JP2021155887A - Liquid crystal polyester fiber and its manufacturing method - Google Patents

Abstract

[Problem] To provide a long liquid crystal polyester fiber with small variation in strength over its entire length. [Solution] The liquid crystal polyester fiber is a continuous fiber weighing 10 kg or more, the entire length of the continuous fiber is divided into 50 equal parts in the longitudinal direction, and the average value (A1) obtained from the strength measurement data of the 50 points is 18 cN/dtex or more, and the strength variation calculated from the average value (A1) and standard deviation (σ1) obtained from the strength measurement data according to the following formula is 8.0% or less. Strength variation = (σ1/A1) x 100 [Selected figure] None

Description

The present invention relates to continuous liquid crystal polyester fibers and a method for producing the same.

Conventionally, it is known that excellent fibers having a high strength of 18 cN / dtex or more can be obtained by melt-spinning a liquid crystal polyester resin and heat-treating the obtained spun yarn. For example, in Patent Document 1 (Japanese Patent Publication No. 55-20008), a melt-molded article formed from a synthetic linear polymer capable of forming an anisotropic melt is heat-treated to improve its strength by at least 50%. A powerful improvement method for the molded article is disclosed.

In Patent Document 2 (Japanese Unexamined Patent Publication No. 1-92408), an aromatic polyester capable of forming an anisotropic melt is prepared at a temperature higher than the flow temperature of the polymer by 10 ° C. or more and a shear rate of 10 ³ sec ^{−. The} fibers are spun from a nozzle so as to be 1 or more, and the spun fibers are heat-treated in an inert atmosphere at a temperature equal to or lower than the flow temperature of the fibers for a time in which the strength of the fibers does not increase by 50% or more, and then under an active atmosphere. Discloses a method for producing an aromatic polyester fiber, which comprises heat-treating for a time to further increase its strength by 50% or more.

Patent Document 3 (Japanese Unexamined Patent Publication No. 2013-133575) discloses a liquid crystal polyester multifilament for splitting, characterized in that the degree of fusion between single fibers (F) is 1 ≦ F ≦ 5. In the present invention, it is described that it is preferable to heat-treat (solid-phase polymerization) the fibers obtained by melt spinning in a package form from the viewpoint of improving productivity.

Such high-strength liquid crystal polyester fibers take advantage of their high strength and low water absorption compared to other types of high-strength fibers such as aramid fibers, and are used for general industrial materials such as ropes, cords, slings, and submarine telegraphs. Widely used for tension members of cables and optical cables.

Many of these applications have a long total distance. For example, when used for marine ropes and submarine cables, the deepest point in the deep sea is about 11,000 m, and the laying distance of submarine cables for information and communication is more than 30 km in the Dover Strait and several thousand km in the Atlantic Ocean and the Pacific Ocean. , The raw material fiber material with a total length longer than these straight distances, considering that the tension members used in the cable may be processed into a spiral shape, the deflection during use, the undulations of the seabed, etc. Is required. At present, these marine ropes and submarine cables are operated by adding short textile materials and providing relay points.

Special Publication No. 55-20008 Japanese Unexamined Patent Publication No. 1-92408 Japanese Unexamined Patent Publication No. 2013-133575

However, in such a long application, when connecting fiber materials to the desired length, a structure for connecting end points such as knots, adhesive points, and joint parts is required, and the weight and size of only the relevant parts are required. It is not preferable because it becomes large and it becomes easy to break in tension. Further, even if the product is used for a product shorter than the raw material fiber material, the long length is advantageous in the process of continuously manufacturing the product, and in the case of the short fiber, the manufacturing apparatus is stopped or decelerated each time the fiber end appears. As a result, the work of switching the raw material fiber material to the next lot occurs frequently, resulting in high manufacturing cost and low production efficiency.

Therefore, in long-term applications, if the raw material fiber material with a distance equivalent to the total length can be continuously supplied, it becomes unnecessary to relay such a discontinuous structure, and the production of the target object and the operation of the raw material fiber material make a leap. It is thought that the efficiency will be improved. Further, even if the product is used for a shorter period of time than the raw material fiber material, if a longer fiber material can be used, the number of operations for switching lots of the fiber material can be reduced in the process of continuously manufacturing the product. Therefore, it leads to reduction of manufacturing cost and improvement of production efficiency.

However, with the conventional method for producing liquid crystal polyester fibers, it has been difficult to produce continuous long fibers having more uniform physical properties over the entire length in the longitudinal direction of the fibers when the amount of fibers is large. That is, the liquid crystal polyester fiber is first melt-spun as a low-strength (for example, 10 cN / dtex or less) raw yarn using the liquid crystal polyester resin as a raw material, and then heat-treated (this is called solid phase polymerization) to have high strength. (For example, 18 cN / dtex or more) is exhibited, but in solid phase polymerization, a batch method is generally used in which a fiber package in which a spinning yarn is wound on a perforated bobbin at a predetermined winding density is heat-treated in a heat treatment furnace. Has been done. Since long products generally have a large weight, when solid-phase polymerization is performed by a batch method, if the weight of the fibers wound around the bobbin increases, the size of the package in the thickness direction or height direction of the bobbin increases. , The inner and outer layers of heat and airflow become uneven and the height becomes uneven. As a result, the degree of improvement in the mechanical properties also varies, and it becomes difficult to obtain a heat-treated yarn having no variation in the mechanical properties.

