KR0160478B1 - Process for preparing polyester - Google Patents

Abstract

None.

Description

How to prepare polyester

The present invention relates to a method for producing polyester, and more particularly, to a method capable of suppressing excessive crystallization during molecular orientation of polyester.

Polyesters typified by polyethylene terephthalate have excellent physical and chemical properties, and therefore are widely used for various applications, especially fibers. Polyester fibers are usually produced by melt spinning, stretching, and hot cetyl. In recent years, with the advance of the manufacturing technology, it is possible to greatly increase the winding speed during melt spinning from the conventional 1000-1500 m / min to 2000 m / min or more. Particularly oriented unstretched yarn obtained at a winding speed of 2500 to 4000 m / min is provided to the stretching and combusting process as it is, and its use continues to increase greatly to become the mainstream of the spinning technology.

On the other hand, ultra-fast spinning with a winding speed of 4000 m / min or more has also been tested, but such high-speed spinning has a drawback in that the thread during spinning is more frequent and the strength of the final product yarn is significantly lowered. In order to overcome this drawback, we are testing the optimization of spinning conditions (e.g., spinning temperature, cooling air volume, cooling wind temperature, etc.) and structural improvements of spinning barrels and spinning nozzles, but these methods are limited and extensive. No improvement can be expected.

As a result of repeating the investigation by the present inventors about the cause of the above problem, although polyester has a property which is hard to crystallize compared with polyethylene, a polyamide, etc., when the winding speed at the time of melt spinning becomes 2000 m / min or more, it radiates Molecular orientation occurs due to tension, and crystallization occurs with this, and although crystallization of the emitter is not sufficient, the crystallization proceeds greatly, and the above-mentioned problem occurs, and the winding speed is more than 4000 m / min. It turned out that it became more remarkable.

From these facts, polyesters with high orientation and low crystallization in high-speed spinning are continuously examined in terms of their crystallization and molecular orientation behavior, and various additives capable of suppressing crystallization during molecular orientation are found. It has been found that the addition of a hytroquinone has a remarkable effect in the production of polyester and the like, and the present invention has been reached as follows.

In the present invention, in the preparation of a polyester whose main repeating unit is ethylene terephthalate, the hydroquinone or its ester form derivative is 0.2 to the acid component constituting the polyester at any stage before the polymerization reaction is completed. 2.0 mol% is added and made to react.

Paradiacetoxybenzene can be used as an example of the ester-forming derivative of hydroquinone used in this invention. Although the addition time of such hydroquinone or its ester formation derivative is not specifically limited, It is convenient for process to add in the stage from the time when esterification or transesterification reaction is actually started until just before the polycondensation reaction starts.

In addition, when the addition amount is too small, the crystallization inhibitory effect in the molecular orientation referred to in the present invention is not obtained. On the contrary, when the addition amount is too high, the softening point of the polyester obtained is lowered and the color is deteriorated. It is good to set it as the range of 0.2-2.0 mol% with respect to dicarboxylic acid used.

The polyester used in the present invention is mainly a polyethylene terephthalate using a terephthalic acid component and an ethylene glycol component, but a part of a dicarboxylic acid component or a glycol component (15 mol% in total) for improving physical properties of the polyester. The polyester which substituted the following) with another component may be sufficient. The polyester may contain various additives such as a scavenger such as titanium oxide, a dyeing agent, a flame retardant, an antistatic agent, a hydrophilic agent, a colorant and a stabilizer. According to the present invention, the thread trimming during the high-speed spinning and stretching process with a spinning speed of 3000 m / min or more is significantly reduced, so that the process is stabilized and productivity is greatly improved.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

However, the present invention is not limited by the examples, and parts represent parts by weight.

[Example 1-4, Comparative Examples 1,2]

As shown in Table-1, the polyester containing the hydroquinone unit (intrinsic viscosity 0.64-0.66) was discharged through the spinning nozzle at a spinning temperature of 285 ° C and discharged at 44.5 g / min, and air at 15 ° C was discharged at 0.5 m / min. After cooling by blowing, focusing and emulsification were carried out, and then wound at a speed of 4000 m / min to obtain an undrawn yarn, which was stretched to a draw ratio of 1.332. The incidence of trimming at this time is shown in Table-1.

[Example 5-6, Comparative Example 3]

As shown in Table 2, the polyester containing the hydroquinone unit (intrinsic viscosity 0.64-0.66) was discharged through the spinning nozzle at a spinning temperature of 285 ° C and discharged at 42.5 g / minute, and air at 15 ° C was flowed at a speed of 0.5 m / min. After blowing to cool, focused and emulsified, then wound at a speed of 6500m / min. The incidence of trimming at this time is shown in Table-2.

Claims (1)

In preparing polyesters whose main repeating unit is ethylene terephthalate, hydroquinones or their ester-forming derivatives may be prepared during the steps from when the esterification or transesterification reaction is substantially started to just before the start of the polycondensation reaction. 0.2 mol to 2.0 mol% of the acid component constituting the ester is added and reacted.