KR100996845B1 - Method for Manufacturing Polyethylene-2,6-naphthalate fibers having improved indexes of evenness - Google Patents

Abstract

The present invention relates to a method for producing polyethylene naphthalate fibers having high strength and improved leveling agent by applying a high speed low temperature airjet to undrawn yarn. The process according to the invention comprises (A) spinning 20 to 200 solid phase polymerised polyethylene-2,6-naphthalate chips containing at least 85 mol% of ethylene-2,6-naphthalate units and having an intrinsic viscosity ranging from 0.80 to 1.20. Melting spinning at a draft ratio to produce a melt-emitting yarn; (B) solidifying the molten yarn through a delayed cooling zone and a rapid cooling zone to which a high speed low-temperature air jet is applied; (C) winding the yarn at a spinning speed such that the birefringence rate of the undrawn yarn is 0.001 to 0.015; And (D) multi-stretching the wound yarn to a total draw ratio of 4.0 or more.

Polyethylene-2,6-naphthalate, unstretched yarn, birefringence, high strength, leveling agent

Description

Method for Manufacturing Polyethylene-2,6-naphthalate fibers having improved indexes of evenness}

Figure 1 shows a schematic diagram of the delayed cooling section and the rapid cooling section of the present invention.

The present invention relates to a method for producing polyethylene naphthalate fiber having high strength and improved uniformity by applying a high-speed, low-temperature airjet to undrawn yarn, and more specifically, (A) ethylene-2,6-naphthalate unit Molten spinning a solid-state polymerized polyethylene-2,6-naphthalate chip containing 85 mol% or more and having an intrinsic viscosity in the range of 0.80 to 1.20 at a spinning draft ratio of 20 to 200 to produce a melt-emitting yarn, (B) the melting Solidifying the discharged yarn through a delayed cooling zone and a rapid cooling zone to which a high-speed cold jet is applied, (C) winding the yarn at a spinning speed such that the birefringence of the undrawn yarn is 0.001 to 0.015, and ( D) A method for producing polyethylene naphthalate fibers, comprising the step of stretching the wound yarn to a total draw ratio of 4.0 or more and multistage.

Polyethylene-2,6-naphthalate containing naphthalate units in the polymer repeating unit has a higher glass transition temperature, crystallization temperature, and melting temperature than polyethylene terephthalate due to the large structure of naphthalate units. There is a difficulty in spinning at high temperatures in order to form an adequate melt viscosity, which results in significant decomposition of the melt, resulting in poor workability and yarn properties. This problem has been solved by setting a delayed cooling zone of 300mm or more under the detention to lower the spinning temperature, but the undrawn and drawn yarn produced by the above process due to the occurrence of another problem such as a decrease in the radial tension is not very good. It was.

Conventional techniques for producing fibers with excellent leveling agents include Japanese Patent Application Laid-Open No. 3-145253, 4-276011, 4-329260, and the like. In Japanese Patent Laid-Open No. 3-145253, the temperature of the heating tube under the spinneret is somewhat lower than 350 ° C., so that the orientation of the unstretched yarn is sufficiently lowered so that it is not possible to draw it, and thus it is difficult to obtain high strength filament yarn. In the case of 4-276011, the length of the spinneret is too long, so the stretchability is good, but the uniformity of the yarn is uneven. In addition, in the case of high-speed spinning in 4-329260, it is impossible to obtain high strength filament yarn although the uniformity is good.

An object of the present invention is to delay the installation of a heating tube of an appropriate length and temperature to prevent the high degree of orientation of sharkskin and unstretched yarn under the spinneret caused by the increased viscosity of polyethylene-2,6-naphthalate. Cooling and rapid cooling at the bottom thereof with high speed, low temperature air provide a process for producing polyethylene-2,6-naphthalate fibers having high strength and improved uniformity (U%).

In the following the present invention will be described in detail by using an embodiment, but will not be described in detail or known matters. However, this is for a clear understanding of the present invention and is not intended to exclude such things from the scope of the present invention.

The process for producing high strength polyethylene-2,6-naphthalate fiber with improved homogenization according to the present invention comprises the following steps:

(A) Melt spinning a solid-phase polymerized polyethylene-2,6-naphthalate chip containing at least 85 mol% of ethylene-2,6-naphthalate units and having an intrinsic viscosity in the range of 0.80 to 1.20 with a spinning draft ratio of 20 to 200. Generating a discharge yarn; (B) solidifying the molten yarn through a delayed cooling zone and a rapid cooling zone to which a high speed low-temperature air jet is applied; (C) winding the yarn at a spinning speed such that the birefringence rate of the undrawn yarn is 0.001 to 0.015; And (D) multistage stretching the wound yarn with a total draw ratio of 4.0 or more.

In step (B) the delay cooling zone preferably has a length of 250 to 700 mm, and the temperature is advantageously increased to at least 30 ° C. or more relative to the spinning temperature.

