Method for producing liquid crystal polyester filament

Abstract

To provide a method for producing a liquid crystal polyester filament that maintains a high strength, high elastic modulus and high heat resistance, has no fibril defects and has an abrasion resistance without causing a problem in weaving property and weaving quality, and in particular, improves a yarn running property of a liquid crystal polyester monofilament having a small single fiber fineness, thereby improving an operating property.SOLUTION: There is provided a method for producing a liquid crystal polyester filament, which has different atmospheric temperatures at an inlet and an outlet of a heat treatment step, when a package of the liquid crystal polyester filament is solid-phase polymerized, and then the solid-phase polymerized liquid crystal polyester filament is unwound from the package and heat-treated without being wound up.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a liquid crystal polyester filament having excellent strength, elastic modulus and abrasion resistance. [Background technology]

[0002] Liquid crystal polyester is a polymer consisting of rigid molecular chains, and in melt spinning, the molecular chains are highly oriented in the fiber axis direction, and then heat-treated at high temperatures to cause solid-phase polymerization, resulting in the highest strength and elastic modulus of any fiber obtained by melt spinning (see Non-Patent Document 1). Liquid crystal polyester fibers also have low moisture absorption properties, and have been used in ropes and nets for fishery materials. In recent years, there has been an increasing demand for liquid crystal polyesters with relatively low fineness, such as gauze fabrics for screen printing, sail cloth, cord reinforcements for various electrical products, protective gloves, plastic reinforcements, tension members for optical fibers, and base fabrics for membranes.

[0003] However, because the rigid molecular chains of liquid crystal polyester fibers are highly oriented in the fiber axis direction, they are weak in the direction perpendicular to the fiber axis, and are prone to fibrillation and have poor abrasion resistance. In addition, liquid crystal polyester fibers are highly oriented in the fiber axis direction and produce dense crystals, but the structural difference between the crystalline and amorphous parts is large and the interaction is low, so when an external force is applied, a shift occurs between the crystalline and amorphous parts, and fibrillation progresses from the structural defect as the starting point of destruction. For this reason, the generation of fluff in the advanced processing of fibers causes a deterioration in process passability, and the inclusion of fluff causes a decrease in the quality and performance of the product, so there is a demand for improving the abrasion resistance of liquid crystal polyester fibers. In particular, in filters and screen printing gauze, there is a demand for reducing defects at the openings in order to improve performance. The defects at the openings are caused by the fibers being scraped and fibrillated by friction during the weaving process, and the fibrils block the openings, so there is a strong demand for improving the abrasion resistance of liquid crystal polyester fibers.

[0004] To improve this wear resistance, core-sheath composite fibers composed of a core component of liquid crystal polyester and a sheath component of polyphenylene sulfide (see Patent Document 1), and sea-island composite fibers composed of an island component of liquid crystal polyester and a sea component of a flexible thermoplastic polymer have been proposed (see Patent Document 2). With these technologies, although the wear resistance can be improved by forming a flexible polymer on the fiber surface, since the fraction of components other than liquid crystal polyester is large, the strength of the fiber is inferior, and in the solid-phase polymerization of the fiber required for increasing the strength of liquid crystal polyester, the low-melting-point fiber surface fuses, causing defects and fibrillation. Furthermore, in core-sheath composite spinning, the discharge amount of each of the core and sheath is smaller than that of single-component spinning. When the discharge amount is reduced for making the fiber fineness finer, the melt viscosity changes due to gelation or thermal decomposition accompanying an increase in the residence time of the polymer, resulting in a problem of impairing the longitudinal uniformity of the fiber such as thickness unevenness or composite abnormality in the longitudinal direction of the fiber.

[0005] In addition, a technique has been proposed to enhance the wear resistance by heat-treating a composite fiber composed of liquid crystal polyester and a flexible thermoplastic resin at a temperature of 20 °C or more above the melting point of the flexible thermoplastic resin (see Patent Documents 3 and 4). However, with this technique, since the wear resistance is improved by making the flexible thermoplastic resin in an amorphous state, the obtained fiber has a problem of inferior heat resistance. Also, due to being composite spinning, there is a problem of impairing the longitudinal uniformity as described above.

[0006] In addition, a technique has been proposed in which a liquid crystal polyester fiber is heat-cured (solid-phase polymerized) at a temperature lower than the melting point, and then the fiber is stretched at a temperature of 220 °C to 500 °C, usually within a range of 50 °C of the curing temperature, by 10% to 400% to increase the strength and elastic modulus (see Patent Document 5). However, this technique aims to further enhance the orientation of molecular chains by stretching at a temperature at which the crystallinity can be maintained, thereby increasing the strength and elastic modulus. Due to the fiber structure having a high crystallinity and a high orientation of molecular chains, the wear resistance cannot be improved.

[0007] Techniques for improving the abrasion resistance of liquid crystal polyester fibers by heat treatment at a temperature above the melting point have been disclosed (see Patent Documents 6 and 7). These techniques describe solid-phase polymerization in the form of a package, unwinding, removing an anti-fusing agent, and heat treatment at a high temperature above the melting point. Although it is possible to improve the abrasion resistance of liquid crystal polyester fibers, in these processes, the treated fibers are wound up each time, resulting in inevitable increases in costs such as winding equipment costs and labor costs for operating personnel. In addition, since the liquid crystal polyester fibers after unwinding and before heat treatment are inferior in abrasion resistance, fibrillation could not be avoided in the winding process before heat treatment.

[0008] Further, there is provided a method for producing liquid crystal polyester fibers, which comprises forming the liquid crystal polyester fibers into a package, subjecting them to solid-phase polymerization, continuously heat-treating them without once winding up the solid-phase polymerized liquid crystal polyester fibers unwound from the package, wherein the temperature of the heat treatment is set to be not less than the endothermic peak temperature (Tm1) + 60°C of the liquid crystal polyester fibers after solid-phase polymerization, and the speeds of the fibers before and after the heat treatment are regulated by a first roller and a second roller, respectively (see Patent Document 8). In this method, the running stability of the fibers is improved by regulating the fiber speed, but the decrease in tension caused by heat treatment cannot be solved, and the deterioration of operability due to yarn vibration becomes a problem. When stretching is applied to compensate for the decrease in tension, conversely, the orientation of the fibers increases, and a decrease in abrasion resistance cannot be avoided.

[0009] From the above, in the prior art, no method has been proposed to prevent the yarn vibration of liquid crystal polyester filaments with high abrasion resistance and no fibril defects while maintaining high strength, high elastic modulus, and high heat resistance, and to improve operability.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Document

[0011]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] The problem of the present invention is to provide a liquid crystal polyester filament that has high strength, high elastic modulus, high heat resistance, no fibril defects, and wear resistance without problems in weaving property and fabric quality, particularly to improve the yarn running property of a liquid crystal polyester filament with a small single fiber fineness and to provide a manufacturing method for improving the operability.

Means for Solving the Problems

[0013] To solve the above problems, the present invention has the following configuration. That is, the present invention is a method for producing a liquid crystal polyester filament, which comprises subjecting a package of the liquid crystal polyester filament to solid-phase polymerization, then unwinding the solid-phase polymerized liquid crystal polyester filament from the package and heat-treating it without winding it up once, wherein the atmospheric temperatures at the inlet and outlet of the heat-treatment step are different.

