There are many types of air filters, which can be grouped in two classes according to their field of application and performance: fine-dust and coarse-dust filters (according to ISO 16890) and HEPA filters (high-efficiency submicron particulate air filters according to DIN EN 1822: 2011).

Which type of filter is used depends on the application and the particle concentrations that are to be achieved. The fields of application of air filters include

• Air conditioning systems, ventilation systems (e.g. in living spaces, public buildings, and production facilities)
• Clean room facilities (e.g. in the medical or food industry, aerospace, and nuclear engineering)

Air filters are manufactured in a variety of designs and must fit perfectly to the respective application. In addition to filter media, polyurethane, epoxy, and hotmelt adhesives play a decisive role in the performance of air filters. Here, RAMPF Polymer Solutions offers numerous products.

Filter elements are fixed in the filter frame by casting compounds (compact and hard foam). The frames are made mostly of the thermoplastic plastics acrylonitrile-butadiene-styrene copolymer (ABS) or polystyrene (PS) as well as aluminum or medium-density fiberboards (MDF).

RAMPF has developed compact, two-component RAKU® PUR polyurethane casting systems that are highly flowable, silicone-free, and (if required) antibacterial. Due to the good adhesion to plastic, especially ABS and PS, the connecting bridge can be used as a supporting element, which increases the stability of the filter elements.

Filled hard foams are used to fix the filter medium in the frame. For this purpose, RAMPF’s RAKU® PUR systems exhibit high mechanical strength, highly abrasion-resistant surfaces, very good adhesion properties, and high chemical resistance

The filter elements must be sealed before they are installed into the ventilation systems. For this purpose, the filter elements are partially equipped with a foamed seal.

Liquid and thixotropic RAKU® PUR sealing foams are used to seal the filter elements. These systems are available with antibacterial properties, exhibit fast curing and fast process times as well as a good compression set, i.e. there is only a low residual deformation of the foam after pressure load.

There are numerous applications in the filter industry in which hotmelt systems are used, among others for fixing the individual filter elements (pleating) and for bonding the individual filter papers. Hotmelts from RAMPF are used for bonding the filter papers.

These RAKU® MELT products have been certified for use in applications in the food industry and exhibit short curing times as well as high temperature and chemical resistance.