Further, in step (B), the high-speed low temperature airjet preferably has a temperature of 5 to 25 ° C. and a wind speed of 1.5 to 2.5 m / sec.

The polyethylene naphthalate chip used in the present invention may include at least 85 mol% or more of ethylene-2,6-naphthalate units, and preferably contains only ethylene-2,6-naphthalate units.

Optionally, the polyethylene-2,6-naphthalate may comprise a small amount of units derived from one or more ester-forming components other than ethylene glycol and 2,6-naphthalene dicarboxylic acid or derivatives thereof as copolymer units. Can be. Other ester forming components copolymerizable with polyethylene naphthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and the like, terephthalic acid, isophthalic acid. Dicarboxylic acids such as hexahydroterephthalic acid, stilbene dicarboxylic acid, dibenzoic acid, adipic acid, azelaic acid.

Polyethylene naphthalate chip according to the present invention is preferably a melt mixture prepared by melt-mixing naphthalene-2,6-dimethylcarboxylate (NDC) and ethylene glycol raw material at 190 ℃ in a 2.0 to 2.3 ratio transesterification reaction ( At 220 to 230 ° C. for about 2 to 3 hours) and condensation polymerization (about 2 to 3 hours at 280 to 290 ° C.) to produce low chips having an intrinsic viscosity of 0.42 to 0.50, followed by temperatures of 240 to 260 ° C. and It can be prepared by the method of solid-phase polymerization to have an intrinsic viscosity of 0.80 to 1.20 and a moisture content of 30 ppm or less under vacuum.

In step (A), the polyethylene naphthalate chip can be melt spun through a pack and a nozzle at a spinning draft ratio of 20 to 200 (linear speed on the first take-up roller / linear speed on the nozzle) at a temperature of 300 to 320 ° C. And thereby the lowering of the viscosity of the polymer by thermal decomposition and hydrolysis can be prevented. If the spin draft ratio is less than 20 from above, the uniformity of the filament cross section is worse, the drawing workability is significantly lowered, and if it exceeds 200, the filament breakage occurs during spinning, making it difficult to produce a normal yarn.

In step (B), polyethylene-2,6-naphthalate has high primary and secondary transition temperatures due to the naphthalene units of the main chain, resulting in high orientation of undrawn yarn due to high melt viscosity and high solidification. There arises a problem that the subsequent stretching operation is very difficult. In order to solve such a problem, the method according to the present invention attaches a heating tube to the bottom of the spinneret as shown in FIG.

In Figure 1 the spinneret 1 extrudes the PEN melt to form a seal and the hood heater 2 heats the spinneret 1 to lower the spinning temperature. The hood heater 2 serves to prevent the lowering of the intrinsic viscosity and to suppress the rapid orientation of the extruded yarn. The air jet unit 3 provided below serves to rapidly cool and solidify the yarns that have been delayed cooled through the air jet nozzle 3-1. By the air jet unit 3, a proper tension is imparted to the thread, thereby improving the evenness of the thread. The air jet nozzle 3-1 may be a cylindrical slit nozzle.

The length of the heating vessel in step (B) is preferably 250 to 700 mm. If the length is less than 250mm, sufficient heat cannot be supplied to the surface of the spinning nozzle and the extruded filament yarns, resulting in the phenomenon of Sharkskin or howitzer, so that a uniform yarn cannot be manufactured. There is a problem that the proper tension is not formed in the undrawn yarn, the flow of the undrawn yarn is severe, so that the uneven yarn or the uniformity of the drawn yarn is significantly worsened.

On the one hand the temperature of the heating vessel may be at least 30 ° C. or higher than the spinning temperature, preferably 40-80 ° C. higher. If the spinning temperature is less than 30 ° C., it is impossible to supply sufficient heat to the surface of the spinning nozzle and the extruded filament yarn, so that a phenomenon such as Sharkskin or howitz occurs, and thus a uniform yarn cannot be manufactured.

The temperature of the rapid cooling section is preferably 5 to 25 ℃. If the temperature of the cooling section is less than 5 ℃ the skin-core structure is generated in the filament yarn is not able to draw enough stretch can not produce a high strength yarn. On the other hand, if the cooling section has a temperature of 25 ° C. or more, crystal nucleating agent is generated, and a high strength yarn cannot be manufactured.

The wind speed of the rapid cooling section is preferably 1.5 to 2.5m / sec. If the speed is less than 1.5m / sec does not form a sufficient tension in the extruded yarn, which causes a problem that the uniformity of the undrawn yarn and drawn yarn worsens. On the other hand, if it exceeds 2.5 m / sec, the shaking of the yarn becomes so large that the uniformity is also poor.