[0014] Furthermore, it is preferable that the atmospheric temperature at the inlet of the heat-treatment step is 20°C or higher than the atmospheric temperature at the outlet.

[0015] Furthermore, it is preferable that the atmospheric temperature at the outlet of the heat-treatment step is (the endothermic peak temperature Tm1 of the liquid crystal polyester filament after solid-phase polymerization + 80)°C or higher.

Advantages of the Invention

[0016] According to the present invention, a liquid crystal polyester filament having high strength, high elastic modulus, high heat resistance, high wear resistance and no fibril defects can be produced at low cost and in high yield by improving the yarn running property and the operability while maintaining the above properties.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the method for producing the liquid crystal polyester filament of the present invention will be described.

[0018] The liquid crystal polyester used in the present invention is a polyester that can form an anisotropic molten phase, i.e., a liquid crystalline phase, when melted. This property can be confirmed, for example, by placing a sample made of the liquid crystal polyester on a hot stage, heating it while raising the temperature under a nitrogen atmosphere, and observing the transmitted light of the sample under polarized light.

[0019] The liquid crystal polyester used in the present invention is, for example (1) A polymer of an aromatic oxycarboxylic acid, (2) A polymer of an aromatic dicarboxylic acid, an aromatic diol, and an aliphatic diol, (3) The copolymer of the above (1) and (2) Examples include the like, but for high strength, high elastic modulus, and high heat resistance, the wholly aromatic polyester of the above (1) that does not use an aliphatic diol is preferred. Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid, etc., or alkyl-substituted products, alkoxy-substituted products, halogen-substituted products, etc. of the above aromatic oxycarboxylic acid.

[0020] Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylethane dicarboxylic acid, etc., or alkyl-substituted products, alkoxy-substituted products, halogen-substituted products, etc. of the above aromatic dicarboxylic acid.

[0021] Furthermore, examples of the aromatic diol include hydroquinone, resorcin, dioxydiphenyl, naphthalenediol, etc., or alkyl-substituted products, alkoxy-substituted products, halogen-substituted products, etc. of the above aromatic diol, and examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, etc.

[0022] Examples of the liquid crystal polyester used in the present invention include those in which a p-hydroxybenzoic acid component, a 4,4'-dihydroxybiphenyl component, a hydroquinone component, a terephthalic acid component and / or an isophthalic acid component are copolymerized, those in which a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component are copolymerized, those in which a p-hydroxybenzoic acid component, a 6-hydroxy-2-naphthoic acid component, a hydroquinone component, and a terephthalic acid component are copolymerized, etc. These have excellent spinnability, can achieve high strength and high elastic modulus, and are preferred examples because the wear resistance is improved by performing heat treatment at a high temperature after solid-phase polymerization.

[0023] In the present invention, it is particularly preferable that the liquid crystal polyester is composed of the following structural units (I), (II), (III), (IV), and (V). In the present invention, the structural unit refers to a unit that can constitute a repeating structure in the main chain of the polymer.

[0024]

Chemical formula

[0025] Due to this combination of structural units, the molecular chain comes to have appropriate crystallinity and non-linearity, that is, a melting point at which melt spinning is possible. Therefore, at the spinning temperature set between the melting point and the thermal decomposition temperature of the polymer, good spinning properties are obtained, fibers that are uniform in the longitudinal direction are obtained, and due to having appropriate crystallinity, the strength and modulus of elasticity of the fibers can be increased.

[0026] Furthermore, it is important to combine components composed of highly linear diols that are not bulky, such as structural units (II) and (III). By combining the above structural units, the molecular chain takes an ordered and less disordered structure in the fiber, and the crystallinity does not increase excessively and the interaction in the direction perpendicular to the fiber axis can also be maintained. As a result, in addition to obtaining high strength and modulus of elasticity, particularly excellent wear resistance can also be obtained by performing high-temperature heat treatment after solid-phase polymerization.

[0027] Also, for the above-mentioned structural unit (I), 40 to 85 mol% is preferable, more preferably 65 to 80 mol%, and still more preferably 68 to 75 mol% with respect to the total of structural units (I), (II), and (III). By setting such a structural unit ratio, the crystallinity can be made appropriate, high strength and modulus of elasticity can be obtained, and the melting point is also within the range where melt spinning is possible.

[0028] The structural unit (II) is preferably 60 to 90 mol%, more preferably 60 to 80 mol%, and still more preferably 65 to 75 mol% based on the total of the structural units (II) and (III). By setting such a structural unit ratio, the crystallinity does not increase excessively and the interaction in the direction perpendicular to the fiber axis can be maintained. Therefore, the wear resistance can be improved by performing heat treatment at a high temperature after solid-phase polymerization.

[0029] The structural unit (IV) is preferably 40 to 95 mol%, more preferably 50 to 90 mol%, and still more preferably 60 to 85 mol% based on the total of the structural units (IV) and (V). By setting such a structural unit ratio, the melting point of the polymer becomes appropriate, and it has good spinnability at the spinning temperature set between the melting point and the thermal decomposition temperature of the polymer. Therefore, fibers that are uniform in the longitudinal direction can be obtained. In addition, since the linearity of the polymer is moderately disturbed, the fibril structure is easily disturbed by heat treatment at a high temperature after solid-phase polymerization, the interaction in the direction perpendicular to the fiber axis is increased, and the wear resistance can be improved.

[0030] As described above, by using three or more structural units, a polymer having appropriate crystallinity and polymer linearity can be obtained, and fibers having excellent strength and elastic modulus can be obtained.

[0031] The preferred ranges of the respective structural units of the liquid crystal polyester used in the present invention are as follows. The total of the following structural units (I) to (V) is 100 mol%. By adjusting the composition ratio of the structural units within this range, the liquid crystal polyester filament of the present invention can be preferably obtained. Structural unit (I) 45 to 65 mol% Structural unit (II) 12 to 18 mol% Structural unit (III) 3 to 10 mol% Structural unit (IV) 5 to 20 mol% Structural unit (V) 2 to 15 mol% Furthermore, it is preferable that the total amount of the structural unit (IV) and the structural unit (V) and the total amount of the structural unit (II) and the structural unit (III) are equimolar.

[0032] In addition to the above monomers, other monomers may be copolymerized with the liquid crystal polyester used in the present invention to the extent that the liquid crystallinity is not impaired.

[0033] Also, other polymers can be added and used in combination with the liquid crystal polyester used in the present invention as long as the effects of the present invention are not impaired. The addition and combined use mean mixing the polymers with each other, or in the case of composite spinning of two or more components, partially mixing and using another polymer in one component or a plurality of components, or using it entirely. When adding and using polymers in combination, it is preferable that the melting point is within ±30°C of the melting point of the liquid crystal polyester in order not to impair the yarn manufacturing property. In order to improve the strength and elastic modulus of the resulting fiber, and to suppress the generation of fuzz and yarn breakage due to peeling at the polymer interface, the amount added and used in combination is preferably 50% by weight or less, more preferably 5% by weight or less, and most preferably not adding and using other polymers.

[0034] The liquid crystal polyester used in the present invention may contain a small amount of various additives such as various metal oxides, inorganic substances such as kaolin and silica, and coloring agents, matting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, end group blocking agents, compatibilizers, etc. within the range that the effects of the present invention are not impaired.