In Patent Documents 1 to 3, solid-phase polymerization is performed by a batch method in a state of being wound around a bobbin, and the fiber weight of the fiber package used for solid-phase polymerization is 6 kg in Patent Document 2, and in Patent Document 3, It is in the range of 1.0 kg to 6.0 kg, and in none of the documents, solid-phase polymerization is performed on fibers having a high weight of 10 kg or more. Therefore, the current situation is that liquid crystal polyester fibers having a long length and a small variation in strength over the entire length have not yet been obtained.

Therefore, an object of the present invention is to provide a liquid crystal polyester fiber which is long and has a small strength variation over its entire length, and a method for producing the same.

As a result of diligent studies to achieve the above object, the inventors of the present invention carry the spun yarn of the liquid crystal polyester fiber at a specific elongation ratio, perform continuous heat treatment, and solid-phase polymerize the fiber. Since the heat treatment can be performed in a more uniform environment in the longitudinal direction, it has been found that the strength variation can be suppressed over the entire length of the fiber even if the fiber is heavy, and the present invention has been completed.

That is, the present invention can be configured in the following aspects.
[Aspect 1]
It is a continuous fiber having a weight of 10 kg or more, the total length of the continuous fiber is divided into 50 equal parts in the longitudinal direction, and the average value (A ₁ ) obtained from the strength measurement data of these 50 points is 18 cN / dtex or more (preferably 20 cN /). It is dtex or more, more preferably 23 cN / dtex or more), and the intensity _{variation calculated according to the following formula based on the average value (A 1} ) and standard deviation (σ ₁ ) obtained from the intensity measurement data is 8.0% or less (). A liquid crystal polyester fiber, preferably 5.0% or less, more preferably 3.0% or less).
Strength variation = (σ ₁ / A ₁ ) x 100
[Aspect 2]
The liquid crystal polyester fiber according to the first aspect, wherein the total fineness is 220 dtex or more (preferably 500 to 50,000 dtex, more preferably 1000 to 30,000 dtex).
[Aspect 3]
A higher-order processed product using at least a part of the liquid crystal polyester fiber according to the first or second aspect.
[Aspect 4]
The method for producing a liquid crystal polyester fiber according to the first or second aspect.
At least a step of heat-treating the spun yarn of the liquid crystal polyester fiber is included, and in the heat treatment step, the spun yarn may have an elongation ratio of 1.00 to 1.200 times (preferably 1.001 to 1.150 times). A method for producing a liquid crystal polyester fiber, which carries out heat treatment by transporting the fiber at a speed of 1.002 to 1.100 times, more preferably 1.003 to 1.050 times).
[Aspect 5]
A method for producing a liquid crystal polyester fiber according to the fourth aspect, wherein the strength ratio before and after the heat treatment is 1.5 times or more (preferably 1.8 times or more, more preferably 2.0 times or more).
[Aspect 6]
A method for producing a liquid crystal polyester fiber according to the production method according to the fourth or fifth aspect, wherein in the heat treatment step, the heat treatment is performed while transporting the spun yarn in a roll-to-roll manner.

According to the liquid crystal polyester fiber of the present invention, although it is a heavy long product, the variation is small over the entire length, so that it can be suitably used for long applications, and processing using the liquid crystal polyester fiber. The production efficiency of the product can be improved.

Further, according to the production method of the present invention, it is possible to efficiently produce a liquid crystal polyester fiber which is a long product having a high weight and has a small variation in strength over the entire length.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description purposes only and should not be used to define the scope of the invention. The scope of the present invention is determined by the appended claims.
It is the process schematic in the production of the liquid crystal polyester fiber of Example 1. FIG.

[Liquid crystal polyester fiber]
The liquid crystal polyester fiber of the present invention is composed of liquid crystal polyester. The liquid crystal polyester is composed of a repeating structural unit derived from, for example, an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, etc., and as long as the effects of the present invention are not impaired, the aromatic diol, the aromatic dicarboxylic acid, the aromatic The structural unit derived from the hydroxycarboxylic acid is not particularly limited in terms of its chemical composition. Further, the liquid crystal polyester may contain a structural unit derived from an aromatic diamine, an aromatic hydroxyamine or an aromatic aminocarboxylic acid as long as the effect of the present invention is not impaired. For example, as a preferable structural unit, examples shown in Table 1 can be mentioned.

