JPH04136216A - Method and spinneret for melt-spinning polyester fiber - Google Patents

Abstract

PURPOSE:To stably and readily provide the subject fiber having a high strength and a high quality in good spinning stability by extruding a polyester under a specific condition with a spinneret, having a tapered portion between an extrusion opening portion and a narrow portion disposed above the extrusion opening portion of an extrusion hole. CONSTITUTION:When a polyester is melt-spun through the extrusion hole 2 of a spinneret 1 having a >=0.6mmphi extrusion opening portion 6, the spinneret 1 is employed and the polyester is extruded so that a shear rate at a narrow portion 4 is >=1000sec<-1> and a pressure loss is >=29kg/cm<2>, thus melt-spinning the polyester into the objective fiber, the spinneret 1 having the extrusion hole 2 which has the narrow portion 4 having a diameter d1 smaller than the diameter d2 of the extrusion opening 6 and which further has a tapered portion 5 whose diameter is enlarged in the extrusion direction at an angle theta of <=15 deg., based on the central axis of the extrusion hole 2 from the narrow portion 4 over the extrusion opening portion 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a specific spinneret and a method for melt spinning using the same, and particularly to a method and a spinneret for melt spinning polyester under specific conditions.

[Prior art] Polyester fibers, especially polyethylene terephthalate fibers, have well-balanced properties in terms of strength, modulus, and dimensional stability (low shrinkage), and are used for tires, belts, conveyor belts, safety belts, civil engineering materials, etc. It is widely used in industrial material applications. Polyester fibers used for tire cords or other industrial applications must have physical properties that give them high strength.For example, in tire manufacturers, high strength can improve tire durability and reduce the amount of yarn used. , the cost of tires can be reduced.

Many attempts have been made to achieve even higher strength. For example, in Japanese Patent Application Laid-Open No. 60-162830, undrawn yarn with a low degree of orientation obtained by melt spinning is drawn to a high magnification, and the strength of 12a is 12a. /de high strength yarn is obtained.

However, industrial polyester fibers are now required to have increasingly higher performance. For example, for tire cords, high modulus is required to improve yield during tire molding, and to reduce shrinkage and improve riding comfort. In addition, for the application of large tires, it is necessary to improve fatigue resistance.

On the other hand, cords for belts are required to be maintenance-free and have high modulus, and cords for large, high-load lap belts are required to have high elongation, high toughness, and fatigue resistance.

In response to the above quality requirements, the polyester fiber obtained by the high-speed spinning and drawing method, which has been developed and put into practical use in recent years, has a low shrinkage rate, and if this feature is utilized as a cord,
It is possible to maintain a shrinkage rate equal to or lower than that of conventional polyester cords, and to make the cohedo highly modulus. In particular, as proposed in Japanese Patent Application Laid-Open No. 5358032, tire cords that start from an undrawn system with a higher whiteness than before and use drawn fibers have high modulus, low shrinkage, and fatigue resistance. It is significantly improved compared to conventional polyester cords, and has excellent handling stability and ride comfort when driving at high speeds.1. In addition, there are fewer irregularities (so-called punto bulges) during tire molding, so it is being used favorably.

However, polyester fibers obtained by high-speed spinning and drawing methods such as those disclosed in JP-A-53-58032 have high modulus,
Although it has low shrinkage, it has the disadvantage that it is difficult to obtain high strength compared to the conventional method of starting from undrawn yarn with a low degree of orientation. In order to compensate for this drawback, attempts have been made to obtain fibers with high modulus, low shrinkage, and at the same time high tenacity.

For example, in JP-A-1-282306, after melt spinning, the yarn is taken off at a relatively high spinning speed of 1500 to 2600 m/min to obtain a high distribution degree undrawn yarn, so-called POY. Heat-stretched at a relatively low magnification of 65 times, resulting in low shrinkage and at the same time approximately 9-5 g/d.
A method for producing polyester fibers having a high strength of up to e is disclosed.

[Problems to be Solved by the Present Invention] However, in any of these methods, in order to obtain high strength, it is necessary to draw at a high magnification and tension as much as possible. This method is prone to breakage and has poor process performance, making it difficult to apply to industrial fields that require stable and efficient production.

The process conditions for spinning and drawing are intricately related to a number of factors, including polymer conditions, spinning conditions, and drawing conditions, but among them, it is important to ensure that the polymer is stably discharged from the spinneret and that a homogeneous undrawn system is obtained. This is the most important requirement for improving process conditions.

For example, in JP-A-63-120109, a spinneret with a tapered discharge hole is used to suppress the generation and growth of foreign matter adhering to the vicinity of the discharge hole, thereby maintaining a stable discharge state. , a method for improving process conditions is disclosed.

