JPH0772367B2 - Highly elastic fiber manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a highly elastic fiber made of a wholly aromatic polymer, and provides a highly strong and highly elastic fiber useful in the field of industrial materials. To do.

[Prior art]

A method of spinning a polyester capable of forming an anisotropic melt and performing heat treatment without tension without stretching to improve the strength is disclosed in JP-B-55-20008, and 6-hydroxy- It is known, for example, from JP-A-60-239600 to produce a high-strength fiber by heat-treating a polyester of 2-naphthoic acid and p-hydroxybenzoic acid without stress.

[Problems to be solved by the invention]

Polyesters of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid have very good fiber-forming properties, high strength and high elastic modulus, and excellent properties such as heat resistance and chemical resistance. It is an excellent super fiber that is well balanced in terms of production and performance (Japanese Patent Laid-Open No. 54-77691). However, in the field of composites and fields used as tension members such as optical fibers, the initial elastic modulus is insufficient, and improvement is desired. Although it is possible to improve the initial elastic modulus by changing the polymer composition,
The intended product could not be obtained because the spinnability was remarkably deteriorated and the physical properties were deteriorated.

Therefore, it is an object of the present invention to find a method for significantly improving the initial elastic modulus without the above-mentioned drawbacks.

[Means for solving problems]

The present invention melts a polymer in which the proportion of the repeating constitutional units of the following [I] and [II] is 80% by weight or more,
After being discharged at a shear rate of 0000 to 100,000 sec ^-1 and solidified, the cutting elongation of 20 to 20 ° C below the melting point
A method for producing a highly elastic fiber, which comprises stretching 90%, Furthermore, the present invention relates to a method of heat-treating the fiber to obtain a fiber having higher elasticity and higher strength, or a method of heat-treating the fiber without tension to improve the strength while maintaining a high elastic modulus. .

In the present invention, a polymer containing 80% by weight or more of a portion consisting essentially of repeating constitutional units [I] and [II] means, for example, one or more of the structural units shown below as the third component.
You may contain less than weight%.

Alternatively, titanium oxide, kaolin, silica, barium sulfate, carbon black, pigment, etc., or an antioxidant,
It may contain an ultraviolet absorber, a light stabilizer and the like.

The preferable ratio of the structural units is [I] / [I] in mol% ratio.
I] = 1/9 to 9/1. From the viewpoint of melt spinning,
A more preferable ratio is 6/4 to 8/2.

The preferred logarithmic viscosity (η _inh ) of the polymer is 3 to 12 d.
l / g. The logarithmic viscosity referred to in the present invention is obtained by the following method.

Dissolve 0.1% by weight of sample in pentafluorophenol (6
0-80 ℃), 60 ℃ in a constant temperature bath, Uzperode type viscometer.

When η _inh is 3 or less, the fiber-forming ability is remarkably poor, and the strength and initial elastic modulus of the obtained fiber are remarkably low. If it is 13 or more, it becomes impossible to obtain a fiber, particularly a fine denier fiber having a denier of 10 or less.

A higher η _inh is preferable in terms of physical properties, but a more preferable range is η _inh of 4 to 10 from the viewpoint of operational spinning stability and fiber performance.

Spinning temperature is 10 ℃ or higher than polymer melting point (MP), MP + 80
C. or less is preferable.

The melting point of the polymer referred to in the present invention is the differential scanning calorimeter (DS
It is determined by observing the melting transition peak appearing in C).

The shear rate referred to in the present invention is calculated by the following equation in the case of a circular nozzle.

However, r: radius of nozzle hole (cm) Q: discharge amount of polymer per single hole (cm ³ / sec) FIG. 1 shows the relationship between the shear rate and the melt viscosity of a polymer with η _inh = 6.0 as an example. In the case of atypical nozzles, the value is the radius of a circle with the same hole area. At a low shear rate, even a polymer with a very high viscosity and poor fiber formation, when the shear rate is 4000 sec ^-1 or more, the melt viscosity decreases, the spinnability becomes good, and the initial elastic modulus of the obtained fiber improves. . If it exceeds 100,000 sec ^-1 , the nozzle diameter is too small, and problems such as nozzle clogging and poor cleaning occur frequently, making it practically unusable. More preferable range is 10,000 to 50,000 sec ^-1
Is.

The obtained fiber possesses excellent strength and elastic modulus as will be shown later in Comparative Example, but after solidification, it is stretched by 20 to 90% of the cutting elongation at a temperature not higher than 20 ° C. lower than the melting point. Thereby, the initial elastic modulus is remarkably improved. More specifically, the expression that the initial elastic modulus is remarkably improved according to the present invention means that the initial elastic modulus is improved by 50 g / d or more.

The drawing can be performed by a spin draw method in which the spun yarn is continuously drawn between two or more rollers, or a method in which the spun yarn is once taken in a bobbin or a can and then drawn between two or more rollers. is there. Even if the stretching ratio is less than 20% of the cutting elongation, the initial elastic modulus can be slightly improved, but it is less than 50 g / d, which is unsatisfactory for the purpose of the present invention. 90% or more fluff,
Thread breakage easily occurs and cannot be practically adopted.

Regarding the drawing temperature, the yarn may be heated to MP-20 ° C. or lower by any method of a heating roller, a contact type hollow heater and a non-contact type hollow heater. A more preferable temperature is the α dispersion peak temperature (T) of tan δ measured by dynamic viscoelasticity (vibron).
From α) to MP-30 ° C, the maximum initial elastic modulus is obtained in this range.

The high elasticity fiber thus obtained can be subjected to the following two improvement methods depending on the purpose.

(Purpose 1) To further improve the initial elastic modulus,
Improves elongation and enhances thermal stability.