[0035] The weight average molecular weight in terms of polystyrene (hereinafter referred to as molecular weight) of the liquid crystal polyester used in the present invention is preferably 30,000 or more. By setting the molecular weight to 30,000 or more, it has an appropriate viscosity at the spinning temperature and the yarn manufacturing property can be enhanced. The higher the molecular weight, the higher the strength, elongation, and elastic modulus of the resulting fiber, but if the molecular weight is too high, the viscosity becomes high and the fluidity deteriorates, and finally it does not flow, so the molecular weight is preferably less than 250,000, more preferably less than 200,000. The weight average molecular weight in terms of polystyrene referred to here means the value measured by the method described in the examples.

[0036] The melting point Tm2 of the liquid crystal polyester used in the present invention is preferably 200 to 380 °C in order to widen the temperature range where melt spinning is possible, and more preferably 250 to 360 °C in order to enhance the spinnability. The melting point of the liquid crystal polyester polymer refers to the value measured by the method described in the examples.

[0037] In melt spinning, although known techniques can be used for the melt extrusion of the liquid crystal polyester, it is preferable to use an extruder-type extruder in order to eliminate the ordered structure generated during polymerization. The extruded polymer is metered by a known metering device such as a gear pump via a pipe, and after passing through a filter for removing foreign matter, it is led to a die. At this time, the temperature from the polymer pipe to the die (spinning temperature) is preferably set to be equal to or higher than the melting point of the liquid crystal polyester in order to enhance fluidity, and more preferably (melting point + 10) °C or higher of the liquid crystal polyester. However, if the spinning temperature is excessively high, the viscosity of the liquid crystal polyester increases, leading to deterioration of fluidity and spinning performance, so it is preferably set to 500 °C or lower, and more preferably 400 °C or lower. It should be noted that it is also possible to independently adjust the temperature from the polymer pipe to the die. In this case, the temperature of the part closer to the die is made higher than the temperature on its upstream side, so that the discharge becomes stable.

[0038] The polymer discharged from the die holes is passed through a heat preservation and cooling region to be solidified, and then taken up by a roller (godet roller) rotating at a constant speed. If the heat preservation region is excessively long, the spinning performance deteriorates, so it is preferably set to 200 mm or less from the die surface, and more preferably 100 mm or less. It is also possible to increase the ambient temperature in the heat preservation region using heating means, and the temperature range is preferably 100 °C or higher and 500 °C or lower, and more preferably 200 °C or higher and 400 °C or lower. For cooling, an inert gas, air, water vapor, etc. can be used, but it is preferable to use an air flow ejected in parallel or annularly from the viewpoint of reducing the environmental load.

[0039] The take-up speed is preferably 50 m / min or more, more preferably 500 m / min or more, for the purpose of improving productivity and reducing the fineness of single fibers. The liquid crystal polyester cited as a preferred example in the present invention has suitable drawability at the spinning temperature, so the take-up speed can be increased to a high speed, and the upper limit is not particularly limited. However, from the viewpoint of drawability, it is about 2000 m / min.

[0040] In melt spinning, it is preferable to apply an oil agent between the cooling and solidification of the polymer and the winding up in order to improve the handleability of the fiber. Known oil agents can be used, but it is preferable to use a general spinning oil agent or the solid-phase polymerization oil agent described later in terms of improving the unwindability when unwinding the fiber obtained by melt spinning in the rewinding step before solid-phase polymerization.

[0041] Winding can be performed using a known winding machine to form a package in the form of a bobbin, cheese, cone, etc. However, it is preferable to use a bobbin winding method in which the roller does not contact the package surface during winding, because it does not apply frictional force to the fiber and does not cause fibrillation.

[0042] In the present invention, it is preferable to perform solid-phase polymerization after applying a solid-phase polymerization oil agent to the liquid crystal polyester filament. The solid-phase polymerization oil agent referred to in the present invention is an oil agent that suppresses fusion between fibers when the oil agent is adhered to the liquid crystal polyester filament and solid-phase polymerization is performed. Known ones can be used, but from the viewpoints of suppressing fusion and easy washability, it is preferable to use a mixture of inorganic particles A and a phosphoric acid compound B. In the present invention, even when it does not contain an oil component like the mixture of inorganic particles A and phosphoric acid compound B, it is referred to as a solid-phase polymerization oil agent.

[0043] The inorganic particles A in the present invention are known inorganic particles. Examples include minerals, metal hydroxides such as magnesium hydroxide, metal oxides such as silica and alumina, carbonate compounds such as calcium carbonate and barium carbonate, sulfate compounds such as calcium sulfate and barium sulfate, and CB. By applying such inorganic particles with high heat resistance onto the fiber, it is possible to reduce the contact area between single fibers and avoid fusion generated during solid-phase polymerization.

[0044] Inorganic particle A is preferably easy to handle in consideration of the coating process and is easily water-dispersible from the viewpoint of reducing environmental impact, and is desirably inert under solid-phase polymerization conditions. From these viewpoints, it is preferable to use silica or silicate. In the case of silicate, phyllosilicate having a layered structure is particularly preferable. Examples of phyllosilicate include kaolinite, halloysite, serpentine, nickel silicate ore, smectite group, pyrophyllite, talc, mica, etc. Among these, it is most preferable to use talc and mica in consideration of easy availability.

[0045] In addition, as the phosphate compound B in the present invention, compounds represented by the following chemical formulas (1) to (3) can be used.

[0046]

Chemical formula

[0047] Here, R1 and R2 are hydrocarbons, M1 is an alkali metal, M2 is an alkali metal, hydrogen, hydrocarbon, or oxygen-containing hydrocarbon. Note that n represents an integer of 1 or more. The upper limit of n is preferably 100 or less, more preferably 10 or less, from the viewpoint of suppressing thermal decomposition.

[0048] Considering the generated gas due to thermal decomposition during solid-phase polymerization, from the viewpoint of reducing environmental impact, it is preferable that R1 does not contain a phenyl group in its structure, and it is more preferably composed of an alkyl group. The number of carbon atoms of R1 is preferably 2 or more from the viewpoint of affinity for the fiber surface, and preferably 20 or less from the viewpoints of suppressing the weight loss rate due to the decomposition of the organic component accompanying solid-phase polymerization and preventing the carbide generated by the decomposition during solid-phase polymerization from remaining on the fiber surface.

[0049] In addition, as R2, a hydrocarbon having 5 or less carbon atoms is preferable from the viewpoint of solubility in water, and more preferably has 2 or 3 carbon atoms. As M1, sodium and potassium are preferable from the viewpoint of manufacturing cost.

[0050] In order to uniformly apply while optimizing the adhesion amounts of inorganic particles A and phosphate compound B, it is preferable to use a mixed oil agent in which inorganic particles A are added to a dilution of phosphate compound B. From the viewpoint of safety, it is preferable to use water as the dilution. From the viewpoint of suppressing fusion, the concentration of inorganic particles A in the dilution is desirably high, 0.01 wt% or more, more preferably 0.1 wt% or more, and the upper limit is preferably 10 wt% or less, more preferably 5 wt% or less from the viewpoint of uniform dispersion. Also, the concentration of phosphate compound B is desirably high from the viewpoint of uniform dispersion of inorganic particles A, 0.1 wt% or more, more preferably 1.0 wt% or more. The upper limit of the concentration of phosphate compound B is not particularly limited, but it is preferably 50 wt% or less, more preferably 30 wt% or less for the purpose of avoiding excessive adhesion due to an increase in the viscosity of the mixed oil agent and adhesion spots due to an increased temperature dependence of the viscosity.

