Nonwoven laminated composite article capable or readily undergoing pleating to form a stable pleated depth gaseous filtration medium

摘要

An improved nonwoven multi-layered composite article is provided that is well amenable to pleating and service as a depth gaseous filtration medium. The components utilized to form the multi-layered composite consist essentially of polyester continuous filaments and staple fibers (as described in detail hereafter) and are mechanically secured together by needle-punching. At least one surface is lightly resin coated following the needle-punching in order to impart additional stiffness to the overall nonwoven laminated composite. The resulting article is capable of readily undergoing pleating to form a pleated filtration medium. In a preferred embodiment the resulting composite is free of any component that is capable of substantial moisture retention thereby enhancing the stability and shape retention properties of the product over a broader range of operating conditions. Additionally, in a preferred embodiment an outer surface of the composite article has been subjected to a heat relaxation treatment prior to resin coating in order to reduce the size of needle holes and to enhance the particle arrestance and dust holding capacity of resulting article.