JPH07278953A - Liquid crystal polyester fiber - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal polyester fiber having high strength and high modulus of elasticity, comprising a melt liquid crystal forming polyester showing optical anisotropy in a melt state. CONSTITUTION:A thermotropic liquid crystal forming polyester comprising 80-90mol% based on the total of a mixture of a structural unit formed from p-hydroxybenzoic acid and a polyester structural unit composed of 4,4'- dioxybiphenyl and terephthalic acid in the molar ratio of 80/20 to 95/5 and 20-10mol% of a polyester structural unit composed of ethylene glycol and terephthalic acid is subjected to melt spinning to form a liquid crystal polyester fiber. The fiber shows the degree of orientation of formula I of <=2.5 and the plane orientation ratio of formula II of <=2.8 when peak strengths Iy and Ix of C=C stretching vibration band of benzene ring in measurement of polarized light horizontal and vertical to a fiber axis by laser Raman spectroscopy and peak strengths Iyy and Ixx of carbonyl group stretching vibration band have correlations of the degree of orientation A=Iy/Ix, the degree of orientation C=Iyy/Ixx and the degree of plane orientation D = the degree of orientation C/the degree of orientation A.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to liquid crystal polyester fibers. More specifically, the present invention relates to a liquid crystal polyester fiber composed of a molten liquid crystal-forming polyester exhibiting optical anisotropy in a molten state and having a small difference in inner and outer layer structure.

[0002]

2. Description of the Related Art In recent years, the demand for higher performance of synthetic fibers has increased, and synthetic fibers having various new properties have been provided on the market. Among such novel performance fibers, it has been noted that fibers made of liquid crystal polyester exhibiting optical anisotropy in a molten state have excellent mechanical properties. Such a liquid crystal polyester can be made into fibers with high strength and high elastic modulus only by melt spinning, and fibers after spinning can be made into fibers with higher strength and higher elastic modulus by heat treatment in an inert gas or vacuum. Urugato Special Public Sho 55-2
A large number of them are disclosed, including Japanese Patent Laid-Open No. 0008 and Japanese Patent Laid-Open No. 50-158695.

The melted liquid crystal-forming polyester is characterized in that it easily flows and has a low viscosity when a shear is added in a molten state. This is a characteristic of resin molding, which is excellent in thin-wall moldability. However, in the fiber production, when liquid crystal polyester is discharged from the spinneret in a molten state, it easily flows, so that the discharge hole wall side of the spinneret is highly oriented, and the central part of the discharge hole is not so oriented, which is obtained. The fibers after spinning exhibit a large difference in the degree of orientation between the inner and outer layers. The fiber after spinning, which has a large difference in the orientation degree of the inner and outer layers, has the drawback that the strength utilization efficiency is low and it is difficult to obtain a sufficiently high strength because the strength is retained solely by the highly oriented outer layer portion. Further, when the fiber after spinning is heat-treated in an inert gas or in vacuum, the highly oriented outer layer portion is selectively polymerized, and the inner layer portion is less likely to be polymerized.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems, that is, to provide a liquid crystal polyester fiber having good strength and a small difference in orientation degree between inner and outer layers.

[0005]

The structure of the present invention for achieving the above object of the present invention is as follows. A liquid crystal polyester fiber characterized by having a degree of orientation ratio B represented by the following formula of 2.5 or less, the fiber being composed of a molten liquid crystal-forming polyester.

[0006]

[Equation 3] (Iy: peak intensity of C = C stretching vibration band (around 1600 cm ^-1 ) of the benzene ring when measuring polarization parallel to the fiber axis by laser Raman, Ix: benzene ring when measuring polarization perpendicular to the fiber axis by laser Raman C = C stretching vibration band (around 1600 cm ⁻¹ ) peak intensity) Hereinafter, the present invention will be described in detail. The molten liquid crystal-forming polyester (hereinafter simply referred to as liquid crystal polyester) in the present invention refers to a polyester that exhibits optical anisotropy when heated and melted. Examples of such polyesters include A.I. Aromatic oxycarboxylic acid polymer, B.I. A polymer of an aromatic dicarboxylic acid, an aromatic diol and an aliphatic diol, C.I. Examples thereof include copolymers of A and B. A conventionally known method can be used for polymerizing the liquid crystal polyester.

