JPH0465514A - Production of polyester yarn - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing industrial polyester fibers.

More specifically, the present invention relates to a method for producing polyester fibers suitable for applications requiring high strength, high toughness, and high durability, such as tire cord applications or seat belt applications.

[Prior Art] Polyester fibers have excellent mechanical properties and are therefore widely used in industrial applications, particularly tire cords and seat belts.

There is always a demand for high strength and high durability for these industrial yarns, and various methods are being considered. Among these, increasing the degree of polymerization of polymers improves strength and durability, so in recent years, for example,
As described in the above publication, polymers with a high degree of polymerization have come to be used.

[Problems to be Solved by the Invention] However, in ordinary melt spinning methods, when the polymerization degree of the polymer is increased beyond a certain level, it becomes difficult to increase the strength, and in extreme cases, the strength may decrease. It was found that there is a limit to increasing the degree of polymerization of the polymer.

The present inventors conducted intensive research on this phenomenon of strength reduction and found that one of the causes thereof is a decrease in molecular weight when drawing a highly polymerized undrawn yarn.

That is, when the degree of polymerization of the polymer is increased beyond a certain level, the molecular weight decreases significantly during stretching, resulting in a decrease in strength. Therefore, in order to improve performance, it is necessary to draw undrawn yarn with a high degree of polymerization while suppressing a decrease in molecular weight as much as possible.

An object of the present invention is to provide a method for producing polyester fibers having high strength, high toughness, and high durability and suitable for industrial use, based on the above findings.

[Means for Solving the Problems] The object of the present invention is to melt-spun polyester having ethylene terephthalate as a main repeating unit and draw it to obtain a drawn yarn having a strength of 7.0 g/d or more. This can be achieved by a method for producing polyester fiber, which is characterized in that an undrawn yarn that satisfies the following formula obtained by melt-spinning a polyester that satisfies formulas , B, and C is drawn so as to satisfy formula E below. .

A, Tc5160℃ B, T≦260℃ C, [η] PO≧0.90 D, [η] Uy≧0.80 E, △ [η≦0.020 The polyester of the present invention mainly contains ethylene terephthalate. The polyester used as a repeating unit is preferably a homopolyester that does not contain commonly used additives, third components, etc.

The present inventors have conducted research on the drawing process of highly polymerized undrawn yarns, and have conducted intensive studies on methods for suppressing the reduction in molecular weight, that is, the reduction in intrinsic viscosity [η] during the drawing process. As a result, it was found that there is a correlation between the crystallinity of the polymer and the degree of reduction in [η] during stretching. It has been found that the decrease in [η] can be suppressed.

The crystallinity of a polymer can be shown by the measurement value of DSC (differential scanning calorimeter).
60℃ or higher and 1st ru corresponding to the crystal size
It has been found that when the melting peak temperature Tw of n is 260° C. or less, the decrease in [η] during stretching can be significantly suppressed.

When a polymer has a Tc of less than 160°C or a TmI of more than 260°C, the [ηJ decrease during drawing is large, resulting in a decrease in the strength and durability of the drawn yarn.

The reason for this is thought to be that in the case of a polymer with a Tc of less than 160°C, that is, a relatively fast crystallization rate, microcrystals are generated during cooling during the spinning process, and the microcrystals are present in the undrawn yarn.

Furthermore, when Tm exceeds 260° C., that is, when the crystal size in the polymer is large, it is thought that the crystals are not completely melted by the heat applied during melt spinning and remain in the undrawn yarn.

It is speculated that if there is a remaining part of microcrystals or dissolved crystals in the undrawn yarn, stress will be concentrated in this part during drawing, making molecular chains more likely to break. be done. Therefore, Tc needs to be 160°C or higher, more preferably 170°C or higher, and 180°C or higher.
It is more preferable that it is above. Also, Tm is 260
It needs to be below 258°C, preferably below 258°C.

Intrinsic viscosity of the supply polymer of the polyester used in the present invention [
η],. must be 0.90 or more.

The purpose of the present invention is to increase the strength and durability of fibers by increasing the molecular weight of the polymer, [η]. If it is less than 0.90, it is insufficient in terms of strength and durability.

Therefore, the intrinsic viscosity [η] PO of the supplied polymer is 0.95
It is preferable that it is above.

For the same reason, the intrinsic viscosity [η] U of the undrawn yarn of the present invention
Y needs to be 0.80 or more. For example, by increasing the spinning temperature, [η]1. By lowering , it is possible to reduce the decrease in [η] during stretching, but
The original purpose of increasing strength and durability by increasing the molecular weight cannot be achieved. Therefore, [η] UY of undrawn yarn is 0
．． It is preferable that it is 85 or more. The strength of the drawn yarn obtained in the present invention must be 7.0 g/d or more, and [η] UY-[η] is a measure of molecular weight reduction during the drawing process.
, Y1, that is, Δ[η, needs to be 0.020 or less. If the strength is less than 7.0 g/d, the strength is insufficient for industrial use. Therefore, the strength of the drawn yarn is 8. Or
/d or more is preferable.