[0051] Also, as a method for applying inorganic particles A and phosphate compound B to the fiber, it may be performed between melt spinning and winding, but in order to increase the adhesion efficiency, it is preferable to apply to the yarn while rewinding the melt-spun and wound yarn, or to adhere a small amount by melt spinning and perform additional application while rewinding the wound yarn.

[0052] The adhesion method may be the guide oil supply method, but for uniform adhesion to fibers with a fine total fineness, adhesion by a kiss roll (oiling roll) made of metal or ceramic is preferable. When the fiber is in a cake shape or a tow shape, it can be applied by immersing it in the mixed oil agent.

[0053] The adhesion rates of inorganic particles A and phosphate compound B to the fiber are not particularly limited as long as they can prevent fusion between fibers during solid-phase polymerization. When the adhesion rate of inorganic particles A is a wt% and the adhesion rate of phosphate compound B is b wt%, it is preferable to set the adhesion rate a of inorganic particles A to 0.01 wt% or more to obtain the effect of suppressing fusion by the inorganic particles. From the viewpoint of uniform adhesion, the upper limit of the adhesion rate a is preferably 10 wt% or less. Also, the adhesion rate b of the phosphate compound B is preferably 10 wt% or more, more preferably 15 wt% or more, and even more preferably 20 wt% or more. Note that from the viewpoints of adhesion spots in the fiber longitudinal direction and handling, the upper limit is preferably less than 40 wt%.

[0054] Note that the oil adhesion rate (a + b) of the solid-phase polymerization lubricant exceeds 10 wt%, but by performing solid-phase polymerization with a large amount of oil adhering in excess of 10 wt%, a high inhibitory effect on fiber fusion during solid-phase polymerization can be obtained. The higher the oil adhesion rate (a + b) of the solid-phase polymerization lubricant, the higher the fusion inhibitory effect, so the oil adhesion rate is preferably more than 15 wt%, and more preferably more than 20 wt%. On the other hand, from the viewpoint of suppressing adhesion spots in the longitudinal direction, the upper limit is preferably 40 wt% or less. Note that the oil adhesion rate (a + b) of the solid-phase polymerization lubricant to the fiber refers to the value of the oil adhesion rate obtained by the method described in the examples for the fiber after application of the solid-phase polymerization lubricant. Here, the adhesion rate a of the inorganic particles A and the adhesion rate b of the phosphate compound B refer to the values calculated by the following formula. Adhesion rate a of inorganic particles A = (a + b) × Ca / (Ca + Cb) Adhesion rate b of phosphate compound B = (a + b) × Cb / (Ca + Cb) Here, Ca refers to the concentration of inorganic particles A in the solid-phase polymerization lubricant, and Cb refers to the concentration of phosphate compound B in the solid-phase polymerization lubricant.

[0055] Also, regarding the adhesion rate a wt% of the inorganic particles A and the adhesion rate b wt% of the phosphate compound B, it is preferable that b / a ≥ 1. By setting the adhesion rate b of the phosphate compound B to be equal to or higher than the adhesion rate a of the inorganic particles A, the excellent detergency derived from the formation of condensed salts during solid-phase polymerization of the phosphate compound B becomes more prominent, and it is also preferable from the viewpoint of suppressing the fixation and detachment between the inorganic particles A and the fiber.

[0056] In the present invention, solid-phase polymerization is carried out after applying a solid-phase polymerization oil agent. As a result, the molecular weight increases, and the strength, elastic modulus, and elongation also increase. Solid-phase polymerization can be carried out in a cake shape, a column shape (for example, placed on a metal mesh or the like), or continuously as a thread between rollers, but it is preferably carried out in a package shape in which the fiber is wound around a core material from the viewpoint of simplifying the equipment and improving productivity.

[0057] Solid-phase polymerization can be carried out in an inert gas atmosphere such as nitrogen, in an active gas atmosphere containing oxygen such as air, or under reduced pressure, but it is preferably carried out in a nitrogen atmosphere for simplifying the equipment and preventing oxidation of the fiber or core material. At this time, the atmosphere for solid-phase polymerization is preferably a low-humidity gas with a dew point of -40°C or lower.

[0058] When the endothermic peak temperature of the liquid crystal polyester filament used for solid-phase polymerization is defined as Tm1 °C, the maximum temperature reached is preferably (Tm1 - 60) °C or higher. By setting such a high temperature near the melting point, solid-phase polymerization proceeds rapidly, and the strength of the liquid crystal polyester filament can be improved. Here, Tm1 generally refers to the melting point of the liquid crystal polyester filament, and in the present invention, it refers to the value obtained by the measurement method described in the examples. It is preferably that the maximum temperature reached is less than Tm1 °C to prevent fusion. Further, increasing the solid-phase polymerization temperature stepwise or continuously with respect to time can prevent fusion and improve the time efficiency of solid-phase polymerization, which is more preferable. In this case, since the melting point of the liquid crystal polyester filament increases as the solid-phase polymerization proceeds, the solid-phase polymerization temperature can be increased to about (Tm1 + 100) °C of the liquid crystal polyester filament before solid-phase polymerization. However, also in this case, it is preferable that the maximum temperature reached in solid-phase polymerization is (Tm1 - 60) °C or higher and less than Tm1 °C of the liquid crystal polyester filament after solid-phase polymerization from the viewpoint of increasing the solid-phase polymerization rate and preventing fusion.

[0059] The solid-phase polymerization time is preferably 5 hours or more, more preferably 10 hours or more, at the maximum temperature in order to sufficiently increase the molecular weight of the liquid crystal polyester filament, i.e., the strength, elastic modulus, and elongation. On the other hand, since the effect of increasing the strength, elastic modulus, and elongation is saturated with the passage of time, it is preferable to set the solid-phase polymerization time to 50 hours or less in order to increase productivity.

[0060] In the present invention, it is preferable to remove the solid-phase polymerization oil while running the liquid crystal polyester filaments after solid-phase polymerization. A known method can be used to remove the solid-phase polymerization oil, but it is preferable to use a liquid-gas mixed fluid spray nozzle after immersing the liquid crystal polyester filaments in a liquid to swell them.

[0061] The solid-state polymerization oil remaining on the fiber surface after solid-state polymerization accumulates on guides, reeds, and the fiber itself during the weaving process, which is a post-processing step of the fiber, generating debris called scum. If this scum gets mixed into the product, it can cause product defects or can hinder the shedding movement of the yarn, leading to yarn breakage. Therefore, in the production of liquid crystalline polyester filaments, it is important to wash off the solid-state polymerization oil after solid-state polymerization.

[0062] In particular, there is a growing demand for higher density weaving (higher mesh) and reduced gauze thickness to improve the performance of filters made of filaments, as well as an increased demand for higher opening ratios, and in order to achieve this, finer filament fineness is being required. In addition, as the density increases, the load and number of beatings on the filaments increases during weaving, and scum from solid-phase polymerization oil remaining on the fiber surface increases, resulting in more broken weave threads and more product defects (scum), and so there is a demand for stronger washing than ever before.

