Air filter comprising polymer foam/adsorbent (e.g. zeolite)/antibacterial metal

Air filters Field of the Invention The present invention relates to air filters, methods of making and uses thereof. In particular, the present invention relates to air filters comprising an antimicrobial or antibacterial material and a material for removing volatile organic compounds by adsorption. The present invention also relates to polymer foams suitable for use in said air filters and which provide at least antibacterial and/or antiviral properties and methods of making said polymer foams. The present invention also relates to composite materials which possess antimicrobial or antibacterial and adsorptive properties for use in said air filter and methods of making said composites. The present invention also relates to the polymer foams and composite materials obtainable from said methods. The air filters in accordance with the present invention are useful in a range of environments and are particularly useful in the airline industry, including in aircraft cabins. Background of the Invention Air filters are used in a broad range of environments. There are particularly stringent requirements placed on air filters which are used in various environments such as the health industry and the airline industry, for example in aircraft cabins. It is desirable for such a filter to be capable of removing volatile organic compounds (VOC), odours and trapping, and preferably killing, bacteria and/or virus and/or fungus. Providing an air filter that is able to provide all of these functions presents an on-going challenge and there is an on-going significant need to provide such a filter for use in a range of environments. Currently in air filters suitable for use in aircraft cabins, generally air passes from the bottom of the cabin through recirculation filters into a mixing chamber where it is mixed with outside air. Typically, the air is mixed with outside air (about 50/50 by volume) and then passed back into the cabin. Standard airline cabin air exchange rates range from 15 to 20 air changes per hour. The ventilation capacity varies substantially, dependent on the aircraft type but typically averages 4.7L/S (10ft<3>/min). Some filters are used on commercial aircraft where air is circulated every 3 to 5 minutes. Many filters which are currently in use simply trap the bacteria and do not kill them. So called High Efficiency Particulate Arrestance, or Arresting (HEPA) filters are one of the types of air filters currently used in medical facilities, automobiles, aircraft and homes. To qualify as HEPA by US government standards an air filter must remove from air that passes through it, 99.97% of particles that have a size of 0.3pm. However, there are a number of disadvantages associated with HEPA filters. HEPA filters cannot be cleaned to remove particulate, microbial agents and dust loading and must be replaced as a complete assembly often at significant cost. As the particle load increases so will the resistance to air flow and hence a pressure drop across the filter will occur. In some applications, uneven filter loading will cause non uniform airflow through the filter and decreased effectiveness. Polymer foams are used in a wide variety of applications such as packaging and insulation. Polymer foams are made up of a solid and gas phase mixed together to form a foam. The resulting foam has a polymer matrix with air bubbles and/or air tunnels incorporated in it which may be referred to as a closed cell or an open cell structure. The gas that is used in the foam is termed a blowing agent and may be chemical or physical in nature. Physical blowing agents are gases that do not react chemically with the foaming process and are therefore inert to the polymer forming the matrix. Chemical blowing agents are chemicals that take part in a reaction or decompose giving off chemicals in the process.