GB1562887A

GB1562887A - Grease or oil filter material and method of detecting the saturation thereof

Info

Publication number: GB1562887A
Application number: GB3822/78A
Authority: GB
Original assignee: Riensch & Held
Current assignee: Riensch & Held
Priority date: 1977-02-26
Filing date: 1978-01-31
Publication date: 1980-03-19
Also published as: DE2708435B1; DE2708435C2; SE419506B; FR2381555B1; SE7801243L; DD135420A5; FR2381555A1

Description

(54) GREASE OR OIL FILTER MATERIAL AND METHOD OF DETECTING THE SATURATION THEREOF (71) We, RiENSCH & HELD, a Kom manditgesellschaft organised under the laws of West Germany, of Danziger Strasse 17, 2000 Hamburg 1, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the fol lowing statement: This invention relates to methods of de tecting the saturation with grease or oil of non-woven fabric filter material for filter ing grease or oil vapours from flows of air or other gases, especially filter material for vapour extraction hoods. It also relates to filter materials for carrying out such methods.

Such filter material is used domestically for vapour extraction hoods, such as cooker hoods, which are employed in air recircula tion or air extraction operations.

In order to ensure satisfactory function ing of these installations, the filter material must possess good absorption and distribu tion properties for greasy and oily vapours -or substances, but must also be highly per meable to air, so that the passage of air and the retention of foreign substances are still as large as possible.

Numerous non-woven fabrics of various qualities are used as filter materials for such purposes. These satisfactorily fulfil the aforementioned requirements. A disadvan tage, however, is noticeable in these grease filters.. in that it is not possible to tell, with .out considerable difficulty, when the filter has reached state of saturation, i.e. when it can no longer absorb any further foreign substances such as oil and grease, thus mak ing cleaning or replacement of the filter ma terial necessary; This applies both to dis posable grease filters and to grease filters which - can be.re-used several times after cleaning.

In - normal use of the grçase estraction -installation, renewal or. cleaning of the filter is necessary every two to three months to ensure satisfactory functioning. Neverthe less, this represents only an average time, so that taking into account various sizes of household and differing durations of use of the installation, considerable deviations from this time can occur. In order to establish whether and to what extent the filter material is already "used up" or saturated, the extraction hood or other installation must be opened and the filter ma terial must be tested by feeling it. Such a subjective assessment of the degree of saturation does not give a very reliable re sult.Usually, this testing is too tiresome for the housewife, so that the filter material is either used for too long or is renewed early, when its capacity is not yet fully exhausted.

The object of the present invention is to provide a method, by which the state of saturation of grease filter material can be easily and reliably detected by being made visible, in order that the correct time for replacement of saturated grease filter ma terial in order to ensure correct functioning in vapour extraction installations can be simply and reliably established.

A further object of the present invention is to provide a grease filter material for use in the detection technique just described.

Thus, according to one aspect of this in vention, we provide a method of detecting the saturation with grease or oil of-non woven fabric sheet filter material for filter ing grease or oil vapour from a flow of air or other gases, the- material having.two op posed faces through which the gas and vapour flow from one face to the other face, wherein a colouring substance is ap plied to only the other of the opposed faces of-thefilter material, this substance migrates through the grease or oil deposited in the filter material, and the one of the opposed faces of the filter material is observed, visibility of the substance on the one face 1n- dicating that the filter material is saturated with grease or oil.

Non-woven fabric sheet filter material for filtering grease or oil vapour from a flow of air or other gases, the material having two opposed faces through which, in use, the gas or vapour flow and being for use in the method in accordance with the invention, is characterised, in accordance with an other aspect of the invention, in that a grease-soluble or oil-soluble coating is provided on one only of the opposed faces of the filter material, the coating comprising a colouring substance, the colour of which is different from that of the filter material and is invisible from the other of the opposed faces.

The coating can be applied, for example, by flexoprinting using a screen roller or a rubber block onto the one side of the filter material layer, in such a manner that it cannot be directly seen from the other side.

Tn operation, the filter material may then be placed in a vapour extraction hood in such a manner that the coated side is uppermost and towards the interior of the hood The coating is traversed to the same extent as the filter material by the air flow charged with water, grease, oil and solid particles.

The greater part of these suspended substances are at first absorbed by the fine filter material on its lower side and later, due to the distribution and suction effect which then occurs, are absorbed by the entire volume of the filter material through its full thickness. In this manner, the greasy and oily deposits after a certain time come into contact with the applied coating, the grease-soluble or oil-soluble constituents of which are then dissolved, so that the colouring substance migrates in its full area from the upper face of the filter, which is not visible in the closed state of the extraction hood, to the lower face of the filter material and becomes visible there when the filter is completely saturated, so that the replacement or cleaning can then be carried out at the correct time.As a result, the grease filter material becomes environmentally acceptable and also economical.

The colour-containing coating can be applied in the most varied ways, for example by printing or spraying.

The coating contains a - grease-soluble or oil-soluble but water-insoluble colouring substance, the colour of which is different from that of the filter material. In this way, assurance is provided that the saturation-of the filter is easily visible.

