title

• B29C65/4895

  Solvent bonding, i.e. the surfaces of the parts to be joined being treated with solvents, swelling or softening agents, without adhesives · CPC title

• B01D2239/0654

  Support layers · CPC title

• B01D2239/025

  comprising nanofibres · CPC title