Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1998-12-15
2001-04-03
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S297400, C428S372000, C428S359000, C428S221000, C428S296700, C428S397000
Reexamination Certificate
active
06210798
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fibers made from polymers containing hard particles that have improved resistance to cutting.
BACKGROUND OF THE INVENTION
Improved resistance to cutting with a sharp edge has long been sought. Cut-resistant gloves are beneficially utilized in the meat-packing industry and in automotive applications. As indicated by U.S. Pat. Nos. 4,004,295, 4,384,449 and 4,470,251, and by EP 458,343, gloves providing cut resistance have been made from yarn which includes flexible metal wire or which consists of highly oriented fibers having high modulus and high tensile strength, such as aramids, thermotropic liquid crystalline polymers, and extended chain polyethylene.
A drawback with gloves made from yarn that includes flexible metal wire is hand fatigue with resultant decreased productivity and increased likelihood of injury. Moreover, with extended wear and flexing, the wire may fatigue and break, causing cuts and abrasions to the hands. In addition, the wire will act as a heat sink when a laundered glove is dried at elevated temperatures, which may reduce tensile strength of the yarn or fiber, thereby decreasing glove protection and glove life.
Improved flexibility and comfort and uncomplicated laundering are desirable in cut-resistant, protective apparel. Therefore, there is a need for a flexible, cut-resistant fiber that retains its properties when routinely laundered. Such a fiber may be advantageously used in making protective apparel, in particular highly flexible, cut-resistant gloves.
Polymers have been mixed with particulate matter and made into fibers, but not in a way that significantly improves the cut resistance of the fiber. For example, small amounts of particulate titanium dioxide has been used in polyester fiber as a delustrant. Also used in polyester fiber is a small amount of colloidal silicon dioxide, which is used to improve gloss. Magnetic materials have been incorporated into fibers to yield magnetic fibers. Examples include: cobalt/rare earth element intermetallics in thermoplastic fibers, as in published Japanese Patent Application No. 55/098909 (1980); cobalt/rare earth element intermetallics or strontium ferrite in core-sheath fibers, described in published Japanese Patent Application No. 3-130413 (1991); and magnetic materials in thermoplastic polymers, described in Polish Patent No. 251,452 and also in K. Turek et al.,
J. Magn. Magn. Mater.
(1990), 83 (1-3), pp. 279-280.
Various kinds of gloves have been made in which metal has been included in the fabrication of the glove to impart protective qualities to the glove. For example, U.S. Pat. Nos. 2,328,105 and 3,185,751 teach that a flexible, X-ray shield glove may be made by treating sheets of a suitable porous material with a finely divided, heavy metal which may be lead, barium, bismuth or tungsten, or may be made from a latex or dispersion containing heavy metal particles. As illustrated by U.S. Pat. No. 5,020,161, gloves providing protection against corrosive liquids have been made with a metal film layer. These gloves also do not appear to have significantly improved cut resistance.
SUMMARY OF THE INVENTION
A cut-resistant fiber and yarns based on that fiber are made from a fiber-forming polymer by including a hard filler distributed uniformly in the fiber. The hard filler has a Mohs Hardness value greater than about 3 and is present in an amount of about 0.05% to about 20% by weight. The fiber has cut resistance properties that are improved by at least 10% compared with the same fiber without the hard filler as measured by the Ashland Cut Protection Performance Test, described below. A method of making cut-resistant fabric is also taught. In this method, a uniform blend of a fiber-forming polymer and about 0.05% to about 20% by weight of a hard filler having a Mohs Hardness value greater than about 3 is made. The uniform blend is spun into a fiber or yarn, which is then fabricated into fabric having improved cut resistance in comparison with fabric made from the same fiber-forming polymer without the hard filler. The cut-resistant fabric may optionally also include other polymeric fibers and/or reinforcing inorganic fibers, which may be ceramic, metal or glass.
A new method of making a synthetic fiber or yarn more resistant to cutting with a sharp edge is also disclosed. The improved method comprises the step of including a hard filler having a Mohs hardness value greater than 3 in the synthetic fiber or yarn in sufficient quantity to improve the cut protection of the fiber or yarn by at least 20%, and preferably by at least 35%, as measured by the Ashland Cut Protection Performance Test. This is generally achieved by making a uniform blend of the molten polymer or polymer solution (dope) and then spinning the molten polymer or polymer solution (dope) into a fiber or yarn having improved cut protection performance. The preferred method is melt spinning.
The fibers and yarns described above can be made into fabrics that have improved resistance to cutting using any of the methods that are currently used for making fibers and yarns into fabrics, including weaving and knitting. The fibers and yarns can also be made into non-woven fabrics that have improved cut-resistance. Both the fabrics and the methods of making cut-resistant fabrics and the resulting fabrics are new. Additionally, the cut-resistant fabrics are made into apparel with improved cut protection, such as gloves that are resistant to slicing with a knife.
DETAILED DESCRIPTION OF THE INVENTION
As indicated above, a flexible cut-resistant fiber useful for the manufacture of protective apparel may be produced when a hard filler is included in the fiber. The fiber may be made of any fiber-forming polymer, and may be produced by any of the methods normally used in making fibers. The polymer preferably is melt processable, in which case, the cut-resistant fiber is typically made by melt spinning. For polymers that cannot be spun into fibers in the melt, wet spinning and dry spinning may also be used to produce fibers having improved cut resistance. Amorphous polymers, semi-crystalline polymers and liquid crystalline polymers may all be used in this invention. Of these, semi-crystalline and liquid crystalline polymers are preferred.
The description of this invention is written with respect to fibers. The term fiber includes not only conventional single fibers and filaments, but also yarns made from a multiplicity of these fibers. In general, yarns are utilized in the manufacture of apparel, fabrics and the like.
In one preferred embodiment of this invention, the fiber-forming polymer is an isotropic semi-crystalline polymer. “Isotropic” means polymers that are not liquid crystalline polymers, which are anisotropic. Preferably, the isotropic semi-crystalline polymer is melt processable; i.e., it melts in a temperature range which makes it possible to spin the polymer into fibers in the melt phase without significant decomposition. Semi-crystalline polymers that will be highly useful include poly(alkylene terephthalates), poly(alkylene naphthalates), poly(arylene sulfides), aliphatic and aliphatic-aromatic polyamides, and polyesters comprising monomer units derived from cyclohexanedimethanol and terephthalic acid. Examples of specific semi-crystalline polymers include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene naphthalate), poly(phenylene sulfide), poly(1,4-cyclohexanedimethanol terephthalate), wherein the 1,4-cyclohexanedimethanol is a mixture of cis and trans isomers, nylon-6 and nylon-66. Polyolefins, particularly polyethylene and polypropylene, are other semi-crystalline polymers that may be used in this invention. Extended chain polyethylene, which has a high tensile modulus, is made by the gel spinning or the melt spinning of very or ultrahigh molecular weight polyethylene. Extended chain polyethylene already has a high cut resistance, but can be made even more cut resistant by adding particles to the fiber in accordance with this invention. All of the above polymers
Carter Michele C.
Clear William F.
Flint John A.
Gillberg-LaForce Gunilla E.
Haider Mohammed Ishaq
Alston & Bird LLP
Dixon Merrick
Honeywell International , Inc.
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