In order to improve the stability of the polymer discharged from the spinneret, it is necessary not only to take into account the shape of the outlet of the discharge hole of the spinneret, but also to control the pressure at the time of extrusion through the discharge hole, the linear discharge velocity, and the spinning directly under the spinneret. For example, if the diameter of the discharge hole is increased to increase the spinning draft expressed by the following formula, the stress in the spun yarn directly under the spinneret increases and the discharge condition becomes stable, but on the other hand, The discharge layer between single yarns increases.

On the other hand, if the diameter of the discharge hole is made small, the discharge layer between the single yarns will be small, but the stress of the spun yarn under the spinneret will be reduced, resulting in poor spinning stability.

Take-up roller speed Spinning draft - Linear speed of discharge from the spinneret Also, changing the discharge hole diameter of the spinneret changes the spinning draft and the stress of the spun yarn directly under the spinneret, which has a large effect on the degree of orientation of the spun yarn. In particular, when attempting to obtain high modulus, low shrinkage polyester fibers using the above-mentioned high-speed spinning and drawing method, it is necessary to obtain undrawn yarns with high whiteness.
It is advantageous for the discharge hole diameter of the spinneret to be large so that the spinning draft is large and it is easy to obtain high orientation.

However, if the diameter of the discharge hole is increased, on the other hand, the process condition will deteriorate due to the deterioration of the discharge amount as described above, so in consideration of both quality and process condition, a spinneret with a discharge hole diameter of 0.5 mm or less is used. It was common to do so.

An object of the present invention is to provide a method for stably producing high-strength polyester fibers with good spinning stability and process performance by solving the above-mentioned contradictory problems of conventionally known spinnerets.

[Means for Solving Problem R] In order to achieve the above-mentioned object, the present inventor conducted a thorough study on the behavior of the polymer inside and outside the spinneret, and found that the cause of deterioration of the process condition when the discharge hole diameter is increased is the back pressure of the spinneret. We found that the causes were deterioration in ejection stability due to a decrease in ejection stability and deterioration in homogeneity of the undrawn system due to a decrease in shear rate at the nozzle outlet hole.As a result of further experiments, we found that We have developed a spinneret that has a significant effect on improving process conditions.

That is, when melt-spinning polyester through the discharge hole of a spinneret having a discharge opening of 0.6-φ or more, the present invention provides a narrowing portion having a smaller diameter than the discharge opening at a position upstream of the discharge opening of the discharge hole. , using a spinneret having a discharge hole in which a tapered part is formed with a larger diameter in the discharge direction at an angle of 15 degrees or less with respect to the central axis of the discharge hole from the narrowed part to the discharge opening, and the shear at the narrowed part is speed is 100
o sec or more and a pressure loss of 20 kg/cJ or more, and in a spinneret of a melt spinning apparatus, a discharge opening is provided at a position upstream of the discharge opening of the discharge hole. A constricted part with a smaller diameter, a shear rate of 100Q SeC or more, and a pressure loss of 20 k (1/aJ or more) is provided, and the angle from the constricted part to the discharge opening is 15° or less with respect to the central axis of the discharge hole. This spinneret is characterized by forming a tapered portion having a larger diameter in the discharge direction, and having a discharge opening having a diameter of 0.6 or more.

Here, the shear rate and pressure loss at the narrowed portion of the mouthpiece are values calculated by the following equations.

d, H Pressure loss Δp (kQ/cj) 0.9465x10 ・μ ・ l ・Q where, Q: Polymer discharge amount per spindle (a/-1n) d: Diameter of the narrowed part of the discharge hole (-1) H. Number of holes in spinneret μ: Melt viscosity of polymer (1) O7slJl
: Length of the narrowing part (-) ρ : Density of the polymer (a/c haze 3) The polymer constituting the polyester fiber of the present invention contains 90 mol% or more of ethylene terephthalate repeating units in the molecular chain, preferably 95 mol% or more. It is a polyester containing mol% or more. As such polyester, polyethylene terephthalate is suitable, but 1
Examples of such copolymerization components that may contain other copolymerization components in a proportion of less than 0 mol%, preferably less than 5 mol%, include isophthalic acid, naphthalene dicarboxylic acid, adipic acid, oxybenzoic acid, diethylene glycol. , propylene glycol, trimellitic acid, pentaerythritol and the like. These polyesters may also contain additives such as stabilizers and colorants.

Next, the present invention will be explained in more detail using the drawings. 1st
The figure is a sectional view of the discharge hole of the spinneret used in the present invention.

In the figure, the molten polymer flows into the discharge hole 2 of the spinneret 1 from the polymer inflow M3, passes through the narrowed part 4 having a hole diameter d1 and a length 11, and then has a length 1 which is increased in diameter in the discharge direction.
It passes through the 2-tapered portion 5 and is discharged from the discharge side port 6 having a hole diameter d2.

Here, the discharge opening diameter d2 is closely related to the spinning draft as described above, and by increasing the spinning draft by increasing d2, the stress in the spun yarn directly under the spinneret can be increased. At this time, in order to stabilize the discharge state and obtain a good process condition, the value should be 0.6- or more, preferably (
It is preferable that L is 8 mm or more.

