Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Spun-bonded nonwoven fabric
Reexamination Certificate
2001-06-18
2004-12-14
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Spun-bonded nonwoven fabric
C442S361000, C442S362000, C442S364000, C442S382000, C442S389000, C442S392000, C442S400000, C428S373000, C428S374000
Reexamination Certificate
active
06831025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to multiple component spunbond nonwoven fabrics and composite sheets thereof, which are soft, drapeable, and strong and which can be used in medical applications which require sterilization with gamma-radiation.
2. Description of Related Art
Nonwoven fabrics comprising multiple component fibers are known in the art. For example, Sugihara et al. U.S. Pat. No. 4,477,516 describes nonwoven fabrics obtained by forming a fiber aggregate of hot-melt-adhesive composite fibers composed of a first component of a polyethylene resin composition consisting of 50 to 100 weight percent of a straight chain low density polyethylene and 50 to 0% of another kind of polyethylene and a second component of a fiber-formable polymer having a melting point higher than either polyethylene in the first component by 30° C. or more. The nonwoven fabrics are described as being prepared by processes such as carding, air-laying, dry pulping, and wet paper-making processes. Tabor et al. U.S. Pat. No. 5,372,885 describes preparation of bicomponent fibers and nonwoven fabrics therefrom by contacting under thermally bonding conditions (a) a first component being at least one high performance polymer such as poly(ethylene terephthalate), poly(butylene terephthalate), nylon or the like, and (b) a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by including in the second component at least one grafted olefinic polymer having pendant succinic acid or succinic anhydride groups. Preferably the second component comprises at least one grafted ethylene polymer. Filaments comprising the acid-containing grafted linear ethylene polymer or polymer blends are dyeable.
Multi-layer nonwoven laminates comprising spunbond and melt-blown layers, such as spunbond-meltblown-spunbond (“SMS”) nonwovens are known in the art. In SMS nonwoven laminates, the exterior layers are spunbond nonwoven webs that contribute strength to the overall composite, while the middle or core layer comprises a meltblown web which provides barrier properties. Similarly, composite nonwovens comprising additional layers of spunbond or meltblown webs can be prepared, as in spunbond-meltblown-meltblown-spunbond (“SMMS”) nonwovens. Terakawa et al. U.S. Pat. No. 6,187,699 describes multi-layer nonwoven fabrics which comprise (a) a composite continuous filament spunbond nonwoven composed of a low melting point resin component and a high melting point resin component with the low melting point resin forming at least a portion of the surface of the spunbond fibers and (b) a composite meltblown extra-fine-fiber nonwoven fabric having a fiber diameter of 10 &mgr;m or less and being composed of a low melting point resin and a high melting point resin with the low melting point resin forming at least a portion of the surface of the meltblown fibers. The fibers in each of the nonwoven layers are thermally fused. Examples of combinations of resins that can be used to prepare the composite filaments or fibers include high density polyethylene/polypropylene, high density polyethylene/polyethylene terephthalate, and a mixture of linear low-density polyethylene and high-density polyethylene/polypropylene. The composite fibers can be sheath-core, side-by-side, multi-layer, etc.
For certain nonwoven end uses, such as medical garments, it is desirable that the nonwoven fabrics have good strength and barrier properties while also being as soft and drapeable as possible. For medical end uses, it is also desirable that the nonwoven fabrics be made of fibers of polymers which can be sterilized with gamma radiation. SMS fabrics have traditionally been polypropylene-based and have the limitation that they cannot be sterilized with gamma radiation because the fabrics are discolored and weakened as a result of the sterilization process. In addition, gamma-irradiation of polypropylene based fabrics results in the generation of unpleasant odors. This presents a significant problem for polypropylene-based SMS fabrics because radiation sterilization is commonly used throughout the medical industry.
There remains a need for low-cost nonwoven fabrics which have an improved combination of strength, barrier properties, drapeability, and softness and which can be sterilized by gamma radiation without significantly degrading the properties of the fabric and/or generating unpleasant odors.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the present invention is a spunbond nonwoven fabric comprising continuous multiple component filaments having a cross-section, a length, and a peripheral surface and comprising a polyester component and a polyethylene component arranged in substantially distinct zones across the cross-section of the multiple component filaments and extending substantially continuously along the length of the multiple component filaments, at least a portion of the peripheral surface of the multiple component filaments comprising the polyethylene component, and the polyethylene component comprising a blend of linear low density polyethylene and high density polyethylene, the high density polyethylene being present in an amount greater than 50 weight percent of the polyethylene component.
Another embodiment of the present invention is directed to a composite sheet comprising a first layer having a first side and an opposite second side; and a second layer attached to the first side of the first layer comprising a spunbond web of continuous multiple component filaments, the multiple component filaments having a cross-section, a length, and a peripheral surface and comprising a polyester component and a polyethylene component arranged in substantially distinct zones across the cross-section of the multiple component filaments and extending substantially continuously along the length of the multiple component filaments, the polyethylene component comprising a blend of linear low density polyethylene and high density polyethylene, at least a portion of the peripheral surface of the multiple component filaments comprising the polyethylene component.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed toward a multiple component continuous filament spunbond web and composites thereof. The multiple component spunbond web is comprised of filaments which include a polyester component and a polyolefin component. The polyolefin component comprises a first linear low density polyethylene and a high density polyethylene. The polyester component imparts strength to the bicomponent fibers while the polyethylene component imparts a soft hand and lowers the overall bending modulus of the fibers. In a preferred embodiment, two layers of the multiple component spunbond web are bonded to opposite sides of a multiple component meltblown web wherein the multiple component meltblown fibers comprise a second linear low density polyethylene. The first and second linear low density polyethylenes are copolymers of ethylene and an alpha-olefin. The same alpha-olefin is preferably used to prepare the first and second linear low density polyethylenes. The multiple component spunbond fabrics of the current invention are radiation sterilizable. A fabric is considered to be “radiation sterilizable” when sterilization of the fabric with gamma radiation does not cause a reduction in the strength of the fabric, noticeably change the appearance of the fabric, or cause the generation an objectionable odor.
High density polyethylenes generally spin well in conventional spunbond processes, with very low levels of volatile materials being emitted during spinning, resulting in substantially no formation of deposits on the spinning apparatus. However high density polyethylenes generally yield relatively stiff filaments which makes it difficult to lay the filaments down uniformly on a collecting surface during a spunbond process and provides non-uniform spunbond webs having a hard hand. In addition, the bonding window for high density polyethylene filaments is somewh
Bansal Vishal
Davis Michael C.
Rudisill Edgar N.
Befumo Jenna-Leigh
E. I. du Pont de Nemours and Company
Juska Cheryl A.
LandOfFree
Multiple component spunbond web and laminates thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiple component spunbond web and laminates thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiple component spunbond web and laminates thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3319827