FiltreAutomobile et transports
Articles professionnels

High-performance adhesives for the manufacture of filter media

Air filters in vehicles and buildings are high-performance products. They ensure a constant supply of fresh and especially clean air. Filter media are very diverse and are frequently composed of different materials. Powerful adhesives for the manufacture of filters are not only characterised by a broad range of adhesion to the different materials but also facilitate superior products and efficient manufacturing processes.

Air filters in the automotive industry fulfil many functions: cabin filters keep the air clean inside the vehicle, engine intake air filters protect the engine against potential damages from contaminants like rust, pollen or dust. They are manufactured in a wide range of different processes in which tailor-made adhesives play a major role. The adhesives are adapted to the requirements in production such as fast line speeds as well as to downline processing and to the function of the high-performance filter. Jowat, the adhesives manufacturer from Detmold, presented at Filtech 2016 their adhesive portfolio for the manufacture of filter media and can look back on a successful trade fair. Especially a newly developed polyolefin hot melt adhesive for pleating and frame assembly attracted wide interest among visitors.

New high-performance adhesive for pleating and filter frame bonding
Pleated filter media consist of different materials, for instance paper or diverse nonwoven fabrics. Thermoplastic filter adhesives from Jowat for pleating and frame assembly are characterised by a broad spectrum of adhesion and have been developed for sealing and forming properties which also promote the largest possible process safety. Due to the special performance of these adhesives, the shape of the filters remains unchanged over their entire life, even when the material compound is exposed to mechanical forces or high temperatures. The thermoplastic adhesives facilitate a high bond strength even with a small application surface, long durability and superior quality of the filter elements.

Jowat has now added a new product to the series of polyolefin-based adhesives for pleating and frame assembly: The PO hot melt adhesive is characterised for instance by an increased heat resistance (cf. Jowat-Hightherm® 263.15). This property is a prerequisite especially when filter papers impregnated with phenolic resins are used since the curing takes place after pleating at temperatures of up to 180 °C in an oven. The adhesive applied in bead form for the lateral bonding of the filter pockets and to hold the folds in place has to resist to these temperatures, have the necessary flow properties and not sag into the substrate to ensure that the filter pockets do not develop leaks. In addition, the hot melt adhesive has an excellent resistance to oxidation in the melt. This leads to less charring and cleaning and therefore reduces downtimes. In addition, the new PO hot melt adhesive can be processed at lower temperatures and consequently provides a major input into energy efficiency. As an “all-rounder”, it can be used in filter frame assembly as well as in pleating, and therefore the same adhesive can be used in all bonding applications in the manufacture of filters. The processing characteristics of the hot melt can be adapted easily to the process cycles and requirements in production.

When the filter is assembled, the adhesive is applied onto the frame by flat coating and the ends of the pleats are embedded in it. This gives the filter medium the necessary solidity because filters are frequently exposed to heavy deformation during installation and change, especially due to the increasingly more compact engine compartments of cars. The bondline may not fail, the performance of the filter element may not be impaired. PO hot melt adhesives support the necessary properties of filter media due to high levels of strength and flexibility. The assembly inside the engine compartment also requires superior levels of temperature resistance: the filter bond may be exposed to temperatures from 80 to 130°C.

Lamination of activated charcoal filter media
Thermoplastic PO and reactive PUR hot melt adhesives facilitate flat surface bonds of activated charcoal media with a high permeability of the filter medium. Due to their special characteristics, these adhesives ensure effective and fast production processes and end products of superior quality. The adsorption and air permeability of the filter media is supported by the lamination of the multi-layer filter materials. When bonding the activated charcoal onto the carrier material only a low adhesive grammage is needed to achieve a high compound strength of the filter medium. This ensures that the open surface of the activated charcoal remains as large as possible for the filtration and a constant supply of fresh air – for an optimum performance of the activated charcoal filter.

The optimum spraying properties and high green strength of Jowat PO and PUR hot melt adhesives for the lamination of activated charcoal media allows fast downline steps and thereby efficient processes in the production of filter media. Due to their high flexibility, these adhesives support all downline processing steps like reeling and unreeling, cutting and pleating of the coated fleeces. The adhesive systems based on polyolefin and polyurethane meet the requirements of the specific manufacturing process and are characterised by different relevant process parameters such as open time, heat resistance or processing temperature. The suitable adhesive is selected according to the requirements of the manufacturing process and the purpose of the end product. Both adhesive systems are characterised by low fogging and emissions and are odourless.

EVA hot melt adhesives building filters
Jowat supplies special hot melt adhesives based on EVA for the pleating of filters for ventilation systems in the industries, office buildings or hospitals. These high-performance adhesives are characterised by optimum flow properties, do not shrink and in addition are available in pure white, a colour version which is demanded for clean room applications, for instance in hospitals.

By choosing an adhesive which is adapted optimally to the manufacturing requirements and to the properties of the end product, processors will enhance the performance of the filter medium and therefore its function for a constant supply of fresh air.
Different studies have shown that the air quality in the workplace can affect the performance of employees. Diseases caused by dusty environments in the workplace can be reduced significantly if suitable filters are used.

The Jowat hot melt adhesives for the manufacture of filters for ventilation systems in buildings are characterised by an optimum flexibility in the filter package and minimal emissions. They facilitate a highly efficient production due to lower energy consumption and good processing characteristics and therefore provide a major input into to the creation of value.

The professional article is published in the magazine 'F&S Filtrieren und Separieren' in German language. You can download the original article down below.