Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2003-01-03
2004-05-25
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C528S298000, C528S302000, C528S307000, C528S308000, C528S308600, C525S437000, C525S440030, C525S443000
Reexamination Certificate
active
06740402
ABSTRACT:
TECHNICAL FIELD
The present invention relates to polyester fibers and more particularly it relates to polyester fibers having resistances to hydrolysis and fatigue from flexing at high levels and suitably usable for applications of papermaking canvas, tire cord and sterilized fabrics.
BACKGROUND ART
As well known, copolyesters have widely been used for fibers, resins, films or the like due to excellent performances thereof. Especially, polyester fibers are excellent in dimensional stability, heat, chemical and light resistances and the like and utilized in various fields regardless of clothing and non-clothing uses.
In the situation, polyester fibers have recently been utilized even for papermaking canvas such as dryer canvas, tire cord and sterilized fabrics such as medical clothes from the viewpoint of excellence in strength and resistance to fatigue from flexing. Among them, high resistances to fatigue and hydrolysis sufficient to withstand uses at high temperature and humidity are required in the applications of the dryer canvas and sterilized fabrics. The copolyesters, however, have problems that the lowering of molecular weight and the like are caused by hydrolysis at high temperature and humidity due to chemical characteristics thereof and the copolyester is resultantly unsuitable for long term uses at high temperature and humidity.
In order to solve the problems, for example, JP-A No. 54-6051 (1976) and JP-A No. 3-104919 (1991) (hereinafter, JP-A means Japanese Unexamined Patent Publication) propose methods for adding an epoxy compound or a carbodiimide compound as methods for reducing the terminal carboxyl group concentration of polyethylene terephthalate. Although resistance to hydrolysis is improved to some extent according to the methods, the copolyester are incapable of withstanding long-term uses and the problems have not yet been solved.
On the other hand, JP-A No. 8-120521 (1996) proposes filaments using a polytrimethylene terephthalate as a method for raising the resistance to fatigue from flexing. Although resistances to both fatigue from flexing and hydrolysis are considerably improved, the resistance of the filaments to hydrolysis for long-term and continuous uses at high temperature and humidity has not yet reached a sufficient level due to a low glass transition point of the polytrimethylene terephthalate.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to solve the problems heretofore possessed by the above prior art and to provide polyester fibers having resistances to both hydrolysis and fatigue from flexing which are capable of withstanding long-term and continuous uses at high temperature and humidity.
BEST MODE FOR CARRYING OUT THE INVENTION
The mode for carrying out the present invention will be detailed hereinafter.
In the present invention, it is necessary for a copolyester which is formed into the polyester fibers to simultaneously satisfy the following respective requirements (a) to (c).
(a) a terephthalic acid component in an amount of 0 to 100 mol % and a 2,6-naphthalenedicarboxylic acid component in an amount of 100 to 0 mol % respectively based on the whole dicarboxylic acid component, wherein the total amount, of the terephthalic acid component and the 2,6-naphthalenedicarboxylic acid component, accounts for 90 mol % or more based on the whole dicarboxylic acid component,
(b) a trimethylene glycol component accounts for 22 to 100 mol % and a 1,4-cyclohexanedimethanol component accounts for 78 to 0 mol % respectively based on the whole glycol component, wherein the total amount, of the trimethylene glycol component and the 1,4-cyclohexanedimethanol component, accounts for 90 mol % or more based on the whole glycol component and
(c) the sum total value of mol % of the 2,6-naphthalenedicarboxylic acid component and mol % of the 1,4-cyclohexanedimethanol component is 2 mol % or more.
The respective requirements (a) to (c) in the present invention will be detailed hereinafter.
When the total amount of the terephthalic acid component and the 2,6-naphthalenedicarboxylic acid component is less than 90 mol % based on the whole dicarboxylic acid component, the resistances to hydrolysis and heat, hand touch and the like of the resulting fibers are lowered.
When the 1,4-cyclohexanedimethanol component is not contained as the glycol component of the copolyester in the present invention, the case where the amount of the terephthalic acid component is 98 mol % or more and/or the amount of the 2,6-naphthalenedicarboxylic acid component is less than 2 mol % is unfavorable because the resistance of the resulting fibers to hydrolysis becomes insufficient.
As to the amounts of the terephthalic acid component and the 2,6-napthalenedicarboxylic acid component, it is preferable to make the terephthalic acid component account for 5 to 95 mol % and the 2,6-napthalenedicarboxylic acid component account for 95 to 5 mol % and keep the total amount of the terephthalic acid component and 2,6-naphthalenedicarboxylic acid component within the range of 92 mol % or more based on the whole dicarboxylic acid component and it is more preferable to make the terephthalic acid component account for 8 to 92 mol % and the 2,6-naphthalenedicarboxylic acid component account for 92 to 8 mol % and keep the total amount of the terephthalic acid component and the 2,6-naphthalenedicarboxylic acid component within the range of 95 mol % or more based on the whole dicarboxylic acid component.
When the total amount of the trimethylene glycol component and the 1,4-cyclohexanedimethanol component is less than 90 mol % based on the whole glycol component, the resistances to hydrolysis and heat, hand touch and the like of the resulting fibers are lowered.
When the 2,6-naphthalenedicarboxylic acid component is not contained as the dicarboxylic acid component of the copolyester in the present invention, the case where the amount of the trimethylene glycol component is less than 22 mol % and/or the amount of the 1,4-cyclohexanedimethanol component is larger than 78 mol % is unfavorable because the resulting fibers have hard hand touch and the melting point is increased to lower the molding processability. Furthermore, the resistance of the resulting fibers to hydrolysis becomes insufficient if the amount of the trimethylene glycol component is 98 mol % or more and/or the amount of the 1,4-cyclohexanedimethanol component is less than 2 mol %.
As to the amounts of the trimethylene glycol component and the 1,4-cyclohexanedimethanol component, it is preferable to make the trimethylene glycol component account for 22 to 95 mol % and the 1,4-cyclohexanedimethanol component account for 78 to 5 mol % and keep the total amount of the trimethylene glycol component and the 1,4-cyclohexanedimethanol component within the range of 92 mol % or more based on the whole glycol component and it is more preferable to make the trimethylene glycol component account for 22 to 92 mol % and the 1,4-cyclohexanedimethanol component account for 78 to 8 mol % and keep the total amount of the trimethylene glycol component and the 1,4-cyclohexanedimethanol component within the range of 95 mol % or more based on the whole glycol component.
In addition, it is necessary for the sum total value of mol % of the 2,6-naphthalenedicarboxylic acid component and mol % of the 1,4-cyclohexanedimethanol component in the copolyester of the present invention to be 2 mol % or more. The object of the present invention can only be achieved by the sum total value kept within the range.
Components other than the terephthalic acid component, 2,6-naphthalenedicarboxylic acid component, trimethylene glycol component and 1,4-cyclohexanedimethanol component may be copolymerized with the copolyester formed into the polyester fibers of the present invention within the range so as not to deteriorate characteristics of the copolyester, preferably within the range of 5 mol % or less based on the whole dicarboxylic acid component.
Examples of the copolymerization component include aromatic dicarboxylic acids such as isophthalic acid, o-p
Acquah Samuel A.
Teijin Limited
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