Examples of the aromatic oxycarboxylic acid as used herein include hydroxybenzoic acid, hydroxynaphthoic acid and the like, and alkyl, alkoxy and halogen substitution products of these aromatic oxycarboxylic acids. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, and the like, or alkyl of these aromatic dicarboxylic acids, Examples thereof include alkoxy and halogen substitution products. Further, examples of the aromatic diol include hydroquinone, resorcin, dioxydiphenyl, naphthalene diol, and the like, and alkyl, phenyl, alkoxy, and halogen-substituted products of these aromatic diols. Furthermore, examples of the aliphatic diol include ethylene glycol, butanediol, neopentyl glycol and the like. Particularly, in the present invention, a structural unit formed from p-hydroxybenzoic acid and
Consists of structural units of polyester produced from 4,4'-dioxybiphenyl and terephthalic acid and structural units of polyester produced from ethylene glycol and terephthalic acid. The total of structural units and structural units is preferably 80 to 90 mol % Structural units are preferably 20 to
When a liquid crystal polyester occupying 10 mol% and having a structural unit / molar ratio of preferably 80/20 to 95/5 is used, the spinning stability is extremely good, and the difference in the inner / outer layer structure of the fiber can be controlled. In addition to being easy to perform, it has a sufficient tensile strength, and a fiber having a high bending abrasion strength and a high knot strength can be obtained.

At this time, if the total of the structural units and the structural units is larger than 90 mol% of the whole, the melt fluidity is lowered and the solidification is apt to occur during the polymerization, and if it is smaller than 80 mol%, the heat resistance is lowered or the heat resistance is obtained. The strength of the fiber tends to be low. When the molar ratio of structural unit / is less than 80/20 or more than 95/5, the heat resistance tends to be low and the fluidity tends to be low.

Although it is not clear that the above polyester can easily control the difference in the inner and outer layers of the fiber and the flexural abrasion strength, it is not clear that the structural unit or the rigid molecular chain of the structural unit contains ethylene glycol. It is considered that the structural unit of polyester produced from terephthalic acid exists as a flexible molecular chain. When the structural unit is present in the above range, it is possible to suppress a significant decrease in viscosity with respect to an increase in shear rate, and it is possible to reduce the difference in the fiber inner / outer layer structure at the time of discharging from the discharge hole of the spinneret. It is considered to be a thing. Further, since the structural unit exists as a flexible molecular chain, it is considered that the resistance to bending is improved and the above effect can be exhibited.

In the present invention, the orientation degree ratio B is 0.
It is the ratio of the orientation degree A at 5μ to the orientation degree A at the yarn central portion, and is calculated by the following equation.

[0011]

[Equation 4] The orientation degree A was measured by laser Raman spectroscopy with polarized light parallel to the fiber axis, and the peak intensity Iy of the C = C stretching vibration band (near 1600 cm ^-1 ) of the benzene ring and the perpendicular intensity to the fiber axis were measured. It is the ratio to the peak intensity Ix of the C = C stretching vibration band (near 1600 cm ^-1 ) of the benzene ring measured by polarized light, and is calculated by the following formula.

[0012]

[Equation 5] Although the details of the evaluation method will be described later, as a sample, a liquid crystal polyester fiber embedded in an epoxy resin and polished to prepare a longitudinal section of a single fiber (section parallel to the fiber axis) is used. Ramanor U-10 as a measuring device
Using a Raman microprobe of 00I tail (Jobin Yvon / manufactured by Atago Bussan Co., Ltd.), the sample is irradiated with polarized Kr ⁺ laser having a diameter of 1 μm.

The liquid crystal polyester fiber having an orientation degree ratio B of more than 2.5 has a too large difference in orientation degree between the inner and outer layers, and the strength is retained mainly by the highly oriented outer layer portion, resulting in low strength utilization efficiency. Further, when the fiber after spinning is heat-treated in an inert gas or in a vacuum, the highly oriented outer layer portion is selectively polymerized, and the inner layer portion is less likely to be polymerized, so that it becomes difficult to obtain sufficient strength. Therefore, in the present invention, the orientation degree ratio B needs to be 2.5 or less, and in order to exert the effect of the present invention more, the orientation degree ratio B is preferably 1.9 or less.

