JP2776003B2 - Method for producing polyester fiber - Google Patents

Description

The present invention relates to a method for producing an industrial polyester fiber. More specifically, the present invention relates to a method for producing a polyester fiber 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 in tire cord applications and seat belt applications. There is always a demand for high strength and high durability for these industrial yarns, and various methods are being studied. Of these, as the degree of polymerization of the polymer is increased, the strength and durability are improved.
For example, as described in JP-B-50-16446, polymers having a high degree of polymerization have been used.

[Problems to be Solved by the Invention] However, in the ordinary melt spinning method, when the polymerization degree of the polymer is increased to a certain level or more, it becomes difficult to increase the strength, and in extreme cases, the strength decreases. Therefore, it has been found that there is a limit in increasing the degree of polymerization of the polymer.

The present inventors have conducted intensive studies on this phenomenon of strength reduction, and as a result, have found that one of the causes is a decrease in the molecular weight when drawing an undrawn yarn having a high degree of polymerization.

In other words, when the degree of polymerization of the polymer is increased beyond a certain level, the molecular weight decreases during stretching, and the strength is reduced. Therefore, in order to improve the performance, it is necessary to stretch an undrawn yarn having a high degree of polymerization while minimizing a decrease in molecular weight.

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

[Means for Solving the Problems] An object of the present invention is to melt-spin a polyester containing ethylene terephthalate as a main repeating unit and stretch it to obtain a drawn yarn having a strength of 7.0 g / d or more.
A polyester fiber satisfying the formula C is melt-spun, and an undrawn yarn satisfying the following formula D is drawn so as to satisfy the following formula E.

A.Tc ≧ 160 ℃ B.Tm ≦ 260 ℃ C. [η] _PO ≧ 0.90 D. [η] _UY ≧ 0.80 E. △ [η] ≦ 0.020 The polyester of the present invention is a polyester containing ethylene terephthalate as a main repeating unit, and is preferably a homopolyester containing no commonly used additives, third components and the like.

The present inventors have conducted research on the drawing process of the undrawn yarn having a high degree of polymerization, and have conducted intensive studies on a method for suppressing a decrease in the molecular weight during the drawing process, that is, a decrease in the intrinsic viscosity [η]. As a result, they found that there was a correlation between the crystallinity of the polymer and the degree of the decrease in [η] at the time of stretching. It has been found that the decrease in [η] can be suppressed.

The crystallinity of the polymer can be indicated by a DSC (differential scanning calorimeter) measurement value. Among them, the temperature rise crystallization peak temperature Tc of the 2nd run indicating the crystallization rate of the polymer is 160 ° C. or higher, and It was found that when the melting peak temperature Tm of the first run corresponding to the crystal size was 260 ° C. or less, the decrease in [η] during stretching could be significantly suppressed.

In the case of a polymer having a Tc of less than 160 ° C. or a Tm of more than 260 ° C., the [η] at the time of stretching is large, and the strength and durability of the drawn yarn are reduced. As a cause, it is considered that in the case of a polymer having a Tc of less than 160 ° C., that is, a polymer having a relatively high crystallization rate, microcrystals are generated during cooling in the spinning process, and microcrystals are present in the undrawn yarn.

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

In this way, if there is a microcrystal or undissolved portion of the crystal in the undrawn yarn, it is presumed that during drawing, concentration of stress occurs in this portion and molecular chains are likely to be cut. You. Therefore, Tc needs to be 160 ° C. or higher, more preferably 170 ° C. or higher, and further preferably 180 ° C. or higher. Further, Tm needs to be 260 ° C. or lower, and preferably 258 ° C. or lower.

The intrinsic viscosity [η] _PO of the polyester supply polymer used in the present invention must be 0.90 or more. An object of the present invention is to increase the strength and durability of the fiber by increasing the molecular weight of the polymer. When [η] _PO is less than 0.90, the strength and durability are insufficient. Therefore, the intrinsic viscosity [η] _PO of the supplied polymer is
It is preferably 0.95 or more.

For the same reason, the intrinsic viscosity [η] of the undrawn yarn of the present invention _UY
Must be at least 0.80. For example, when the [η] _UY of the undrawn yarn is reduced by a method such as raising the spinning temperature, the decrease in [η] during drawing can be reduced, but it is said that the high molecular weight increases the strength and improves the durability. It cannot fulfill its intended purpose. For this reason, [η] _UY of the undrawn yarn is preferably 0.85 or more. The strength of the drawn yarn obtained in the present invention is 7.0 g
/ d or more, and [η] _UY − [η] _DY , which is a measure of molecular weight reduction in the stretching process, that is, △ [η] is 0.02
Must be 0 or less. If the strength is less than 7.0 g / d, the strength is insufficient as a yarn for industrial use. Therefore, the strength of the drawn yarn is preferably 8.0 g / d or more.

