JPH11293522A - Thermotropic liquid crystal polyester fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermotropic liquid crystal polyester fiber having a fine denier size, excellent in mechanical properties, and useful as a resin reinforcing agent or the like by forming a mixture comprising a thermotropic liquid crystal polyester or the like into a fiber under a specific condition. SOLUTION: This thermotropic liquid crystal polyester fiber having <=3 de, preferably <=1 de size is obtained by melt-spinning a mixture comprising 95-99.9 pts.wt. thermotropic liquid crystal polyester obtained from an aromatic dial, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid or the like, and 0.1-5 pts.wt. polymer such as polystyrene incompatible with the thermotropic polyester, under a condition of >=50 ratio of the velocity of winding to the linear velocity of extrusion (a draft ratio) and 1,500-9,000 m/min winding velocity. Preferably, the thermotropic liquid crystal polyester fiber includes 0.1-5 wt.% methacrylate-based polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine denier fused liquid crystalline polyester fiber and an efficient method for producing the same.

[0002]

2. Description of the Related Art Hitherto, it has been known that a molten liquid crystalline polyester fiber has a high strength and a high elastic modulus, and has been developed for various uses. However, since the molten liquid crystalline polyester fiber is highly oriented and crystallized only by melt-spinning, there is a problem that the drawing cannot be further performed to reduce the fineness. In general, when the film is drawn at a high degree, oriented crystallization and fine denier progress. However, such a technique cannot be applied to a molten liquid crystalline polyester fiber which is highly oriented and crystallized at the stage of a spun yarn. From the above, a method for obtaining a fine denier molten liquid crystalline polyester has been studied.

[0003] For example, after spinning sea-island type fibers, a sea component is eluted with a solvent or decomposed and removed with a decomposing agent to obtain only island components as ultrafine fibers, or a method of preparing two or more incompatible polymers from incompatible polymers. Japanese Patent Application Laid-Open Nos. 54-77691 and 1-174408 disclose a method of spinning a conjugated fiber and dividing the polymer into pieces by the action of a chemical solution or impact to obtain ultrafine fibers. ing.

However, in the above method, a special spinneret having a complicated structure is required at the melt spinning stage, and a special process for elution or division is required. Therefore, there is a problem that the cost is extremely high in industrial production. On the other hand, in order to achieve fine denier, a pore nozzle with a diameter of 0.1 mm or less is used, the melt viscosity of the polymer, the shearing speed when passing through the nozzle, the discharge linear speed at the nozzle, the winding speed, the draft,
Japanese Patent Application Laid-Open No. 166909/1994 discloses a method of performing spinning with the spinning nozzle temperature and quenching conditions in specific ranges. However, in such a method, the production efficiency is low, and if the fineness is small, thread breakage or the like is likely to occur, and there is a limit to the denier of the fiber that can be efficiently produced.

Japanese Patent Application Laid-Open No. Hei 6-257015 discloses that a liquid crystalline polyester having a melt viscosity of 500 poise or less is blended to produce a fiber having a denier of 3 denier or less. Since it is necessary to compound a large amount of a liquid crystalline polyester having a melt viscosity of 500 poise or less, there is a problem that the spinnability and the fiber performance are apt to be reduced. In particular, it is practical to produce fibers of 1 d or less industrially. Was difficult. In view of the above problems, an object of the present invention is to provide a molten liquid crystalline polyester fiber of 3d or less, especially 1d or less, efficiently without impairing high fiber performance.

[0005]

According to the present invention, there is provided (1) a fiber containing a molten liquid crystalline polyester, which contains 0.1 to 5% by weight of a polymer incompatible with the molten liquid crystalline polyester; A molten liquid crystalline polyester fiber having a fineness of 3d or less, (2) a fiber containing the molten liquid crystalline polyester, comprising 0.1 to 5% by weight of a polymer incompatible with the molten liquid crystalline polyester, and 3. The molten liquid crystalline polyester fiber according to claim 1 or 2, which is a fiber containing the molten liquid crystalline polyester and containing 0.1 to 5% by weight of a methacrylate-based polymer. A polyester fiber, (4) a mixture containing 95 to 99.9 parts by weight of a molten liquid crystalline polyester and 0.1 to 5 parts by weight of a polymer incompatible with the liquid crystalline polyester; And the ratio of winding speed (draft) 5
0 to a method for producing a molten liquid crystalline polyester fiber having a fineness of 3 d or less, which is melt-spun at a winding speed of 1500 to 9000 m / min.

