JPS6252049B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a novel undrawn polyester yarn, and more particularly to an undrawn polyester yarn containing a styrene polymer and having excellent productivity. [Prior Art] When melt-spinning polyester fibers, increasing the amount of ejection from the spinneret as much as possible is an extremely effective method for increasing productivity. Especially in recent years, there has been a marked trend towards finer fibers. This is highly desirable in order to increase productivity and reduce spinning costs. One way to achieve this objective is to increase the spinning take-off speed to increase the amount of yarn discharged from the spinneret. However, in this method, since the take-off speed is high, the molecular orientation of the spun yarn increases, and the residual elongation of the obtained undrawn yarn decreases. As a result, as a matter of course, the stretching ratio during the subsequent stretching or stretch false twisting becomes small, and the effect of increasing the discharge amount due to the increase in the take-up speed is offset by the decrease in the stretching ratio.
That is, when trying to obtain a drawn yarn or drawn false twisted yarn with a constant fineness, if the drawing ratio decreases, the amount of polymer discharged from the spinneret must be reduced accordingly, and the take-up speed must be increased. This results in canceling out the increase in discharge amount brought about by this. In order to solve this problem, it is necessary to prevent the molecular composition of the spun yarn from increasing even if the spinning take-off speed is increased.One way to do this is to install a heated spinning tube directly below the spinneret. A method has been proposed in which the polymer discharge flow is slowly cooled and solidified. However, this method requires a special heating device and has the disadvantage that it is extremely difficult to control the cooling process of the spun yarn. On the other hand, a method has also been proposed in which polyester is copolymerized with a chain branching agent such as pentaerythritol as a third component to increase the discharge amount and stretching ratio and improve productivity (Japanese Patent Application Laid-Open No. 53-292). However, this method requires the adoption of special polymerization conditions;
Furthermore, there are problems in that the spinning condition tends to deteriorate and, in addition, the mechanical properties of the obtained yarn deteriorate. [Object of the Invention] An object of the present invention is to provide an undrawn polyester yarn that exhibits a high degree of residual elongation by a simple means without requiring any special modifications to the raw material polymer or spinning device. [Structure of the Invention] As a result of intensive studies to achieve the above-mentioned goals, the present inventors have determined that, contrary to the conventional concept, a high-speed It was discovered that undrawn polyester yarn with high residual elongation without increased molecular orientation could be obtained only by applying a spinning take-off speed, and therefore it was possible to draw at a high draw ratio and increase productivity. . Thus, according to the present invention, a polyester containing 0.5 to 10% by weight of a styrene polymer having a degree of polymerization of 20 or more is melted and spun from a spinneret to obtain a polyester of 2500 to 8000% by weight.
Polyester undrawn yarn I (%) = (ELb/ ELo-1)×100 [However, ELb is the residual elongation (%) of the undrawn yarn of the present invention, and ELo is the residual elongation (%) of the undrawn yarn of the present invention when the styrene polymer component is not included. )
shows. ] will be provided. The polyester used in the present invention is a polyester having fiber-forming ability containing aromatic dicarboxylic acid as the main acid component, and examples thereof include polyethylene terephthalate, polytetramethylene terephthalate, polycyclohexane dimethylene terephthalate, and polyethylene-2,6-naphthalene. Dicarboxylate and the like can be mentioned. Furthermore, these polyesters may be copolymers obtained by copolymerizing other alcohols or other carboxylic acids such as isophthalic acid or 5-sodium sulfoisophthalic acid as a third component, or may be mixtures of these various polyesters. . Among them, polyethylene terephthalate is most suitable. These polyesters may contain a matting agent, a heat stabilizer, an ultraviolet stabilizer, an antistatic agent, a terminal stopper, a fluorescent whitening agent, etc., as necessary. Further, it is desirable that these polyesters have an intrinsic viscosity of 0.5 to 1.1 from the viewpoint of spinnability and filament properties. On the other hand, the styrene polymers added to polyester include styrene, α-methylstyrene, p-
A polymer of styrene derivatives such as methoxystyrene, vinyltoluene, chlorstyrene, dichlorostyrene, or a copolymer mainly composed of these.
It is necessary that the degree of polymerization is 20 or more. In other words, in the case of prepolymers or polymers with a degree of polymerization of 20 or more, the effect of increasing the elongation of undrawn yarn is recognized, but if the degree of polymerization is less than 20, the molecular weight becomes too low and the molecular motion of the polyester changes. It does not have the effect of increasing residual elongation. Further, the amount of the styrene polymer added is preferably 0.5 to 10% by weight, preferably 1 to 6% by weight. 0.5%
If it is less than that, the residual elongation improving effect of the present invention is too small;
On the other hand, if it exceeds 10%, single filament breakage and take-up roller winding occur frequently during the spinning process, resulting in poor spinning quality, and the mechanical properties such as strength and elongation of the resulting yarn also deteriorate. Addition of styrenic polymer to polyester