As a result of further studies on the higher-order structure of the liquid crystal polyester fiber, the inventors have found that benzene rings are laminated (plane oriented) in the circumferential direction on the surface layer of the fiber. This plane orientation can be controlled by keeping the shear rate in the spinneret discharge hole within a predetermined range and by allowing the structural unit of the polyester produced from ethylene glycol and terephthalic acid to exist within the predetermined range in the liquid crystal polyester. I understood. According to the experiments conducted by the present inventors, the plane orientation can be reduced by setting the structural unit within the above range and setting the shear rate to 5 × 10 ⁴ sec ⁻¹ or less. In the case of highly plane-oriented fibers, when the fiber after spinning is heat-treated in an inert gas or in a vacuum, the highly plane-oriented outer layer portion selectively polymerizes, and the inner layer portion becomes difficult to polymerize. Since the structural difference between the inner and outer layers becomes noticeable, the plane orientation ratio E is preferably 2.8 or less.
The plane orientation ratio E is calculated by the following formula.

[Equation 6] Here, Iyy is the stretching vibration band (1730 cm) of the carbonyl group when measuring polarization parallel to the fiber axis by laser Raman.
^-1 ) and Ixx is the peak intensity of the stretching vibration band (near 1730 cm ^-1 ) of the carbonyl group at the time of polarization measurement perpendicular to the fiber axis by laser Raman.

The liquid crystal polyester fiber of the present invention includes both as-spun yarns and solid-state polymerized yarns obtained by heat-treating (solid-state polymerization) the yarns. When the as-spun yarn is heat-treated (solid state polymerization), the strength of the fiber is dramatically improved. The heat treatment is preferably performed at least above the glass transition temperature of the liquid crystal polyester, near the liquid crystal onset temperature, or higher. The heat treatment is preferably performed in a stream of an inert gas such as nitrogen gas or in a vacuum, but can be performed in air. At this time, various solid phase polymerization catalysts may be used in combination.

Next, the method for producing the liquid crystal polyester fiber of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of a melt spinning apparatus for spinning the liquid crystal polyester fiber of the present invention. FIG. 2 shows an example of one discharge hole of a spinneret for spinning a liquid crystal polyester fiber, A is a schematic sectional view thereof, and B is a schematic plan view showing an arrangement of pores of the spinneret. Further, FIG. 3 shows another example of one discharge hole of a spinneret for spinning a liquid crystal polyester fiber, A is a schematic sectional view thereof, and B is a schematic plan view showing an arrangement of pores of the spinneret. is there.

In FIG. 1, 1 is a spin block, 2 is a spin pack, and 3 is a spinneret. The melted liquid crystal polyester polymer (hereinafter, simply referred to as polymer) is metered by a metering pump, guided to a spinning pack 2, discharged from a spinneret 3, cooled and thinned, and then a predetermined oil agent is applied by an oil agent applying device 4. , The first godet roll 5 and the second godet roll 6 and the winder 7.

Here, since one discharge hole of the spinneret 3 in FIG. 2 is formed with a plurality of pores 9 of the same diameter in close proximity to each other, a polymer uniformly distributed in each pore is a normal one. As compared with the case where only a single discharge hole is formed as in the spinneret, the discharge is performed at a lower shear speed. Then, since the central pores and the outer pores are discharged at the same shear velocity, the polymer flow merged directly under the mouthpiece becomes a single polymer flow having the same orientation both in the central part and the outer side.

Further, the discharge hole of the spinneret 3 in FIG. 3 is a No. 1 plate 1 in which a plurality of pores 9 having the same diameter are closely formed.
No. 2 plate 11 having a single discharge hole 8 after the center hole and the outer hole are discharged at the same shear velocity.
As compared with the case where only a single discharge hole is formed as in a normal spinneret, the central portion also has a relatively high orientation polymer flow. The liquid crystal polyester fiber thus obtained has an orientation ratio B of 2.5 or less, and is a fiber having a small difference in orientation degree between the inner and outer layers.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples. The peak intensities Ix, Iy, Ixx, and Iyy of the stretching vibration band by laser Raman in this example were measured by the following methods.

