KR20090072050A - A method for producing high modulus - low shrinkage polyester multifilament yarn - Google Patents

Abstract

A manufacturing method of high intensity - low shrinkage polyester multifilament yarn is provided to decrease difference of a degree of orientation of fiber filament inside and outside by injecting cooling air at different temperature. A manufacturing method of high intensity - low shrinkage polyester multifilament yarn comprises the following steps of: manufacturing yarn by extruding a solid-state polymerization polyester chip of which inherent viscosity is 1.0 ~ 1.2 and containing an ethyleneterephthalate unit of 85 mole % with temperature of 290 ~ 300°C; solidifying the yarn with supercooling(3); winding the undrafted yarn with proper spinning speed; and drafting the winded yarn with multi-stages. In a solidification step, the yarn is cooled with the cooling air of 40 -50°C in an upper cooling region and the cooling air of 20-30°C in a lower cooling region.

Description

A Method for Producing High Modulus-Low Shrinkage Polyester Multifilament Yarn}

FIELD OF THE INVENTION The present invention relates to a process for producing improved polyester multifilament yarns having high modulus and low shrinkage, and more particularly to a process for producing polyester multifilament yarns by controlling the cooling temperature under a spinning nozzle. will be.

In general, polyester fiber is widely used as an industrial material due to its high strength, and is widely used in industrial fields including rubber cords, seat belts, conveyor belts, V-belts and hoses. .

In particular, in order to be applied as a fiber reinforcing material of rubber tires, it has to have excellent dimensional stability and strength when converted to a treatment cord through latex treatment and heat treatment.

US Pat. No. 4,101,525 and US Pat. No. 4,491,657 disclose industrial polyester multifilament yarns having high initial modulus and low shrinkage. However, the yarn disclosed in the above patents has the disadvantage that the strength is reduced when converted to the treatment cord, so that it does not have the necessary characteristics of the tire cord.

In order to solve this problem, as a method of increasing the strength of the multifilament polyester fiber, US Patent No. 4,690,866 proposes a method of spinning using polyester chips having a high intrinsic viscosity (I.V.) of 1.2 or more. Increasing the viscosity of the chip increases the radial tension to increase the orientation of the non-drawn yarn and the formation of tie chains that connect the crystals to the crystals, thereby making it possible to exhibit excellent strength when converted to treatment codes. However, the high intrinsic viscosity polyester used in the above method has a great difference in intrinsic viscosity between the surface and the central portion during solid phase polymerization, so that when melt-spinning, the radioactivity decreases due to the viscosity unevenness and filament cuts are generated, resulting in fairness and appearance. Not only does this become poor, but also needs to be melt-spun at a high temperature, so that pyrolysis and hydrolysis occur, and thus the fiber spun actually has a problem that the chip does not have as high a viscosity as the chip has.

In addition, after the molten polyester polymer passes through the spinning nozzle, the fibers are solidified by the cooling air. As such, in the solidification process of cooling the high-temperature polymer with low temperature air, a difference in orientation occurs between the inside of the fiber filament and the outside of the fiber filament in direct contact with air, and finally, the drawing process is prevented from stretching at a high draw ratio. The physical properties of the tire cord, which is the final product, are degraded, and when stretching at high magnification, fairness and appearance are deteriorated.

The present invention has a technical problem to provide a method for producing a polyester fiber suitable for the use of a tire cord and the like excellent in heat resistance and chemical stability.

In the present invention, the cooling zone is divided into two stages to reduce the difference in the degree of orientation of the inside and outside of the fiber filament by injecting cooling air at different temperatures, and in particular, the chemical stability and the heat resistance of the inside and outside of the fiber filament have a uniform and high degree of orientation. It is possible to obtain this improved polyester fiber.

Method for producing a polyester fiber according to the present invention is a process of extruding a solid-phase polymerized polyester chip containing ethylene terephthalate unit at a temperature of 290 ~ 300 ℃ to make a discharge yarn, the quenched by passing the discharge yarn through a cooling zone Manufacturing a polyester fiber comprising a process of solidifying the process, winding the yarn at an appropriate spinning speed by adjusting the birefringence rate and density of the unstretched yarn, and stretching the wound yarn in several stages as an appropriate draw ratio. The process of solidifying by quenching includes dividing a cooling zone into two stages and injecting cooling air of different temperatures, wherein the cooling air has a temperature of 20 to 30 ° C. in the lower cooling zone, and upper cooling. Zone is a temperature of 40 to 50 ℃ to produce a polyester fiber The features.

