FIELD OF INVENTION This invention relates to an assembly for attracting and neutralising contaminants from air. It further relates to a method of manufacturing a such assembly, to air filter units and to uses of a such assembly.

BACKGROUND OF INVENTION The Applicant is aware of existing graphene coatings for air filtration (see, for example, W02018006744A1). However, a coating for filtration application, by the Applicant’s definition, relies on principles of physical filtration of pollutants on a physical filter. The Applicant’s desires to improve on this idea through a coating assembly which differs in components, preparation methods and can be applied on any dielectric surface to remove contaminants from the air through static attraction, but not through physical filtration.

SUMMARY OF INVENTION

Accordingly, the invention provides an assembly for attracting and neutralising contaminants from air, comprising: a substrate; a graphite solution; wherein the substrate is treated with the graphite solution; and ionising means configured to apply a static charge to the substrate by ionising particles. The term “contaminants” may include pathogens, bacteria, viruses, microbes, etc.

The term “graphite” may include any crystalline form of the element carbon with its atoms arranged in a hexagonal structure, including graphene, multiple layers of graphene and exfoliated graphene.

The term “treating” may include coating the substrate as well as imbuing the substrate.

The ionising means may be configured such that a flow of ionising particles is directed towards the substrate treated with graphite, thus ionising the graphite disposed in or on the substrate.

The ionising means may include an electronic ioniser. The ioniser may emit (1- 10 ⁶ ) pcs/cm ³ 8 kVA particles. The ioniser may be a 6-8 kV ioniser. The ioniser (or an outlet thereof) may be spaced less than 20 mm, preferably less than 10 mm, ideally approximately 5 mm from the surface. The ioniser may be assembled in an independent protective housing or in the frame in case of panel application. The ioniser may, in use, consume 2 W or less of power. The ioniser may be operational permanently or indefinitely.

The ionising means may comprise a pair of electrodes connected to the substrate. The electrodes may be brass or copper electrodes and may be connected to a power pack which preferably provides A/C electrical power. However, the electrodes may also operate on a D/C power supply. The voltage may be 12-24 V. The electrodes may be spaced apart and parallel.

The substrate may be a foam. The foam may be a dielectric-type foam and/or a polyurethane foam. The foam layer may be 10-40 mm, preferably 20-30 mm thick. Alternatively, the substrate may be an air filter material, preferably a polyester material. The filter material may be pleated. There may be five pleats per 30 mm of filter material. The substrate may be arranged on a support structure, e.g. a frame.

The graphite solution may include graphene. The graphite solution may include graphite powder. The graphite solution may include exfoliated graphene. The invention extends to a method of manufacturing an assembly as described above, the method including: mixing graphite powder with an acid and a bonding agent; stirring the mixture to exfoliate it into amorphous particle fullerene graphene structures; and applying the mixture to the substrate.

The stirring may be for 5-10 minutes. The stirring may be continuous.

The applying may include spraying. The spraying may be with an airless-type spray gun. The mixture may be sprayed to a thickness of 1-2 mm.

The method may include drying the substrate in an oven or similar heat applicator. The drying may be between 40 and 80°C, preferably 50 and 70°C. The drying may be until the mixture is dry.

The exfoliated graphite, graphite or graphene powder may be 7-9 microns in diameter. The graphite solution may include between 10% and 90%, preferably between 20 % and 80% (by weight) exfoliated graphite, graphite or graphene powder. If applying the graphite solution to the substrate includes coating the substrate, the graphite solution may include between 50% and 90%, preferably between 60 % and 80% (by weight) exfoliated graphite, graphite or graphene powder.

If applying the graphite solution to the substrate includes imbuing the substrate, the graphite solution may include between 10% and 50%, preferably between 20 % and 40% (by weight) exfoliated graphite, graphite or graphene powder.

The graphite solution may include an acid. The graphite solution may include between 5 % and 25%, preferably between 5% and 15% (by weight) acid. The acid may be phosphoric acid. The bonding agent may be acrylic or polyurethane-type. The graphite solution may include the bonding agent in a concentration of 10%-30% (by weight).

An air filter unit may include an assembly as described above or an assembly manufactured as described above. The substrate may be arranged on a panel. The substrate may be arranged on a cylindrical surface. The air filter unit may be configured as a standalone air purifier unit. The assembly may be part of an air guide housing including a fan and pre- and/or post-filters located up- and/or downstream of the assembly.

An automobile ventilation unit may include an assembly as described above or an assembly manufactured as described above.

