Abstract: Polyolefin/polyester composite fibers having a low apparent Young's modulus and a filter element using the composite fibers are produced by subjecting a polyolefin as sheath component and a polyester as core component to composite spinning, stretching the resulting unstretched filaments to twice or more the original length at a temperature higher than the secondary transition point of the polyester by 20.degree. C. or higher and lower than the melting point of the polyolefin and annealing the stretched filaments at the above-mentioned temperature for 30 seconds or more, and having an apparent Young's modulus of 210 Kg/cm.sup.2 or less, and by winding up the above composite fibers on a core while heating the composite fibers to the melt-adhesion temperature of the sheath component, adjusting the void content to a desired one, followed by cooling and taking out the core.

Abstract: A method for making nonwoven fabrics includes the steps of preparing heat-adhesive composite fibers including first and second components, forming a web of the composite fibers alone or containing at least 20% by weight of the composite fibers, and heat-treating the web at a temperature higher than the melting point of the second component but lower than the melting point of the first component, while increasing the temperature of the web at a rate of temperature rise of 100.degree. C./30 seconds and more. The first component is polypropylene having specific physical values with respect to density, isotactic pentad ratio, pentad ratio having two different kinds of configurations, and melt flow rate, and the second component is a polymer composed mainly of polyethylene.

Abstract: A hot-melt-adhesive composite fiber having a broad temperature range of hot-melt adhesion, exhibiting a low heat-shrinkage over the whole temperature range thereof, having a high tenacity and suitable to production of a non-woven fabric having superior restoring properties, bulkiness, draping properties and feeling is provided, which composite fiber comprising a fiber-forming component and an adhesive component, the fiber-forming component comprising 0.5 to 30% by weight of a copolymer of a carboxyl group containing modified polyolefin with a polyamide, and the adhesive component comprising a carboxyl group-containing modified polyolefin, an unmodified polyolefin or a mixture thereof.

Abstract: In a process for producing tubular shaped fibrous articles of small diameter by heating and cooling a fibrous bundle containing at least 20 weight % of hot-melt-adhesive composite fibers, the improvements comprise using a shaping apparatus including an injecting chamber, an injecting hole formed in the wall of the chamber, a fibrous bundle outlet provided with a nozzle of a desired shape in cross-section, a cylindrical pipe for introducing the fibrous bundle, which has a cross-sectional area larger than that of the outlet, is located at a position opposite to the outlet and projects toward the outlet and terminates in the injecting chamber, and a core pipe which is open at its base on the outside of the injecting chamber, has its one end inserted through the cylindrical pipe and extending into the nozzle through the injecting chamber, and having a vent in its portion exposed within the injecting chamber, and passing the fibrous bundle through the cylindrical pipe to the outlet, while injecting a hot compresse