In the structural unit of Table 1, m is an integer of 0 to 2, and Y in the formula is independently a hydrogen atom and a halogen atom (for example, a fluorine atom, in the range of 1 to the maximum number of substitutables, respectively. Chlorine atom, bromine atom, iodine atom, etc.), alkyl group (for example, alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, isopropyl group, t-butyl group, etc.), alkoxy group (for example, methoxy group, Ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), aralkyl group (eg, benzyl group (phenylmethyl group), phenethyl group (phenylethyl group), etc.), Examples thereof include an aryloxy group (for example, a phenoxy group) and an aralkyloxy group (for example, a benzyloxy group).

More preferable structural units include the structural units described in Examples (1) to (18) shown in Tables 2, 3 and 4 below. When the structural unit in the formula is a structural unit capable of exhibiting a plurality of structures, two or more such structural units may be combined and used as the structural unit constituting the polymer.

In the structural units of Tables 2, 3 and 4, n is an integer of 1 or 2, and the respective structural units n = 1 and n = 2 may exist alone or in combination, and Y ₁ and Y may exist. ₂ are independently hydrogen atom, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (for example, methyl group, ethyl group, isopropyl group, t-butyl group, etc.). Alkyl groups with 1 to 4 carbon atoms, alkoxy groups (eg, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl groups (eg, phenyl group, naphthyl group, etc.), aralkyl groups (eg, aralkyl groups). , A benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group, etc.), an aryloxy group (for example, a phenoxy group, etc.), an aralkyloxy group (for example, a benzyloxy group, etc.) and the like. Of these, a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group is preferable.

Further, as Z, a substituent represented by the following formula can be mentioned.

The liquid crystal polyester may preferably be a combination having a naphthalene skeleton as a constituent unit. It is particularly preferable to include both the structural unit (A) derived from hydroxybenzoic acid and the structural unit (B) derived from hydroxynaphthoic acid. For example, the constituent unit (A) includes the following formula (A), and the constituent unit (B) includes the following formula (B). From the viewpoint of improving melt moldability, the constituent unit (A) and the constituent unit (A) are configured. The ratio of the unit (B) may be preferably in the range of 9/1 to 1/1, more preferably 7/1 to 1/1, and even more preferably 5/1 to 1/1.

Further, the total of the constituent units of (A) and (B) may be, for example, 65 mol% or more, more preferably 70 mol% or more, and further preferably 80 mol% with respect to all the constituent units. It may be% or more. Among the polymers, liquid crystal polyester in which the constituent unit of (B) is 4 to 45 mol% is particularly preferable.

Further, the constituent unit of (A), that is, the constituent unit derived from 4-hydroxybenzoic acid may be contained in an amount of 50 mol% or more, preferably 53 mol% or more, and more preferably 60 mol% or more. good. The upper limit of the content of the constituent unit derived from 4-hydroxybenzoic acid in the liquid crystal polyester is not particularly limited, but may be, for example, 90 mol% or less, preferably 88 mol% or less, and more preferably 85 mol% or less. It may be as follows.

Further, the liquid crystal polyester may contain a structural unit derived from 4-hydroxybenzoic acid as an aromatic hydroxycarboxylic acid, and may contain a structural unit derived from an aromatic dicarboxylic acid and a structural unit derived from an aromatic diol. For example, at least one selected from the group consisting of the following formula (C) and the following formula (D) may be used as the structural unit derived from the aromatic dicarboxylic acid, and the following formula may be used as the structural unit derived from the aromatic diol. At least one selected from the group consisting of (E) and the following formula (F) may be used. Preferably, the structural unit (A) derived from 4-hydroxybenzoic acid (the above formula (A)), the structural unit (C) derived from terephthalic acid as an aromatic dicarboxylic acid (the following formula (C)), and isophthalic acid A liquid crystal polyester containing a structural unit (D) derived from an acid (formula (D) below) and a structural unit (E) derived from 4,4'-dihydroxybiphenyl as an aromatic diol (formula (E) below). Constituent unit (A) derived from 4-hydroxybenzoic acid (formula (A) above), constituent unit (C) derived from terephthalic acid as an aromatic dicarboxylic acid (formula (C) below), and derived from isophthalic acid. The structural unit (D) (the following formula (D)), the structural unit (E) derived from 4,4'-dihydroxybiphenyl as an aromatic diol (the following formula (E)), and the structural unit derived from hydroquinone (the following formula (E)). It may be a liquid crystal polyester or the like containing F) (the following formula (F)).

Further, the liquid crystal polyester contains a structural unit derived from hydroxynaphthoic acid containing a naphthalene skeleton as an aromatic hydroxycarboxylic acid, and may contain a structural unit derived from an aromatic dicarboxylic acid and a structural unit derived from an aromatic diol. good. Preferably, the structural unit (B) derived from 6-hydroxy-2-naphthoic acid (the above formula (B)) and the structural unit (C) derived from terephthalic acid as an aromatic dicarboxylic acid (the following formula (C)). A liquid crystal containing a structural unit (G) derived from 2,6-naphthalenedicarboxylic acid (the following formula (G)) and a structural unit (F) derived from hydroquinone as an aromatic diol (the following formula (F)). It may be polyester or the like.