[0063] The packaged solid-phase polymerized yarn after the washing process can be unwound. However, in order to suppress fibrillation when peeling off the slight fusion caused by solid-phase polymerization, it is preferable to unwind the yarn in the direction perpendicular to the rotation axis (fiber winding direction) while rotating the solid-phase polymerization package, that is, to unwind it by so-called side-taking. As such an unwinding method, there are a method of actively driving at a constant rotational speed using a motor or the like, a method of adjusting the speed while controlling the rotational speed using a dancer roller, and a method of unwinding while pulling the fiber with an adjustable speed roller by placing the solid-phase polymerization package on a free roll.

[0064] The washing method of the solid-phase polymerized liquid crystal polyester filament is as follows: First, while running the solid-phase polymerized liquid crystal polyester filament, it is immersed in a liquid in which the solid-phase polymerization oil agent can be dissolved or dispersed. The method of immersing in the liquid may be a method of contacting with the liquid using a kiss roll, etc. However, the method of running the liquid crystal polyester filament in a bath filled with the liquid is preferable in that the amount of the liquid used can be reduced, scattering of the liquid to the surroundings can be prevented, and the contact time with the liquid can be lengthened.

[0065] The liquid used for washing by immersion is preferably water in order to reduce the environmental load. A higher temperature of the liquid can improve the removal efficiency, and it is preferably 30°C or higher, more preferably 40°C or higher. However, when the temperature is too high, the evaporation of the liquid becomes remarkable, so it is preferably the boiling point of the liquid - 20°C or lower, more preferably (boiling point - 30)°C or lower.

[0066] From the viewpoint of improving the washing efficiency, it is preferable to add a surfactant to the liquid used for washing. The addition amount of the surfactant is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.5% by weight, in order to enhance the removal efficiency and reduce the environmental load.

[0067] Furthermore, in order to improve the cleaning efficiency, it is preferable to apply vibration or a liquid flow to the liquid used for cleaning by immersion. In this case, there are methods such as ultrasonic vibration of the liquid, but from the viewpoints of equipment simplification and energy saving, it is preferable to apply a liquid flow. Methods of applying a liquid flow include methods such as stirring in a liquid bath and applying a liquid flow with a nozzle. Since it can be easily implemented by performing the supply when circulating the liquid bath with a nozzle, applying a liquid flow with a nozzle is preferable. Also, as a method of immersing the fiber in the liquid, a method of guiding the fiber into the bath using a guide or the like may be used. However, in order to suppress fibrillation of the solid-phase polymerization fiber due to contact resistance with the guide, slits are provided at both ends of the bath so that the fiber can pass through the bath through these slits, and it is preferable not to provide a thread guide in the bath.

[0068] Next, cleaning is performed using a mixed fluid spray nozzle of a liquid and a gas. By using a mixed fluid spray nozzle of a liquid and a gas, fine liquid particles are made to collide with the residue of the solid-phase polymerization oil agent on the fiber surface, and the residue of the solid-phase polymerization oil agent can be efficiently removed without applying an excessive load to the running yarn.

[0069] The running tension of the running yarn immediately after cleaning with a mixed spray nozzle of a liquid and a gas is preferably 1.0 cN or more and 20.0 cN or less. Setting it to 1.0 cN or more is preferable because the running state is stable. If it exceeds 20.0 cN, fibrils and fuzz are likely to occur due to rubbing against a guide or the like during the process, which is not preferable. More preferably, it is 5.0 cN or more and 15.0 cN or less.

[0070] The adhesion amount of the solid-phase polymerization oil agent on the liquid crystal polyester filament after cleaning is preferably 0.20% by weight or less, more preferably 0.10% by weight or less, and most preferably 0.07% by weight or less from the viewpoints of improving the process passability of the fiber and the fabric quality in high-order processing steps and weaving steps. Note that the adhesion amount of the solid-phase polymerization oil agent after cleaning refers to the value measured by the method for measuring the oil adhesion rate described in the examples for the fiber wound up immediately after the cleaning step.

[0071] In addition, in order to improve the abrasion resistance of the liquid crystal polyester filament, it is preferable to perform a high-temperature heat treatment at a temperature of Tm1 or higher after washing. Here, Tm1 refers to the value obtained by the measurement method described in the examples. Tm1 is the melting point of the liquid crystal polyester filament, but by performing a heat treatment on the liquid crystal polyester filament at a temperature higher than the melting point, the peak half-width at Tm1 becomes 15 °C or more, and by reducing the crystallinity and crystal perfection of the entire fiber, the abrasion resistance is greatly improved. Note that the heat treatment has an effect of improving the abrasion resistance for both monofilaments and multifilaments, but in the case of multifilaments, unevenness is likely to occur between single filaments, and the improvement in abrasion resistance, which is the effect of the heat treatment, is more remarkable in the case of monofilaments.

[0072] In terms of heat treatment, there is solid-phase polymerization of the liquid crystal polyester filament. In this case, if the treatment temperature is not below the melting point of the liquid crystal polyester filament, the fibers will fuse and break. In the case of solid-phase polymerization, since the melting point of the liquid crystal polyester filament increases with the treatment, the final solid-phase polymerization temperature may be higher than the melting point of the fiber before treatment. Even in that case, the treatment temperature is lower than the melting point of the liquid crystal polyester filament being treated, that is, the melting point of the liquid crystal polyester filament after heat treatment. That is, the high-temperature heat treatment referred to here does not involve solid-phase polymerization, but rather reduces the structural difference between the dense crystal part and the amorphous part formed by solid-phase polymerization, that is, it improves the abrasion resistance by reducing the crystallinity and crystal perfection.

[0073] In addition, there is heat drawing of the liquid crystal polyester filament as another heat treatment. Heat drawing tensions the fiber at a high temperature, and the fiber structure has a high orientation of molecular chains, increasing the strength and elastic modulus, while maintaining the crystallinity and crystal perfection, that is, ΔHm1 remains high and the peak half-width of Tm1 remains small. Therefore, it has a fiber structure with inferior abrasion resistance, which is different from the heat treatment of the present invention aimed at improving the abrasion resistance by reducing the crystallinity (decrease in ΔHm1) and crystal perfection (increase in peak half-width). Note that in the high-temperature heat treatment referred to in the present invention, since the crystallinity decreases, the strength and elastic modulus do not increase.

[0074] It is preferable to perform the high-temperature heat treatment while continuously running the liquid crystal polyester filament because it can prevent fusion between fibers and enhance the uniformity of the treatment. At this time, in order to prevent the generation of fibrils and perform uniform treatment, it is preferable to perform non-contact heat treatment. As heating means, there are atmosphere heating, radiation heating using lasers or infrared rays, etc. However, heating by a slit heater using a block or plate heater has both the effects of atmosphere heating and radiation heating, and is preferable because the stability of the treatment is enhanced. Also, the high-temperature heat treatment is desirably performed at a high temperature for a short time in order to sufficiently lower the crystallinity while preventing fiber breakage and relaxation of the molecular chain orientation.

[0075] The treatment temperature is preferably high in order to sufficiently lower the crystallinity and crystal perfection. It is preferably (Tm1 + 80) °C or higher of the liquid crystal polyester filament, and more preferably (Tm1 + 120) °C or higher of the liquid crystal polyester filament. Also, as the upper limit of the treatment temperature, it is the temperature at which the liquid crystal polyester filament melts, and it varies depending on the tension, speed, single fiber fineness, and treatment length, but is about (Tm1 + 300) °C.

