GB2078807A - Filtering Medium - Google Patents

Abstract

The filtering medium is based on synthetic or mineral fibres, such as glass fibres. The fibres form a mat in which they are arranged flat, in several thicknesses, and held by a binder such as a silicone resin. The filter is useful for the filtration of any fluids, and especially water and hydrocarbons, in order to remove the solid or liquid impurities therefrom. It can be produced by dispersing the fibres homogeneously in a solution and sedimenting them, the sedimented layer being subsequently calendered, dried, and impregnated

Description

SPECIFICATION Filtering Medium The invention relates to a fibre-based filtering medium and a process for its preparation.

The filtering medium of the invention is intended, in particular, for the filtration of fluids in temperature ranges which can reach 1 800C, in particular for the filtration of water and hydrocarbons, in order to remove the solid or liquid impurities therefrom (in this case by promoting coalescence phenomena).

The object of the invention is to obtain a filtering medium which can be used in a plane or curved configuration and in which the fibres ensure filtration without creating, between the inlet and the outlet of the medium passages which are capable of letting through the impurities to be filtered off.

The filtering medium of the invention is characterised in that the fibres form a mat in which they are arranged flat and held by a binder.

The flat arrangement permits permanent compression of the filtering medium. The desired density is achieved by squeezing the filtering medium to a greater or lesser extent.

In the prior art, the fibres were held by being entangled with one another in all directions in space, this being the case, for example, when fibres are obtained by spraying a solution of a fibre-generating substance (German Application 1,920,769).

The fibres of the mat preferably form superposed identical layers bound by the same binder as that which binds the fibres in each layer, each layer comprising one or more thicknesses of fibres.

In principle, the fibres are the same throughout the whole thickness of the filtering medium.

According to the invention, a process for preparing a filtering medium of this type comprises dispersing and sedimenting the fibres, in a homogeneous manner, in a solution which is capable of wetting the fibres and which is less dense than the fibres.

The product obtained, preferably after calendering and drying, is immersed in a solution of resin. The filtering medium is obtained after polymerisation of the resin.

The synthetic or mineral fibres are, for example, polyethylene, polyamide, polyester, polyacrylontrile, glass or carbon fibres. The binder is preferably a thermosetting resin, especially a polymerisable resin, for example an epoxy resin, a polyester resin or a polyamide-based resin. These examples do not imply a limitation.

In a typical example, the fibres are glass fibres having a thickness of a few tens of microns, for example of the order of 40 microns, and the resin is a silicone resin. The mat is obtained, for example, by dispersing and sedimenting the glass fibres in a chlorinated solvent. In a variant, the fibres are polyethylene fibres and the preparation medium is heptane.

The majority of the fibres preferably have a length of less than 5 mm.

Preferably, the resin, which coats the fibres to a greater or lesser extent, forms, on the mat, a film having an average thickness of less than two microns.

Preferably, the mat has a thickness of 1 to 3 mm.

It will be understood that the fibres lie substantially in a plane parallel to the principal surfaces of the filter medium. Instead of lying in all possible directions in space they are confined to a layer of small thickness in which they run in all directions and overlap one another to form a non-woven mat.

Claims

1. A filtering medium comprising synthetic or mineral fibres and a binder, said fibres lying flat and forming a mat composed of several thicknesses.

2. A filtering medium as claimed in claim 1, in which the fibres form superposed layers held by the binder.

3. A filtering medium according to claim 1 or 2, in which the majority of the fibres have a length of less than 5 mm.

4. A filtering medium according to one of claims 1 to 3, characterised in that the mat has a thickness of 1 to 3 mm.

5. A filtering medium according to one of Claims 1 to 4, characterised in that the binder forms, on the mat, a film having an average thickness of less than 2 microns.

6. A filtering medium according to one of claims 1 to 5, characterised in that the binder is a thermosetting resin.

7. A filtering medium according to one of claims 1 to 6, characterised in that the fibres are glass fibres and the binder is a silicone resin.