The aromatic polyester capable of forming an anisotropic melt phase used in the present invention is, for example, a polymer obtained from an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, or the like. Polymers composed of a combination of repeating structural units shown in Chemical formulas 1 to 3 are exemplified.

[0007]

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[0008]

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[0009]

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The melting point Tm of the molten liquid crystalline polyester is from 260 to 360 ° C., particularly from 270 to 320
C. is preferred. Particularly preferably, the portion composed of the structural units of (A) and (B) shown in Chemical Formula 3 is 60 mol%.
The above-mentioned molten liquid crystalline polyester, particularly (A)
The aromatic polyester in which the component (B) is 5 to 45 mol% based on the total amount of (B) and (B) is most preferable in view of spinnability and fiber properties. The components may contain other polymers or additives (pigments, carbon, heat stabilizers, ultraviolet absorbers, lubricants, fluorescent whitening agents, etc.) as long as the strength is not substantially reduced.

[0011] The present invention provides a fine denier fiber without impairing high fiber performance by blending a small amount of an incompatible polymer (hereinafter sometimes simply referred to as an incompatible polymer) with a molten liquid crystalline polyester. Has been found to be able to be produced efficiently. It is not clear why fine denier fibers can be obtained by blending the incompatible polymer, but the incompatible polymer acts as a lubricant and changes in elongation fluidity suppresses oriented crystallization, resulting in fine denier. It is estimated that this will be easier. According to the invention, 3 denier or less, in particular 1 denier or less, and even 0.
Fibers of 6d or less can be produced efficiently and without substantially impairing fiber performance.

The immiscible polymer referred to in the present invention is:
When the polymer is blended with a molten liquid crystalline polyester and observed with a transmission microscope (TEM), the polymer is present as island components (particles) in the molten liquid crystalline polyester phase. When a polymer having high compatibility is used, the effects of the present invention cannot be obtained. In the present invention, the incompatible polymer is preferably finely dispersed in the molten liquid crystalline polyester, and the diameter of the island formed by the incompatible polymer is preferably 3 μm or less, particularly preferably 1 μm or less.

[0013] The incompatible polymer that can be used in the present invention is not particularly limited, but it is particularly preferable because it has a small effect on various properties of the fiber and a fine denier fiber can be obtained without significantly impairing the spinnability and the fiber performance. It is preferable to use one having the repeating unit shown in Chemical formula 4. Here, R1 and R2 are substituents obtained by combining arbitrary atoms selected from C, H, N, O, S, P and halogen atoms, and n represents an integer of 1 or more. From the viewpoint of fine denier, the sum of the molecular weights of R1 and R2 is preferably 40 or more, and the molecular weight of the incompatible polymer is preferably 1000 or more.

[0014]

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Specifically, polymethacrylate and its derivatives, polyacrylate and its derivatives, polystyrene and its derivatives, poly (4-methyl-1-pentene),
Examples include polyoctadicene-1, polyvinylbenzyl and derivatives thereof. In particular, it is preferable to use a methacrylate polymer and / or a styrene polymer, and it is particularly preferable to use a methacrylate polymer (PMMA). When PMMA is used, it is difficult to obtain efficiently by ordinary methods while maintaining high fiber performance.
d or less, especially 0.6 d or less.

The incompatible polymer is preferably used in an amount of 0.1 to 5% by weight / fiber weight, particularly preferably 1 to 4% by weight / fiber weight. In the present invention, a remarkable denier effect can be obtained only by adding a very small amount of the incompatible polymer, and an excellent effect can be obtained because the effect on the fiber performance is small.

The method for producing the fiber of the present invention is not particularly limited, but is preferably produced by the following method. First, 95 to 99.9 parts by weight (preferably 96 to 99 parts by weight) of the molten liquid crystalline polyester and 0.1 to 0.1 parts by weight of the incompatible polymer are added.
5 parts by weight (preferably 1 to 4 parts by weight) are mixed to produce a spinning tip. The spinning tip is preferably dried before spinning to remove water.