In the case of step (C), the yarn is wound at a spinning speed such that the birefringence rate of the undrawn yarn is 0.001 to 0.015 in the feed roller, and in this case, the preferred spinning speed is 300 to 1500 m / min. According to the present invention, the birefringence rate of the undrawn yarn may be selected as a factor for controlling the microstructure of the undrawn yarn. If the birefringence is less than 0.001, the crystallization rate is too slow in the drawing step to sufficiently induce the formation of tie chains between the crystals. If the birefringence is more than 0.015, the crystallization during the drawing proceeds too rapidly, resulting in poor elongation. It becomes difficult to manufacture history yarns.

In the case of step (D), after the yarn passing through the feed roller is wound, a separate stretching process, for example, a multi-stage stretching while passing through a series of stretching rollers by a spin draw method is obtained as a final stretched yarn. Specifically, it is wound 4 to 8 turns and is wound to 4 to 8 turns to the first stretching roller which is heated to 130 to 170 ℃ and rotated to 400 to 1200 m / min. And one step stretching by winding four to eight times on a second stretching roller heated to 130 to 200 ° C. and rotating at 2000 to 3500 m / min, and again the drawn yarn is heated to 210 to 250 ° C. and 2500 to 4000 m / min. It winds 4 to 8 times to the 3rd extending roller which rotates in 2 steps, and extending | stretching is performed two steps. In this case, the draw ratio is 60 to 95% of the first draw ratio of the first draw. The obtained two-stage stretched yarn is wound 4 to 8 times on a fourth stretching roller heated to 110 to 220 ° C. and rotated at 2400 to 3950 m / min, and the heat is fixed while the tension applied to the yarn is relaxed.

Stretched polyethylene naphthalate fibers produced according to the method of the present invention

(a) Unoriented orientation: Δn ≤ 0.012

(b) Tensile strength: 9.5 g / d or more

(c) Cutting elongation: 9.0% or more

(d) Young's modulus: over 2,500 kg / mm

(e) Increase in municipal stability: Less than 6% of shrinkage at dry heat of 180 ℃

(f) Evenness test: 1.4% or less

Indicates the properties.

Hereinafter, the present invention will be described in detail based on the following examples. However, the following examples are not intended to limit the scope of rights only to illustrate the present invention, and the physical property evaluation in the examples and comparative examples of the present invention was carried out by the following method.

(1) intrinsic viscosity (IV)

After dissolving 0.1 g of the sample in a reagent (90 ° C.) mixed with phenol and 1,1,2,3-tetrachloroethanol at a weight ratio of 6: 4 for 90 minutes to give a concentration of 0.4g / 100ml, Ubbelohde Transfer to a viscometer was carried out for 30 minutes in a 30 degreeC thermostat, and the number of seconds of the fall of the solution was calculated | required using the viscometer and the aspirator. The falling seconds of the solvent was also determined in the same manner, and then the R.V. and I.V. values were calculated by the following equations (1) and (2).

R.V. = Number of drops of sample / number of drops of solvent

I.V. = 1/4 × (R.V.-1) / C + 3/4 × (InR.V./C)

(2) strength

Using Instron 5565 (manufactured by Instron, USA), 250 mm sample length, 300 m / min tensile speed and 80 turns / s under standard conditions (20 ° C., 65% relative humidity) according to ASTM D 885 Elongation was measured under conditions of m.

(3) shrinkage

The sample was left at 20 ° C. and 65% relative humidity for at least 24 hours, and then weighed at a weight equivalent to 0.1 g / d to measure the length (L ₀ ). After the treatment for a minute and left out for 4 hours or more, the load (L) was measured by measuring the shrinkage rate by the following equation (3).

Δ S (%) = (L ₀ -L) / L _o × 100

(4) birefringence

The birefringence was measured using a polarizing microscope equipped with a Berek compensator.

(5) Leveling System (U%)

U% was measured by Keisokki's Eveness Tester 80 Type C at 0.05 g / d for 2 minutes and 30 seconds at a speed of 50 m / min.

Examples 1-6

Table 1 melt-spun polyethylene-2,6-naphthalate polymer having a naphthalene dicarboxylate unit of 90 mol% or more and has an intrinsic viscosity of 0.95 at 315 DEG C through a spinneret to pass through various lengths of heating tubes. Thereafter, while varying the speed of the cold wind in the rapid cooling section, the first stretching roller which is wound around the feed roller at 100 ° C. which rotates at 500 m / min five times and rotated, and then heated at 160 ° C. and rotates at 510 m / min Rotate 6 times. Thereafter, the first drawing is performed by winding seven times on a second drawing roller heated at 165 ° C. and rotating at 2,800 m / min, and again, the drawing yarn is heated to 240 ° C. and rotated at 3,100 m / min to a third drawing roller. Winding 7 times is carried out in two stages of stretching, where the stretching ratio is one stage stretching to 90% of the total stretching ratio, and the second stage stretching is the rest. The two-stage stretched yarn thus obtained is wound seven times on a fourth stretching roller heated to 130 ° C. and rotated at 3,070 m / min, and heat-set while relieving the tension applied to the yarn. Properties of the drawn yarn thus obtained are shown in Table 1 below.