The melting point of the liquid crystal polyester preferably used in the present invention (hereinafter, _{may be referred to as Mp 0} ) is preferably in the range of 250 to 380 ° C., more preferably 255 to 370 ° C., still more preferably 260 to 360 ° C. , Even more preferably 260-330 ° C. The melting point referred to here is the main absorption peak temperature measured and observed by a differential scanning calorimeter (DSC; "TA3000" manufactured by METTLER TEPCO) in accordance with the JIS K 7121 test method. Specifically, after taking 10 to 20 mg of a sample in the DSC apparatus and encapsulating it in an aluminum pan, 100 mL / min of nitrogen is flowed as a carrier gas, and the endothermic peak when the temperature is raised at 20 ° C./min is measured. .. If a clear peak does not appear at 1st run in the DSC measurement depending on the type of polymer, the temperature is raised to a temperature 50 ° C. higher than the expected flow temperature at 50 ° C./min, and after complete melting at that temperature for 3 minutes. It is advisable to lower the temperature to 50 ° C. at a temperature lowering rate of 80 ° C./min, and then measure the endothermic peak at a heating rate of 20 ° C./min.

A thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyetheretherketone, or fluororesin is added to the liquid crystal polyester as long as the effects of the present invention are not impaired. May be good. It may also contain various additives such as titanium oxide, kaolin, silica, barium oxide and other inorganic substances, carbon black, colorants such as dyes and pigments, antioxidants, ultraviolet absorbers and light stabilizers.

The liquid crystal polyester fiber of the present invention is a continuous fiber having a fiber weight of 10 kg or more. The continuous fiber refers to a monofilament or a multifilament in which the length corresponding to the weight of the fiber is continuously continuous. In the case of a multifilament, it is sufficient that the fiber bundle is continuous without a break. In the present invention, for fibers that are continuous by joining treatment such as knot treatment, splice treatment, end loop treatment, entanglement treatment, heat fusion treatment, adhesive, adhesive tape, and joining parts, the treated portion of the treated portion. The front and back are not continuous fibers. The length of the fiber varies depending on the total fineness, but the size of the package in the thickness direction or the height direction of the bobbin when wound around the bobbin varies depending on the weight rather than the length of the fiber. Therefore, when solid-phase polymerization of high-weight fibers is performed by a batch method, the size of the package in the thickness direction or height direction of the bobbin becomes large, which causes unevenness in the inner and outer layers of heat and airflow and unevenness in the height direction. , There are variations in the degree of improvement in mechanical properties. Therefore, by the manufacturing method described later, it is possible to reduce the strength variation over the entire length of the continuous fiber even if the weight is high. The liquid crystal polyester fiber of the present invention may have a fiber weight of preferably 12 kg or more, more preferably 15 kg or more, still more preferably 25 kg or more, from the viewpoint of improving productivity in subsequent product processing. The upper limit of the fiber weight is not particularly limited, but may be, for example, 100 kg or less, preferably 50 kg or less.

The liquid crystal polyester fiber of the present invention has a strength of 18 cN / dtex or more. Further, from the viewpoint of improving the mechanical strength of general industrial materials and high-order processed products such as tension members of submarine telegraph cables and optical cables, the strength is preferably 20 cN / dtex or more, more preferably 23 cN / dtex or more. You may. The upper limit of the strength is not particularly limited, but for example, the value that can be reached by the present invention is about 30 cN / dtex. _{In the present invention, the strength of the liquid crystal polyester fiber means the tensile strength, which is an average value (A 1} ) obtained from the strength measurement data of 50 points obtained by dividing the total length of the continuous fiber into 50 equal parts in the longitudinal direction, which will be described later. It is a value measured by the method described in the Example of.

The liquid crystal polyester fiber of the present invention has a strength variation of the total length of the fiber of 8.0% or less. Although the liquid crystal polyester fiber of the present invention is long, the strength variation is reduced over the entire length of the fiber, and the strength variation is preferable from the viewpoint of improving the mechanical characteristics of the high-order processed product as a whole. It may be 5.0% or less, more preferably 3.0% or less. The lower limit of the strength variation is not particularly limited, but may be, for example, about 0.1%. In the present invention, the strength variation is calculated according to the following formula by dividing the total length of continuous fibers into 50 equal parts in the longitudinal direction and using the average value (A ₁ ) and standard deviation (σ _{1) obtained from the strength measurement data of these 50 points.} It is a value measured by the method described in Examples described later.
Strength variation = (σ ₁ / A ₁ ) x 100

The total fineness of the liquid crystal polyester fiber of the present invention can be appropriately adjusted depending on the intended use, and for example, the total fineness may be 220 dtex or more. Further, it may be preferably 500 to 50,000 dtex, and more preferably 1000 to 30,000 dtex.

