Thermoadhesive conjugate fibers and nonwoven fabric employing them

A method for producing a nonwoven fabric made of thermoadhesive conjugate fibers, the method comprising:

• providing a first thermoplastic resin component comprising a modified polyolefin with at least one type of reactive functional group and a second thermoplastic resin component comprising polyester with a higher melting point than the melting point of the first thermoplastic resin
• component,
• wherein the component ratio of the first component and the second component in fiber cross-section is in the range of 10/90 to 90/10;
• spinning the first thermoplastic resin component and the second thermoplastic resin component at a temperature of from 180 to 350 °, to obtain spun conjugate fibers comprising the first and the second thermoplastic resin components, the first component being formed continuously along the length of at least of a portion of the conjugate fiber surface;
• drawing the spun conjugate fibers at a temperature lower than the melting point of the first thermoplastic resin component to obtain drawn conjugate fibers;
• coating the surfaces of the drawn conjugate fibers with a fiber treating agent comprising a multifunctional compound reacting with the reactive functional group of the modified polyolefin, the coating ranging from 0.1 to 2.0 wt% based on the weight of the fibers, to obtain the thermoadhesive conjugate fibers;
• cutting the thermoadhesive conjugate fibers to form webs of the thermoadhesive conjugate fibers;
• subjecting the webs to heat treatment at a working temperature above the melting point of the first thermoplastic resin component and below the melting point of the second thermoplastic resin component to allow for crosslinking reaction between the multifunctional compound and the reactive group of the modified polyolefin to result in a crosslinked structure at adhesive points between the thermoadhesive conjugate fibers;
• and
• obtaining the nonwoven fabric made of the thermoadhesive conjugate fibers,
• provided that when the multifunctional compound is a polyamine, the polyamine is ethylenediamine or diethylenetriamine.

A method of producing a nonwoven fabric comprising:

• forming a web comprising thermoadhesive conjugate fibers coated with 0.1 to 2 wt% of a fiber treating agent on a surface of the fibers, the fiber treating agent comprising a multifunctional group, the thermoadhesive conjugate fibers comprising first and second thermoplastic resin components, the first component being a modified polyolefin resin with at least one type of reactive functional group, formed continuously along a length of at least of a portion of the conjugate fiber and the second component having a melting point that is greater than a melting point of the first component wherein the component ratio of the first component and the second component in fiber cross-section is in the range of 10/90 to 90/10;
• and
• subjecting the web to heating at a temperature above a melting point of the first component and below a melting point of the second component to crosslink the thermoadhesive conjugate fibers and form the nonwoven fabric, wherein the modified polyolefin reacts with the multifunctional compound of the coating during heating and crosslinks the thermoadhesive conjugate fibers at adhesive points between the thermoadhesive conjugate fibers,
• provided that when the multifunctional compound is a polyamine, the polyamine is ethylenediamine or diethylenetriamine.