Modified polytrimethylene terephthalate

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Reexamination Certificate

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C528S275000, C528S295000, C528S301000, C528S302000, C528S308000, C528S308600, C428S362000, C428S364000, C264S176100, C264S177170, C264S177190, C264S17800F, C264S210800, C264S211200, C525S437000

Reexamination Certificate

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06645619

ABSTRACT:

TECHNICAL FIELD
The present invention relates to poly(trimethylene terephthalate) copolymer (hereinafter poly(trimethylene terephthalate) is referred to as PTT), a method for producing the same, a fiber using the same and a fibrous product thereof. More specifically, it relates to PTT copolymer high in molecular weight to be a material for a PTT fiber dyeable with cationic dye, a method for producing the same, a fiber using the same and a fibrous product thereof.
Even more specifically, the invention relates to PTT copolymer capable of being produced at a high solid-state polymerization rate and having a small loss in melting viscosity, which is excellent in hue and high in molecular weight as a material for PTT fiber dyeable with cationic dye, a PTT fiber dyeable with a cationic dye excellent in processability and high in toughness, which does not shrink much during dyeing or heat-setting, and a fibrous product thereof.
BACKGROUND ART
PTT fiber obtained by melt-spinning polycondensate of terephthalic acid or lower alcohol ester of terephthalic acid and 1,3-propanediol (also referred to as trimethylene glycol) is excellent in touch of soft feeling, drapability and stretchability and is superior in low-temperature dyeability and weather resistance. These qualities have never been seen in an existing synthetic fiber such as poly(ethylene terephthalate) fiber (poly(ethylene terephthalate) is hereinafter referred to as PET) or nylon 6 fiber.
The applicant of this patent application has overcome various problems relating to the development of PTT and PTT fiber and the processing thereof, and has recently marketed a PTT fiber (trade name: Solo Fiber) for the first time in the world.
The PTT fiber could be more widely used by combining it with other fiber material or being post-treated. According to the prior art PTT fiber, however, problems relating the dyeing may occur if the mating fiber to be combined therewith or the processing technique is unsuitable. For example, as the PTT fiber is dyeable substantially solely with a disperse dye, the disperse dye is liable to migrate to the polyurethane elastomeric yarn or resin having a coarse structure to deteriorate a color fastness such as wash-fastness, sweat-fastness or dry cleaning-fastness when the PTT fiber is combined with a polyurethane elastomeric yarn or the fabric of the PTT fiber is treated with polyurethane resin.
To solve the above problems, if the PTT fiber is modified to be dyeable with cationic dye, the cationic dye is ionic-bonded with a sulfonate which is a dyeing seat introduced into PTT, whereby the above-mentioned migration of dye does not occur to result in a high color fastness. Also, there is a characteristic that the clarity of the dyed fabric becomes higher.
The present inventors have already proposed a PTT fiber dyeable with cationic dye (hereinafter referred to as a CD-PTT fiber) for the purpose of further facilitating the excellent features of the PTT fiber while solving the above-mentioned problems regarding the dyeing (WO99/09238). According to this technology, CD-PTT and a CD-PTT fiber formed thereof are provided by esterification-reacting terephthalic acid which is a dicarbonic acid component and/or lower alcohol ester of terephthalic acid, typically dimethyl terephthalate, with 1,3-propanediol which is a diol component, and adding an ester-forming metallic salt of sulfonic acid which is a dyeing seat for cationic dye. Although this technology provides the PTT dyeable with cationic dye, which has been difficult in the prior art, it is still insufficient in view of the industrial production. Also, although the CD-PTT obtained by the above-mentioned technology is excellent in whiteness, this is still unsatisfactory in a use in which whiteness or strength at a higher level is required.
On the other hand, regarding a PTT homopolymer (hereinafter referred to as a homo PTT) other than CD-PTT, Japanese Unexamined Patent Publication No. 8-311177 (Kokai) discloses a method for obtaining a PTT having a b value of 10 or less and a content of oligomer of 1 wt % or less by esterification-reacting 1,3-propanediol with a terephthalic acid component, polycondensating an esterification-reaction product thus obtained to result in a prepolymer having an intrinsic viscosity in a range from 0.7 to 0.8, and polycondensating, in a solid state, the prepolymer thus obtained at a temperature in a range from 190 to 210° C. to result in an intrinsic viscosity of 0.9 or more. Also, Japanese Unexamined Patent Publication (Kokai) No. 2000-159876, disclose a polymerization technology providing a homo PTT excellent in solid-state polymerization speed and melting stability by combining a titanium catalyst with a magnesium catalyst.
However, there are neither a description nor a suggestion, in these publications, regarding the CD-PTT or the significance of the copolymerization of ester-forming metallic salt of sulfonic acid. Particularly, since the melting stability becomes worse in comparison with homo PTT, as described later, when an ester-forming metallic salt of sulfonic acid is used as a copolymerization component, the same effect would not be expected even if the technology used for the homo PTT is applied as it is to the CD-PTT. In the above publication, however, there is neither a description nor a suggestion of the solution thereto. The homo PTT described in either of these publications is unsatisfactory in whiteness. Particularly, according to Japanese Unexamined Patent Publication (Kokai) No. 2000-159876, since a magnesium catalyst is combinatorily used for the polymerization, the L value (brightness) of the polymer becomes less than 70 to result in a blackish polymer, and this technology is not applicable to a CD-PTT requiring a clear color.
Known CD-PTT fibers have problems to be solved similar to CD-PTT. That is, the known CD-PTT fibers are problematic in that 1) since they are formed of a polymer of a low molecular weight, a toughness (the toughness is a fiber stiffness usually represented by the product of a fiber strength and a square root of a fiber elongation) causes a fabric to be easily broken, and 2) as they are excessively drawn in spite of their low molecular weight, the orientation of molecules in an amorphous region is liable to relax by heat during the dyeing or heat-setting process to cause a large fiber shrinkage, which results in a harsh feeling of hand touch of a fabric, and it is difficult that the fabric develops adequately a soft feeling.
DISCLOSURE OF THE INVENTION
The present inventors have found the following problems by diligently studying the polymerization or spinning technology of CD-PTT.
In the melt-spinning process of CD-PTT, as metallic salts of sulfonic acid copolymerized with each other are ionically crosslinked in a melting state, the melting viscosity significantly rises. Thereby, the removal of 1,3-propanediol is inhibited at a polycondensating reaction stage to result in a problem that it is difficult to increase the degree of polymerization. In addition, as CD-PTT has a lower thermal stability in comparison with PET, poly(buthylene terephthalate) or homo PTT, which have similar structures thereto, the molecular weight thereof does not rise even if the polycondensation time is prolonged but the depolymerization occurs due to the heat decomposition before the molecular weight reaches a level necessary for forming fibers, which yellows the polymer itself, and a high-molecular weight CD-PTT is not obtainable.
The present inventors have studied a high-molecular weight CD-PTT and succeeded in obtaining a CD-PTT having a high molecular weight, not achievable through the melt-spinning method, by once preparing a low-molecular weight CD-PTT (hereinafter referred to as a prepolymer) and polymerizing the same in a solid state. As a result of specifically studying the melt-spinning characteristic, hue and solid-state polymerization characteristic, however, the following problems have been found when this technology is carried out on an industrial scale.
That is, if characteristics such as an amount o

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