The spinning tip is melted and discharged into a gas from a nozzle. From the viewpoint of fine denier and spinnability, it is preferable to use a nozzle having a diameter of 0.2 mm or less, particularly 0.11 to 0.15 mm. preferable. At this time, the ratio (draft) of the discharge linear speed to the winding speed is 50 or more, particularly 100 or more, and further preferably 20 or more, from the viewpoints of fine denier, fiber performance and spinnability.
It is preferably 0 or more, especially 300 or more and 500 or less. In the conventional method, there is a problem that the yarn is easily broken when the draft is raised, but in the present invention, the yarn is hardly generated even if the draft is raised, and the fine denier can be greatly reduced. For the same reason, the discharge linear speed is preferably 15 to 80 m / min, particularly preferably 16 to 40 m / min, and the winding speed is 1500 to 9000 m / min.
Especially 2500 to 8500 m / min, and more preferably 5000 to 80
It is preferably set to 00 m / min, especially 6000 to 8000 m / min.

Conventionally, when the winding speed is increased, the draft increases, and the denier can be reduced without impairing the fiber performance. However, there has been a problem that thread breakage tends to occur. In the present invention, the spinning speed is 6000 m / min or more, especially 7000 m / min.
Even in the case of m / min or more, substantially no yarn breakage occurs, and fine denier fibers excellent in fiber performance can be efficiently produced. As the winding speed increases, the production efficiency increases, and a large amount of fibers can be obtained in a short time, so that excellent effects can be obtained in terms of processability and cost.

The shear rate when passing through the spinning nozzle is 10 ⁴
〜１０10 ⁹ sec ⁻¹ , especially 1 × 10 ^{4 -3} × 10 ⁴ sec ⁻¹
It is preferred that Generally, a nozzle having a small nozzle hole diameter is used to obtain a fine denier fiber. However, if the nozzle diameter is too small, the shearing force becomes high, and a problem such as thread breakage easily occurs. However, in the present invention, it is possible to obtain fine denier fibers by increasing the draft without excessively reducing the nozzle hole (excessively increasing the shear rate), so that problems such as thread breakage occur. Excellent effect is obtained. Twice breaks / 8
It is preferable that the heating time is about 1 hour or less, and more preferably 0 to 1 time / 8 hours. The shear rate (γ) referred to in the present invention is calculated as γ = 4Q / πr ³ when the average nozzle radius is r (cm) and the amount of polymer discharged per single hole is Q (cm ³ / sec). You.

The spun yarn obtained according to the present invention may be used as it is, but in some cases, the following heat treatment can be performed to improve the fiber properties of strength and elastic modulus. When a medium such as a gas is supplied, there are a method using radiation from a heating plate, an infrared heater, and the like, a method using contact with a heat roller, a plate, and the like, and an internal heating method using high frequency and the like. . As the gas used as the heating medium, an inert gas such as nitrogen, or a mixed gas of nitrogen and oxygen, carbon dioxide, or the like, and air are used. The heat treatment atmosphere is preferably a gas having a dew point of -20 ° C or less, preferably -40 ° C or less. The heat treatment may be performed under tension or without tension depending on the purpose. In addition, the shape may be a scallop, cheese, tow (processed on a wire net), or between rollers. Preferred heat treatment temperature conditions are Tm-60
A pattern in which the temperature is sequentially increased from Tm-40 ° C within a range of from 0 ° C to Tm + 20 ° C (where Tm is the melting point of the molten liquid crystalline polyester) is more preferable. The heat treatment time can be from several seconds to tens of hours depending on the desired performance.

According to the present invention, fine denier fibers can be obtained without practically impairing fiber performance. Fiber strength is 12
g / d or more, preferably 15 g / d or more, more preferably 20 g / d or more, and especially preferably 25 g / d or more, and the elastic modulus is 400 g / d or more, further 500 g / d or more, particularly 550 g / d or more. Is preferred.

The fibers of the present invention can be used in any form. For example, filament yarn, cut fiber, spun yarn, string, rope, cloth (woven, knitted,
Nonwoven fabric). In particular, since the fibers are fine denier fibers, excellent effects can be obtained in the case of fabrics.
Of course, it may be used in combination with other fibers.

