Search

US-20260124566-A1 - PULSE FILTER

US20260124566A1US 20260124566 A1US20260124566 A1US 20260124566A1US-20260124566-A1

Abstract

Filter media, filter arrangements and filters, such as air filters and pulse filters, are provided. A filter medium comprises a base web of cellulose fibers. The base web comprises a first and a second layer of cellulose fibers and a transition region between the first and the second layers. The cellulose fibers of the first layer and the cellulose fibers of the second layer are intertwined in the transition region. The the base web has a specific volume of from 4 m 3 /g to 9 m 3 /g. The first layer may comprise more cellulose fibers, expressed as mass of cellulose fibers per unit area, than the second layer.

Inventors

  • Armin Niederhuber
  • Anja Kampe

Assignees

  • NEENAH GESSNER GMBH

Dates

Publication Date
20260507
Application Date
20251105
Priority Date
20241107

Claims (20)

  1. 1 . A filter medium comprising a base web of cellulose fibers, wherein the base web comprises a first layer of cellulose fibers and a second layer of cellulose fibers and a transition region between the first and the second layers, wherein the cellulose fibers of the first layer and the cellulose fibers of the second layer are intertwined in the transition region, wherein the base web has a specific volume from about 4 m 3 /g to about 9 m 3 /g.
  2. 2 . The filter medium of claim 1 , wherein the first layer comprises more cellulose fibers, expressed as mass of cellulose fibers per unit area, than the second layer.
  3. 3 . The filter medium of claim 1 , wherein the base web of cellulose fibers is a two-layered base web consisting of the first and the second layer of cellulose fibers with the transition region between them.
  4. 4 . The filter medium of claim 1 , wherein the base web comprises an air permeability from about 400 to about 800 l/m 2 s.
  5. 5 . The filter medium of claim 1 , wherein the base web has a thickness thereof from about 150 μm to about 300 μm.
  6. 6 . The filter medium of claim 1 , wherein the base web has a basis weight from about 25 to about 55 g/m 2 .
  7. 7 . The filter medium of claim 1 , wherein the base web has a tensile strength ratio MD/CD thereof is from about 2 to about 3.2.
  8. 8 . The filter medium of claim 1 , wherein the base web has a maximum pore size from about 90 μm to about 130 μm.
  9. 9 . The filter medium of claim 1 , wherein the second layer contains curled fibers, in an amount of 15 wt.-% to 40 wt.-%, in terms of the weight of the cellulose fibers of the second layer.
  10. 10 . The filter medium of claim 1 , wherein the second layer comprises uncurled fibers, in an amount of 60 to 85 wt.-%, in terms of weight of the cellulose fibers of the second layer.
  11. 11 . The filter medium of claim 1 , wherein the base web contains about 15 to 40 wt.-% of curled fibers, in terms of the weight of the cellulose fibers of the base web in total.
  12. 12 . The filter medium of claim 1 , wherein the cellulose fibers of the second layer are softwood fibers.
  13. 13 . The filter medium of claim 1 , wherein the base web is a non-impregnated base web of cellulose fibers.
  14. 14 . A filter comprising the filter medium of claim 1 .
  15. 15 . The filter of claim 14 , wherein the filter is a pulse filter.
  16. 16 . A filter arrangement comprising: a first filter a base web of cellulose fibers, wherein the base web comprises a first layer of cellulose fibers and a second layer of cellulose fibers and a transition region between the first and the second layers, wherein the cellulose fibers of the first layer and the cellulose fibers of the second layer are intertwined in the transition region, wherein the base web has a specific volume from about 4 m 3 /g to about 9 m 3 /g and; a second filter.
  17. 17 . The filter arrangement of claim 16 , wherein the second filter comprises a glass filter.
  18. 18 . The filter arrangement of claim 16 , wherein the second filter comprises a paper filter.
  19. 19 . The filter arrangement of claim 16 , wherein the second filter comprises a meltblown filter.