An assembly as described above or an assembly manufactured as described above may be used for attracting and neutralising contaminants from air.

The coating assembly may further find application in systems or apparatus which cause or control airflow, e.g., HVAC (Heating, Ventilation, and Air-Conditioning) systems in buildings, vacuum cleaners, portable fans, etc. In one implementation, the coating system may be applied on foam in a panel installed in or adjacent an HVAC inlet or outlet. The panel maybe in, or close to, a ceiling of a building. The ceiling may be a suspended ceiling or a solid ceiling. The panel may be approx. 600 mm x 400 mm or a size to fit the application.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings:

FIG. 1 shows a side view of preferred embodiment of an assembly in accordance with the invention;

FIG. 2 shows a top view of the assembly in FIG. 1 ;

FIG. 3 shows a three-dimensional view from a top of a panel, incorporating the assembly in FIG. 1 ;

FIG. 4 shows a three-dimensional view from a bottom of the panel of FIG. 3;

FIG. 5 shows a top plan view of the panel of FIG. 3;

FIG. 6 shows a cross-sectional view through section A-A of the panel of FIG. 3;

FIG. 7 shows an air filter unit, according to a second aspect of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiments described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiments are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiments is provided as illustrative of the principles of the present invention and not a limitation thereof.

FIG. 1-2 show a side view and a top view of an assembly with a foam 206 as a substrate and ionising means which combine a pair of electrodes 202, 203 and an ioniser 204.

The foam 206 as a substrate has a plane surface which is coated using graphite coating 201 . The coating 201 is produced by the following procedure:

• Providing a natural graphite powder having a particle size of 7-9 microns.

• Mixing the graphite powder with phosphoric acid and a bonding agent of an acrylic or polyurethane type in the following proportions (by weight): 70% graphite powder, 10% phosphoric acid, and 20% bonding agent.

• Mixing for a duration of 5-10 minutes continuously, to ensure that the graphite is exfoliated into amorphous particle fullerene graphene structures (which may be flakes or nanotubes).

• Spraying the mixture with an airless type spray gun onto one side of the foam layer 206 for a thickness of 1-2 mm, such that it is deposited onto a surface of the foam layer 206 and does not penetrate the foam layer 206.

• Drying the foam layer 206 with the sprayed mixture in a suitable oven at approximately 60°C until dry, thereby to form the graphite coating 201.

An ioniser emitter 204 is provided such that the emitter emits ionized particles into the plane of the coating 201 . Furthermore, the assembly comprises two electrodes 202 and 203 which have a cylindrical form arranged with its cylindrical surface lying in the plane of the coating 201 , thus contacting the coating 201 and coated surface 206. The two electrodes 202 and 203 are placed in parallel, encompassing the ioniser emitter 204. The electrodes 202 and 203 may be operated to electrify the coating 201 such that the electrification may be tested at any place on the coating 201. In other embodiments not shown, the assembly may comprise only the ioniser 204 or the electrodes 202 and 203. In a further embodiment, there may be end electrodes 205 arranged on the circumference of the entire assembly.

FIGS 3-6 illustrate a panel 100 for an air circulation system. Some details are most apparent from FIG. 6 (the cross-sectional view). The panel 100 has a foam layer 102 with a graphite coating 104 provided on one side of the foam layer 102. More specifically, the foam layer 102 is dielectric-type open pore foam made of polyurethane with or without charcoal filling. The foam layer 102 is about 25 mm thick.

The foam layer 102 is coated on one side (one side only, in this example) with a graphite coating 104 similar to the embodiment of FIG. 3-4

This process may ensure that one side of the panel 100 is electrified or charged evenly to ensure conductivity through an entire surface of the panel 100.

A pair of metal, e.g., copper or brass, electrodes 110 are provided in electrical contact with the graphite coating 104 adjacent opposite sides of the panel 100 and orientated parallel and transversely spaced apart from each other. The electrodes 110 may be operated to electrify the graphite coating 104 such that the electrification may be tested at any place on the graphite coating 104.

While the electrodes 110 may be rigid and provide a degree of support, the panel 100 includes a support structure 112, 114 in the form of a support layer 112 and a support frame 114. The support layer 112 is in the form of a plastic grid 112 comprising orthogonal members resembling an egg crate. The plastic grid 112 is rigid compared to the foam layer 102 and resists bending and twisting. The plastic grid 122 could have been affixed directly to the graphite coating but in this example is attached (e.g., adhered) to the electrodes 110.