The fibers of the present invention can be used for any purpose,
For example, the following can be mentioned. 1. Used for resin reinforcement (including compounding with carbon and glass fiber) Ski and golf clubs, hockey, gate ball heads and shafts, rackets for tennis, badminton, squash, etc. Helmets, bats, eyeglass frames, printed boards, slots for motor rotors, insulators, pipes, high-pressure containers, motorcycles, motorcycles, automobiles, trains, linear motor cars,
Residential building materials, such as primary or secondary structures such as ships, helicopters, airplanes, and spacecraft, wallboards, columns, etc.

2. 2. Materials used for rubber reinforcement Materials for rubber reinforcement such as tires, conveyor belts, power transmission belts, various timing belts, and hoses. Used in pulp form 1) Wear material (mixed use with other fibers, resin reinforcement) Brake lining, clutch facing, bearing 2) Other packing material, gasket, filter material, abrasive material

4. 4. Cut fiber, used in chopped yarn form Paper (insulating paper, heat-resistant paper), speaker vibration material, cement reinforcement material, resin reinforcement material 5. Filaments, spun yarns, control cables, heater cores, tension members (optical fibers, electric wires, head cones, etc.), ropes, cords, ropes, lifelines, fishing lines, fishing nets, longlines Used in woven or knitted forms Screen gauze, yacht sale, tent, membrane, bulletproof vest, safety gloves, safety net, heat-resistant supplies, protective equipment such as apron, rubber reinforcing base cloth, automobile, train, linear motor car, Lining of ships, airplanes, airships and the like.

Among them, since it is excellent in mechanical performance and the like and has fine denier, it is suitable for clothing and industrial uses such as artificial leather, various fabrics, wiping cloths, filters, screen gauze, and electric insulating paper. Can be widely used.

[0028]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. The measurement of the weight average molecular weight described in Examples and Comparative Examples was performed as follows. [Melting point ° C] Melting point of molten liquid crystalline polyester (MP)
Is a differential scanning calorimeter (DSC: manufactured by mettler, for example, T
A3000), the peak temperature of the main endothermic peak observed is measured (JIS K7121). Specifically, DSC (for example,
10 ~ 2 samples in a Mettler TA3000) device
After taking 0 mg and enclosing it in an aluminum pan, nitrogen is supplied as a carrier gas at a flow rate of 100 cc / min, and an endothermic peak is measured when the temperature is raised at 20 ° C./min. The above 1 depends on the type of polymer.
If no clear endothermic peak appears in st Run,
/ Min to a temperature that is 50 ° C. higher than the expected flow temperature at a heating rate of / min.
Cool to 50 ° C. at a rate of 80 ° C./min.
The endothermic peak is measured at a temperature rise rate of ° C./min.

[Melt viscosity MV] 300 ° C., shear rate r =
The measurement was performed using a Toyo Seiki Capillograph Model 1C under the conditions of 1000 sec ^-1 . [Logarithmic viscosity ηinh] Convert sample to pentafluorophenol
0.1% by weight was dissolved (60-80 ° C), and the relative viscosity (ηrel) was measured using an Upperod viscometer in a thermostat at 60 ° C.
ηinh = ln (ηrel) / c. Here, c is the polymer concentration (g / dl).

[Measurement of weight average molecular weight] 8.6 mg of sample
Was dissolved in 10 ml of pentafluorophenol at 60 to 80 ° C., and cooled to 30 ° C., and 18.6 ml of chloroform (reagent, special grade) was added thereto. Pentafluorophenol / chloroform = 35/65 mobile phase, flow rate 1.0
ml / min, injection volume 200 μl, using a differential refractometer as the detector. The weight average molecular weight was determined from the obtained molecular weight distribution curve by a conventional method (for example, “Polymer Science Experiment Method” edited by The Society of Polymer Science, Tokyo Kagaku Dojin P202 (1986) Tokyo).

[Strength g / d, elongation%] JIS L10
Test length 20cm, initial load 0.1g / d, tensile speed 10cm according to 13.
The breaking elongation at break was determined under the condition of / min, and an average value of 5 or more points was adopted. [Elastic modulus g / d] A strength-elongation curve is created, and the elastic modulus = (w / D) / (ΔL / L) is calculated from a straight line portion according to Hooke's law near the origin of the curve. In addition,
w is the load g when ΔL is extended, D is the denier of the fiber,
ΔL indicates the length extended by the load, and L indicates the original fiber length.