  20. 20 . The filter arrangement of claim 15 , further comprising at least one nonwoven filter layer arranged upstream of the first filter or downstream of the second filter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of European Patent Application No. EP24211515.2, filed Nov. 7, 2024, the complete disclosure of which is incorporated herein by reference for all purposes. BACKGROUND This description generally pertains to the field of filtration. More specifically, it relates to cleanable filter media for air filters, pulse filters and the like. There is an increasing demand for filter materials that are environmentally friendly and biodegradable, while simultaneously maintaining high filtration performance and efficiency. Prior art discloses filter materials based on cellulose fibers, such as the air and gas filter described in US 2012/167771 A1, as well as water-disintegrable cellulose acetate fiber tow filters disclosed in JP-H09103280 A. CN 102691234 A describes a multi-layer paper filter material, primarily intended for cigarettes, with an emphasis on environmental protection. However, the filter materials disclosed in US 2012/167771 A1, JP-H09103280 A, and CN 102691234 A are single-use and are not intended to be cleanable or reusable. Methods for producing multilayer paper-based filter materials have been disclosed, including US 2010/000693 A1, which describes the formation of multilayer paper using cellulose fibers, and EP 3540119 A1, which teaches production of multilayer-ply webs with variable pulp compositions using specialized fiber web machinery. Multi-phase filter media based on hardwood and softwood fibers are disclosed in US 2010/116138 A1, which employs rotoformers in the examples. Similarly, U.S. Pat. No. 6,464,830 B1 describes the formation of multilayer paper webs using hard and softwood fibers. However, none of these references address the need for cleanable filter materials capable of repeated use. Some filter materials are designed as cleanable or reusable filters due to their structural characteristics. For example, in surface filtration, the first filtration layer in the flow direction comprises smaller pores, while subsequent layers contain progressively larger pores. This arrangement ensures that the majority of particles, regardless of size, are captured at the outermost layer, forming a filter cake. The filter cake can be removed through cleaning steps such as tapping, shaking, washing, pressure shock, or backwashing, allowing the filter to be reused for multiple cycles, also known as pulse cycles. The lifetime of a cleanable filter is determined by the number of cycles it can endure without excessive pressure drop or incomplete particle removal, which are critical performance characteristics in practical applications. WO 2013/029697 A2 discloses a multilayer cleanable filter material, including surface filter elements for separating solid impurities in gases and liquids. To improve fine particle separation, the filter material includes an upstream melt-blown layer formed from thermoplastic material. While effective, the use of multiple layers of different materials, including melt-blown thermoplastics, presents environmental concerns and leaves room for improvement in terms of sustainability and end-of-life degradation. Accordingly, there remains a need for a cleanable filter medium that is environmentally friendly, provides excellent general filtering properties such as air permeability and dust capture, and maintains a long operational lifetime during repeated cleaning or pulse cycles. SUMMARY This following is intended merely to introduce a simplified summary of some aspects of one or more embodiments of the subject matter discussed herein. Further areas of applicability of the subject matter will become apparent from the detailed description provided hereinafter. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the subject matter. Rather, its purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description below. Filter media, filter arrangements and filters, such as air filters and pulse filters, are provided. In one aspect, a filter medium comprises a base web of cellulose fibers. The base web comprises a first and a second layer of cellulose fibers and a transition region between the first and the second layers. The cellulose fibers of the first layer and the cellulose fibers of the second layer are intertwined in the transition region. The base web has a specific volume of from 4 m3/g to 9 m3/g. In embodiments, the first layer may comprise more cellulose fibers, expressed as mass of cellulose fibers per unit area, than the second layer. In embodiments, the base web of cellulose fibers is a two-layered base web consisting of the first and the second layer of cellulose fibers with the transition region between them. In embodiments, the base web comprises an air permeability from about 400 to about 800 l/m2s. In embodiments, the base web has a thickness thereof from