If ま た [η] in the drawing process exceeds 0.020, the strength and durability of the drawn yarn are reduced. Even if the drawn yarns have the same strength, a yarn having a large △ [η] has many defects in fiber structure and is inferior in durability. △ [η] in the stretching step is preferably 0.15 or less, more preferably 0.010 or less.

The stretching method used in the present invention is preferably a multi-stage stretching. Stretching in multiple stages is more effective in reducing 全 [η] than stretching in one stage. As the heating means, non-contact heating is preferably performed because た め [η] increases with normal pin heating and hot roller heating. Stretching in a plasma atmosphere is also one of the methods for reducing △ [η].

Further, the present inventors have found that the magnitude of △ [η] is affected by the stress during stretching. Since 延伸 [η] increases as the stretching stress increases, it is important to keep the stretching stress as low as possible. For this reason, the stretching stress is preferably 3.5 g / d or less, and more preferably 3.0 g / d or less. The above-described stretching by non-contact heating or stretching in a plasma atmosphere is an effective method for lowering the stretching stress. The drawing stress is obtained by dividing the drawing tension by the fineness of the drawn fiber.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples. The physical properties in the examples were determined as follows.

A.Tm, Tc Perkin Elmer DSC4 type, sample 10 mg, in a N ₂ atmosphere, the temperature from 50 ° C. at a heating rate 16 ° C. / min up to 280 ° C. was raised D
Find the SC curve (1st run). The melting endothermic peak temperature of the crystal at this time is defined as Tm. Further, following the first run, the sample was left at 280 ° C. for 5 minutes, rapidly cooled to room temperature, and again heated from 50 ° C. to 280 ° C. in a N ₂ atmosphere at a rate of 16 ° C./min.
Find the SC curve (2nd run). The peak temperature of the heat of crystallization at this time is defined as Tc.

B. Intrinsic Viscosity [η] A sample (0.1 g) was dissolved in orthochlorophenol (10 ml) and measured at 25 ° C. using an Ostwald viscometer.

C. Strong elongation Using a Toyo Baldwin Tensilon tensile tester, a strong elongation curve (SS) with a test length of 25 cm and a tensile speed of 30 cm / min.
Curve), and the elongation was calculated.

D. Fatigue Resistance (GY Fatigue Life) In the GY fatigue test (Goodyear Mallory Fatigue Test), the time until the tube bursts was determined according to ASTM-D885. The number of cords injected into the tube was 30 per inch, and vulcanization was performed at 160 ° C. for 20 minutes. The measurement was performed under the following conditions.

Tube inner pressure: 3.5 kg / cm ² G Rotation speed: 850 rpm Tube angle: 90 degrees Good for more than 300 minutes, slightly bad for more than 250 minutes to less than 300 minutes, bad for less than 250 minutes.

Example 1 100 parts of dimethyl terephthalate and 50 parts of ethylene glycol.
To 2 parts, 0.04 part of manganese acetate tetrahydrate was added, and a transesterification reaction was carried out by a conventional method.

Next, after adding 0.02 part of phosphoric acid to the obtained product, 0.03 part of germanium dioxide was added, and a polymerization reaction was performed at a polymerization temperature of 285 ° C. for 3 hours and 5 minutes. The obtained polymer was preliminarily dried at 160 ° C. for 5 hours, and then subjected to solid-phase polymerization at 225 ° C. to obtain a polymer having an intrinsic viscosity [η] _PO = 1.07. The Tc of the resulting polymer is
189 ° C and Tm were 256.5 ° C.

The polymer is extruded at an extruder spinning temperature of 295.
Spun at ℃. The cap used had a hole diameter of 0.6 mmφ and 240 holes. The thread discharged from the mouthpiece is 15cm long and 25cm inside diameter
After passing through a heating cylinder having a diameter of 300 ° C., the mixture was cooled and solidified by applying chimney cooling air, and after lubrication, it was taken out at a spinning speed of 2000 m / min. The obtained undrawn yarn is 2.49 times, 2.78 times, 2.96 times.
Each of the yarns was drawn by a factor of 2 to obtain drawn yarns of Experiment Nos. 1 to 3. The stretching was performed in two steps, the first step was performed with a heated hot roller, and the second step was performed in an oven that was heated continuously to the first step. By changing the discharge amount during spinning, the fineness of the drawn yarn was set to approximately 1000 denier.