As a sample, a liquid crystal polyester fiber embedded in epoxy and polished to prepare a longitudinal section of a single fiber (a section parallel to the fiber axis) is used. As a measuring device, Ramanor U-1000I (Jobin Yvon /
Raman microprobe manufactured by Atago Bussan Co., Ltd. is used. A BH-2 type microscope manufactured by Olympus was used as the microprobe. As a light source, Coherent Innova 90K 6471A
Kr ⁺ laser was used. 1 m Czerny as a spectrometer
-Turner type Double Monochromator was used. The peak intensity Ix is Kr with a diameter of 1 μm that is polarized perpendicular to the fiber axis.
^This is a value obtained by irradiating the sample with a laser and measuring the peak intensity of the C = C stretching vibration band (around 1600 cm ^-1 ) of the benzene ring. The peak intensity Iy was measured by irradiating the sample with a Kr ⁺ laser having a diameter of 1 μm and polarized in parallel with the fiber axis, and the C = C stretching vibration band of the benzene ring (around 1600 cm ^-1 )
Is a value obtained by measuring the peak intensity of. The peak intensity Ixx is a value obtained by irradiating the sample with a Kr ⁺ laser having a diameter of 1 μm and polarized perpendicularly to the fiber axis, and measuring the peak intensity of the stretching vibration band (near 1730 cm ⁻¹ ) of the carbonyl group.
The peak intensity Iyy is the diameter 1 with polarized light parallel to the fiber axis.
This is a value obtained by irradiating the sample with a Kr ⁺ laser of μm to measure the peak intensity of the stretching vibration band (around 1730 cm ⁻¹ ) of the carbonyl group.

Example 1 P-hydroxybenzoic acid was added to a polymerization vessel in an amount of 80 mol% based on the whole amount.
7 mol% of 4-4'dioxybiphenyl, 7 mol% of terephthalic acid, and 13 mol% of polyethylene terephthalate having an intrinsic viscosity of about 0.6 were charged, and deacetic acid polymerization was carried out under the following conditions. . First, after reacting for 2.5 hours at 250 to 300 ° C. in a nitrogen gas atmosphere, 300 ° C.
The pressure was reduced to 0.2 mmHg, and the reaction was further continued for 3.25 hr to complete the polycondensation. As a result, almost the theoretical amount of acetic acid was distilled off to obtain a beige polymer.

The resulting liquid crystal polyester polymer is p-
Consisting of structural units produced from acetoxybenzoic acid, structural units of polyester produced from 4,4-dioxybiphenyl and terephthalic acid, and structural units of polyester produced from ethylene glycol and terephthalic acid. 87 mol% and structural units accounted for 13 mol% of the whole, and the molar ratio of structural unit / was 92/8. The obtained polymer chip was discharged at a spinning temperature of 330 ° C. using a spinning device shown in FIG. 1 and a spinning spinneret having seven adjacent fine holes (diameter 0.07 mmφ) shown in FIG. 2 with 50 holes. Amount 27.8g / min
The melt spinning was carried out under the conditions of a spinning speed of 1000 m / min and a single yarn fineness of 5 denier. At this time, the pores 1
The shear rate per hole is about 3.3 × 10 ⁴ sec ⁻¹ . The orientation degree A of the obtained liquid crystal polyester fiber in the yarn surface layer of 0.5 μ was 30.8 (Ix = 9.1, Iy = 28.
0, Iy / Ix = 30.8), the degree of orientation A at the center of the yarn is 19.7 (Ix = 8.7, Iy = 171, Iy /
Ix = 19.7), and the orientation ratio B is 1.6 (the orientation degree A at the yarn surface layer 0.5 μ / the orientation degree A at the yarn central portion).
= 30.8 / 19.7). In addition, the yarn surface layer 0.5
The degree of orientation C at μ is 25.0 (Ixx = 2.4, Iy
y = 60, Iyy / Ixx = 25.0), and the degree of plane orientation D
Is 0.81 (orientation degree C / orientation degree A = 25.0 / 30.
8), and the degree of orientation C at the center of the yarn is 13.5 (I
xx = 4.3, Iyy = 58, Iyy / Ixx = 13.
5), the surface orientation degree D is 0.69 (orientation degree C / orientation degree A =
13.5 / 19.7), and the plane orientation ratio E is 1.2.
(The degree of surface orientation D in the yarn surface layer 0.5 μ / the degree of surface orientation D in the central portion of the yarn D = 0.81 / 0.69).