Furthermore, if Δ[η] exceeds 0.020 during the stretching process,
The strength and durability of the drawn yarn will decrease.

Even if drawn yarns have the same strength, those with a large Δ[η] will have many defects in fiber structure and will be inferior in durability. Δ[η] during the stretching process is preferably 0.015 or less, more preferably 0°010 or less.

The stretching method used in the present invention is preferably multistage stretching. - It is more effective to perform the stretching in multiple stages than to perform the entire stretching in one stage in reducing [η]. Further, as a heating means, non-contact heating is preferably used since normal pin heating and hot roller heating increase Δ[η]. Stretching in a plasma atmosphere is also one way to reduce Δ[η.

Furthermore, the inventors' studies have revealed that the magnitude of Δ[η] is influenced by the stress during stretching. The higher the stretching stress, the larger Δ[η], so it is important to keep the stretching stress as low as possible. Therefore, the stretching stress is preferably 3.5 g/d or less, and 3.0 g/d or less.
It is more preferable that it is d or less. The above-mentioned stretching by non-contact heating or stretching in a plasma atmosphere is
This is an effective method to reduce stretching stress.

Note that the stretching stress is the stretching tension divided by the fineness of the fiber after stretching.

[Example] The present invention will be explained in more detail with reference to the following example. Note that the physical properties in the examples were determined as follows.

A, Tm STc Sample 10a+ using PerkinElmer DSCd type
g, from 50°C to 2°C at a heating rate of 16°C/min in a N2 atmosphere.
Raise the temperature to 80°C and obtain the DSC curve (1st run
). The melting endothermic peak temperature of the crystal at this time is defined as Tm.

Also, following the 1st run, the sample was heated at 280℃ for 5 minutes.
After standing for a minute, the temperature was rapidly cooled to room temperature, and then the temperature was raised from 50°C to 280°C at a heating rate of 16°C/min in a N2 atmosphere.
Find the curve (2nd run). The peak temperature of crystallization exotherm at this time is defined as Tc.

B. Intrinsic viscosity [η] 0.1 g of a sample was dissolved in orthochlorophenol loml and measured at 25°C using an Ostwald viscometer.

C0 strength elongation Using a Tensilon tensile tester manufactured by Toyo Baldwin,
The strength and elongation curve (S
-8 curve) was determined and the strength elongation was calculated.

D. Fatigue resistance (GY fatigue life) The GY fatigue test (Goodyear Mallory Fatigue test) was conducted in accordance with ASTM-D885 to determine the time until the tube bursts. The number of cords inserted into the tube was 30 per inch, and vulcanization was performed at 160° C. for 20 minutes. Measurements were conducted under the following conditions.

Tube internal pressure: 3.5kg/cJG Rotation speed: 8
50rp■ Tube angle = 90 degrees 300 minutes or more is good, 250 minutes or more and less than 300 minutes is somewhat poor, and less than 250 minutes is poor.

Example 1 100 parts of dimethyl terephthalate and 5 parts of ethylene glycol
Add 0.04 parts of manganese acetate tetrahydrate to 0.2 parts,
Transesterification reaction was carried out by a conventional method.

Then, after adding 0.02 part of phosphoric acid to the obtained product,
Add 0403 parts of germanium dioxide and polymerization temperature 285
The polymerization reaction was carried out at ℃ for 3 hours and 5 minutes.

After pre-drying the obtained polymer at 160°C for 5 hours,
Solid state polymerization at °C, intrinsic viscosity [η],. =1.07 polymer was obtained. The obtained polymer has a TC of 189°C and a Tm of 2
The temperature was 56.5°C.

This polymer was spun using an extruder type spinning machine at a temperature of 295
Spinning was carried out at ℃. A cap with 240 holes and a hole diameter of 0.6 mm was used. The length of the thread discharged from the nozzle is 15 cm.
, after passing through a heating cylinder with an inner diameter of 25 cmφ and a temperature of 300°C.
Chimney cooling air was applied to cool and solidify the material, and after oiling, the material was taken off at a spinning speed of 2000 .mu./min. The obtained undrawn yarns were drawn at magnifications of 2.49 times, 2.78 times, and 2.96 times, respectively, to obtain drawn yarns of Experiment Nos. 1 to 3. The stretching was carried out in two stages, the -th stage stretching was carried out using heated hot rollers, and the second stage stretching was carried out in a heated oven following the first stage stretching. By changing the discharge amount during spinning,
The fineness of the drawn yarn was approximately 1000 denier.

Table 1 shows the strength of the drawn yarn obtained and the amount of decrease in [η] during drawing.

As can be seen from Table 1, Experiment No. 1 to 3 are all △
[η] is small and satisfies the requirements of the present invention. After applying a 49T/ioc+++ first twist to this drawn yarn in the S direction, two yarns were combined and a 49T/1Oca+ first twist was applied in the Z direction to form a raw cord. Apply adhesive to this raw cord,
A treatment code was obtained by applying heat treatment. When applying an adhesive and heat-treating it to form a Tee-treated cord, the adhesive mainly consists of resorcinol-formalin-latex and "Parkapond E" manufactured by Parnax, and the adhesive liquid is I let it pass. The adhesive (treatment liquid) concentration was 20%, and the amount of adhesive applied was adjusted to 3%.