Any method can be used, for example, it may be carried out in a polyester polymerization step, or the polyester and the styrene polymer may be melt-mixed, extruded, cooled, and then cut into chips. Furthermore, after mixing both in the form of chips, they may be melt-spun as they are. In this case, in order to increase the degree of kneading, it is preferable to use a screw type melt extruder. Whichever method is adopted, it is necessary to perform sufficient mixing so that the styrene polymer is dispersed and mixed in the polyester in molecular order. If the kneading is insufficient and the styrene polymer is mixed in the polyester in a sea-island pattern, the effect of improving the residual elongation will not be observed and the undesirable phenomenon of fibrillation will occur. When obtaining the undrawn polyester yarn of the present invention, it is important to control the spinning take-off speed from 2500 to 8000.
m/min. Spinning take-off speed is 2500
m/min, as will be described later, the added styrene polymer does not function as a "roller" for the molecular chain orientation of the polyester, and the effect of increasing the residual elongation of the spun undrawn yarn is Practically not allowed. On the other hand, as the spinning take-off speed increases, the effect of increasing the residual elongation increases; however, when the speed exceeds 8000 m/min, the addition of the styrene polymer becomes a drawback, and the strength and elongation of the spun and undrawn yarn decreases. A phenomenon called so-called weakening of the threads, in which the fibers become weaker, begins to appear. [Function/Effect] The undrawn polyester yarn spun and taken in this way has a higher residual elongation than the undrawn polyester yarn spun under the same conditions except that no styrene polymer is added. are doing. That is, when the elongation increase rate (I) defined by the following formula is preferably 8% or more, it is 15% or more. I (%) = (ELb/ELo-1) x 100 [However, ELb is the residual elongation (%) of the undrawn yarn of the present invention, and ELo is the residual elongation (%) of the undrawn yarn of the present invention that contains a styrene polymer component. Residual elongation (%) without
shows. ] Therefore, the undrawn yarn of the present invention can be drawn at a higher drawing ratio than the undrawn yarn that does not contain a styrenic polymer. As the residual elongation increases, the draw ratio improvement rate (J) shown by the following formula also increases. J (%) = DRb/DRo-1) x 100 [However, DRb is the drawing ratio of the undrawn yarn of the present invention, DRo
indicates the drawing ratio of an undrawn yarn not containing a styrenic polymer that gives the same residual elongation as the residual elongation of the drawn yarn when the undrawn yarn of the present invention is drawn at the draw ratio of DRb. ] Now, in melt spinning of polyester, the discharge amount Q (g/min) of the molten polymer is generally determined by setting the target fineness of the drawn yarn to de and the spinning take-off speed to V.
(m/min) and the stretching ratio is DR, it is expressed as Q=1/9000de×V×DR. Therefore, if the spinning take-off speed is constant and the drawing ratio can be increased by J%, the discharge amount during spinning can be increased by J%, and productivity can be improved accordingly. When the elongation increase rate (I) is 8% or more, the stretch ratio improvement rate (J) is 5%.
This results in an increase in productivity of 5% or more. It is not fully clear why the addition of a styrene polymer in the present invention has a specific effect on improving discharge productivity. Probably due to the characteristics of the chemical structure of styrenic polymers, being amorphous,
As a result of the overlap between the characteristics of the styrenic polymer molecule itself, such as low mobility, and the characteristics caused by the combination of polymers, such as compatibility with polyester molecules and the state of dispersion in the blend, the styrenic polymer molecule It is thought that this may act like a "roller" on the deformation of polyester. Perhaps because of this mechanism, adding a sterene oligomer with a degree of polymerization of less than 20 has almost no effect. When the degree of polymerization is 20 or more, the effect becomes more significant as the degree of polymerization increases. However, if the degree of polymerization of the styrenic polymer becomes too large, the spinnability tends to deteriorate slightly, so care must be taken. As described above, the present invention has been able to dramatically improve spinning productivity by extremely simple means, and has extremely great industrial significance. [Example] Example 1 Intrinsic viscosity is 0.64, and titanium oxide is used as a matting agent.
After drying polyethylene terephthalate chips containing 0.5% at 160°C for 4 hours, polystyrene (trade name Styron 683, polymerization degree approximately 700, manufactured by Asahi Dow Co., Ltd.) was mixed in various ratios in the form of chips, and a screw with a diameter of 25 mm was added. Melt and mix at 300℃ using a molded melt extruder,
Polyethylene molecules were diffused into polyethylene terephthalate molecules. Next, the molten polymer was discharged from a spinneret having 24 nozzles with a diameter of 0.35 mm, and cooled and solidified by blowing room temperature air at a speed of 10 m/min through a side-blown spinning tube installed 10 to 110 cm below the spinneret. After treatment with an oil agent, the yarn was taken off at a speed of 3500 m/min to obtain an undrawn yarn of 72 de. The spinnability, strength, residual elongation, and elongation increase rate (I) of the obtained undrawn yarn were as shown in the following table.