According to the present invention, the cooling zone is divided into two stages during the solidification process of the fiber to reduce the difference in the degree of orientation of the inside and outside of the fiber filament by injecting cooling air at different temperatures. Due to this, it is possible to obtain a polyester fiber having improved chemical stability and heat resistance. Polyester multifilament yarn according to the present invention can be utilized for tire cords.

The present invention is described in more detail as follows.

      The process for producing a polyester fiber according to the present invention is (a) extruded a solid-phase polymerized polyester chip containing 85 mol% or more of ethylene terephthalate units and having an intrinsic viscosity in the range of 1 to 1.2 at a temperature of 290 to 300 ° C. (B) passing the discharged yarn through a cooling zone to solidify it by quenching, (c) adjusting the birefringence and density of the undrawn yarn, and winding the yarn at an appropriate spinning speed; and (d) It includes a process of stretching the wound yarn in several stages as a proper draw ratio.

1 shows an apparatus for carrying out such a manufacturing process.

As shown in FIG. 1, the polyester chips first stored in the pack 1 are subjected to low temperature melt spinning at a suitable temperature, for example 290 to 300 ° C., using the spinning nozzle 2. The low temperature melt spinning is to prevent a decrease in the viscosity of the polymer by thermal decomposition and hydrolysis. And in order to control the final yarn fine yarn fineness in the process of adjusting the fineness of the discharge yarn. The emission yarn 4 discharged through the spinning nozzle 2 is quenched after passing through the hood.

The zone to be quenched is called the cooling zone 3 and is cooled by the cooling air. The hood is provided with a heating device (not shown) and generally has a length L of 140 to 220 mm and a temperature of 250 to 380 ° C. In the cooling zone (3), cooling air is blown for quenching, and according to the method of blowing the cooling air, open cooling, circular closed cooling, and radial outflow cooling are performed. Quenching). In general, the temperature of the cooling air injected for quenching in the cooling zone 3 is controlled to 20 to 50 ° C. Rapid cooling using such a rapid temperature difference between the hood and the cooling zone 3 is to increase the freezing point and spinning tension of the spun polymer to increase the orientation of the undrawn yarn and the formation of tie chains.

However, as described above, quenching causes rapid temperature gradients in and out of the emitting yarn or filament, which causes a large difference in the degree of internal and external orientation affecting the heat resistance and strength of the entire filament. Therefore, the present invention is characterized in that the temperature of the cooling air injected by dividing the cooling zone into two stages in order to reduce the difference in the internal and external orientation of the filament in the cooling zone 3 as described above and to obtain a higher degree of fiber. . According to an embodiment of the present invention, the temperature of the cooling air was found to be most suitable to be 40 to 50 ° C. in the upper cooling zone and 20 to 30 ° C., which is a general cooling air temperature in the lower cooling zone.

In the present invention, if the temperature of the cooling air in the upper cooling zone exceeds 50 ℃ because the glass transition temperature of the polyester 78 ℃ level has no cooling effect, if the temperature of the cooling air in the upper cooling zone is less than 40 ℃ cooling delay The effect is not great. In general, as the rapid cooling is performed directly under the spinneret, the degree of orientation of the produced fiber is decreased.

In addition, the friction between the single yarn is increased, the strength is not only lowered due to the unevenness of the arrangement, etc., but also the toughness is increased. On the contrary, when the cooling zone is divided into two stages according to the present invention, the temperature of the cooling air is adjusted to a temperature of 40 to 50 ° C. in the upper cooling zone and 20 to 30 ° C. in the lower cooling zone. Due to the presence of the upper cooling zone, the effect of delaying the cooling point occurs, the difference in the orientation of the inside and outside of the fiber is reduced, and the orientation of the finally produced polyester fiber is increased. It has been shown that chemical stability is increased and chemical stability is obtained. In the above, the injection speed of the cooling air is 0.3 m / sec to 0.8 m / sec, but can be adjusted as necessary.