The total length of the liquid crystal polyester fiber of the present invention is not particularly limited as long as the weight is 10 kg or more, and can be appropriately adjusted depending on the intended use. For example, when the total fineness is 220 dtex or more and less than 500 dtex, the total length of the fiber is It may be 200,000 to 2300000 m, preferably 2400,000 to 2300000 m.
When the total fineness is 500 dtex or more and less than 1000 dtex, it may be 100,000 to 1,000,000 m, preferably 12,000 to 1,000,000 m.
When the total fineness is 1000 dtex or more and less than 3000 dtex, it may be 33,000 to 500,000 m, preferably 40,000 to 500,000 m.
When the total fineness is 3000 dtex or more and less than 10000 dtex, it may be 1000 to 170000 m, preferably 12000 to 170000 m.
When the total fineness is 10000 dtex or more and less than 50,000 dtex, it may be 2000 to 50000 m, preferably 2400 to 50000 m.

In the liquid crystal polyester fiber of the present invention, the single fiber fineness can be appropriately adjusted depending on the application and the like. For example, the single fiber fineness may be 0.5 to 50 dtex, preferably 1.0 to 15 dtex, more preferably 1.0 to 15 dtex. It may be 1.5 to 10 dtex.

When the liquid crystal polyester fiber of the present invention is a multifilament, the number of filaments can be appropriately adjusted depending on the application and the like. For example, the number of filaments may be 5 to 20000, preferably 10 to 4000, more preferably. May be 30 to 3000 pieces.

The liquid crystal polyester fiber of the present invention may be in the form of a fiber package wrapped around a bobbin. The bobbin used for forming the fiber package is not particularly limited as long as it has a tubular shape, and a known rolled fiber package such as pan, cheese, or corn can be used. Since the liquid crystal polyester fiber of the present invention has a high weight, the fiber package may be wound around the bobbin so as not to collapse. For example, the winding density is 0.7 to 1.4 g / cm ^3. May be good.

[Manufacturing method of liquid crystal polyester fiber]
The method for producing a liquid crystal polyester fiber of the present invention includes at least a step of heat-treating the spun yarn of the liquid crystal polyester fiber, and in the heat treatment step, the spun yarn is conveyed at an elongation ratio of 1.00 to 1.200 times. Heat treatment may be performed.

In the solid-phase polymerization of the spun yarn of the liquid crystal polyester fiber, the inventors of the present invention sufficiently create a more uniform heating environment in the longitudinal direction of the fiber by simply performing continuous heat treatment by transporting, and the strength variation is sufficient. It has been found that it cannot be suppressed, and that the strength variation can be suppressed over the entire length of the fiber even if the fiber is heavy in weight, by transporting the fiber at a specific elongation ratio and performing continuous heat treatment.

As the spinning yarn of the liquid crystal polyester fiber, the method of fiberization is not limited, but a fiber obtained by melt spinning can be usually used. Melt spinning can be performed by a known or conventional method. For example, a fiber-forming resin for obtaining a spinning yarn composed of liquid crystal polyester is melted in an extruder and then discharged from a nozzle at a predetermined spinning temperature. Can be obtained.

In the heat treatment step, the strength of the spun yarn can be improved by performing solid phase polymerization by heat-treating the spun yarn. From the viewpoint of improving the strength, the heat treatment temperature may be 230 ° C. or higher, preferably 240 ° C. or higher, and more preferably 250 ° C. or higher. Further, the heat treatment temperature may be lower than the melting point (Mp) of the liquid crystal polyester fiber (spun yarn) subjected to the heat treatment to prevent melting, and for example, in the range of 230 ° C. or higher, (Mp-80) ° C. or higher (Mp-80) ° C. or higher ( It may be less than Mp) ° C., preferably (Mp-50) ° C. or higher and lower than (Mp) ° C., and more preferably (Mp-30) ° C. or higher and lower than (Mp) ° C. However, since the melting point of the liquid crystal polyester fiber rises as the solid phase polymerization progresses, the initial temperature in the heat treatment step may be set to be lower than the melting point (Mp) of the liquid crystal polyester fiber (spun yarn), and the heat treatment temperature may be set to the solid phase polymerization. By increasing the temperature stepwise according to the progress of the above, the heat treatment can be performed at a higher temperature than when the heat treatment is performed at a constant temperature. It is preferable to raise the heat treatment temperature stepwise or continuously with respect to time in that fusion can be prevented and the time efficiency of solid phase polymerization can be improved.

The heat treatment time may be 5 to 1000 minutes, preferably 8 to 500 minutes, more preferably 10 to 100 minutes, still more preferably 15 to 60 minutes, from the viewpoint of improving the strength and the production efficiency. May be good. Here, the heat treatment time means the time for heat-treating the same portion of the spinning yarn.

As the heat treatment, a known method can be used, and examples thereof include means such as atmospheric heating and contact heating. As the atmosphere, air, an inert gas (for example, nitrogen, argon) or an atmosphere in which they are combined is preferably used. Further, the heat treatment may be performed under reduced pressure.