Further, regarding the hole diameter d and length 11 of the narrowed portion 4, the shear rate f in the narrowed portion 4 is 1000 Sec' or more,
Good*shi<ha20005ec-1 or more, pressure loss Δp in ff19 part 4 is 20J/cj or more, preferably 30
It is necessary to set d ・l so that it is greater than or equal to k(1?'aj). If the shear rate is lower than the above range, the discharge stability will deteriorate and at the same time the unevenness will increase, which is the purpose of the present invention. However, it is not possible to improve the process condition or obtain high-strength yarn.

The tapered portion 5 from the narrowed portion 4 to the discharge hole opening 6 has a large diameter with an angle θ of 15° or less, preferably 2° to 10°, with respect to the central axis of the discharge hole 2, and has a diameter of 0- It is necessary that the discharge hole opening 6 has a hole diameter of 6- or more.

If the angle θ of the tapered portion 5 becomes larger than the above range, the polymer will separate from the middle of the tapered portion 5, resulting in unstable discharge and causing problems such as thread breakage and single thread breakage.

Although the angle θ of the tapered portion 5 may be less than 2°, the ratio of the opening to the narrowed portion 4 becomes small, and there is a limit to increasing the diameter of the discharge opening 6.

The shape of the mouthpiece from the inlet 3 to the narrowed part 4 is not necessarily limited to the shape shown in FIG. 1, and any shape such as a straight shape, a tapered shape, a hyperpolished shape, etc. can be used as appropriate. Further, the material of the cap is generally stainless steel, but other metal materials, ceramics, etc. can be appropriately selected and used. Note that FIG. 2 shows a discharge hole of a spinneret that has been commonly used in the past, and in this case, the diameter of the narrowed part is the diameter of the narrowed part and the diameter of the open part is the same.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Melt viscosity at 300°C is approximately 3000 polse
Polyethylene terephthalate chips were spun using an extruder type spinning machine at a spinning temperature of 300° C. using spinnerets shown in Table 1 and shown in Figures 1 and 2.

After passing through a heating cylinder of 30C through a spinning machine block and a heat insulating plate under the nozzle, it was cooled and solidified while blowing cooling air of 25C at a rate of 500Nm3/min.
Next, after applying an oil agent with an oiling roller, the yarn is taken up by a take-up roll that rotates at a predetermined speed to control the spinning speed, and then the taken-up yarn is rolled three times without being wound up.
After the step-stretching heat treatment, 4% relaxation was applied with a relaxation roll and the film was wound up with a winder.

At this time, the temperature of each stretching roll is 100°C for the supply roll, 120°C for the first stretching roll, 140°C for the second stretching roll, and 140°C for the third stretching roll.
The stretching roll was set at 240°C and the relaxing roll was set at 150°C. The winding speed was 3000 m/min to 5000 m/min, and the stretching ratio was 90% of the maximum stretching ratio. Note that the maximum stretching ratio refers to the average value of the eel size stretching fa ratios that can be stretched at n=5.

The spinning discharge amount was changed depending on the drawing and winding speed, but the fineness of the drawing system was adjusted to 1500 de. Table 1 shows the process conditions under the above spinning conditions and the properties of the drawn yarn obtained.

(The following is a blank space) Effects of the Invention As explained above, according to the present invention, it is possible to stably and easily obtain high-strength polyester fibers with good spinning stability and process conditions, and excellent quality. It has a remarkable effect.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a discharge hole portion of a spinneret for explaining the present invention in detail, and FIG. 2 is a cross-sectional view of a conventional discharge hole portion.

Claims (1)

[Claims] 1. When polyester is melt-spun through the discharge hole of a spinneret having a discharge opening of 0.6 mmφ or more, a constricted part with a smaller diameter than the discharge opening is provided at a position upstream of the discharge opening of the discharge hole. A spinneret is used which has a discharge hole in which a tapered part is formed with a diameter increasing in the discharge direction at an angle of 15 degrees or less with respect to the central axis of the discharge hole from the narrowed part to the discharge opening. Shearing rate is 1000sec^-
1. A method for melt spinning polyester fibers, characterized in that the polyester fibers are discharged so that the pressure loss is ^1 or more and the pressure loss is 20 kg/cm^2 or more. 2. In the spinneret of the melt spinning device, the discharge hole has a diameter smaller than the discharge opening at a position upstream of the discharge opening, a shear rate of 1000 sec^-^1 or more, and a pressure loss of 20 k
g/cm^2 or more is provided, and a tapered part is formed from the narrowed part to the discharge opening with a larger diameter in the discharge direction at an angle of 15 degrees or less with respect to the central axis of the discharge hole, A spinneret characterized in that the diameter of the discharge opening is 0.6 mm or more.