[0076] The treatment time is preferably long in order to lower the crystallinity and crystal perfection. 0.01 seconds or more is preferable, 0.05 seconds or more is more preferable, and 0.1 seconds or more is even more preferable. Also, the upper limit of the treatment time is preferably 5.0 seconds or less, more preferably 3.0 seconds or less, and even more preferably 2.0 seconds or less in order to reduce the equipment load and because if the treatment time is long, the molecular chain orientation is relaxed and the strength and elastic modulus decrease.

[0077] The treatment speed depends on the treatment length, but the higher the speed, the more possible it is to perform high-temperature short-time treatment, the higher the effect of improving wear resistance, and the higher the productivity. Therefore, 100 m / min or more is preferable, 200 m / min or more is more preferable, and 300 m / min or more is even more preferable. The upper limit of the treatment speed is about 1000 m / min due to the running stability of the fiber.

[0078] The treatment length depends on the heating method. In the case of non-contact heating, in order to perform uniform treatment, 100 mm or more is preferable, 200 mm or more is more preferable, and 500 mm or more is even more preferable. Also, if the treatment length is excessively long, uneven treatment and fiber melting will occur due to yarn shaking inside the heater, so 3000 mm or less is preferable, 2000 mm or less is more preferable, and 1000 mm or less is even more preferable.

[0079] If the treatment tension is excessively high, melting due to heat is likely to occur. Also, when performing heat treatment under excessive tension, the decrease in crystallinity is small and the effect of improving abrasion resistance is low. Therefore, it is preferably as low as possible. If the tension is low, the running of the fiber becomes unstable and the treatment becomes non-uniform. Thus, 0.001 cN / dtex or more and 1.0 cN / dtex or less is preferable, 0.01 cN / dtex or more and 0.5 cN / dtex or less is more preferable, and 0.1 cN / dtex or more and 0.3 cN / dtex or less is even more preferable. To set the tension within a preferable range, the speeds of the fiber before and after the heat treatment are regulated by the first roller and the second roller respectively. When the speed difference between the rollers (stretch ratio = (second roller speed - first roller speed) / (second roller speed)) required for maintaining the tension is large, the heat treatment is in a form close to stretching, and the orientation and crystallinity of the fiber are maintained even after the heat treatment. Therefore, the stretch ratio is desirably -0.02 or more and 0.05 or less, and more preferably -0.01 or more and 0.03 or less.

[0080] Also, when the linearity of the liquid crystal polyester polymer is low, etc., the relaxation rate of the molecular chain orientation is fast, and in heat treatment, it may be difficult to keep the treatment temperature, treatment tension, and stretch ratio within a preferable range. In such a case, it is effective to use a multi-stage heater in heat treatment and create a temperature difference between the heater inlet and outlet. By setting the heater temperature at the inlet higher than that at the outlet and quickly preheating to a temperature just before the crystallinity of the fiber decreases, and then setting the temperature at the outlet to a temperature at which the crystallinity of the fiber decreases, it is possible to minimize the unstable and low-tension state in which the orientation structure of the fiber changes, prevent deterioration of operability, decrease the crystallinity, and improve the abrasion resistance. Also, even when sufficient heat treatment can be performed using a single-stage heater, by similarly creating a temperature difference between the heater inlet and outlet for high-temperature heat treatment, the yarn running property is improved, and further improvement in operability can be expected. Such heat treatment can be sufficiently carried out by a heater capable of two-stage temperature setting or by connecting two heaters in series. However, in order to minimize the heater heating time, a structure in which the fiber is cooled during the process is not desirable. Therefore, as a preferable type of heating device, a heat treatment device is cited in which a plurality of heaters with individually adjustable temperatures continuously heat the fiber without interruption within a single insulated heating box. As the temperature difference between the heaters at the inlet and outlet, it is preferable that the heater temperature at the outlet is 20°C or more lower than the heater temperature at the inlet, and more preferably 30°C or more lower. Note that the present invention does not limit the number of stages of heater temperature setting, the number of heaters, the method of connecting the heaters, etc.

[0081] Note that the above-described washing and heat treatment are preferably carried out continuously in a single process without once winding up in the middle. Particularly when winding up the liquid crystal polyester filament after solid-phase polymerization, fibrillation of the fiber occurs due to rubbing at the winder, etc. Therefore, after washing, it is preferable to subsequently perform heat treatment to enhance the abrasion resistance.

[0082] Also, from the perspective of improving process passability in subsequent processes such as washing and heat treatment, it is preferable to apply a finishing oil agent. As the finishing oil agent, a finishing oil agent generally used for polyester fibers can be preferably applied.

[0083] Regarding the adhesion rate of the finishing oil agent, 0.1% by weight or more is preferable based on the fiber weight for improving wear resistance by enhancing surface smoothness and improving process passability. Since the effect increases with more oil content, 0.3% by weight or more is more preferable. However, if the oil content is too high, the adhesion force between fibers increases, which not only inhibits process passability but also generates process stains. Therefore, 2.0% by weight or less and 1.5% by weight or less are preferable. The adhesion rate of the finishing oil agent referred to here means the value obtained by subtracting the adhesion rate value of the residual solid-phase polymerization oil agent of the fiber from the oil content adhesion rate value obtained by the method described in the examples for the fiber after applying the finishing oil agent.

[0084] In the above manner, the liquid crystal polyester filament of the present invention can be obtained. The liquid crystal polyester filament obtained in the present invention desirably has a strength of 10.0 to 20.0 cN / dtex. More desirably, the strength is 10.0 cN / dtex or more. The liquid crystal polyester filament obtained in the present invention desirably has an elongation of 1.5 to 4.5%. More desirably, it is 3.5% or less. The liquid crystal polyester filament obtained in the present invention desirably has an elastic modulus of 650 to 850 cN / dtex. More desirably, it is 830 cN / dtex or less. Also, the liquid crystal polyester filament of the present invention can be made into multifilament according to the application and is not limited to monofilament. Further, the liquid crystal polyester filament of the present invention desirably has a fine fineness, 10 T or less, desirably 8 T or less, and more desirably 6 T or less, but can also have a fineness of 10 T or more according to the application, and the fineness is not limited.

Examples

[0085] Hereinafter, the liquid crystal polyester filaments of the present invention will be specifically described with reference to examples. The measured values in the examples were measured by the following methods.

[0086] A. Denier The fiber was reeled for 300 m by a reeler, the weight (g) was multiplied by 100 / 3, and 10 measurements were taken for each level. The average value was taken as the denier (dtex).

[0087] B. Strength, elongation, modulus of elasticity In accordance with the method described in JIS L1013:1999, under the conditions of a sample length of 500 mm and a tensile speed of 50 mm / min, using a Tensilon UTM-100 manufactured by Orientec Co., Ltd., 20 measurements were continuously taken in the fiber longitudinal direction for each level, and the average values were taken as the strength (cN / dtex), elongation (%), and modulus of elasticity (cN / dtex). The modulus of elasticity refers to the initial tensile resistance.