The transfer method in the heat treatment step may be either contact transfer (for example, conveyor method, support roll method, heat treatment method on a heated roller) or non-contact transfer (roll-to-roll method). A heat treatment furnace is used while transporting the spun yarn in a roll-to-roll manner from the viewpoint of avoiding heat unevenness due to contact, performing treatment in a more uniform environment, and suppressing variations in mechanical properties in the fiber longitudinal direction. It is preferable to perform heat treatment. Further, the processing path does not have to be a straight line, and the heat treatment may be performed by arranging a folding roller or a guide in the apparatus and appropriately changing the length, angle, curvature, etc. of the processing path.

For example, when a heat treatment furnace capable of non-contact continuous heat treatment is used, its structure is not particularly limited. The heat treatment furnace may have a structure in which there is no contact from the inlet to the outlet and the fiber transfer path is in a straight line, or a two-stage or more folded fiber transfer path in which rollers are arranged in the furnace or on the side surface of the furnace. It may have. The folding roller may be one that is rotationally driven by itself, or may be one that rotates depending on the fibers to be conveyed. In this case, in order to prevent the generation of fibrils and perform uniform treatment, the temperature of the portion of the roller arranged for folding back the fiber transport path in contact with the fibers is preferably (Mp-50) ° C. or lower. , Room temperature (40 ° C. or lower) is more preferable.

For the transfer in the heat treatment step, the spun yarn may be conveyed at an elongation ratio of 1.00 to 1.200 times. By stretching and transporting at a specific elongation ratio, single fibers can be aligned in parallel without slack at all points in the fiber longitudinal direction in the case of multifilament, so that the mechanical properties in the fiber longitudinal direction can be improved. It is possible to suppress the variation and also to suppress the decrease in strength due to elongation.

The elongation ratio is a numerical value indicating how many times the liquid crystal polyester fiber is stretched before and after stretching. When stretching is performed by two rollers with different speeds, it is calculated from the speed ratio. When stretching is performed by a device that cannot be expressed by the speed ratio, such as stretching by the load of a dancer roller, it is calculated from the total fineness ratio of the fibers before and after stretching (before and after heat treatment). The elongation ratio is not limited in the range as long as the strength is not significantly reduced by the elongation, but from the viewpoint of aligning the single fibers, it may be preferably 1.001 to 1.150 times, and more. It may be 1.002 to 1.100 times, more preferably 1.003 to 1.050 times.

The extension method is not particularly limited to a specific extension ratio, but for example, when heat treatment is performed by a roll-to-roll method, the rotation speed of the drive roller on the downstream side is changed to the transfer roller on the upstream side. A method of increasing the rotation speed of the fiber, a method of performing heat treatment while applying a constant load using a dancer roller during transportation, a method of passing a heated Nelson roller, and a method of fixing the thread with a pin or the like to perform heat treatment. As a result, a method of stretching by utilizing the fact that the liquid crystal polyester fiber has a negative thermal expansion coefficient with respect to the fiber axis direction can be mentioned.

A drawing technique is widely known as a technique for performing heat treatment while stretching a fiber, and this drawing technique is applied to a fiber having a low molecular orientation to improve the strength and elasticity of the thread. Therefore, it is not a technique that is supposed to be applied to a fiber having a highly oriented higher-order structure such as the liquid crystal polyester fiber of the present invention. Further, suitable treatment conditions are also different, and in the drawing technique, the drawing ratio is often set to 1.5 times or more in order to increase the orientation as much as possible, but in the present invention, the single fibers are stretched to be aligned with each other. Therefore, the elongation ratio is preferably in the range of 1.00 to 1.200 times, and if the treatment is performed at a magnification exceeding this, defects occur in the higher-order structure through slippage of the molecular chain and the like, and the strength is increased. Is likely to cause a decrease in. As described above, since the stretching technique of the present invention is different from the stretching technique, the term stretching ratio is used in the present invention instead of the stretching ratio.

Further, the tension applied during the heat treatment can be adjusted according to the total fineness of the liquid crystal polyester fiber to be subjected to the heat treatment, but from the viewpoint of stabilizing the yarn path and suppressing the yarn breakage, for example, 0.001 to 0. It may be 06 cN / dtex, preferably 0.003 to 0.05 cN / dtex, and more preferably 0.005 to 0.04 cN / dtex.

In the method for producing a liquid crystal polyester fiber of the present invention, the strength ratio of the liquid crystal polyester fiber before and after the heat treatment may be 1.5 times or more, preferably 1.8 times or more, and more preferably 2.0 times or more. You may. Here, the strength ratio before and after the heat treatment refers to a value obtained by dividing the tensile strength of the liquid crystal polyester fiber after the heat treatment by the tensile strength of the liquid crystal polyester fiber (spun yarn) before the heat treatment. Since the strength of the spun yarn of the liquid crystal polyester fiber is generally 12 cN / dtex or less, the strength of the liquid crystal polyester fiber can be increased by performing solid phase polymerization under appropriate conditions so that the strength ratio before and after the heat treatment is within the above range. Can be improved.