(Purpose 2) Strength and elongation are remarkably improved and thermal stability is enhanced while maintaining the initial elastic modulus.

The purpose 1 is achieved by heat treatment under tension. According to the present invention, heat treatment under tension means that the yarn is
A method of winding the bobbin with a tension of 1 g / d or more and a method of continuously heat treating by applying a tension of 1 g / d or more between two or more rollers are possible. The heat treatment can be performed in air, an inert gas, or vacuum. The preferred temperature condition is MP-60 ℃ to MP + 20 ℃, MP-40 ℃
A pattern in which the temperature is sequentially increased from the following is preferable. The processing time can be several seconds to several tens hours depending on the desired performance.

For the purpose 2, a method of performing shrinkage heat treatment between rollers, a method of continuously placing on a net and processing, a method of winding on a bobbin to a winding density of 0.9 g / cc or less, and the like are adopted. The heat treatment conditions can be the same as those for the purpose 1.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The invention is not limited by these examples.

Example 1 A wholly aromatic polyester polymer having the structural units [I] and [II] of 7/3 was prepared. The properties of this polymer were η _inh = 6.0 dl / g MP = 278 ° C.

This polymer was extruded from a single-screw vent type extruder, passed through a filter composed of a sand (stainless powder) layer and a fine metal wire, and then spun at 320 ° C. Nozzle is 0.1
2φ x 300H.

It was wound at a discharge rate of 167 g / min and a spinning speed of 1000 m / min. = 39,000s
It was ec ^-1 , and the fiber performance of this product was as follows.

Yarn Denier (DR) 1503dr Strength (DT) 13.7g / d Elongation (DE) 2.5% Initial elastic modulus (IM) 548g / d Tα 91 ℃ This spinning yarn is the first roller temperature 120 ℃, 220 ℃ furnace length A device comprising a 1 m hollow heater and a second roller was used for continuous stretching treatment at a cutting elongation of 60% (R = 60%; stretching ratio 1.5%). The performance of the obtained hydrochloric acid fiber is as follows.
Has improved by 47.8%.

DR: 1480dr DT: 14.0g / d DE: 2.1% IM: 810g / d Comparative Example 1, Examples 2 and 3 The spinning raw yarns obtained in Example 1 were changed from Example 1 only in the draw ratio. The results obtained are shown in Table 1.

In Comparative Example 1, the IM was slightly improved, but the improvement of 50 g / d or more, which is the object of the present invention, was not achieved. In Examples 2 and 3, remarkable improvement in IM is observed.

Comparative Example 2, Examples 4, 5 and 6 Table 2 shows the results obtained by changing only the temperature of the hollow heater of the drawing temperature of Example 1 in the spun yarn obtained in Example 1.

When the drawing temperature was 260 ° C, many fluffs occurred and sampling could not be performed. In each of the examples, the IM is significantly improved.

Example 7 The drawn yarn obtained in Example 1 was wound on a perforated aluminum bobbin at a winding density of 0.58 g / cc and heated at 260 ° C. for 1 hour and 280 ° C. for 2 hours.
Treated in a stream of nitrogen. The performance of the heat treated yarn obtained is shown below.

DR: 1475dr DT: 23.5g / d DE: 4.1% IM: 808g / d The initial elastic modulus remained almost unchanged, and the strength and elongation could be significantly improved.

Example 8 The result of performing the same heat treatment as in Example 7 in air is shown below.

DR: 1475dr DT: 23.5g / d DE: 3.9% IM: 811g / d Although the strength was slightly lower than that of Example 7, almost the same results were obtained.

Example 9 The drawn yarn obtained in Example 1 was wound up on a stainless bobbin having a diameter of 20 cm with a tension of 1.5 kg, put into an external heating cylinder having an inner diameter of 35 cm, and heated nitrogen was flown into the heating cylinder. Heat treated. Nitrogen and heating cylinder temperature are the same, 260 ℃ 1
The temperature was 270 ° C. to 280 ° C. for 3 hours and 280 ° C. to 285 ° C. for 5 hours. The characteristics of the obtained heat treatment system are as follows.

DR: 1460dr DT: 25.3g / d DE: 3.5% IM: 903g / d It can be seen that this tension heat treatment gives fibers with a further improved initial elastic modulus.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the shear rate and the melt viscosity of a polymer having a logarithmic viscosity (η _inh ) of 6.0.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoichi Yamamoto Yoichi Yamamoto 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (56) References JP-A-57-56235 (JP, A) JP-A-61-239013 (JP) , A) JP 58-191219 (JP, A) JP 54-77691 (JP, A) JP 57-24407 (JP, B2) JP 56-34646 (JP, B2)

Claims (4)

[Claims] 1. A polymer which comprises essentially 80% by weight or more of a repeating constitutional unit of the following [I] and [II] is melted and discharged at a shear rate of 4,000 to 100,000 sec ⁻¹ to be solidified. And then 20% to 90% of the cutting elongation at a temperature not higher than 20 ° C. lower than the melting point and then stretched, thereby producing a highly elastic fiber. 2. A polymer having a proportion of 80% by weight or more of a repeating constitutional unit of the following [I] and [II] is melted and discharged at a shear rate of 4,000 to 100,000 sec ⁻¹ to be solidified. After that, 20% to 90% of the cutting elongation is stretched at a temperature not higher than 20 ° C. lower than the melting point, and then heat treatment is performed, followed by heat treatment. 3. The method for producing a highly elastic fiber according to claim 2, wherein the heat treatment is a heat treatment under tension. 4. The method for producing a highly elastic fiber according to claim 2, wherein the heat treatment is a heat treatment under substantially no tension.