GB2239194A - Treating foam plastics filter material - Google Patents

Abstract

Polyurethane foam for filtering air in an I.C. engine intake filter is rendered sticky, to retain dust particles, by impregnating with an organo-phosphate which softens or plasticises the foam. The reagent is applied by spraying or dipping then squeezing and may be tris (2 chloroisopropyl)phosphate or a mixture of chlorinated paraffin with phosphoric acid. 2,2-bis (chloromethyl) 1,3-propanediyil tetrakis 2-chloroethyl (ester).

Description

FILTRATION FOAMS This invention relates to filtration foams and more particularly to a method of treating a filtration foam for use in the filtration of gases such as air. An example of the application of the invention is to the treatment of air filters for internal combustion engines, such as those formed of reticulated polyurethane foam.

In the case of foam engine air filters, previous proposals for increasing the filtration efficiency so far as concerns removal of suspended solid matter in the air passing through the filter include the treatment of the body of the filter with engine oil to produce an adherent effect on the surfaces of the filter foam, excess oil being removed by squeezing or rolling.

Such a technique has the benefit that the liquid material used for treating the foam is relatively widely avaiable and the treatment technique is relatively straightforward. However, the limitatiions of this prior proposal include the fact that the adherent qualitities produced in the foam are not particularly high and the effect is not as persistent as could be desired. It is necessary to remove the engine oil and re-treat the filter at regular intervals. This represents an extra maintenance task and increased cost. A further factor is that the engine oil itself represents a fire harzard in the engine compartment.

An object of the present invention is to provide a method of treating filtration foams, particularly those for use in the filtration of gases such as air, for example engine air filters, offering improvements in relation to one or more of the matters discussed herein, or generally.

There is disclosed in EPO 0253467 (Baxter) a filtration foam in which a wetting agent is applied thereto to defoam blood passing through the foam screen. The wetting agent is provided at a location so as to have its effect only on the blood foam, and not on the main body of the blood. The wetting agent has no effect on the body of the foam filter as such, but exerts effects solely by its own presence.

According to the invention there is provided a method of treating a filtration foam as claimed in the accompanying claims.

In a preferred embodiment there is provided a method of treating a filtration foam, the foam being for use in the filtration of gases such as air and comprising a reticulated polymeric material such as polyurethane. The method is carried out in order to enhance the filtration properties of the foam for the removal of solid matter suspended in the gases. The method comprises treating a body of the foam with a liquid to produce an adherent effect on the surfaces of the filter foam, excess of the liquid being removed prior to use of the foam for filtration purposes. The method includes the notable step of employing as said liquid for treating the foam a reagent which produces a degree of softening or plasticization of the polymeric material of the foam, but without causing structural change to the foam.

In a preferred embodiment, the reagent comprises a chlorinated organo phosphate such as tris (2 chloroisopropyl) phosphate.

In another embodiment, the reagent comprises a complex organo phosphate, for example phosphoric acid, 2, 2 - bis (chloromethyl) 1, 3 - propanediyl tetrakis 2 - chloromethyl (ester). The organo phosphate may be blended with a chlorinated paraffin for example it may be blended with 60% to 80% by volume of such chlorinated paraffin.

In the preferred embodiment, the efficiency of the filter is increased and the flame retardation is likewise significantly improved.

An embodiment of the invention will now be described by way of example.

A body of reticulated poylurethane foam, of the kind used previously for automotive air filters, is treated by spraying or dipping with a reagent comprising tris (2 chloroisopropyl) phosphate.

Where the reagent is applied by a dipping technique, the foam is subsequently passed between a pair of in running rollers to remove excess of the reagent.

After such treatment, the foam is ready for incorporation into known automotive filter medium mounting structures, such as cartridge - type filter cases, without modification to the previously used techniques for such mounting of the foam.

Treatment of the filter foam in the manner described produces a small degree of softening or plasticization of the filter foam, but without affecting its structural integrity. As a result, the surface of the filter foam, as exposed to the air passed therethrough in use, is rendered compartively tacky or adherent so that a "fly paper" effect is produced whereby trapping of particulate matter within the body of the filter is greatly improved.

As a result, the efficiency of the filter, as measured by upstream and downstream measurements of particulate material content in an air stream, is dramatically improved.

Moreover, the treatment of the filtration foam in the manner described produces significantly improved performance of the filter in relation to fire retardency.

In a second embodiment, the chlorinated organo phosphate of the first embodiment is replaced by a complex organo phospate, such as the material available under the trade name "Amgard V6 from Albright & Wilson Ltd, blended with a chlorinated paraffin such as Cereclor" 51L obtainable from ICI Chlor-Chemicals. The amount of the chlorinated paraffin is about 60% to 80% by volume of the phophoric acid compound, about 70% is the optimium dilution.

In this embodiment, the technique of treatment of the foam and the results obtained therefrom are substantially the same as in the preceding embodiment.

Claims (10)

1 A method of treating a filtration foam for use in the filtration of gases such as air, the foam comprising a reticulated polymeric material such as polyurethane, in order to enhance the filtration properties of the foam for the removal of solid matter suspended in said gases, the method comprising: a) treating a body of the foam with a liquid, to produce an adherent effect on the surfaces of the filter foam; and b) removing, if necessary, any excess of said liquid prior to use of the foam for filtration purposes; characterised in that c) said liquid used for treating the foam comprises a reagent which produces a degree of softening or plasticization of the polymeric material of the foam but without causing structural change to the foam.

2 A method according to claim 1 characterised in that said body of the foam is treated with said liquid by dipping the body in said liquid, followed by rolling the body between two rollers to remove excess liquid.

3 A method according to claim 1 characterised in that said body of foam is treated with said liquid by spraying.

4 A method according to any one of the preceeding claims characterised in that said reagent comprises a chlorinated organo phosphate.

5 A method according to claim 4 characterised in that said reagent comprises tris (2 chloroisopropyl) phosphate.

6 A method according to any one of claims 1 to 3 characterised in that said reagent comprises a complex organo phosphate.

7 A method according to claim 6 characterised in that said complex organo phosphate comprises phophoric acid, 2, 2 - bis (chloromethyl) 1, 3 - propanediyil tetrakis 2 chloroethyl (ester).

8 A method according to claim 7 characterised in that said complex organo phosphate is blended with a chlorinated paraffin.

9 A method according to claim 8 characterised in that said chlorinated paraffin is provided in an amount of about 60% to 80% volume of said liquid.

10 A method of treating a filtration foam, substantially as described herein.