Donaldson Company Unveils New Polysulfone and Poly (N-vinyl lactam) Alloys for Micro and Nanofiber Filters with Improved Performance

FIG. 4  is a SEM photo micrograph of Donaldson polysulfone and a poly (N-vinyl lactam)alloy microfiber for filtration.

Donaldson Company, Inc. (Minneapolis, MN)  patented improved filtration alloy material, as well as nanofiber and microfiber materials made from the improved alloy. The nanomaterial can be utilized in liquid filter systems, i.e. wherein the particulate material to be filtered is carried in a liquid. Such a material can be used in aqueous filtration at low pressure drop and acceptable efficiency. Also, in certain arrangements the nanofibers may be used in mist collectors, for example arrangements for filtering fine mists from air.

The Donaldson alloy includes a polysulfone and a poly (N-vinyl lactam). Inventors Ismael Ferrer, Richard S. Cardinal and Veli Kalayci “surprisingly found” that the polysulfone polymers can be alloyed with an N-vinyl lactam polymer.

The polymer materials, which are disclosed in U.S. Patent  7,641,055,  have substantially improved resistance to the undesirable effects of heat, humidity, aqueous liquids, solvent streams, high flow rates, high particle loads, reverse pulse cleaning, operational abrasion, submicron particulates, cleaning of filters in use and other demanding conditions in both gas and liquid filtration. The improved microfiber and nanofiber performance is a result of the improved character of the polymeric materials forming the microfiber or nanofiber, according to

Further, the filter media of the invention using the improved polymeric materials of the invention provides a number of advantageous features including higher efficiency, lower flow restriction, high durability (stress related or environmentally related) in the presence of abrasive particulates and a smooth outer surface free of loose fibers or fibrils. The overall structure of the filter materials provides an overall thinner media allowing improved media area per unit volume, reduced velocity through the media, improved media efficiency and reduced flow restrictions.

The fine fiber can be made of the polymer alloy or a polymer alloy plus additive or other material. The polymer alloy can be formed into single chemical specie such that it shows a single T.sub.g and the Differential Scanning Calorimeter analysis reveals a single polymeric material. Such a material, when combined with a useful additive material, can form a surface coating of the additive on the microfiber that provides oleophobicity, hydrophobicity or other associated improved stability when contacted with high temperature, high humidity and difficult operating conditions. Such microfibers can have a smooth surface comprising a discrete layer of the additive material or an outer coating of the additive material that is partly solubilized or alloyed in the polymer surface, or both structures.

The blending of the polysulfone and poly (N-vinyl lactam) polymers is used to tailor existing commercial polymers to specific end use requirements. The blending of polysulfones with polymers presents opportunities, but at the same time poses some significant technical challenges. Miscibility of PSF or PES with any nonsulfone-based polymer is extremely rare. Blends comprising PSF, PES, and PPSF and poly (N-vinyl lactam) are miscible, although their blends form mechanically compatible mixtures with relatively stable phase morphologies

FIG. 5 is a SEM photo micrograph of a Donaldson microfiber for filtration.

FIG. 6 is a SEM photo micrograph of a Donaldson polysulfone and a poly (N-vinyl lactam) alloy for filtration.

Polysulfones are rigid and tough, with practical engineering strength and stiffness properties even without reinforcement. Their strength and stiffness at room temperature are high compared to traditional aliphatic backbone amorphous plastics. The polymers exhibit ductile yielding over a wide range of temperatures and deformation rates. The room temperature mechanical properties of bisphenol A, bisphenol S, and bisphenol-based polysulfones are shown above. The tensile and flexural properties as well as resistance to cracking in chemical environments can be substantially enhanced by the addition of fibrous reinforcements such as chopped glass fiber.

Polysulfones exhibit excellent inherent burning resistance characteristics compared to many engineering thermoplastics. The wholly aromatic polysulfones such as PES and PPSF possess particularly outstanding flame retardancy and very low smoke release characteristics.

Polysulfones offer excellent electrical insulative capabilities. The resins exhibit low dielectric constants and dissipation factors even in the GH.sub.z (microwave) frequency range. This performance is retained over a wide temperature range and has permitted many applications.

The blending of the polysulfone and poly (N-vinyl lactam) polymers is used to tailor existing commercial polymers to specific end use requirements. The blending of polysulfones with polymers presents opportunities, but at the same time poses some significant technical challenges. Miscibility of PSF or PES with any nonsulfone-based polymer is extremely rare. Blends comprising PSF, PES, and PPSF and poly (N-vinyl lactam) are miscible, although their blends form mechanically compatible mixtures with relatively stable phase morphologies. 


FIG. 15 and 18 are SEM photo micrographs of Donaldson nanometer polysulfone and a poly (N-vinyl lactam) alloys for filtration.

Donaldson's micro and nano polymer materials  have substantially improved resistance to the undesirable effects of heat, humidity, high flow rates, reverse pulse cleaning, operational abrasion, submicron particulates, cleaning of filters in use and other demanding conditions. The improved microfiber and nanofiber performance is a result of the improved character of the polymeric materials forming the microfiber or nanofiber. 

Further, the filter media using the improved polymeric materials provides a number of advantageous features including higher efficiency, lower flow restriction, high durability (stress related or environmentally related) in the presence of abrasive particulates and a smooth outer surface free of loose fibers or fibrils. The overall structure of the filter materials provides an overall thinner media allowing improved media area per unit volume, reduced velocity through the media, improved media efficiency and reduced flow restrictions.