EP-4741034-A1 - FILTRATION MEDIUM

EP4741034A1EP 4741034 A1EP4741034 A1EP 4741034A1EP-4741034-A1

Abstract

This invention relates to a filtration medium, more particularly, to a filtration medium comprising at leastone layer and a resin binder composition comprisinga lignin modified phenolic resin such as may be used for filtering fluids in automotive, industrial and domestic applications. It also relates to a filter element comprising the filter medium, a paper, methods of preparing the filter medium and element, and use of the filter medium or element.

Inventors

FRITZE, Urs Fabian
HÖRL, Werner

Assignees

Neenah Gessner GmbH

Dates

Publication Date: 20260513
Application Date: 20241108

Claims (15)

A filter medium comprising: at least one layer and a resin binder composition, wherein the resin binder composition comprises a lignin modified phenolic resin, wherein when the filter medium is subjected to the leaching test, it loses: 2.5% or less by mass relative to the total mass of the filter medium prior to the test; and/or 10% or less by mass relative to the total mass of the resin binder composition prior to the test.
The filter medium according to claim 1, a) wherein the at least one layer is fibrous and optionally comprises 10 to 100% by weight of natural fibers and 0 to 90% by weight of synthetic and/or inorganic fibers, based on the total weight of the fibers in the layer, optionally wherein the synthetic fibers are polyester fibers, and/or b) wherein the filter medium comprises 5 to 40% by weight of the resin binder composition, based on the total weight of the filter medium.
The filter medium according to any previous claim, wherein the at least one layer is a wet-laid layer.
The filter medium according to any previous claim, wherein the at least one layer has a full-life efficiency equal to or higher than 90.00%.
The filter medium according to any previous claim, wherein i) the amount of formaldehyde released is less than 0.1 g/kg; and/or ii) the bursting strength is 140-1000kPa; and/or iii) the bursting strength after 24h at 160°C is 130 - 1000 kPa; and/or iv) the air permeability is 3 - 800 L/(m 2 s); and/or v) the flame retardant classification of F1 is achieved with DIN53438 1984 both before and after the leaching test.
The filter medium of any previous claim, wherein the lignin modified phenolic resin is obtained by reacting together phenol, formaldehyde, and lignin.
The filter medium of claim 6, i) wherein the lignin has a density of 1.25 - 1.45 g/cm 3 ; and/or ii) wherein the lignin is present in the reaction in an amount of greaterthan 15% by mass based on the total mass of the phenol, formaldehyde, and lignin.
The filter medium of any previous claim, wherein the filter medium is obtained by contacting the at least one layer with the resin binder composition, optionally wherein: i) in the contacting step the resin binder composition comprises in addition to the lignin modified phenolic resin at least one of a solvent, a crosslinking agent, a polymer based on acrylic esters, and a flame retardant; and/or ii) a drying step is carried out after the contacting step; and/or iii) a curing step is carried out after the contacting step and/or the drying step.
The filter medium according to any previous claim, wherein the lignin modified phenolic resin i) has a viscosity at 20°C of 250 - 600 mPas; and/or ii) has a content of free formaldehyde of less than 0.1 mass% on the basis of the lignin modified phenolic resin; and/or iii) has a content of free phenol of less than 2 mass% on the basis of the lignin modified phenolic resin; and/or iv) has a B-transformation time at 130°C of 3 - 8 minutes; and/or v) has a weight average molecular weight of 500 - 5000 g/mol; and/or vi) has a number average molecular weight of 150 - 350 g/mol; and/or vii) has a molecular weight distribution of 5 - 12.
A filter element comprising the filter medium according to any of the previous claims.
A paper comprising a resin binder composition, wherein the resin binder composition comprises a lignin modified phenolic resin, and wherein when the paper is subjected to the leaching test, it loses: 2.5% or less by mass relative to the total mass of the paper prior to the test; and/or 10% or less by mass relative to the total mass of the resin binder composition prior to the test.
A method of preparing a filter medium according to any of claims 1-9, comprising the steps of i) contacting the at least one layer with the resin binder composition comprising the lignin modified phenolic resin; and ii) optionally drying the contacted layer; and/or iii) optionally curing the contacted layer.
The method of preparing a filter medium according to claim 12, further comprising the step of reacting together phenol, formaldehyde, and lignin to obtain the lignin modified phenolic resin.
A method of preparing a filter element according to claim 10, comprising introducing the filter medium according to any of claims 1-9 into a filter unit.
Use of the filter medium or filter element according to any of claims 1 - 10 for air filtration.