This liquid crystalline polyester fiber was heat-treated in a nitrogen atmosphere from 240 ° C. to 310 ° C. at a heating rate of 4 ° C./hr to obtain a strength of 20.5 g / d and an elastic modulus of 650 g.
A fiber of / d was obtained. Since the liquid crystal polyester fiber has a small difference in the degree of alignment between the inner and outer layers and high strength utilization efficiency, the liquid crystal polyester fiber has higher strength and higher elastic modulus than the yarn (Comparative Example 1) obtained by using an ordinary spinneret described later. . Also, it had good flexural wear strength and knot strength.

Example 2 The same chip as in Example 1 was used in the spinning machine shown in FIG. 1 and No. 1 plate having 50 discharge holes having five adjacent fine holes (diameter 0.08 mmφ) shown in FIG. Using a spinneret having 50 discharge holes (No. 2 plate) having a diameter of 0.13 mm and a spinning temperature of 330 ° C. and a discharge amount of 27.8 g.
/ Min and a spinning speed of 1000 m / min, melt spinning was carried out with a single yarn fineness of 5 denier. The shear rate per hole of No. 1 plate is about 3.1 × 10 ⁴ sec ^−1.
Is.

The degree of orientation A of the obtained liquid crystal polyester fiber in the yarn surface layer of 0.5 μ was 30.2 (Ix = 8.7,
Iy = 263, Iy / Ix = 30.2), and the degree of orientation A at the center of the yarn is 15.9 (Ix = 9.9, Iy = 15).
7, Iy / Ix = 15.9), and the orientation ratio B is 1.
9 (the degree of orientation A at the yarn surface layer 0.5 μ / the degree of orientation A at the center of the yarn A = 30.2 / 15.9). The degree of orientation C at the yarn surface layer of 0.5 μ is 47.9 (Ixx =
2.4, Iyy = 115, Iyy / Ixx = 47.9)
Then, the plane orientation degree D is 1.59 (the orientation degree C / the orientation degree A = 4.
7.9 / 30.2), and the degree of orientation C in the center of the yarn
Is 15.2 (Ixx = 4.4, Iyy = 67, Iyy /
Ixx = 15.2), the plane orientation degree D is 0.96 (orientation degree C / orientation degree A = 15.2 / 15.9), and the plane orientation degree ratio E is 1.7 (yarn surface layer 0. The degree of plane orientation D at 5 μ / the degree of plane orientation D at the center of the yarn D = 1.59 / 0.96).

This liquid crystalline polyester fiber was heat-treated in a nitrogen atmosphere from 240 ° C. to 310 ° C. at a temperature rising rate of 4 ° C./hr to obtain a strength of 18.6 g / d and an elastic modulus of 600 g.
A fiber of / d was obtained. Since the liquid crystal polyester fiber has a small difference in orientation between the inner and outer layers and high strength utilization efficiency, the liquid crystal polyester fiber has higher strength and higher elastic modulus than the yarn (Comparative Example 1) obtained by using a normal spinneret. Also, it had good flexural wear strength and knot strength.

Example 3 The same chip as in Example 1 was used with the spinning device shown in FIG.
Using a spinneret having 50 discharge holes of 13 mmφ, the spinning temperature is 330 ° C., the discharge rate is 27.8 g / min, and the spinning speed is 1.
Melt spinning winding with a single yarn fineness of 5 denier was carried out under the condition of 000 m / min. The displacement rate per discharge hole is about 3.6 × 10 ⁴ sec ⁻¹ .

