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

An improved nonwoven laminated composite article capable of readily undergoing pleating to form a pleated depth gaseous filtration medium consisting essentially of:

• (a) an outer substantially fully bonded air-permeable continuous filament polyester web containing a fiber component of at least 85 mole percent polyethylene terephthalate having a denier per filament of approximately 2 to 5 and a unit weight of approximately 3 to 5 oz./yd..sup.2,
• (b) an outer substantially fully bonded air-permeable high loft polyester batt containing a fiber component of at least 85 mole percent polyethylene terephthalate and comprising a randomly-dispersed blend of crimped fibers having lengths of approximately 1 to 3 inches and having at least two different deniers wherein one of the deniers is within the range of approximately 4 to 8 and another of the deniers is within the range of approximately 12 to 18, and said web has a unit weight of approximately 1 to 4 oz./yd..sup.2, and
• (c) an intermediate substantially unbonded air-permeable continuous filament polyester web containing a fiber component of at least 85 mole percent of polyethylene terephthalate disposed between web (a) and batt (b) having a denier per filament of approximately 1.5 to 4 and a unit weight of approximately 0.75 to 2 oz./yd..sup.2,
• wherein said webs at intermittent locations are mechanically secured together in a juxtaposed surface-to-surface relationship through the use of needle-punching wherein needles having a fiber-advancing configuration have been introduced successively through batt (b), web (c), and web (a) prior to their withdrawal with the retention of substantial loft within batt (b), and at least the outer surface of web (a) was lightly resin coated subsequent to said needle-punching while retaining permeability for gaseous filtration.

An improved nonwoven laminated composite article capable of readily undergoing pleating to form a stable pleated depth gaseous filtration medium consisting essentially of:

• (a) an outer substantially fully bonded air-permeable continuous filament polyester web containing a fiber component of at least 85 mole percent polyethylene terephthalate having a denier per filament of approximately 4 and a unit weight of approximately 4 oz./yd..sup.2,
• (b) an outer resin bonded high loft polyester batt containing a fiber component of at least 85 mole percent polyethylene terephthalate and comprising a randomly-dispersed blend of crimped fibers having lengths of approximately 2 inches wherein approximately 60 percent by weight of the fibers have a denier of approximately 6 and approximately 40 percent by weight of the fibers have a denier of approximately 15, and said web has a unit weight of approximately 3 oz./yd..sup.2, and
• (c) an intermediate substantially unbonded air-permeable continuous filament polyester web containing a fiber component of at least 85 mole percent polyethylene terephthalate disposed between web (a) and batt (b) having a denier per filament of approximately 2.2, and a unit weight of approximately 1 oz./yd..sup.2,
• wherein said webs at intermittent locations are mechanically secured together in a juxtaposed surface-to-surface relationship through the use of needle-punching wherein needles having a fiber-advancing configuration have been introduced successively through batt (b), web (c), and web (a) prior to their withdrawal with the retention of substantial loft in web (b) at a frequency of approximately 275 to 325 penetrations per square inch;
• the outer surface web (a) following said needle-punching has been subjected to a heat relaxation step by contact with a heated roll which was rotated in the direction opposite to the movement of web (a);
• the outer surfaces of web (a) and batt (b) were lightly coated with an acrylate resin following said heat relaxation step wherein the acrylate resin is applied in a total concentration of 6 to 12 percent by weight based upon the total weight of the composite article while retaining permeability for gaseous filtration;
• and wherein no component capable of substantial moisture retention is present.