TABLE 1

Example One 2 3 4 5 6 Chip IV (dl / g) 0.95 Heater length (mm) 400 400 400 450 450 450 Heater temperature (℃) 350 380 420 350 380 420 Speed of cold wind (m / sec) 2.0 2.0 2.0 2.0 2.0 2.0 Strength (g / d) 9.79 9.71 9.53 9.69 9.67 9.51 Shinto (%) 9.1 9.9 10.9 9.7 10.2 11.1 Dry Heat Shrinkage (%) 3.3 2.8 2.3 3.1 2.6 2.1 U% 1.7 1.6 1.5 1.4 1.1 1.3 Unoriented orientation 0.013 0.011 0.008 0.008 0.006 0.005

Examples 7-11

Table 2 shows the results obtained by fixing the length and temperature of the heating tube and changing the temperature when the yarns were manufactured as in Examples 1 to 5.

TABLE 2

Example 7 8 9 10 11 Chip IV (dl / g) 0.95 Heater length (mm) 450 Heater temperature (℃) 380 Speed of cold wind (m / sec) 1.5 1.7 2.0 2.2 2.5 Strength (g / d) 9.64 9.75 9.65 9.85 9.99 Shinto (%) 9.2 9.0 10.1 8.8 8.8 Dry Heat Shrinkage (%) 2.8 3.2 2.6 3.4 3.4 U% 1.3 1.4 1.1 1.3 1.3 Unoriented orientation 0.010 0.009 0.007 0.008 0.009

Comparative Examples 1 and 2

In the above example, the cold air was spun at 0.4 m / sec or 2.7 m / sec.

TABLE 3

division One 2 Change condition 0.4 m / sec 2.7 m / sec Chip iv 0.95 Heater length (mm) 450 Heater temperature (℃) 380 burglar 9.45 9.75 Shinto 9.2 9.3 Dry heat shrinkage 2.9 3.1 U% 1.8 1.9 Unoriented orientation 0.008 0.010

In the comparative examples 1 and 2, the speed of the quenching jet is 0.5 m / sec, which is worse in strength, elongation, and homogeneity than in Example 9, and in the case of 2.7 m / sec, it is not good in elongation and homogenization.

Polyethylene-2,6-naphthalate fibers made from the present invention are suitable for various applications requiring resistance to tensile deformation and high heat resistance due to high strength, high elongation and excellent uniformity. The properties and working effects of the polyethylene-2,6-naphthalate fiber thus produced are as follows.

(a) Unoriented orientation: Δn ≤ 0.012

(b) Tensile strength: 9.5 g / d or more

(c) Cutting elongation: 9.0% or more

(d) Young's modulus: over 2,500 kg / mm

(e) Increase in municipal stability: Less than 6% of shrinkage at dry heat of 180 ℃

(f) Evenness test: 1.4% or less.

Polyethylene-2,6-naphthalate fibers prepared according to the present invention have high strength and improved uniformity (U%), so the treatment cords formed therefrom have excellent dimensional stability and strength and are suitable as reinforcements for rubber products. Has

Claims (4)

In the method for producing polyethylene-naphthalate fiber, (A) Melt spinning a solid-phase polymerized polyethylene-2,6-naphthalate chip containing at least 85 mol% of ethylene-2,6-naphthalate units and having an intrinsic viscosity in the range of 0.80 to 1.20 with a spinning draft ratio of 20 to 200. Generating a discharge yarn; (B) the molten yarn is passed through a delayed cooling zone, and the solidified by passing through a rapid cooling zone to which a high-temperature low-temperature air jet having a temperature of 5 to 25 ° C. and a wind speed of 1.5 to 2.5 m / sec is applied. step; (C) winding the yarn at a spinning speed such that the birefringence rate of the undrawn yarn is 0.001 to 0.015; And (D) a manufacturing method comprising the step of stretching the wound yarn to a total draw ratio of 4.0 or more and multistage. The method according to claim 1, wherein the length of the delayed cooling zone of step (B) is 250 to 700 mm and the temperature is at least 30 ° C. or higher than the spinning temperature. delete Polyethylene-2,6-naphthalate fiber satisfying the following physical properties produced by the method of claim 1 (a) Unoriented orientation: Δn ≤ 0.012 (b) Tensile strength: 9.5 g / d or more (c) Cutting elongation: 9.0% or more (d) Young's modulus: over 2,500 kg / mm (e) Increase in municipal stability: Less than 6% of shrinkage at dry heat of 180 ℃ (f) Evenness test: 1.4% or less.

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