The orientation degree A of the obtained liquid crystal polyester fiber in the yarn surface layer of 0.5 μ was 31.3 (Ix = 8.7,
Iy = 272, Iy / Ix = 31.3), and the orientation degree A at the yarn central portion is 12.5 (Ix = 8.8, Iy = 11).
0, Iy / Ix = 12.5), and the orientation ratio B is 2.
5 (the degree of orientation A at the yarn surface layer 0.5 μ / the degree of orientation A at the center of the yarn A = 31.3 / 12.5). In addition, the orientation degree C in the yarn surface layer 0.5μ is 80.6 (Ixx =
1.6, Iyy = 129, Iyy / Ixx = 80.6)
Then, the plane orientation degree D is 2.58 (the orientation degree C / the orientation degree A = 8.
0.6 / 31.3), and the degree of orientation C at the center of the yarn
Is 11.4 (Ixx = 4.9, Iyy = 56, Iyy /
Ixx = 11.4), the plane orientation degree D is 0.91 (orientation degree C / orientation degree A = 11.4 / 12.5), and the plane orientation degree ratio E is 2.8 (yarn surface layer 0. The degree of plane orientation D at 5 μ / the degree of plane orientation D at the central portion of the yarn D = 2.58 / 0.91), and the difference in the degree of orientation between the inner and outer layers tended to be slightly large.

The liquid crystal polyester fiber was heat-treated in a nitrogen atmosphere at a temperature rising rate of 240 ° C. to 310 ° C. at a temperature rising rate of 4 ° C./hr, resulting in a strength of 17.5 g / d and an elastic modulus of 5
80 g / d of fiber was obtained. The liquid crystal polyester fiber had a relatively small difference in the degree of alignment between the inner and outer layers, and had higher strength and higher elastic modulus than a yarn (Comparative Example 1) obtained by using an ordinary spinneret described later.

Comparative Example 1 Using the same chip as in Example 1 and using a spinning device shown in FIG. 1 and an ordinary spinneret having a diameter of 0.09 mmφ and 50 discharge holes, a spinning temperature of 330 ° C. and a discharge amount of 27. 8 g / min,
Melt spinning winding with a single yarn fineness of 5 denier was carried out under the conditions of a spinning speed of 1000 m / min. The displacement rate per discharge hole is about 1.08 × 10 ⁵ sec ^-1 .

The orientation degree A of the obtained liquid crystal polyester fiber in the yarn surface layer of 0.5 μ was 32.5 (Ix = 8.5.
Iy = 276, Iy / Ix = 32.5), and the orientation degree A at the yarn central portion is 10.4 (Ix = 8.9, Iy = 9).
3, Iy / Ix = 10.4), and the orientation ratio B is 3.
1 (the degree of orientation A at the yarn surface layer 0.5 μ / the degree of orientation A at the center of the yarn A = 32.5 / 10.4). Further, the degree of orientation C at the yarn surface layer of 0.5 μ is 95.0 (Ixx =
1.4, Iyy = 133, Iyy / Ixx = 95.0)
Then, the plane orientation degree D is 2.92 (the orientation degree C / the orientation degree A = 9.
5.0 / 32.5), and the degree of orientation C at the center of the yarn
Is 9.6 (Ixx = 5.6, Iyy = 54, Iyy / I
xx = 9.6) and the plane orientation degree D is 0.92 (orientation degree C /
Orientation degree A = 9.6 / 10.4, and plane orientation degree ratio E is 3.2 (plane orientation degree D at yarn surface layer 0.5 μ / plane orientation degree D at yarn central portion D = 2.92 / 0). .92), and the difference in the degree of alignment between the inner and outer layers was extremely large.