[Table] In sample No. 1, no polystyrene was added, and in sample No. 2, the amount of mixture was small, so the residual elongation was low. In sample No. 8, since the amount of polystyrene mixed was too large, yarn breakage occurred frequently and spinnability deteriorated. The residual elongation of undrawn yarn increases as the mixing ratio of polystyrene increases, and the elongation increase rate (I) ranges from 9 to
It reaches 128%. Example 2 Each undrawn yarn of samples No. 1 to 7 in Example 1 was preheated at a temperature of 75°C, a slit heater temperature of 180°C,
Stretching was performed at a stretching speed of 300 m/min, and the stretching ratio (DR) at which the residual elongation of the drawn yarn after stretching was 25% was determined. The results are shown in the table below.

【table】

[Table] In the undrawn yarns of Example 1 No. 3 to No. 7 according to the present invention, the drawing ratio improvement rate and productivity improvement rate ranged from 5% to
Reaching 42%. Example 3 3% polyvinyltoluene with a degree of polymerization of 550 was added to the polystyrene terephthalate used in Example 1, and the mixture was melted and discharged under the same conditions as in Example 1, and taken off at various take-off speeds to obtain undrawn yarn of 192 de. Ta. The spinnability at this time and the strength of the obtained undrawn yarn,
The residual elongation and elongation increase rate (I) were as shown in the following table.

[Table] Example 4 Each undrawn yarn of samples No. 1 to 6 in Example 3 was stretched under the same conditions as in Example 2, and the drawing ratio (DR) at which the residual elongation of the drawn yarn was 25% was determined. Ta. The results are shown in the table below.

[Table] In the undrawn yarns of Example 3-Nos. 2 to 5 according to the present invention, the drawing ratio improvement rate, that is, the productivity improvement rate was 5 to 5.
Reaching 39%. Example 5 Various types of polystyrene terephthalate and 5-sodium sulfoisophthalate copolymer (5-mol % copolymer of 5-sodium sulfoisophthalate) were used, each having an intrinsic viscosity of 0.60 and containing 0.5% titanium oxide as a matting agent. The spinning was carried out under the same conditions as in Example 1, except that 3% of polyp-methoxyethylene with a polymerization degree of
An undrawn yarn of 72 de was obtained. For comparison, a fiber without polyp-methoxystyrene was also spun. The spinnability, residual elongation and elongation increase rate (I) of the obtained undrawn yarn were as shown in the following table.

[Table] Since the degree of polymerization of polyp-methoxystyrene in sample No. 1 was less than 20, almost no effect on improving residual elongation was observed. In addition, sample No. 4 is
Although the degree of polymerization became a little too high and the spinning condition deteriorated a little, the effect of improving the residual elongation was extremely large.

Claims (1)

[Scope of Claims] 1. A styrenic polymer having a degree of polymerization of 20 or more from 0.5 to
Elongation increase rate (I) obtained by melting polyester containing 10% by weight, spinning it from a spinneret, and taking it off at a speed of 2500 to 8000 m/min, and shown by the following formula:
8% or more of polyester undrawn yarn. I (%) = (ELb/ELo-1) x 100 [However, ELb is the residual elongation (%) of the undrawn yarn of the present invention, and ELo is the residual elongation (%) of the undrawn yarn of the present invention that contains a styrene polymer component. Residual elongation (%) without
shows. 2. The undrawn polyester yarn according to claim 1, wherein the content of the styrene polymer is 1 to 6% by weight.