Since the liquid crystal polyester fiber of the present invention is long and has reduced strength variation over its entire length, it can be suitably used for long applications and improves production efficiency when manufacturing high-order processed products. Can be done. Therefore, the liquid crystal polyester fiber of the present invention can be suitably used as general industrial materials such as ropes, cords and slings, and higher-order processed products such as tension members of submarine telegraph cables and optical cables.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited by these. In the following Examples and Comparative Examples, various physical properties were measured by the following methods.

(Total fineness, single fiber fineness)
Based on JIS L 1013: 2010 8.3.1 A method, 100 m of liquid crystal polyester fiber was removed using a measuring instrument "Wrap Reel by Motor Driven" manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd., and its weight (g). Was multiplied by 100 and measured twice per level, and the average value was taken as the total fineness (dtex) of the obtained liquid crystal polyester fiber. The quotient obtained by dividing this value by the number of filaments was defined as the single fiber fineness (dtex).

(Melting point)
According to JIS K 7121, the measurement was performed using a differential scanning calorimeter (DSC; manufactured by METTLER, "TA3000"), and the observed main absorption peak temperature was taken as the melting point. Specifically, after 10 to 20 mg of a sample was taken in the DSC apparatus and sealed in an aluminum pan, nitrogen was flowed as a carrier gas at a flow rate of 100 mL / min, and the endothermic peak when the temperature was raised at 20 ° C./min. Was measured.

(Strength, strength variation)
Fifty 1 m measurement samples were collected from the continuous liquid crystal polyester fibers without breaks. These measurement samples were taken in a range having a width of ± 0.5% from the point where the total length of the fiber was divided into 50 equal parts in the longitudinal direction. For the total length of the fiber, the length calculated from the fiber weight and the total fineness measured above was used.
Next, referring to JIS L 1013: 2010 8.5.1, using the autograph "AGS-100B" manufactured by Shimadzu Corporation, the test length was 10 cm, the initial load was 2.94 mN / dtex, and the tensile speed was 10 cm / min. _{The tensile test was carried out under the conditions of (1} ), and the strength at break was measured once for each of the 50 measurement samples, and the average value (A 1) of a total of 50 measurements was taken as the strength (cN / dtex).
_{Further, the quotient obtained by dividing the standard deviation (σ 1} ) in the results of 50 measurements by the average value (A ₁ ) was multiplied by 100 to obtain the intensity variation (%).
Strength variation (%) = (σ ₁ / A ₁ ) x 100

[Example 1]
_{A liquid crystal polyester (α) (Mp 0} : 281 ° C.) in which the structural units (A) and (B) represented by the following formulas are (A) / (B) = 73/27 (molar ratio) was used. This was melt-extruded by an extruder, and the polymer was supplied to the spinning head while being weighed by a gear pump. The spinning head is equipped with a spinneret having a hole diameter of 0.125 mmφ, a land length of 0.175 mm, and a number of holes of 300. Got At this time, a 2% by weight aqueous solution of sodium dodecyl phosphate (manufactured by Wako Pure Chemical Industries, Ltd., Wako First Class) was applied to the spinning yarn from an oiling guide arranged directly under the spinning cap. The amount of this aqueous solution applied was 8.4 g / min, and the adhesion ratio of sodium dodecyl phosphate to the spinning yarn was calculated to be 0.1% by weight. The melting point (Mp) of the spun yarn was 281 ° C.