Description

FIELD OF THE INVENTION This invention relates to a filtration medium, more particularly, to a filtration medium comprising at least one layer and a resin binder composition comprising a lignin modified phenolic resin such as may be used for filtering fluids in automotive, industrial and domestic applications. It also relates to a filter element comprising the filter medium, a paper, methods of preparing the filter medium and element, and use of the filter medium or element. BACKGROUND TO THE INVENTION Improving the sustainability of products is one of the key challenges of our time. Many products are currently made using components derived from petroleum. Partly replacing such components with those derived from renewable sources is one way among many of improving the sustainability of the product. However, partly replacing existing products using components derived from renewable sources is a significant challenge. This is because existing products are normally highly optimized based on the components derived from petroleum - making it difficult to produce a new product using renewable sources yet achieving the same balance of properties. Filter media are used in automotive, industrial and domestic applications to remove undesirable materials (i.e. particles) from a liquid or gas by passing the liquid or gas through the filter media. Due to the increasing pollution of the ambient air with fine dust and soot, the requirements for the degree of separation of filter materials and filter elements made from them are constantly increasing, e.g. in the fields of ventilation and air conditioning technology for buildings and vehicle interiors or for the air supply of internal combustion engines. These filter media, especially in the automotive sector, must be stable against the corresponding environment, such as air, water, fuels, or oils. For this purpose, layers are impregnated with binders. Before employment of the filter media, a chemical cross linking of the binder is usually carried out. Efforts have also been made to make filters having improved sustainability (see WO2022008614A1). However, for the reasons laid out above, it is a significant challenge to replace the existing filters with increased components derived from renewable sources without sacrificing the filter properties. Accordingly, there remains a need for a filter medium with improved sustainability that can be used in the field of fluid filtration, and more specifically in the field of air filtration. TECHNICAL PROBLEM Therefore, it is an objective of the present invention to provide a filter medium with improved sustainability that can be used in the field of fluid filtration, and more specifically in the field of air filtration. It is also an objective to provide a filter element comprising the filter medium, or a paper. An objective is also to provide methods of preparing the filter medium and element, and use of the filter medium or element. SUMMARY OF THE INVENTION The present invention solves the above problems by providing a filter medium comprising: at least one layer and a resin binder composition, wherein the resin binder composition comprises a lignin modified phenolic resin, wherein when the filter medium is subjected to the leaching test, it loses: 2.5% or less by mass relative to the total mass of the filter medium prior to the test; and/or 10% or less by mass relative to the total mass of the resin binder composition prior to the test. The use of the lignin modified phenolic resin means that the filter medium has improved sustainability, and excellent properties in the field of fluid filtration, and more specifically in the field of air filtration. These properties are comparable to those of existing filter media with lower sustainability. The present invention also relates to a filter element comprising the filter medium, or a paper, as well as methods of preparing the filter medium and element, and use of the filter medium or element. The present invention encompasses the following embodiments. 1. A filter medium comprising: at least one layer and a resin binder composition,wherein the resin binder composition comprises a lignin modified phenolic resin,wherein when the filter medium is subjected to the leaching test, it loses: 2.5% or less by mass relative to the total mass of the filter medium prior to the test; and/or10% or less by mass relative to the total mass of the resin binder composition prior to the test.2. The filter medium according to embodiment 1, a) wherein the at least one layer is fibrous and optionally comprises 10 to 100% by weight of natural fibers and 0 to 90% by weight of synthetic and/or inorganic fibers, based on the total weight of the fibers in the layer, optionally wherein the synthetic fibers are polyester fibers, and/orb) wherein the filter medium comprises 5 to 40% by weight of the resin binder composition, based on the total weight of the filter medium.3. The filter medium according to any previous