[0088] C. Oil adhesion rate 1.0 ± 0.1 g of the fiber was sampled, and the weight after drying at 60°C for 10 minutes was measured (W0). The fiber was immersed in a solution in which sodium dodecylbenzenesulfonate was added at 2.0% by weight based on the fiber weight to water 100 times or more the fiber weight, ultrasonically cleaned at room temperature for more than 20 minutes, the washed fiber was washed with water, and the weight (W1) after drying at 60°C for 10 minutes was measured. The oil adhesion rate was calculated by the following formula: (oil adhesion rate (% by weight)) = (W0 - W1) × 100 / W1.

[0089] D. Tm1 of the liquid crystal polyester filament, peak half-width at Tm1, heat of fusion ΔHm1, melting point (Tm2) of the liquid crystal polyester polymer Differential calorimetry was performed using a DSC2920 manufactured by TA Instruments. When measured under the temperature rising condition of 20°C / min from 50°C, the temperature of the endothermic peak observed was taken as Tm1 °C, and the peak half-width (°C) and heat of fusion ΔHm1 (J / g) at Tm1 were measured.

[0090] Regarding the liquid crystal polyester polymer shown in the reference example, after observing Tm1, it was held at a temperature of (Tm1 + 20)°C for 5 minutes, then once cooled to 50°C under a temperature decrease condition of 20°C / min, and when measured again under a temperature increase condition of 20°C / min, the endothermic peak observed was defined as Tm2, and Tm2 was taken as the melting point of the polymer.

[0091] E. Weight-average molecular weight (molecular weight) in terms of polystyrene Using a mixed solvent of pentafluorophenol / chloroform = 35 / 65 (weight ratio) as the solvent, the liquid crystal polyester was dissolved so that the concentration was 0.04 to 0.08 wt / vol% to prepare a sample for GPC measurement. If there were insoluble substances even after standing at room temperature for 24 hours, it was allowed to stand for another 24 hours, and the supernatant was used as the sample. This was measured using a GPC measuring device manufactured by Waters, and the weight-average molecular weight Mw was determined by conversion to polystyrene. Columns: Two Shodex K-806M and one K-802 Detector: Differential refractive index detector RI Temperature: 23 ± 2°C Flow rate: 0.8 mL / min Injection volume: 200 μL F. Abrasion resistance Both ends of the fiber applied at a contact angle of 10° to a ceramic rod guide with a diameter of 4 mm (rod guide manufactured by Yuasa Yarn Route Industry Co., Ltd., material YM-99C, hardness Hv1800) were gripped by a stroke device (yarn friction holding force tester manufactured by Toyo Seiki Seisakusho Co., Ltd.). While applying a stress of 0.88 cN / dtex to the fiber, the fiber was rubbed at a stroke length of 30 mm and a stroke speed of 75 m / min. After that, the number of fibril generations of the fiber within the stroke length was counted. The total number of fibril generations of 10 samples was summed up, and the abrasion resistance was evaluated according to the following criteria. 〇: The number of fibril generations is 5 or less, with excellent abrasion resistance and no hairiness generated during weaving. △: The number of fibril generations is 6 or more and 10 or less. Hairiness is generated during weaving, but in small amounts and not a fatal problem. ×: The number of fibril generations is 11 or more, and hairiness is frequent during weaving.

[0092] G. Heater yarn shaking The yarn shaking of the heater during yarn running was evaluated according to the following criteria. 〇: No yarn shaking occurs at all. △: Yarn shaking occurs, but it is possible to wind the yarn. ×: Intense yarn shaking occurs, making it impossible to wind the yarn or frequent yarn breakage occurs.

[0093] Example 1 870 parts by weight of p-hydroxybenzoic acid, 327 parts by weight of 4,4'-dihydroxybiphenyl, 89 parts by weight of hydroquinone, 292 parts by weight of terephthalic acid, 157 parts by weight of isophthalic acid, and 1460 parts by weight of acetic anhydride (1.10 equivalents in total of phenolic hydroxyl groups) were charged into a 5 L reaction vessel equipped with a stirring blade and a distillation tube, and the temperature was raised from room temperature to 145 °C in 30 minutes while stirring under a nitrogen gas atmosphere, and then reacted at 145 °C for 2 hours. Then, the temperature was raised to 335 °C in 4 hours.

[0094] The polymerization temperature was maintained at 335 °C, the pressure was reduced to 133 Pa in 1.5 hours, and the reaction was continued for another 40 minutes. When the torque reached 28 kgcm, the polycondensation was completed. Next, the inside of the reaction vessel was pressurized to 0.1 MPa, and the polymer was discharged as a strand through a die having one circular discharge port with a diameter of 10 mm and pelletized by a cutter. The composition, melting point, and molecular weight of the obtained liquid crystal polyester are as shown in Table 1.

[0095]

Table 1

[0096] After vacuum drying the above liquid crystal polyester at 160°C for 12 hours, it was melted at 330°C using a φ15 mm single-screw extruder manufactured by Osaka Seiki Kogyo Co., Ltd. Then, it was passed through a pipe at a spinning temperature of 340°C, and the polymer was supplied to a spinneret pack while being metered by a gear pump so that the output per orifice was 1.7 g / min. In the spinneret pack, the polymer was filtered using a metal nonwoven fabric filter, and four filaments were discharged from an orifice with an L / D of 2.0. The discharged polymer passed through a 40-mm heat-insulating region and was then cooled and solidified from the outside of the filaments by annular cooling air at 25°C. Thereafter, a spinning finish mainly composed of a fatty acid ester compound was applied, and all the filaments were taken up one by one as monofilaments onto a first godet roll at 1000 m / min. After passing through a second godet roll at the same speed, it was wound into the shape of a package using a spindle traverse type package winder (without contact control contacting the package) via a dancer arm. The spinning draft was 25, and no thread breakage occurred during winding, and the yarn manufacturing property was good. The single fiber fineness of the obtained monofilament was 6.9 dtex, the strength was 7.0 cN / dtex, the elongation was 1.5%, and the elastic modulus was 606 cN / dtex. Also, the filter pressure at the start of spinning was 7.0 MPa, the increase in filter pressure was 0.09 MPa / hr, and spinning could be carried out with good operability for 8 days or more without thread breakage until reaching the upper limit of the filter pressure of 25 MPa.

[0097] Using a winding device (without a touch roll, 8.7 windings, taper angle 45°) in which an electric cylinder RCP-SAC3 manufactured by IAI is connected to the cam box part (traverse device) of the Precision Winders SSP-MV manufactured by Kanzaki Manufacturing Co., Ltd. via a link mechanism, rewinding was performed from this spun fiber package. At this time, the outer diameter of the package was detected with a displacement sensor IL-065 manufactured by Keyence, and based on the detected package diameter, the electric cylinder was driven so that the free length would be constant to move the cam box part. The unwinding of the spun fiber was performed in the longitudinal direction (perpendicular to the fiber winding direction), and lubrication was carried out with a solid-phase polymerization lubricant in which 1.0% by weight of talc, which is talc as the inorganic particles (A), was dispersed in an aqueous solution containing 10.0% by weight of the phosphate compound (B1) represented by the following chemical formula (4) as the phosphate compound (B) using an oiling roller (a stainless steel roll with a matte finish). The oil adhesion rate (a + b) of the solid-phase polymerization lubricant to the monofilament after rewinding was 21.5% by weight.