In addition, after applying the adhesive, the cord was treated at a constant length for 60 seconds in a heating oven at 160°C, and the intermediate elongation of the treated cord was
The elongation rate was changed to approximately 3.5%, and an elongation heat treatment was performed in a heating furnace at 245°C for 70 seconds, and then a relaxation heat treatment was performed in a heating furnace at 245°C for 70 seconds while giving a relaxation of 1%. This is the processing code. Table 1 shows the fatigue resistance of treated cords.
Experiment no.

The fatigue resistance was shown as 1 to 3, and all levels had good fatigue resistance.

Example 2 100 parts of dimethyl terephthalate and 5 parts of ethylene glycol
Add 0.035 part of manganese acetate tetrahydrate to 0.2 part,
Transesterification reaction was carried out by a conventional method. Next, 0.009 part of phosphoric acid was added to the obtained product, 0.0025 part of germanium dioxide was added, and further 0.0125 part of antimony trioxide was added, and the polymerization temperature was 285°C for 3 hours.
The polymerization reaction was carried out for 5 minutes.

The obtained polymer was dried, solid-phase polymerized, and spun in the same manner as in Example 1 to obtain an undrawn yarn. Note that Tc and T+w of the polymer after solid phase polymerization were 185°C and 255.5°C, respectively, and [η] was 1.06. The obtained undrawn yarns were drawn at draw ratios of 2.49 times, 2.78 times, and 2.85 times, respectively, to obtain drawn yarns of Experiment Nos. 64 to 6. The stretching method was the same as in Example 1.

Table 1 shows the strength of the obtained drawn yarn and the Δ[η] due to drawing.

As is clear from Table 1, in Experiments 4 to 6, the strength, △[
η] Both were satisfactory. According to Example 1, an adhesive was applied to the drawn yarn and heat treatment was performed to obtain a treated cord. The fatigue resistance of the treated cords was good at all levels.

(Left below) Comparative Example 100 parts of dimethyl terephthalate and 5 parts of ethylene glycol
0.03 parts of manganese acetate tetrahydrate was added to 0.2 parts, and a transesterification reaction was carried out by a conventional method.

Next, 0.015 part of phosphoric acid was added to the obtained product, and then 0.04 part of antimony trioxide was added, and the polymerization temperature was increased to 285%.
The polymerization reaction was carried out at ℃ for 3 hours and 10 minutes.

The obtained polymer was dried and subjected to solid phase polymerization in the same manner as in Example 1, and the solid phase polymerization time was varied to obtain two types of solid phase polymerized polymers. The Tc/Ta+ of the obtained solid phase polymerized polymer was 152.5°C/281.5°C and 154.5°C/2, respectively.
The temperature was 62°C. These solid-phase polymerized polymers were spun and drawn according to Example 1, and the experiments were conducted with Nα7 to 9 and lO to
Twelve drawn yarns were obtained. Strength of each drawn yarn, △ during the drawing process
[η] is shown in Table 2. Further, according to Example 1.2, an adhesive was applied to the drawn yarn and heat treatment was performed to obtain a treated cord. Table 2 shows the fatigue resistance of the treated cords.

As can be seen from Table 2, experiments Nos. 017 and 10 in which Δ[η] was 0.02 or less had relatively good durability, but the strength was less than 7.0 g/d. On the other hand, experiment No.
8.9 and 12 have sufficient strength but △[η] is 0
．． It exceeds 020 and is inferior in terms of fatigue resistance. Experiment No. 1 lacks both strength and fatigue resistance.

(The following is a blank space) [Effects of the invention] As described above, by using a highly polymerized polymer whose crystallinity is limited to a specific range2, the decrease in intrinsic viscosity [η] during the stretching process is controlled to be below a certain value. This makes it possible to obtain polyester fibers with a high degree of polymerization, high strength, and high durability.

Such high-strength, highly durable polyester fibers are ideal for industrial applications.

Claims (1)

[Claims] When polyester having ethylene terephthalate as a main repeating unit is melt-spun and stretched to obtain a drawn yarn having a strength of 7.0 g/d or more, a polyester that satisfies the following formulas A, B, and C, A method for producing polyester fibers, which comprises drawing an undrawn yarn obtained by melt spinning that satisfies the following formula D so as to satisfy the following formula E. A, Tc≧160°C B, Tm≦260°C C, [η]_P_O≧0.90 D, [η]_U_Y≧0.80 E, △[η]≦0.020 [Tc: Polyester to be subjected to melt spinning 2nd run crystallization exothermic peak temperature (°C) determined by DSC measurement Tm: 1st run melting endothermic peak temperature (°C) determined by DSC measurement of the polyester to be subjected to melt spinning [η]_P_O: Supply polymer Intrinsic viscosity [η]_U_Y: Intrinsic viscosity of undrawn yarn [η] = [η]_U_Y−[η]_D_Y [η]_D_Y: Intrinsic viscosity of drawn yarn]