Example 1 The structural units (A) and (B)
Is a liquid crystalline polyester having a ratio of 73/27 mol% (MP = 280 ° C., MV = 430 poise, ηinh = 5.21 dl /
g, weight average molecular weight 2.68 × 10 ⁵ )) to 97 parts by weight,
3 parts by weight of PMMA (“Delpet 80N” manufactured by Asahi Kasei Corporation: sum of the molecular weights of R1 and R2 in Chemical Formula 4) was mixed in an amount of 3 parts by weight to obtain a spinning tip. Observation of the cross section of the chip with a transmission electron microscope revealed that PMMA formed island components having a diameter of about 1 μm and dispersed in the molten liquid crystalline polyester. The mixture was dried in a vacuum drier at 140 ° C. for 10 hours, and then extruded from a single-screw vent extruder to obtain an average pore size of a sand (stainless powder) layer and a fine metal wire.
After filtration through a 0 μm filter, the nozzle diameter was 0.125.
When the fiber was spun under the conditions of mmφ, a nozzle temperature of 320 ° C., and the conditions shown in Table 1, the spinnability was good and the yarn was not broken at all for 8 hours.

The obtained spun yarn is continuously placed on a stainless steel bobbin with a cushion material (thickness: 1) made of inorganic fiber.
2.50mm) and a winding density of 0.60g
In this state, heat treatment was performed at 150 ° C. for 1 hour, at 200 ° C. for 4 hours and at 280 ° C. for 11 hours in a combination of nitrogen and an air atmosphere. Table 1 shows the mechanical performance of the obtained heat-treated yarn.

Example 2 Spinning was carried out in the same manner as in Example 1 except that the spinning conditions were changed to those shown in Table 1, and the spinning properties were good, and the yarn was not broken at all for 8 hours. In addition, since the winding speed was high, an excellent effect was also obtained in terms of production efficiency. The obtained spun yarn was subsequently heat-treated under the same conditions as in Example 1. Table 1 shows the mechanical performance of the obtained heat-treated yarn.

[Comparative Example 1] Instead of the incompatible polymer, the structural units (A) and (B) shown in Chemical Formula 3 were 73/2.
The same procedure as in Example 1 was carried out except that a mixture prepared by mixing 12 parts by weight of an oligomer having a weight-average molecular weight of 4.25 × 10 ³ at a ratio of 7 mol% was used as a spinning chip. The spinnability was inferior to those of Examples 1 and 2, and the yarn was broken three times during spinning for 8 hours. Table 1 shows the performance of the heat-treated yarn.

[Comparative Example 2] The mixture obtained in Comparative Example 1 was spun under the same conditions as in Example 2 to spin fibers of 1d or less. Occurred and spinning was substantially impossible. Comparative Example 3 The same operation as in Example 1 was performed except that a chip containing no PMMA was used. However, thread breakage occurred five times in one hour, making it impossible to spin substantially.

[0037]

[Table 1]

[0038]

According to the present invention, a molten liquid crystalline polyester fiber having excellent mechanical performance and fine denier (specifically, 3 d or less, particularly 1 d or less) can be efficiently obtained.

Claims (4)

[Claims] 1. A fiber containing a molten liquid crystalline polyester, comprising 0.1 to 5% by weight of a polymer incompatible with the molten liquid crystalline polyester and having a fineness of 3d or less. . 2. A fiber containing a molten liquid crystalline polyester, comprising 0.1 to 5% by weight of a polymer incompatible with the molten liquid crystalline polyester and having a fineness of 1d or less. . 3. The molten liquid crystalline polyester fiber according to claim 1, which is a fiber containing a molten liquid crystalline polyester, wherein the fiber contains 0.1 to 5% by weight of a methacrylate polymer. 4. A molten liquid crystalline polyester 95 to 99.9.
A mixture containing 0.1 to 5 parts by weight of a polymer which is incompatible with the liquid crystalline polyester and a ratio of the discharge linear speed to the winding speed (draft) of 50 or more, and a winding speed of 1500 to 9
A method for producing a molten liquid crystalline polyester fiber having a fineness of 3d or less, which is melt-spun at 000 m / min.