[0098] [Chemical formula]

[0099] Next, solid-phase polymerization of the rewound package was carried out. For the solid-phase polymerization, a sealed oven was used, and the temperature was raised from room temperature to 240 °C in about 30 minutes, held at 240 °C for 3 hours, then the temperature was raised to 290 °C at 4 °C / hour and held for 15 hours to carry out the solid-phase polymerization. The atmosphere was supplied with dehumidified nitrogen at a flow rate of 20 NL / min and exhausted from the exhaust port so that the inside of the chamber would not be pressurized.

[0100] The fineness of the monofilament after solid-phase polymerization obtained was 6.3 dtex, the strength was 25.4 cN / dtex, the elongation was 2.7%, and the elastic modulus was 1138 cN / dtex. Compared with the monofilament before solid-phase polymerization, the strength, elongation, and elastic modulus were improved, and it was confirmed that the solid-phase polymerization had progressed. The Tm1 of the monofilament after solid-phase polymerization obtained was 315 °C, the ΔHm1 was 8.8 J / g, and the peak half-width at Tm1 was 9.5 °C.

[0101] Subsequently, the fibers were unwound from the package after solid-phase polymerization, and washing for removing the solid-phase polymerization lubricant was carried out. The package after solid-phase polymerization was mounted on a free-roll creel (having a shaft and bearings, and the outer layer can rotate freely, without brakes and drive sources), and the yarn was drawn out laterally (fiber circumferential direction) from here. Continuously, the fibers were passed through a bath (without a guide inside that contacts the fibers) with a bath length of 150 cm (contact length 150 cm) having slits at both ends, and the solid-phase polymerization lubricant was washed away. As the cleaning liquid, warm water at 50 °C containing a nonionic-anionic surfactant was used. Thereafter, cleaning was performed using a two-fluid air atomizing nozzle manufactured by Spraying Systems Co., Ltd. Two spray nozzles with a pore diameter of 1.5 mm were used, with a water pressure of 0.20 MPa, a compressed air pressure of 0.20 MPa, and the distance between the spray nozzle injection port and the running yarn being 15.0 mm. The amount of water used was 100 mL / min per nozzle, and the amount of compressed air used was 35 L / min per nozzle. The fibers after washing were passed through a bearing roller guide and then through a first roller with a separate roller. Since the creel is a free roll, by applying tension to the fibers with this roller, unwinding from the solid-phase polymerization package is performed, and the fibers are made to run.

[0102] The fibers that passed through the roller were made to travel between slit heaters that were 1 m in length and had separately adjustable temperatures at the inlet and outlet, with the inlet heated to 460°C and the outlet to 440°C, and high-temperature non-contact heat treatment was performed. No guides were provided inside the slit heaters, and the heater and the fibers were also kept non-contact. The fibers after passing through the heater were passed through a second roller with a separate roller. When the speed of the second roller was set at 400 m / min and the speed of the first roller was changed so that there was no thread sway, thread sway did not occur when the speed of the first roller was 396 m / min or less, so the first roller was set at 396 m / min (stretch ratio 1.0%). The fibers that passed through the second roller were applied with a finishing oil agent mainly composed of a fatty acid ester compound by a ceramic oiling roller and wound up by a spindle traverse type package winder via a dancer arm. The physical properties of the obtained monofilament were as shown in Table 2: strength 18.8 cN / dtex, elongation 2.9%, and elastic modulus 814 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 4, and the abrasion resistance was good.

[0103]

Table 2

[0104] Example 2 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 470°C and the ambient temperature at the outlet was 440°C. When the speed of the first roller was 392 m / min (stretch ratio 2.0%), no thread sway occurred in the heat treatment heater. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 2: strength 18.6 cN / dtex, elongation 2.9%, and elastic modulus 798 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 3, and the abrasion resistance was good.

[0105] Example 3 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 480 °C and the ambient temperature at the outlet was 440 °C. When the speed of the first roller was 388 m / min (stretch ratio 3.0%), although there was some thread vibration in the heat treatment heater, there was no problem with the running property. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 2: strength 18.5 cN / dtex, elongation 3.0%, and elastic modulus 763 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 4, and the abrasion resistance was good.

[0106] Example 4 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 465 °C and the ambient temperature at the outlet was 435 °C. When the speed of the first roller was 396 m / min (stretch ratio 1.0%), there was no thread vibration in the heat treatment heater. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 2: strength 18.9 cN / dtex, elongation 2.9%, and elastic modulus 841 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 7.

[0107] Example 5 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 470 °C and the ambient temperature at the outlet was 430 °C. When the speed of the first roller was 398 m / min (stretch ratio 0.5%), there was no thread vibration in the heat treatment heater. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 2: strength 19.1 cN / dtex, elongation 2.8%, and elastic modulus 866 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 8.

[0108] Example 6 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 440°C and the ambient temperature at the outlet was 460°C. When the speed of the first roller was 388 m / min (stretch ratio 3.0%), although some thread shaking occurred in the heat treatment heater, there was no problem with the running property. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 3: strength 18.4 cN / dtex, elongation 3.0%, and elastic modulus 782 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 7.

[0109] Example 7 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was changed so that the ambient temperature at the inlet was 455°C and the ambient temperature at the outlet was 445°C. When the speed of the first roller was 392 m / min (stretch ratio 2.0%), although some thread shaking occurred in the heat treatment heater, there was no problem with the running property. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 3: strength 18.8 cN / dtex, elongation 2.8%, and elastic modulus 803 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 6.

[0110] Comparative Example 1 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was the same 450°C at both the inlet and the outlet. When the speed of the first roller was 392 m / min (stretch ratio 2.0%), there was significant thread shaking in the heat treatment heater and frequent thread breakage occurred. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 3: strength 18.7 cN / dtex, elongation 2.8%, and elastic modulus 797 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 5.

[0111]

Table 3

[0112] Comparative Example 2 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was the same 460 °C at the inlet and outlet. When the speed of the first roller was 386 m / min (stretch ratio 3.5%), there was significant thread vibration in the heat treatment heater and frequent thread breakage occurred. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 3: strength 18.5 cN / dtex, elongation 3.1%, and modulus of elasticity 757 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 2.

[0113] Comparative Example 3 A liquid crystal polyester monofilament was obtained in the same manner as in Example 1, except that the temperature of the heat treatment heater was the same 440 °C at the inlet and outlet. When the speed of the first roller was 398 m / min (stretch ratio 0.5%), there was no thread vibration in the heat treatment heater. The physical properties of the liquid crystal polyester monofilament obtained by the heat treatment were as shown in Table 3: strength 18.8 cN / dtex, elongation 2.7%, and modulus of elasticity 872 cN / dtex. Also, when the abrasion resistance was investigated by a rubbing test, the number of fibrils was 15.

Claims

1. After subjecting a package of liquid crystal polyester filaments to solid-phase polymerization, while unwinding the solid-phase polymerized liquid crystal polyester filaments from the package, when heat-treating without winding up once, A method for producing liquid crystal polyester filaments in which the atmospheric temperatures at the inlet and outlet of the heat treatment step are different.

2. The atmospheric temperature at the inlet of the heat treatment step is 20°C or higher than the atmospheric temperature at the outlet, and the method for producing liquid crystal polyester filaments according to Claim 1 is characterized in that.

3. The atmospheric temperature at the outlet of the heat treatment step is (The endothermic peak temperature Tm of the liquid crystal polyester filament after solid-phase polymerization １ + 80 ° C) or higher, and the method for producing a liquid crystal polyester monofilament according to claim 1 or 2.

Images