Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1995-01-18
2001-08-14
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S351000, C428S208000, C428S354000, C428S365000
Reexamination Certificate
active
06274238
ABSTRACT:
The present invention is directed to a nonwoven fiber web. More particularly, the present invention is directed to a bonded nonwoven fiber web having improved physical strength.
Nonwoven fabrics produced from thermoplastics have been widely used especially for disposable articles. However, nonwoven fabrics do not tend to exhibit the physical strength of woven fabrics. There have been many attempts to provide nonwoven fabrics having improved physical strength properties. For example, European Patent Application 0 552 013 provides a strength-improved polypropylene nonwoven web produced from a blend of at least two polypropylene resins having different melt flow rates. European Patent Application 0 445 536 discloses a high strength melt spun polyolefin fibers that are selectively subjected to an oxidative degradation process to contain distinct cross sections having different degrees of oxidative degradation.
However, the prior art processes of producing monocomponent fibers having improved strength require a careful selection of different polymers or a complicated production process. Consequently, it would be highly desirable to provide a strength-improved fiber web that can be produced from one polymer without the need for a complicated manufacturing process.
SUMMARY OF THE INVENTION
The present invention provides a high strength autogenously bonded nonwoven fabric containing single polymer conjugate fibers which have at least two substantially the same component compositions. The component compositions of the fibers have one thermoplastic polymer selected from the group consisting of semicrystalline thermoplastic polymers, crystalline thermoplastic polymers and blends thereof, wherein the component compositions are processed with substantially identical processing conditions to form the fibers. In addition, the component compositions of the fibers have substantially the same melt flow rate as measured in accordance with the ASTM 1238-65T testing procedure.
The present invention further provides a process for producing a high strength bonded nonwoven fabric comprising the steps of supplying at least two melt-extrudate streams of a thermoplastic polymer to a sheath-core conjugate fiber forming apparatus to form conjugate fibers, depositing the conjugate fibers onto a forming surface to form a nonwoven fiber web, and thermally bonding the nonwoven fiber web, wherein the melt-extrudates have substantially the same melt flow rate as measured in accordance with the ASTM 1238-65T testing procedure and the thermoplastic polymer is selected from the group consisting of semicrystalline polymers, crystalline polymers and blends thereof.
The bonded nonwoven fabric of the present invention fabricated from single polymer sheath-core conjugate fibers of a semicrystalline or crystalline polymer provides improved physical properties over bonded monocomponent fiber fabric of the same the same polymer.
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Dean, Jr. Ralph H.
Dixon Merrick
Kimberly--Clark Worldwide, Inc.
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