8. Process for preparing a filtering medium according to one of claims 1 to 7, characterised in that it comprises dispersing and sedimenting the fibres in a solution, in a homogeneous manner.

9. Process according to claim 8, characterised in that it comprises calendering and drying the product obtained after sedimentation, immersing it in a solution of resin and polymerising the resin.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Filtering Medium The invention relates to a fibre-based filtering medium and a process for its preparation. The filtering medium of the invention is intended, in particular, for the filtration of fluids in temperature ranges which can reach 1 800C, in particular for the filtration of water and hydrocarbons, in order to remove the solid or liquid impurities therefrom (in this case by promoting coalescence phenomena). The object of the invention is to obtain a filtering medium which can be used in a plane or curved configuration and in which the fibres ensure filtration without creating, between the inlet and the outlet of the medium passages which are capable of letting through the impurities to be filtered off. The filtering medium of the invention is characterised in that the fibres form a mat in which they are arranged flat and held by a binder. The flat arrangement permits permanent compression of the filtering medium. The desired density is achieved by squeezing the filtering medium to a greater or lesser extent. In the prior art, the fibres were held by being entangled with one another in all directions in space, this being the case, for example, when fibres are obtained by spraying a solution of a fibre-generating substance (German Application 1,920,769). The fibres of the mat preferably form superposed identical layers bound by the same binder as that which binds the fibres in each layer, each layer comprising one or more thicknesses of fibres. In principle, the fibres are the same throughout the whole thickness of the filtering medium. According to the invention, a process for preparing a filtering medium of this type comprises dispersing and sedimenting the fibres, in a homogeneous manner, in a solution which is capable of wetting the fibres and which is less dense than the fibres. The product obtained, preferably after calendering and drying, is immersed in a solution of resin. The filtering medium is obtained after polymerisation of the resin. The synthetic or mineral fibres are, for example, polyethylene, polyamide, polyester, polyacrylontrile, glass or carbon fibres. The binder is preferably a thermosetting resin, especially a polymerisable resin, for example an epoxy resin, a polyester resin or a polyamide-based resin. These examples do not imply a limitation. In a typical example, the fibres are glass fibres having a thickness of a few tens of microns, for example of the order of 40 microns, and the resin is a silicone resin. The mat is obtained, for example, by dispersing and sedimenting the glass fibres in a chlorinated solvent. In a variant, the fibres are polyethylene fibres and the preparation medium is heptane. The majority of the fibres preferably have a length of less than 5 mm. Preferably, the resin, which coats the fibres to a greater or lesser extent, forms, on the mat, a film having an average thickness of less than two microns. Preferably, the mat has a thickness of 1 to 3 mm. It will be understood that the fibres lie substantially in a plane parallel to the principal surfaces of the filter medium. Instead of lying in all possible directions in space they are confined to a layer of small thickness in which they run in all directions and overlap one another to form a non-woven mat. Claims

1. A filtering medium comprising synthetic or mineral fibres and a binder, said fibres lying flat and forming a mat composed of several thicknesses.

2. A filtering medium as claimed in claim 1, in which the fibres form superposed layers held by the binder.

3. A filtering medium according to claim 1 or 2, in which the majority of the fibres have a length of less than 5 mm.

4. A filtering medium according to one of claims 1 to 3, characterised in that the mat has a thickness of 1 to 3 mm.

5. A filtering medium according to one of Claims 1 to 4, characterised in that the binder forms, on the mat, a film having an average thickness of less than 2 microns.

6. A filtering medium according to one of claims 1 to 5, characterised in that the binder is a thermosetting resin.

7. A filtering medium according to one of claims 1 to 6, characterised in that the fibres are glass fibres and the binder is a silicone resin.

8. Process for preparing a filtering medium according to one of claims 1 to 7, characterised in that it comprises dispersing and sedimenting the fibres in a solution, in a homogeneous manner.

9. Process according to claim 8, characterised in that it comprises calendering and drying the product obtained after sedimentation, immersing it in a solution of resin and polymerising the resin.