Abstract: The invention refers to a composite filter for filtering a stream of ambient air including at least one non-prebonded upstream tier and one non-prebonded downstream tier, wherein the ratio of absolute pore volume of upstream tier to downstream tier RAPV>2, and the absolute projected fiber coverage of upstream tier and of downstream tier APFC>95%. Further, the invention refers to a method of making such a composite filter including the steps of (a) laying down a filtration material onto a support to form the upstream non-prebonded tier, (b) depositing onto the upstream tier the downstream non-prebonded tier, and (c) bonding the tiers to form a composite filter having a unitary stratified structure.

Abstract: A composite filter for removing particulates entrained in a gas has stack of at least two non-pre-bonded tiers of filter material which are bonded together to form a unitary stratified structure. The tiers can include thermally bindable components such as bicomponent or monocomponent polymer fibers, or adhesively bindable components, such as pulp fibers, especially fluff pulp, split film fibers, mixed electrostatically charged fibers and staple fibers. In addition to vacuum cleaner bags, the novel filter composite can be utilized in applications such as heating ventilation and air conditioning (HVAC) systems, vehicle cabin air filters, high efficiency (so-called “HEPA”) and clean room filters, emission control bag house filters, respirators, surgical face masks and the like.

Abstract: A vacuum filter bag is constructed of layers which include a high air permeability multipurpose layer positioned upstream in the direction of air flow of a second filtration layer. The second filtration layer can be a wet-laid filter paper, a dry-laid filter paper or a spunbond nonwoven. The multipurpose layer can be made of high bulk meltblown nonwoven, dry-laid or wet-laid high dust holding capacity paper spunblown modular or microdenier spunbond. The high dust capacity papers are characterized by greater thickness and higher air permeability than is normally used in traditional filter layers of vacuum cleaner bag structures. These characteristics allow the high capacity papers to filter large dirt particles and to capture within their pores large amounts of dust particles. This protects the downstream second filtration layer from shock loading and enables the composite structure to pass air at high rate at low pressure differential for much longer than conventional vacuum cleaner bags.

Abstract: A disposable vacuum cleaner filter bag is constructed of layers which include a filtration grade meltblown fleece layer having a basis weight of about 10-50 g/m2 and air permeability of about 100-1000 L/(m2×s) and a coarse filter layer in which the coarse filter layer is placed upstream of the filtration grade meltblown fleece layer. The coarse filter layer can include either wet-laid high dust capacity paper, dry-laid high dust capacity paper, high bulk meltblown nonwoven, Spunblown (Modular) nonwoven or microdenier spunbond nonwoven. Juxtaposition of the layers causes the coarse filter layer to capture large dirt particles and permits the filtration grade meltblown fleece layer to capture much of the remaining dust particles. The novel bag exhibits high air permeability and low pressure drop at high dust loading. A method of filtering gas through such a filter is also disclosed.

Abstract: For manufacturing filter material, a non-woven filter web is formed from electrostatically charged dielectric fibers. In order to give dimensional stability to the filter material without adversely affecting the permeability of the filter material, filaments or narrow strips are placed essentially at a distance from each other on at least one of the two sides of the filter web and fixed to the non-woven filter web.

Abstract: A novel pleated fibrous structure is disclosed, which fibrous structure comprises a layer of a pleated split fiber film. The layer of split fiber film may be electrostatically charged. The pleated split fiber film may be part of a composite fibrous structure further comprising a support of a nonwoven or scrim.