Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-11-29
2001-10-16
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S370000, C428S373000, C428S374000, C442S352000, C442S353000, C442S361000, C442S364000
Reexamination Certificate
active
06303220
ABSTRACT:
This invention relates to a polyethylene fiber and a non-woven fabric comprising the polyethylene fiber. More specifically, this invention relates to a polyethylene fiber being soft and having good touch feeling suitable mainly for medical use and to a non-woven fabric using the polyethylene fiber and medical or hygienic materials using the same.
BACKGROUND OF THE INVENTION
Presently, disposable materials made of non-woven fabrics for medical use such as surgical caps, surgical sheets, surgical covering clothes, surgical gowns are spreading rapidly. Problems of hospital infection such as an infection of MRSA (methicillin-resistant Staphylococcus aureus), hepatitis, HIV (human immunodeficiency virus) or O-157 necessitate the use of disposable materials. Further, using disposable non-woven materials requires no necessity for cleaning, so that nursing can be simplified without deteriorating nursing quality. Also it can be one of solutions for a labor shortage that has been becoming serious social problem. The non-woven fabric for medical use is required to have bacteria barrier property, anti-permeability, water repellency, lint free property and so on, but also importantly the fabric is required to have good wear feeling, strong tenacity and cost performance because the fabric is disposable for only one time use.
As raw materials of fibers for a non-woven fabric, polyethylenes, polypropylenes and polyesters are widely used. It is conventional to use these raw materials to make non-woven fabrics for medical use. However, the fabrics made with these raw materials have some disadvantages. For example, non-woven fabrics for medical use are frequently disinfected under radiation. Polypropylene fibers lose their tenacity under radiation because chemical bonds on tertiary carbon atoms are cut, thus making polypropylene not very suitable for as a non-woven fabric material. While radiation does not weaken the tenacity of the polyester fibers, the cost of polyester resins is higher than polyolefin resins. And when polyester non-woven fabric having high basis weight is used to make the fabric tenacious enough to avoid being torn by user's body action, or to make the fabric opaque, the fabric becomes hard and has poor wear feeling, or lacks a light feeling due to the nature of the polyester resin. Because of these disadvantages, polyester non-woven fabrics are not generally used to make fabrics for medical use. Contrary to this, polyethylene resins are useful in making non-woven fabrics for medical because they produce soft non-woven fabrics due to the nature of the resin material. In addition, polyethylene resins do not have tertiary carbon atoms to weaken the tenacity under radiation.
However, conventional polyethylene fibers do not have enough stiffness due to the raw material resin's nature of softness, so it has been a problem that crimps which withstand a tension under carding process cannot be provided. It has been conventionally known that some polyethylene fibers and non-woven fabrics experimentally obtained are very soft, but in view of commercial practice, it has been very difficult to process them into high quality non-woven fabric at low cost, so a polyethylene fiber having good cardability is strongly desired. As a polyethylene fiber for medical use, for example, Japanese Tokkyo Kohyo Koho Hei 6-508892 (corresponds to PCT gazette WO93/01334) discloses a composite fiber composed of a high density polyethylene as a core component and a copolymer of ethylene and other &agr;-olefin (described linear low density polyethylene hereinafter) as a sheath component. However, the above fiber has weak retainability of crimps due to low breaking tensile strength and high breaking elongation, so that when the fiber is wound on a cylinder or doffer during the carding process, it may not be well ejected as a web or sometimes it makes neps. Thus, there some problems associated with conventional polyethylene fibers employed in the prior art.
SUMMERY OF THE INVENTION
This invention aims to present a polyethylene fiber having superior crimp retainability at carding process than conventional polyethylene fibers, and also having excellent radiation resistance, thus making the fibers useful for non-woven fabric for medical uses.
The present inventors have diligently solved the above problems associated with conventional polyethylene fibers by providing a polyethylene fiber having at least 2% of residual percentage crimp and by providing a polyethylene fiber spun and stretched to have at least 60 kg/mm
2
of apparent Young's modulus, at least 1.5 g/d of breaking tensile strength, 150% or less of breaking elongation.
The present invention provides for a polyethylene fiber consisting of at least one polyethylene resin, having at least 60 kg/mm
2
of apparent Young's modulus, at least 1.5 g/d of breaking tensile strength, 150% or less of breaking elongation, and at least 2% of residual percentage crimp.
The present invention also provides for a polyethylene fiber consisting of at least one polyethylene resin, having at least 80 kg/mm
2
of apparent Young's modulus, at least 3.2 g/d of breaking tensile strength, 110% or less of breaking elongation, and at least 2% of residual percentage crimp.
The present invention still further provides for the polyethylene fiber according to the above, wherein the polyethylene resin is a single component of high density polyethylene.
The present invention still further provides for the polyethylene fiber according to the above, wherein the polyethylene resin is a single component of linear low density polyethylene.
The present invention still further provides for the polyethylene fiber according to the above, wherein the fiber has a composite fiber configuration consisting of two different polyethylene resin components having at least 3° C. of melting points difference, wherein the first component is the polyethylene resin having higher melting point and the second component is the polyethylene resin having lower melting point.
The present invention still further provides for the polyethylene fiber according to the above, wherein the fiber has a composite fiber configuration consisting of two different polyethylene resin components having at least 3° C. of melting points difference, and the first component having higher melting point is the high density polyethylene resin and the second component having lower melting point is the linear low density polyethylene resin.
The present invention still further provides for the polyethylene fiber according to the above, wherein the fiber has a composite fiber configuration consisting of two different polyethylene resin components having at least 3° C. of melting points difference, and the first component having higher melting point is the high density polyethylene resin and the second component having lower melting point is the low density polyethylene resin.
The present invention still further provides for the polyethylene fiber according to the above, wherein the fiber has a composite fiber configuration consisting of two different polyethylene resin components having at least 3° C. of melting points difference, and the first component having higher melting point is the linear low density polyethylene resin and the second component having lower melting point is the low density polyethylene resin.
The present invention still further provides for the polyethylene fiber according to the above to be formed into a non-woven fabric.
The present invention still further provides for the non-woven fabric comprising polyethylene fiber according to the above, wherein the polyethylene fiber is mixed with an other fiber which is substantially non-thermo-bondable at a temperature the polyethylene fiber is thermally bonded.
The present invention still further provides for the non-woven fabric comprising the polyethylene fiber according to the above, wherein a web of the polyethylene fiber is point-bonded by point-bonding process.
The invention still further provides for the non-woven fabric comprising the polyethyl
Minamoto Koji
Suzuki Masayasu
Chisso Corporation
Edwards N.
McDermott & Will & Emery
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