COMPONENT

The present invention relates to improvements in filter technology for air purifiers.

WO 2019/167584 (Panasonic) discloses an air purification device equipped with a case in which an intake opening and an exhaust opening are provided, and an air filter which is disposed within the case and is formed by pleating a sheet filter material. The air filter is provided with a substrate layer that supports the filter shape, and a fiber layer that is formed from fibers having a narrower diameter than the fibers forming the substrate layer and that traps particles in the air. The substrate layer has higher air permeability than the fiber layer and includes an adsorbent containing an amine compound. The fiber layer is disposed upstream of the substrate layer relative to the direction of air flow.

Despite the prior art there remains a need for air purifier filters which can eliminate malodorous components from the ambient air.

Air purifiers are highly specialised and have been developed to use less energy and yet be more efficacious at removing particles from the air stream than previously. A significant aspect to their performance is the engineering of the fan, the filter and also the architecture of the device. Anything that affects the pressure gradient affects the efficiency of the device and so designers in the field of air purification typically eschew anything that might increase the pressure drop between the fan and air exiting the device. One of the components that might do this is the particulate filter.

Accordingly, and in a first aspect, there is provided a filter for an air purifier comprising a first woven layer and a second melt blown layer, and wherein said first woven layer comprises a malodour counteracting component.

We have surprisingly found that malodour counteracting components can have a significant and deleterious effect on the performance of air purifiers resulting in their using more energy, making more noise and being less effective.

Despite this, the inventors have discovered that the malodour counteracting effects can be optimised by separating the malodour counteracting from the filtration. This is contrary to the perceived wisdom of using fewer obstructions to the air flow. Further, the materials used in the respective layers also have an impact on performance. Preferably, the first layer has an average air resistance less than 1.0 Pa. Air resistance is measured using an Automated Resistance Tester 8130A commercially available from TSI. The air velocity passing the filter media is 5,33cm/s for the particle size of 0.3 pm and gives pressure drop (Pa) and filtration efficiency (%).

The air resistance is measured in the absence of any added material, for example any malodour counteracting material, in order to properly define the substrate perse. Preferably, the filter is woven. Preferably, the first layer is made from polyethylene terephthalate or polypropylene and examples are commercially available from many sources.

We have surprisingly found that such filters are able to carry a further malodour counteracting component without affecting the overall air resistance of the filter. Similarly, we have found that the air resistance of filters typically used for particulate filtration cannot carry such a malodour component without simultaneously resulting in a significant increase in air resistance. This increased air resistance is not acceptable to the consumer or the designer as it means that more energy is needed to push the air through the device and also the device generates more noise.

Preferably, the filter also comprises a second particulate filtration layer. The second layer has an average air resistance of from 4 to 16 Pa, preferably from 8 to 12 Pa.

Preferably, the malodour counteracting component is selected from colloidal dispersions of particles of silica having a particle size of from 3 nm to 100 nm, to which ions of one or more metals are adsorbed, selected from metals having atomic numbers 21-31 , 39-46, 48-50, 57-82, and 89-93 as described in WO 2017/216285 and aqueous silicate solutions containing ions of metal having an atomic number selected from atomic numbers 21-31 , 39-50, 57-82, and 89-93 as described in WO 2019/020576.

Preferably, the first and second layers are in contact with one another. This enables a smoother air flow through the two layers and so a lower likelihood that the pressure is reduced as the air passes through the two filters.

More preferably, the first and second layers are adhered to one another. By adhered is meant that an adhesive is added to one or both layers either at spots or uniformly. The adhesive will be added in a manner such that the air resistance of the filter is not adversely affected.

Preferably, the first and second layer are pleated. Preferably, the second layer comprises polyolefin or glass fibre. The second layer is a particulate filter layer and captures particles that adhere to the fibres constituting the layer as the air flow passes through it. Preferably, the second layer comprises polyolefin, preferably polypropylene and is melt blown.

In a second aspect, there is provided an air purifier comprising a filter according to the first aspect. The air purifier will comprise means for displacing the air through the purifier from ambient and through a filter according to the first aspect. It is also realised that the air purifier is not necessarily manufactured and marketed with a filter in place and that such a filter will be replaceable by the user.

The filter will also preferably comprise an ioniser for ionising the air as it passes through the device and before the filter in the direction of the air flow through the device. The ioniser ionises the air which makes it easier for the filter to attract the charged particles.

This is particularly relevant for filters of the present invention where managing the air flow is vital to optimal operation of the device. The lower the air resistance the less likely the particles in the air flow are captured by mere physical collision. The reduced air resistance filters of the present invention thus facilitate the removal of more pollutants without reducing air pressure drop and so without having to increase the fan speed.

In a third aspect, there is provided a method of removing malodorous components from ambient air by filtering said ambient air through a filter according to the first aspect.

Preferably, said malodorous component is selected from acetic acid, ammonia, isovaleric acid and formaldehyde.

In a fourth aspect there is provided a filter cassette comprising a substantially rigid case and a particulate filter as described above contained therein.

Embodiments of the invention shall now be described with reference to the following non-limiting figures in which:

Figure 1 is a cross sectional view along a particulate filter consisting of a pair of layers, one of which contains a malodour counteracting constituent; Figure 2 is another cross section across a particulate filter comprising a pair of folded layers, one of which comprises a malodour counteracting constituent; and

Figure 3 is a particulate filter comprising a cassette and a particulate filter medium.

In detail, Figure 1 shows a first layer (1) which has a low air resistance and a second layer (2) which has a malodour component entrained within the layer. The second layer has been soaked in a solution of malodour counteracting material such as is commercially available from Prebona.

Figure 2 shows a similar pair of layers this time formed into a folded configuration. The two layers are adhered to one another.

Figure 3 shows a particulate filter comprising a casing (4) and particulate filter (3) which has a layer with low air resistance and a malodour counteracting material.

EXAMPLES

Example 1

In table 1 is shown a series of air resistance measurements versus air flow speed. The purpose is to illustrate the effect of applying a malodour containing component to the various filter media.

Shown is the change in air resistance as the malodour counteracting component commercially available as OdorControl from Prebona is applied to the particulate filter and also to a new low air resistance filter.

The air resistance of the particulate filter is dramatically increased as the OdorControl is applied whereas the air resistance of the new low air resistance filter is not affected at all.

The consequence is that the OdorControl product may be applied effectively to the backing layer to achieve the odour control effect whereas it may not be applied to the melt-blown layer or the complete filter. Table 1

Example 2

Coating process:

Pour OdorControl into a water basin and put the test filter media in the basin. Let the filter media stay until it has totally soaked the OdorControl. Hang the filter media in the normal room air condition over night until it is dry. The filter media treated with OdorControl is ready to use.