Furthermore, the type, density- and thickness of the non-woven fabric sheet filter material are not particularly critical. For example, the material may consist of synthetic material, such as rayon or nylon and possess a weight of approximately 130 g/m2 and a thickness of about 0 7 mm.

The porosity of the filter material can be so chosen that a satisfactory passage of air through it without clopping can take place. A porosity giving a through air speed of 0 9 m/sec. for a water gauge pressure differential across the material of 5 mm is found to be especially satisfactory.

Likewise, the shape and size of the coating on the filter material employed can be of any desired form.

An example of a method and of filter material in accordance with the invention will now be described with reference to the accompanying drawings, in which: - Figure 1 is a partly broken-away plan of a sheet of the grease filter material; Figure 2 is a cross-section through the grease filter material in the unused state; and Figure 3 is a cross-section through the grease filter material when saturated with grease.

The grease filter material 1 shown in Figure 1 is in the form of a rectangular sheet with a length 2 of 57.5 cm and a width 3 of 38-5 cm. A printed pattern of a coating 4 of a grease-soluble dye consists of a circle, disposed centrally of the grease filter material and having a diameter of 9 cm, and of two semi-circular segments, only one of which is shown.

The grease filter material as shown in cross-section in Figure 2 has a thickness 6 of 0-7 mm and the already mentioned width 3 of 38-5 cm. The upper and lower faces of the filter are referenced 7 and 8. The coating 4 is applied to the face 7 and is recognisable in the unused state by the thickly drawn line in Figure 2. The arrow 9 indicates the suction direction of the air charged with foreign substances 10 through the grease filter material 1 when the filter material 1 is in use. So long as the applied coating 4 has not at all or not sufficiently come into contact with the greasy or oily substances filtered out by the filter material, the applied coating 4 remains completely or largely invisible on the lower face of the filter material.

In Figure 3, the same cross-sectional view as in Figure 2 is shown with the same reference numerals, the grease filter material I being, however, saturated with greasy or oily substances. The grease-soluble and oilsoluble coating 4 has now, due to its solubility behaviour, migrated from the upper face 7 to the lower face 8 and can be clearly seen by an observer from below viewing in the direction 9.

The weight of the filter material was 130 gim2 and an air flow speed of 0 425 m/sec.

with a water gauge pressure differential of 2 mm was applied to it. The tearing strength of the material was 6,000 g/10 cm strip length in the direction of the tear testing machine and 4,000 g/10 cm transversely. Before use, the filter material had a pH value of 5'8 while after use it was neutral. Further, the filter material which was a non-woven fabric possessed fire-retarding properties, tested according to Thappi (International paper standard). The maximum shrinkage was 1% with an evaporation of 20 kg of water from it.

The following composition was used for the applied coating of grease and oil soluble dye: 5 parts of grease and oil-soluble (and water-insoluble) organic dye were stirred with 5-10 parts of a suitable emulsifier possessing the property of dispersing grease and oil-soluble, but not water soluble, organic dyes in water. Next, 30 parts of a water-soluble binding agent suitable for flexoprinting were stirred in, until the mixture was homogeneous.

To this mixture, 55 parts of water were then added with stirring. The resultant composition was printed on to one face of the filter material by flexoprinting.

The filter material was then placed in a vapour extraction hood so that the prin ted face was towards the interior of the apparatus that is uppermost and on the downstream side of the filter material in relation to the flow of air and greasy or oily vapour through it. With normal use of the filter material, the printed coating became visible from the under side of the material after two to three months. In order to regulate the colour indication in relation to time and the drying of the coating during the printing operation, in another composition, 30 parts of water and 25 parts of alcohol were used instead of 55 parts water.It will be understood that the invention is not limited to the aforementioned com positions, and that this applies particu larly to the proportions of water and alcohol, which can be varied according to requirements, as can all the other pro portions.

WHAT WE CLAIM IS: - 1. A method of detecting the saturation with grease or oil of non-woven fabric sheet filter material for filtering grease or oil vapour from a flow of air or other gases, the material having two opposed faces through whcih the gas and vapour flow from one face to the other face, wherein a colouring substance is applied to only the other of the opposed faces of the filter material, this substance migrates through the grease or oil deposited in the filter material, and the one of the opposed faces of the filter material is observed, visibility of the substance on the one face indicating that the filter material is saturated with grease or oil.

2. A method according to claim 1, in which the colouring substance is applied to the filter material by printing or spraying.

3. Non-woven fabric sheet filter material for filtering grease or oil vapour from a flow of air or other gases, the material having two opposed faces through which, in use, the gas and vapour flow and being for use in the method in accordance with claim 1, wherein a grease-soluble or oilsoluble coating is provided on one only of the opposed faces of the filter material, the coating comprising a colouring substance, the colour of which is different from that of the filter material and is invisible from the other of the opposed faces.

4. Filter material according to claim 3, in which the colouring substance is a greasesoluble or oil-soluble, but water-insoluble, dye.