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

As can be seen from Table 1, all of Experiment Nos.
[Η] is small and satisfies the requirements of the present invention. The drawn yarn was twisted at 49 T / 10 cm in the S direction and then twined to form a raw cord at 49 T / 10 cm in the Z direction. An adhesive was applied to the raw cord, and a heat treatment was performed to obtain a treated cord. When a heat treatment is performed by applying an adhesive to form a treatment code, the adhesive is mainly composed of resorcinol-formalin-latex and “Parka Pond E” manufactured by Parnax Corporation. Let it pass. The concentration of the adhesive (treatment liquid) was adjusted to 20%, and the amount of the applied adhesive was adjusted to 3%.

After the adhesive was applied, it was treated in a heating furnace at 160 ° C. for 60 seconds in a constant length state.
Change the elongation rate to 3.5% and heat in a heating furnace at 245 ° C.
Subjected to elongation heat treatment for 2 seconds, and then while giving 1% relaxation
A relaxation heat treatment was performed for 70 seconds in a heating furnace at 245 ° C. to obtain a treatment code. The fatigue resistance of the treated cord is shown in Table 1, Experiment Nos. 1 to 3, and all levels showed good fatigue resistance.

Example 2 100 parts of dimethyl terephthalate and 50 parts of ethylene glycol.
0.035 parts of manganese acetate tetrahydrate was added to 2 parts, and transesterification was carried out by a conventional method. Next, 0.009 parts of phosphoric acid was added to the obtained product, and then germanium dioxide 0.0025 part was added.
, And 0.0125 parts of antimony trioxide was further added, and a polymerization reaction was performed at a polymerization temperature of 285 ° C for 3 hours and 15 minutes. The obtained polymer was dried, solid-phase polymerized and spun in the same manner as in Example 1 to obtain an undrawn yarn. The Tc of the polymer after solid-phase polymerization,
Tm was 185 ° C and 255.5 ° C, respectively, and [η] was 1.06. The obtained undrawn yarn is drawn at a draw ratio of 2.49 times, 2.78 times, 2.85 times.
In each case, the drawn yarns of Experiment Nos. 4 to 6 were obtained. The stretching method was the same as in Example 1. Table 1 shows the strength of the obtained drawn yarn and △ [η] by drawing.

As is clear from Table 1, in Experiments Nos. 4 to 6, the strength, Δ
[Η] were both satisfactory. According to Example 1, an adhesive was applied to the drawn yarn, and a heat treatment was performed to obtain a treated cord. All levels of the fatigue resistance of the treated cord were good.

Comparative Example 100 parts of dimethyl terephthalate and 50 parts of ethylene glycol.
0.03 parts of manganese acetate tetrahydrate was added to 2 parts, and a transesterification reaction was performed by a conventional method. Next, 0.015 parts of phosphoric acid was added to the obtained product, and 0.04 parts of antimony trioxide was added, and a polymerization reaction was performed at a polymerization temperature of 285 ° C. 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 changed to obtain two types of solid-phase polymerization polymers. Tc / Tm of the obtained solid-phase polymerized polymer is 15
2.5 ° C / 261.5 ° C and 154.5 ° C / 262 ° C. These solid-phase polymerized polymers were spun and drawn according to Example 1 to obtain drawn yarns of Experiment Nos. 7 to 9 and 10 to 12. Table 2 shows the strength of each drawn yarn and △ [η] in the drawing process. In addition, according to Examples 1 and 2, an adhesive was applied to the drawn yarn, and a heat treatment was performed to obtain a treated cord. Table 2 shows the fatigue resistance of the treated cord.
Shown in

As can be seen from Table 2, in Experiments Nos. 7 and 10 in which η [η] was 0.02 or less, the durability was relatively good, but the strength was
It is less than 7.0 g / d. On the other hand, in Experiments Nos. 8, 9 and 12, although the strength was sufficient, △ [η] exceeded 0.020, which was inferior in fatigue resistance. In Experiment No. 11, both strength and fatigue resistance were insufficient.

[Effects of the Invention] As described above, by using a polymer having a high degree of polymerization whose crystallinity is limited to a specific range and controlling the decrease in intrinsic viscosity [η] in the stretching process to a certain value or less, high polymerization is achieved. A high-strength, high-durability polyester fiber can be obtained.
Such a high-strength, high-durability polyester fiber is optimal for industrial use.

Claims (1)

(57) [Claims] A polyester having ethylene terephthalate as a main repeating unit is melt-spun and stretched to obtain a strength of 7.
When obtaining a drawn yarn of 0 g / d or more, an undrawn yarn satisfying the following formula D obtained by melt-spinning a polyester satisfying the following formulas A, B and C is drawn so as to satisfy the following formula E. A method for producing a polyester fiber. A.Tc ≧ 160 ℃ B.Tm ≦ 260 ℃ C. [η] _PO ≧ 0.90 D. [η] _UY ≧ 0.80 E. △ [η] ≦ 0.020