Fiber filaments solidified by the above method is made of polyester fibers through a multi-step stretching process.

<Examples and Comparative Examples>

Comparative Example 1

A solid phase polymer polyester chip having an intrinsic viscosity (I.V.) of 1.05 and a moisture content of 20 ppm containing 220 ppm of antimony metal was prepared. The prepared chips were melt spun using an extruder at a discharge rate of 900 g / min and a spin draft ratio of 410 at a temperature of 295 ° C. Subsequently, the discharged yarn was solidified by passing through a heating zone (atmosphere temperature 330 ° C.) and a cooling zone (20 ° C., cooling air blowing with a wind speed of 0.4 m / sec) having a length of 60 mm directly below the nozzle, and then oiled with a spinning emulsion. This undrawn yarn (POY) was wound at a spinning speed of 2700m / min, the first stage stretching was 1.4 times at 60 ℃, the second stage stretching was 1.1 times at 70 ℃, and the third stage was 1.3 times at 70 ℃. The final stretched yarn (yarn) of 1500 denier was prepared by heat setting at 230 ° C., 2% relaxation, and winding.

Comparative Example 2

The final stretched yarn (yarn) was manufactured in the same manner as in Comparative Example 1 except that the cooling air temperature was 25 ° C. and the wind speed of the cooling air was 0.6 m / sec.

Example 1

The same method as Comparative Example 1 except that the cooling air temperature of the upper cooling zone is 40 ° C., the cooling air temperature of the lower cooling zone is 20 ° C., and the wind speed of the upper and lower cooling air is 0.4 m / sec. The final stretched yarn (yarn) was produced.

Example 2

The same method as Comparative Example 1 except that the cooling air temperature of the upper cooling zone is 45 ° C., the cooling air temperature of the lower cooling zone is 25 ° C., and the wind speed of the upper and lower cooling air is 0.6 m / sec. The final stretched yarn (yarn) was produced.

Table 1 below shows the degree of orientation of the fibers produced by the methods of Comparative Examples 1 and 2 and Examples 1 and 2.

TABLE 1

 Comparative Example 1  Comparative Example 2  Example 1  Example 2  Cooling air volume (m / s)  0.4  0.6  0.4  0.6  Cooling temperature of upper cooling zone (℃)  20  25  40  45  Cooling temperature of lower cooling zone (℃)  20  25  20  25 Birefringence (Orientation) (× 10 ^-3 )  32  36  58  62 Density (g / cm ³ )  1.338  1.339  1.348  1.350

The polyester fiber produced according to the method of the present invention as described above can be used for the production of any industrial fiber, but is particularly preferred for fibers having an intrinsic viscosity of 1.0 or more.

While the present invention has been described in detail with reference to the embodiments, it will be apparent to those skilled in the art that the embodiments presented are exemplary and the scope of the present invention is not limited by the modifications and variations of the embodiments described above. It is intended that the scope of the invention only be limited by the following claims.

1 shows a spinning apparatus used in the process of making fibers according to the invention.

Claims (3)

Extruding a solid-phase polymerized polyester chip containing 85 mol% of ethylene terephthalate units and having an intrinsic viscosity of 1.0 to 1.2 at a temperature of 290 to 300 ° C. to produce a discharge yarn, which is passed through a heating zone and a cooling zone. In the method of producing a polyester fiber comprising the step of solidifying by quenching, winding the undrawn yarn at an appropriate spinning speed and stretching the wound yarn in multiple stages, In the step of solidifying by quenching, the cooling zone is divided into two stages, and the high cooling power is cooled by cooling air of 40 to 50 ° C. in the upper cooling zone and cooling air of 20 to 30 ° C. in the lower cooling zone. Process for producing low shrink polyester multifilament yarns. The method according to claim 1, The speed of the cooling air is 0.3 to 0.8 m / sec. High strength-low shrinkage polyester multifilament yarn production method. The method according to claim 1, The polyester multifilament yarn production method of high-strength low-shrink polyester multifilament yarns, characterized in that the ultimate viscosity is 1.0 or more.

Images