Further, the support frame 114 is of metal and extends around a periphery of the foam and support layers 102, 112. Sides of the foam and support layers 102, 112 may be adhered to the support frame 114 or merely clamped therein. The support frame 114 effectively sandwiches the graphite coating 104 between the foam layer 102 and the support layer 112 with the electrodes 110 provided between the graphite coating 104 and the support layer 112. (Attachment formations (not illustrated) may be provided on the support layer 112 and/or the support frame 114.)

An ioniser 120 is provided as part of the panel 100. The ioniser 120 may be integrated with the panel 100, e.g., affixed to the support frame 114, or separate, but mountable to, or adjacent, the foam layer 102. The ioniser 120 is mounted about 5 mm below the foam layer 102 and directed towards the foam layer 102.

In use, a side with the support structure 112 visible (with the graphite layer 104 underneath) is intended to be the front-facing side; in other words, the side which air is to be circulated past. It will be noted that air is not circulated through the foam layer 102 or the graphite coating 104 and the panel 100 is therefore not a filter in the conventional sense. The foam layer 102, with the adjacent ioniser 120, is a back- facing side of the panel 100.

The ioniser 120, in use, is directed towards the foam layer 102 to emit ionised particles 122 towards the foam layer 102. These ionised and charged particles 122 pass through the foam layer 102 and interact with the graphite coating 104 to charge the graphite coating with an electrostatic charge. This charged graphite coating 104 serves to attract contaminants electrostatically, without air actually having to pass through the graphite coating 104. The support layer 112 may, if desired, be shaped and configured to help direct airflow. The graphite coating 104 has anti-microbial properties thus serving to deactivate or sanitise the contaminants. As a further measure, the electrodes 110 may be energised to pass a current through the graphite coating 104 to further destroy or sanitise contaminants extracted from the air passing the panel 100.

The panel 100 may be installed in a building, for example, adjacent air- conditioning inlets or outlets. Differently shaped, e.g., smaller, variants of the panel 100 may be installed in vacuum cleaners or air purifiers, e.g., instead of, or in addition to, HEPA filters. In fact, the panel 100 could be placed at any location that air passes, even buildings without an air-conditioning system but with some degree of airflow.

Without being bound by theory, the Inventor speculates that the panel 100 can be used to kill bacteria and viruses in indoor environments, to ensure pathogen-free air. The panel 100 could be used alone, or in addition to other air filtration apparatus, to promote cleaner, healthier air.

At least one advantage of the present panel 100 over a more conventional filter is that filter can be clogged, leading to blockages. As the panel 100 is not a filter, it will not get clogged completely and not affect the performance; it can be cleaned by vacuuming or other methods.

FIG. 7 shows a diagrammatic view of an air filter unit 10. The air filter unit 10 comprises an air passage 12 defined by metal ducting plates 14. The air passage 12 has an air inlet 16 open to the spaces to be treated (for example a hospital room) and an outlet 18 from which the treated air is returned to the room. About midway along the passage 12 is provided a filter member 22 which spans the passage 12. A fan 24 is provided slightly upstream of the outlet 18. The fan 24 draws air into the inlet 16 through the filter member 22 and then discharges the treated air through the outlet 18.

The filter member 22 comprises a panel of non-woven air and water-resistant material bonded to a frame 26. The frame 26 comprises non-conducting material and is of “C” shape in cross-section (not clearly shown). It is attached to the ducting plates 14.

The filter is treated with a graphite, graphene water solution. The graphene solution is manufactured similarly to the coating 104 of the previous example, however the powdered graphite is only present at 30% by weight. The phosphoric acid is added at 15%.

The solution is then sprayed onto the pleated polyester filter panel, ensuring complete penetration/imbuing throughout the filter. The panel is then placed in a drying oven at 80°C until dry.

A pair of electrodes 28 and 30 each comprising a braded copper strip conductor is attached to the pleated material each lying midway along a pleat. Each copper strip has length of about the length of the pleats, and is located approximately 60 mm from each end of the carbonized panel. The copper conductors are clamped between the pleats; ensuring electrical conductivity. The conductors are provided respectively with terminals. The electrodes 28 and 30 are connected to a power pack (not shown) which provides A/C electrical power at a voltage of 24 volts to 48 volts. The power is provided at 60 cycles per second with a current of 5 MA. This is for a panel size of 250 x 500 mm. For larger panels the current should be increased to 10 MA. The panel will also operate on a D/C power supply, but an A/C power supply is preferred.