5. Filter material according to claim 4, in which the dye is organic.

6. Filter material according to any one of claims 3 to 5, in which the coating contains an emulsifier.

7. Filter material according to any one of claims 3 to 6, in which the coating contains a water-soluble binding agent.

8. A method of making a filter material according to any one of claims 3 to 7, characterised in that a coating containing water and/or alcohol is applied to the filter material.

9. A method according to claim 8 of making a filter material according to claims 4 to 7, in which the coating contains a mixture of 5 parts of the organic, waterinsoluble dye, 10 parts of the emulsifier for dispersing the dye, 30 parts of the watersoluble binding agent for homogenising, 30 parts of water and 25 parts of alcohol when it is applied to the filter material.

10. Filter material according to any one of claims 3 to 6, in which the non-woven fabric sheet material contains synthetic fibres.

11. Filter material according to claim 11, in which the fibres are of nylon.

12. A method according to claim 1, substantially as described with reference to the accompanying drawings.

13. Filter material according to claim 3, substantially as described with reference to the accompanying drawings.

14. A grease or oil vapour extraction hood incorporating filter material in accordance wtih any one of claims 3 to 7 or claim 10, or claim 11, or claim 13, the coat

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Claims

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strength of the material was 6,000 g/10 cm strip length in the direction of the tear testing machine and 4,000 g/10 cm transversely. Before use, the filter material had a pH value of 5'8 while after use it was neutral. Further, the filter material which was a non-woven fabric possessed fire-retarding properties, tested according to Thappi (International paper standard). The maximum shrinkage was 1% with an evaporation of 20 kg of water from it.

The following composition was used for the applied coating of grease and oil soluble dye:

5 parts of grease and oil-soluble (and water-insoluble) organic dye were stirred with 5-10 parts of a suitable emulsifier possessing the property of dispersing grease and oil-soluble, but not water soluble, organic dyes in water. Next, 30 parts of a water-soluble binding agent suitable for flexoprinting were stirred in, until the mixture was homogeneous.

To this mixture, 55 parts of water were then added with stirring. The resultant composition was printed on to one face of the filter material by flexoprinting.

The filter material was then placed in a vapour extraction hood so that the prin ted face was towards the interior of the apparatus that is uppermost and on the downstream side of the filter material in relation to the flow of air and greasy or oily vapour through it. With normal use of the filter material, the printed coating became visible from the under side of the material after two to three months. In order to regulate the colour indication in relation to time and the drying of the coating during the printing operation, in another composition, 30 parts of water and 25 parts of alcohol were used instead of 55 parts water.It will be understood that the invention is not limited to the aforementioned com positions, and that this applies particu larly to the proportions of water and alcohol, which can be varied according to requirements, as can all the other pro portions.

WHAT WE CLAIM IS: - 1. A method of detecting the saturation with grease or oil of non-woven fabric sheet filter material for filtering grease or oil vapour from a flow of air or other gases, the material having two opposed faces through whcih the gas and vapour flow from one face to the other face, wherein a colouring substance is applied to only the other of the opposed faces of the filter material, this substance migrates through the grease or oil deposited in the filter material, and the one of the opposed faces of the filter material is observed, visibility of the substance on the one face indicating that the filter material is saturated with grease or oil.
2. A method according to claim 1, in which the colouring substance is applied to the filter material by printing or spraying.
3. Non-woven fabric sheet filter material for filtering grease or oil vapour from a flow of air or other gases, the material having two opposed faces through which, in use, the gas and vapour flow and being for use in the method in accordance with claim 1, wherein a grease-soluble or oilsoluble coating is provided on one only of the opposed faces of the filter material, the coating comprising a colouring substance, the colour of which is different from that of the filter material and is invisible from the other of the opposed faces.
4. Filter material according to claim 3, in which the colouring substance is a greasesoluble or oil-soluble, but water-insoluble, dye.
5. Filter material according to claim 4, in which the dye is organic.
6. Filter material according to any one of claims 3 to 5, in which the coating contains an emulsifier.
7. Filter material according to any one of claims 3 to 6, in which the coating contains a water-soluble binding agent.
8. A method of making a filter material according to any one of claims 3 to 7, characterised in that a coating containing water and/or alcohol is applied to the filter material.
9. A method according to claim 8 of making a filter material according to claims 4 to 7, in which the coating contains a mixture of 5 parts of the organic, waterinsoluble dye, 10 parts of the emulsifier for dispersing the dye, 30 parts of the watersoluble binding agent for homogenising, 30 parts of water and 25 parts of alcohol when it is applied to the filter material.
10. Filter material according to any one of claims 3 to 6, in which the non-woven fabric sheet material contains synthetic fibres.
11. Filter material according to claim 11, in which the fibres are of nylon.
12. A method according to claim 1, substantially as described with reference to the accompanying drawings.
13. Filter material according to claim 3, substantially as described with reference to the accompanying drawings.
14. A grease or oil vapour extraction hood incorporating filter material in accordance wtih any one of claims 3 to 7 or claim 10, or claim 11, or claim 13, the coat

ing being on the downstream face of the filter material in relation to the direction of flow of the vapour through it and the upstream face of the filter material being visible.