Challenges of Filtering Gels for Manufacturers
Removal of gels from a solution is a common and challenging filtration problem. Gels are formed during a polymerization process (desired) or as a side reaction or under-reaction (undesired) during a manufacturing process. These gels form a cross-linked, networked structure and are not readily dissolved in solvents in the manufacturing state. Instead, they tend to swell to several times their original size when in contact with solvents.
Gels can present a filtration challenge in many diverse applications. These include photo chemicals, photo emulsions, cosmetics, paper coatings, adhesives, silicones, CD/DVD coatings, and magnetic media to name a few. The primary filtration challenge is due to the gel's ability to deform upon application of stress. The degree of deformation is typically dependent upon the level of operating pressure (differential). At low to intermediate differential pressures, the gel particles can sufficiently deform to block filter media. Such complete blockage precludes the formation of a cake resulting in diminished filter life.
However, if the differential pressure is elevated to maintain the flow through the filter, or recommended flow rates of 1 to 3 GPM per 10” (for 0.45 to 3 micron filters) are exceeded, then gels can sufficiently deform and extrude through the media, even those with rated pore diameters significantly less than the dimensions of the swollen gel particle itself. Consequently, the selection of the optimum filter cartridge for gel removal depends upon the viscosity of the solution, the operating differential pressure, and the gel concentration.
Depth media is generally recommended for removal of gels in highly viscous solutions with medium to high concentrations of gel particles. Depth filters, however, tend to be limited by the available surface area (<.75 sq ft per 10” filter) and thus may have short on-stream life. Traditional single layer pleated filters on the other hand have much higher surface area, but lack the depth necessary to prevent extrusion of the gel particles.
QXL™ Series Filter Cartridges
A hybrid pleated/ depth filter such as the QXL overcomes the short-comings of both depth and pleated filters while offering high surface area for long life coupled with a layered depth media to prevent gel extrusion.
It is constructed entirely of polypropylene, which makes it compatible with a broad range of solutions and chemicals. The optimized pleat configuration provides the ideal combination of retention, flow rate and throughput. It features excellent gel and agglomerated particle retention capabilities, thereby reduces defects
Typical applications include CMP P-O-U and bulk slurries, the manufacturing of adhesives, paints, beverages, ink, and coating. It is also available in common end cap configurations and retrofits easily into most existing filter housings.