Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-11-19
2001-01-23
Edwards, Newton (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000
Reexamination Certificate
active
06177192
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyethylene naphthalate fiber. More specifically, it relates to a polyethylene naphthalate fiber capable of exhibiting excellent durability even when used under conditions where the fiber is subjected to a wet heat treatment or a dry heat treatment and, for example, useful as a material for an industrial application such as a dryer canvas for papermaking.
BACKGROUND ART
Heretofore, polyester fibers have been used in various applications due to their excellent properties. But, polyester fibers for industrial applications are often used under severe conditions of high temperature and high humidity from the properties of their applications, and their properties are not satisfactory.
Polyester fibers, especially, for a dryer canvas which is used in a drying process in papermaking, a steel washing blush or the like are required to have sufficient durability for the long use under high temperature and high humidity. However, polyester fibers have had problems, namely in a high-temperature atmosphere in the presence of water, polyesters, especially polyethylene terephthalate, are apt to decompose, and accordingly to lower the degrees of polymerization to weaken a breaking strength, a knot strength and the like of the fibers, and they can not be used for a long time under high temperature and high humidity.
In order to solve these problems, various methods have been studied. For example, Japanese Examined Patent Publication No. 47-15104 proposes a process wherein the concentration of carboxyl terminal groups of polyethylene terephthalate is lowered by adding a combination of a copper salt of a carboxylic acid and a reductive anion. However, this process has such a disadvantageous point that when the above-mentioned stabilizer is added, the polyester is colored in an unfavorable color tone, and further, sufficient durability is not always obtained under severe conditions of high temperature and high humidity.
On the other hand, it is widely known that the use of polyethylene naphthalate, which has naphthalene rings in the molecular skeleton, in stead of polyethylene terephthalate can improve the durability of the fiber.
For example, there are Japanese Examined Patent Publication No. 47-49769, Japanese Examined Patent Publication No. 47-49770, Japanese Examined Patent Publication No. 56-42682, Japanese Unexamined Patent Publication No. 4-100914 and Japanese Unexamined Patent Publication No. 4-194021 regarding polyethylene 2,6-naphthalate fiber, and they describe that polyethylene naphthalate fibers having excellent mechanical properties and thermal stability are produced by specifying the conditions of melt spinning of polyethylene 2,6-naphthalate.
It is known that the polyethylene 2,6-naphthalate fiber can have a higher elastic modulus and tensile strength than the polyethylene terephthalate fiber, which is used widely conventionally, and the polyethylene 2,6-naphthalate fiber is good in resistance to wet heat because it has a high glass transition temperature. As a method for further improving the resistance to wet heat, for example, Japanese Unexamined Patent Publication No. 50-95517, Japanese Unexamined Patent Publication No. 56-85704 and the like disclose methods for reducing concentrations of carboxyl terminal groups of polyesters by adding a carbodiimide compound. However, when these methods are applied, hydrolytic decomposition resistance is improved, but whitening, cracking and fibrillation on bending, which are problems characteristic to naphthalate-based polyester fibers, still occur and proceed not only under a wet heat condition but also under a dry heat condition. These methods therefore are not effective for solving these problems.
That is, since polyethylene 2,6-naphthalate has a rigid molecular chain and a characteristic crystal structure, whitening is apt to occur on a bent part when the fiber is subjected to deformation accompanied by bending such as knotting or the like, and fibrillation and cracking proceed from the whitened part, and resultingly a knot strength and a loop strength are lost especially in the fiber which has a single fiber fineness of 10 denier or more, or which has been kept under high temperature and high humidity for a long time. This has remained as a problem.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a polyester filament, especially its monofilament, satisfying both a bending fatigue durability under wet heat and dry heat, and mechanical properties such as a knot strength, a loop strength and the like at the same time while keeping the characteristic advantageous points of a naphthalate-based polyester, and capable of exhibiting excellent durability even in the application used under severe conditions in which dry heat treatments and wet heat treatments are repeatedly applied as in a dryer canvas for papermaking.
In order to achieve the above-mentioned object, the inventors of the present invention had studied the causes of whitening, cracking and fibrillation on bending which are characteristic phenomena to the naphthalate-based polyester fiber, and they found that the breakage of fibers by compression deformation in the direction of fiber axis causes the phenomena. That is, they made clear that since the naphthalate-based polyester has a characteristic crystal structure, the fiber structure can not sufficiently relieve compression stress against compression deformation, and resultingly the compression stress breaks the fiber and causes whitening, cracking and fibrillation to lower the durability, and they further found that the phenomena can be suppressed without deteriorating the advantageous points characteristic to the naphthalate-based polyester by copolymerizing an alkylene oxide adduct of a phenol with a naphthalate-based polyester. Thus, the present invention has been completed.
That is, the polyethylene naphthalate fiber which can achieve the object of the present invention is characterized in that the fiber comprises a naphthalate-based copolyester in which at least 85 mol % or more of the total recurring units is an ethylene 2,6-naphthalate unit, and 1 to 1.5% of the total diol components is an alkylene oxide adduct of a divalent phenol expressed by the following general formula (I).
H—(OA)
m
—O—Ar—O—(AO)
n—H
(I)
In the formula, A expresses an alkylene group having a carbon number of 2 to 4; m and n are same as or different from each other, and each express an integer of 1 to 5; and Ar expresses a p-phenylene group, a m-phenylene group or a group expressed by the following general formula (II).
—Ph—X—Ph— (II)
In the formula, Ph expresses a p-phenylene group; and X expresses a 2,2-propylene group, a sulfone group, a methylene group, an oxygen atom or a sulfur atom.
BEST MODE FOR CARRYING OUT THE INVENTION
The naphthalate-based copolyester constituting a fiber of the present invention consists of an ethylene 2,6-naphthalate unit in an amount of at least 85 mol % or more of the total of the recurring units, and it is a copolyester obtained by copolymerizing a compound expressed by the above general formula (I), that is, an alkylene oxide adduct of a divalent phenol as a part of the diol component.
In the above general formula (I), A expresses an alkylene group having a carbon number of 2 to 4, and an ethylene group is especially preferred; and m and n are same as or different from each other, and they each express an integer of 1 to 5, preferably an integer of 1 to 3, especially preferably an integer of 1 to 2. When m or n exceeds 5, favorable properties of high strength, high elastic modulus and high glass transition temperature, which are characteristic to the naphthalate-based polyester, are lost.
Further, Ar is a p-phenylene group, a m-phenylene group or a group expressed by the above general formula (II), and in the general formula (II), Ph expresses a p-phenylene group; and X expresses a 2,2-propylene group, a sulfone group, a methylene group, an oxygen atom or a sulfur atom. Especially, Ar is preferably expressed by the
Asano Makoto
Kuroda Toshimasa
Santa Toshihiro
Tsukamoto Ryoji
Edwards Newton
Sughrue Mion Zinn Macpeak & Seas, PLLC
Teijin Limited
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