Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-06-18
2001-05-08
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C428S370000
Reexamination Certificate
active
06228493
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a conjugate fiber and a manufacturing method of the same.
2. Related Arts
An aromatic polyester containing an aromatic moiety, such as polyethylene terephthalate or polybuthylene terephthalate, has been considered to be not biodegradable and thus, in most cases, has been fired after the use. However, since such firing may induce environmental pollution, its effective treatment has been demanded.
On the other hand, a polyester fiber with its weight being reduced by means of an alkaline solution has been widely used as an material for an apparel, because of its good appearance and feeling. However, its reducing process includes a hydrolysis step providing residues, which require more troublesome treatments. Thus a polyester fiber has been demanded, which is free from the above problems associated with treatments of the residues.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fiber which does not produce a huge amount of residues during its reducing process, in the field of a polyester fiber.
Another object of the invention is to provide a reducing technique of a polyester fiber without producing a huge amount of the residues.
Another object of the invention is to provide a fiber with good appearance and feeling and superior characteristics as a fiber, such as a high tensile strength and draw ratio.
The invention provides a conjugate fiber comprising a core spinned from a polyester containing an aromatic moiety and a skin layer surrounding the core, the skin layer spinned from an aliphatic polyester.
The invention also provides a reduced conjugate fiber comprising a core spinned from a polyester containing an aromatic moiety and a skin layer which surrounds the core and is spinned from an aliphatic polyester, the skin layer being reduced by contacting it with an alkaline solution or an enzyme.
The inventors succeeded in manufacturing a conjugate fiber comprising a core spinned from a polyester containing an aromatic moiety and a skin layer spinned from an aliphatic polyester, the latter having biodegradability. The inventors further found that the conjugate fiber was reduced under a mild condition by contacting the conjugate fiber, or a cloth knitted from the fiber, with an alkaline solution or an enzyme.
The inventive conjugate fiber and a fabric made thereof after the reduction show good feeling and appearance as a suitable apparel material. Moreover, the decomposition of the aliphatic polyester constituting the skin layer, by means of an enzyme or an alkaline solution, produces products, which may be easily degradable to carbon dioxide or water by means of environmental microorganisms, that is, may be returned to environmental material recycling system. Thus the conjugate fiber and its reducing technique of the invention do not provide any decomposition product needed to be processed as wastes. Therefore, the invention provides a clean reducing technique of a polyester fiber without a waste management problem.
The inventive conjugate fiber, before its reducing process, comprises a surface tissue entirely different from that of a prior polyester containing an aromatic moiety, while maintaining a tensile strength and a tensile elongation comparable with those of such prior polyester. The inventive fiber is thus applicable to a new medical material such as an artificial blood vessel. Moreover, the conjugate fiber may be stretched at a temperature lower than that needed for stretching prior aromatic polyester fibers.
A polyester containing an aromatic moiety, constituting the core, is a polyester comprising an aromatic compound as its monomer. The aromatic compound may preferably be a polyalkylene terephthalate, more preferably be polyethylene terephthalate, polypropylene terephthalate, or polybutylene terephthalate, and most preferably be polyethylene terephthalate or polybutylene terephthalate. An aliphatic polyester constituting the skin layer comprises an aliphatic compound and substantially no aromatic compound as its monomer, and may preferably be polybutylene succinate, polyethylene succinate, poly-L-lactic acid, poly(&bgr;-hydroxybutylic acid, poly(&bgr;-hydroxybutylic acid/valeric acid), or a copolymer consisting of any combination of the above listed monomers.
When producing the inventive conjugate fiber, a nozzle, first extruder and second extruder are prepared. A core forming space and a skin layer forming space surrounding the core forming space are formed within the nozzle. Melt of a polyester containing an aromatic moiety is supplied into the core forming space and melt of a aliphatic polyester is supplied into the skin layer forming space. The core and skin layer are continuously spinned and formed simultaneously from the spinneret of the nozzle. The inventors found that the thus produced conjugate fiber (before the reducing treatment) had excellent properties needed as a fiber, such as a tensile strength, comparable with those of polyethylelne terephthalate or polybutylene terephthalate fiber.
In the above process, the polyester containing an aromatic moiety may preferably be supplied from a vertical extruder to a nozzle and the aliphatic polyester may preferably be supplied from a horizontal extruder to a nozzle.
The polyester containing an aromatic moiety and aliphatic polyester may be melted in the respective extruders at conventional melting temperatures. The nozzle may preferably be maintained at about 280° C. when spinning the core from polyethylene terephthalate or at about 255° C. when spinning the core from polybutylene terephthalate. The temperature of the nozzle may preferably be further adjusted to stabilize the spinning.
When reducing (the weight of) the conjugate fiber by means of an alkaline solution, to an alkaline solution such as sodium hydroxide or potassium hydroxide solution having a concentration of, for example, 50 weight percent, an equal amount of ethanol or isopropanol may be added to obtain a mixed solution, into which the conjugate fiber is dipped at an appropriate temperature of, for example, 50° C. The enzyme for reducing the conjugate fiber may preferably be Lipase derived from
Pseudomonas cepacia
(such as “Lipase PS” produced by Amano Pharmaceuticals) and Lipase derived from Rizopus Arrhizus (such as “typexI” produced by sigma Inc.) when using polybuthylene succinate, and may preferably be Proteinase K derived from Tritirachium album Limber when using poly-L-lactic acid. The reduction of the conjugate fiber with an enzyme may preferably be carried out at an appropriate pH of, for example, 6 and at an appropriate temperature of, for example, 50° C.
The invention provides a technique to reduce (the weight of) a polyester fiber without providing a large amount of residues as a result of such reducing treatment, or, make it possible to reduce a polyester fiber without providing a large amount of residues. Moreover, the invention provides a fiber with excellent properties needed as a fiber, such as a high tensile strength and an drawing ratio. Moreover, the inventive fiber may be stretched at a temperature lower than that needed for stretching prior aromatic polyester fibers.
REFERENCES:
patent: 4307151 (1981-12-01), Yamauchi et al.
patent: 5593778 (1997-01-01), Kondo et al.
patent: 5990266 (1999-11-01), Tadros et al.
patent: 7-11519 (1995-01-01), None
patent: 7-216656 (1995-08-01), None
patent: 11-302926 (1999-11-01), None
Edwards N.
Kyoto Institute of Technology
Schneller Marina V.
Venable
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