The present invention relates to a nonwoven having a non-symmetrical bonding configuration yielding low tensile strength and high percent elongation in a first direction (e.g., CD) and high tensile strength and low percent elongation in a second direction (e.g., MD).
Spunbond nonwoven fabrics are made of continuous strands or filaments that are laid down on a moving conveyor belt in a randomized distribution. In a typical spunbond process, resin pellets are processed under heat to a melt and then fed through a spinnerette to create hundreds of thin filaments or threads. Jets of air cause the threads to be elongated, and the threads are then blown onto a moving web where they are laid down and sucked against the web in a random pattern to create a fabric. The fabric then passes through a bonding station. Bonding is necessary because the filaments or threads are not woven together.
The typical bonding station includes a bonding roll defining a series of identical raised points (bonding points). These bonding points are generally equidistant from each other and are in a uniform symmetrical pattern extending in both the machine direction (MD) and the cross direction (CD).
Other nonwoven fabrics include fabrics made from staple fibers, meltblown fibers, carded fibers and and short cut fibers. As used herein the terms “spun fibers” and “fibers” include the spun filaments described above as well as staple fibers, meltblown fibers, carded fibers and and short cut fibers.
A non-symmetrical bonding pattern could result in a fabric with an expected or standard elongation in one direction (e.g., MD), but increased elongation in the other direction (e.g., CD). This is a desired attribute in situations where minimal elongation is required in the machine direction and yet high elongation is required in the cross direction. For example, any elongation in the machine direction will disrupt the converting machines that are used to make diapers, while substantial elongation in the cross direction is desired to give each individual diaper some give around the wearer's waist.
Accordingly, it is an object of the present invention to provide a nonwoven having a non-symmetrical bonding configuration.
Another object of the present invention is to provide a nonwoven fabric which is highly extensible in a first direction (typically the CD) as compared to a second direction (typically the MD).
Another object is to provide such a nonwoven having low tensile strength and high percent elongation in the first direction (typically the CD), and high tensile strength and low percent elongation in the second direction (typically the MD).
It is also an object of the present invention to provide such a nonwoven which is simple and economical to manufacture, use and maintain.