This liquid crystal polyester fiber was heat-treated in a nitrogen atmosphere from 240 ° C. to 310 ° C. at a temperature rising rate of 4 ° C./hr, resulting in a strength of 15.7 g / d and an elastic modulus of 5.
It was a fiber of 50 g / d. Examples 4 to 11 As liquid crystal polyesters, structural units formed from p-hydroxybenzoic acid, polyester structural units formed from 4,4-dioxybiphenyl and terephthalic acid, ethylene glycol and terephthalate. In the polymer composed of the structural unit of the polyester produced from the acid, the flow characteristics and heat resistance of the polymer obtained by changing the mol% of the structural unit and the total of structural units and the molar ratio of structural unit / It evaluated and obtained the result of Table 1.

[0034]

[Table 1] As is clear from Table 1, the polymers of Examples 4 to 7 satisfying the requirements of the present invention have good fluidity and heat resistance, and as a result of performing melt spinning under the same spinning conditions as Example 2, stable spinnability was obtained. Met. Note that Examples 8 to 11 tended to have low fluidity and heat resistance.

[0035]

The liquid crystal polyester fiber of the present invention is a fiber having a small degree of difference in orientation between the inner and outer layers, which is not present in conventional products, and has good strength and elastic modulus. It also has good flexion wear strength and knot strength. And since this fiber has high strength utilization efficiency, it has high strength and high elastic modulus as well as low water absorption, low dielectric properties, vibration damping, dimensional stability, heat resistance, chemical resistance, etc. , Reinforcing material for optical fiber,
FRP, belts, helmets, protective clothing, gloves, electrical insulating materials, printed circuit boards, solar cell reinforcing materials, calculator reinforcing materials, electric umbrellas, ropes, friction materials, sliding members, disc brakes, various filters, comming yarns, aircraft. Materials, automobile materials, various wall materials, roofs, floors, blinds, tent pillars, chairs, stepladders, antenna materials, various frames, fishing rods, golf shafts, golf nets, tennis rackets, table tennis rackets, writing instruments It is suitable for a wide range of applications.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a melt spinning apparatus for spinning the liquid crystal polyester fiber of the present invention.

FIG. 2 is a schematic view showing an example of one discharge hole of a spinneret for spinning the liquid crystal polyester fiber of the present invention, A is a sectional view thereof, and B is a plan view showing an arrangement of pores of the spinneret. is there.

FIG. 3 is a schematic view showing another example of one discharge hole of a spinneret for spinning the liquid crystal polyester fiber of the present invention,
Is a sectional view thereof, and B is a plan view showing an arrangement of pores of the spinneret.

[Explanation of symbols]

 1: Spin block 2: Spin pack 3: Spinneret 4: Oil agent applying device 5: 1st Gode roll 6: 2nd Gode roll 7: Winder 8: Discharge hole 9: Pore 10: 1 plate 11: 2 plate

Claims (3)

[Claims] 1. A liquid crystal polyester fiber comprising a melted liquid crystal-forming polyester and having an orientation degree ratio B represented by the following formula of 2.5 or less. [Equation 1] (Iy: peak intensity of C = C stretching vibration band (around 1600 cm ^-1 ) of the benzene ring when measuring polarization parallel to the fiber axis by laser Raman, Ix: benzene ring when measuring polarization perpendicular to the fiber axis by laser Raman C = C stretching vibration band (peak intensity of around 1600 cm ^-1 ) 2. A molten liquid crystal-forming polyester is produced from structural units formed from p-hydroxybenzoic acid, polyester structural units formed from 4,4′-dioxybiphenyl and terephthalic acid, and ethylene glycol and terephthalic acid. Consisting of structural units of polyester, the total of structural units and structural units is 80 to 90 mol% of the total, structural units account for 20 to 10 mol% of the total, and the structural unit / molar ratio is 80/20 to 95/5. The liquid crystal polyester fiber according to claim 1, wherein 3. The plane orientation ratio E represented by the following formula is 2.
It is 8 or less, The liquid crystal polyester fiber of Claims 1-3 characterized by the above-mentioned. [Equation 2] (Iyy: peak intensity of stretching vibration band (around 1730 cm ^-1 ) of carbonyl group when measuring polarization parallel to the fiber axis by laser Raman, Ixx: of carbonyl group when measuring polarization perpendicular to the fiber axis by laser Raman Stretching vibration band (1730 cm ^-1 peak intensity)