Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-04-25
2004-01-20
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S601000, C524S603000, C528S279000
Reexamination Certificate
active
06680353
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polytrimethylene terephthalate-based polyester resin composition containing titanium oxide, and a delustered polyester fiber prepared therefrom by melt spinning and manifesting an appropriate luster. The present invention relates in more detail to an improved polytrimethylene terephthalate fiber that can be obtained from a polymethylene terephthalate resin composition containing an improved fine dispersion of titanium oxide by spinning and drawing steps wherein a rise in the spinning pack pressure and decreases in the fiber strength and fiber wear resistance caused by aggregates of titanium oxide particles during the melt spinning step are significantly suppressed.
The present invention relates to a polytrimethylene terephthalate fiber which solves the problem of a high frictional coefficient specific thereto, and which consequently shows decreased yarn breakage and fluff formation during spinning and in the subsequent treatment steps, namely, which is excellent in spinnability.
BACKGROUND ART
A polytrimethylene terephthalate (hereinafter abbreviated to PTT) fiber is an epoch-making fiber that has such properties similar to those of a nylon fiber as a soft feeling derived from a low elastic modulus, an excellent elastic recovery and easy dyeability, and such properties similar to those of a polyethylene terephthalate fiber as a wash-and-wear property, dimensional stability and a yellowing-resistant property. Applications of the fiber to clothing, carpets and the like have been advanced.
When synthetic fibers represented by a polyethylene terephthalate (hereinafter abbreviated to PET) fiber, a nylon fiber and the like are to be used for clothing, the luster of the fibers is sometimes controlled by adding titanium oxide to the fibers in some applications (titanium oxide being used as a so-called delustering agent). For example, lusterous of lining cloth is not preferred by consumers. The fiber is therefore delustered by adding 0.2 to 1% by weight of titanium oxide thereto. A fiber for use in swimwear and foundation garments for women required to have a bright color is required not to lose luster by decreasing the amount of the titanium oxide.
As explained above, it also becomes necessary to change the luster of a PTT fiber for clothing and carpets by changing the addition amount of titanium oxide in accordance with its application. However, the present inventors have found for the first time, through their investigations, that there are serious problems, explained below, during the production of a PTT fiber containing titanium oxide.
That is, the most serious problem is that when titanium oxide is added to a PTT without a suitable control of the addition procedure, the polyester resin composition thus obtained contains a large amount of aggregates of titanium oxide. A PTT shows a higher tendency toward forming the aggregates than a PET and a polybutylene terephthalate (hereinafter abbreviated to PBT) that have structures similar to that of a PET.
When a resin composition containing many aggregates of titanium oxide is melt spun, the aggregates clog a filter with which the spinning nozzle pack is equipped to cause serious problems about the spinnability and spinning yield: the pressure within the spinning nozzle pack rises in a short period of time; the spinning nozzle orifices are likely to be fouled; and the frequency of the yarn breakage and fluff formation becomes high. Moreover, when the fiber thus obtained contains many coarse aggregates, the aggregates become defects, and as a result the fiber markedly lowers its strength and tends to form fluff.
Furthermore, the aggregates exert adverse effects on the wear resistance of PTT chips and a fiber prepared therefrom. A PTT resin composition differs from a PET or a PBT having a similar structure in that the PTT resin composition becomes highly crystalline chips when the resin composition is polymerized and rapidly cooled to form chips because the crystallization rate is high. Such chips are relatively brittle, and form powder when rubbed against each other during transportation, drying, extrusion within an extruder or the like treatment. It has been found that such a phenomenon is promoted by an increase in the number of aggregates. The formation of powder leads to a decrease in the yield due to a loss of the polymer, and an increase in the fluff caused by the air trapped in powder. On the other hand, such a phenomenon hardly takes place with PET or PBT because the crystallinity of the chips is low. Moreover, the aggregates also lower the wear resistance of the fiber. Since the molecules of a PTT fiber take a Z-shaped markedly bent conformation, the intermolecular force of the PTT fiber is low in comparison with that of the PET fiber or PBT fiber. As a result, the wear resistance of the PTT fiber becomes low. When the aggregates increase, the degree of decrease in the wear resistance becomes more significant. In contrast to the PTT fiber, the aggregates in the PET fiber and PBT fiber that take a conformation close to a fully extended structure do not exert as much adverse effect on the wear resistance as those in the PTT fiber.
A PTT containing titanium oxide has still another problem that the PTT forms large amounts of acrolein and allyl alcohol in comparison with a PTT substantially containing no titanium oxide due to thermal decomposition of the resin composition in the drying step prior to spinning. Since acrolein and allyl alcohol are chemical substances that have toxicity and a tearing property, and that harm the working environment, decreasing the generated amounts is an important problem.
The last problem is one that is associated with a property inherent to a PTT fiber, namely, the problem that a PTT fiber has a particularly large frictional coefficient among synthetic fibers. For example, a polyethylene terephthalate fiber of 50 d/36 f for general purposes having no finishing agent on the surface shows a fiber-metal frictional coefficient of 0.295, whereas a PTT fiber shows 0.378 under the same conditions. That is, the differences in the frictional coefficients are understandable when the following is considered: a PTT fiber has significant rubber-like properties in comparison with other synthetic fibers for general purposes.
As explained above, a PTT fiber has a significantly high frictional coefficient. Accordingly, when a PTT fiber is subjected to a treatment such as spinning and drawing, weaving or knitting, and false twisting, the fiber suffers a frictional resistance, to a very high degree, on guides and rolls in comparison with a PET fiber and a PBT fiber, and the PTT fiber tends to produce yarn breakage and fluff. However, methods for solving the above problems have never been disclosed.
For example, U.S. Pat. No. 5,798,433 discloses a method of using titanium oxide as a polymerization catalyst in an amount from 30 to 200 ppm in terms of titanium. However, the reference refers to neither a problem related to the dispersibility of titanium oxide, nor to a solution of the problem. The method is therefore inappropriate. Moreover, the titanium oxide used herein is an amorphous titanium oxide/silica coprecipitate coprecipitated by hydrolyzing a titanium alkoxide and a silanol, and shows a low delustering capacity and poor dispersibility because the coprecipitate differs in the chemical and crystal structures from crystalline titanium oxide used as a delustering agent. Moreover, since the amorphous titanium oxide/silica coprecipitate used in the reference is highly reactive, a side reaction takes place when added in an amount of 100 ppm or more to cause a problem that the polymer thus obtained is yellowed.
U.S. Pat. No. 3,681,188 discloses in examples a PTT containing 0.1% by weight of titanium oxide. However, there is no description referring to the technological significance of the dispersibility of titanium oxide.
Furthermore, Japanese Unexamined Patent Publication (Kokai) No. 62-18423 describes a method of preparing a titanium slurry for a polyester by making a
Kato Jinichiro
Takahashi Tetsuko
Asahi Kasei Kabushiki Kaisha
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Niland Patrick D.
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