Next, as shown in the process schematic diagram of FIG. 1, the spinning yarn 9 is unwound from the unwinding machine 1, and is passed through the apparatus in the order of the first roller 2, the heat treatment furnace 3, the second roller 4, and the winding machine 5. By winding, continuous heat treatment by transport was performed by a roll-to-roll method, and 15 kg of the heat-treated yarn 12 of this example was continuously obtained. Here, the heat treatment furnace 3 has a furnace pipe 10 made of one ceramic pipe and a control unit 11 having a heater unit for atmospheric heating the inside of the furnace pipe 10. The furnace tube 10 has three heating zones 6 to 8, and the temperature of each heating zone 6 to 8 can be controlled separately by the control unit 11. The conditions for continuous heat treatment were set as follows. The rotation speed of the first roller 2 is set so that the time for passing through the furnace pipe 10 of the heat treatment furnace 3 (distance through which the thread sample passes through the furnace pipe 10 of the heat treatment furnace 3 / transfer speed of the first roller 2) is 60 minutes. I set it. Further, the rotation speed of the second roller 4 was set so that the elongation ratio (rotation speed of the second roller 4 / rotation speed of the first roller 2) was 1.005 times. Further, the inside of the heat treatment furnace 3 had a nitrogen atmosphere, and the temperatures of the three heating zones 6 to 8 were set to 230 ° C., 260 ° C., and 290 ° C. in the order of passage. In addition, in order to adjust the height of the thread path and the like, a ceramic roller and a ceramic guide with a satin-finished surface treatment (both not shown) were also used as appropriate. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 2]
A continuous heat-treated yarn was obtained in the same manner as in Example 1 except that a spinning yarn having a hole diameter of 0.100 mmφ, a land length of 0.140 mm, and a number of holes of 600 was obtained. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 3]
A continuous heat-treated yarn was obtained in the same manner as in Example 1 except that a spinning yarn having a hole diameter of 0.150 mmφ, a land length of 0.210 mm, and a number of holes of 50 was obtained. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 4]
The pore diameter of 0.125 mmφ, the land length of 0.175 mm, the number of holes of 20 spinners were used, the polymer was discharged at a discharge rate of 11.2 g / min, and the amount of sodium dodecyl phosphate aqueous solution applied from the oiling guide. 15 kg of continuous heat-treated yarn was obtained in the same manner as in Example 1 except that the spinning yarn was obtained at 0.56 g / min. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 5]
Two spinning heads and spinning caps used in Example 1 were used at the same time, and the polymers discharged from each at a discharge rate of 167 g / min were stacked as one yarn and wound on a bobbin at a winding speed of 1000 m / min. 15 kg of continuous heat-treated yarn was obtained in the same manner as in Example 1 except that the yarn was obtained. The step of applying the sodium dodecyl phosphate aqueous solution from the oiling guide was carried out at a stage prior to stacking as one yarn, and was applied directly under each spinneret in the same manner as in Example 1. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 6]
Four spinning heads and spinning caps used in Example 1 were used at the same time, and the polymers discharged from each at a discharge rate of 167 g / min were stacked as one yarn and wound on a bobbin at a winding speed of 1000 m / min. 15 kg of continuous heat-treated yarn was obtained in the same manner as in Example 1 except that the yarn was obtained. The step of applying the sodium dodecyl phosphate aqueous solution from the oiling guide was carried out at a stage prior to stacking as one yarn, and was applied directly under each spinneret in the same manner as in Example 1. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 7]
A heat-treated yarn was obtained in the same manner as in Example 6 except that the continuous heat treatment was carried out for a long time and 50 kg of the continuous heat-treated yarn was obtained. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 8]
In the continuous heat treatment, the same spinning yarn and equipment as in Example 1 were used, and the rotation speeds of the first roller 2 and the second roller 4 were set so that the heat treatment time was 16 hours and the elongation ratio was 1.005 times. Obtained 15 kg of continuous heat-treated yarn in the same manner as in Example 1. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 9]
In the continuous heat treatment, the same spinning yarn and equipment as in Example 1 were used, and the rotation speed of the second roller 4 was set so that the elongation ratio was 1.100 times. 15 kg of the heat-treated yarn was obtained. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 10]
In the continuous heat treatment, the same spinning yarn and equipment as in Example 1 were used, and the rotation speed of the second roller 4 was set so that the elongation ratio was 1.000 times. 15 kg of the heat-treated yarn was obtained. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 11]
Instead of the liquid crystal polyester (α) described in Example 1, the molar ratio of each structural unit represented by the following formula is (A) / (C) / (D) / (E) = 65/10/5/20. A spinning yarn was obtained in the same manner as in Example 1 except that a certain liquid crystal polyester (β) (Mp _{0: 348 ° C.) was used.} Then, in the continuous heat treatment, 15 kg of continuous heat-treated yarns were obtained in the same manner as in Example 1 except that the temperatures of the three heating zones 6 to 8 were set to 280 ° C., 280 ° C., and 310 ° C. in the order of passage. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 12]
Instead of the liquid crystal polyester (α) described in Example 1, the molar ratio of each structural unit represented by the following formula is (A) / (C) / (D) / (E) / (F) = 54/15 /. A spinning yarn was obtained in the same manner as in Example 1 except that a liquid crystal polyester (γ) (Mp _{0: 315 ° C.) of 8/16/7 was used.} Then, in the continuous heat treatment, 15 kg of continuous heat-treated yarns were obtained in the same manner as in Example 1 except that the temperatures of the three heating zones 6 to 8 were set to 280 ° C., 280 ° C., and 310 ° C. in the order of passage. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Example 13]
Instead of the liquid crystal polyester (α) described in Example 1, the molar ratio of each structural unit represented by the following formula is (B) / (C) / (G) / (F) = 58/5/16/21. A spinning yarn was obtained in the same manner as in Example 1 except that a liquid crystal polyester (δ) (Mp _{0: 363 ° C.) was used.} Then, in the continuous heat treatment, 15 kg of continuous heat-treated yarn was obtained in the same manner as in Example 1 except that the temperatures of the three heating zones 6 to 8 were set to 300 ° C., 300 ° C., and 330 ° C. in the order of passage. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Comparative Example 1]
15 kg of the spun yarn obtained in the same manner as in Example 1 was wound around a bobbin made of aluminum with Kevlar felt (with a basis weight of 280 g / m ² , thickness 1.5 mm) and rewound at 400 m / min, and heat-treated. I got a bobbin package for. At this time, the traverse width was 200 mm, the innermost diameter of the yarn layer was 100 mm, the average winding density was 0.60 g / cm ³ , and the thickness of the yarn layer was 160 mm. This was heat-treated in a nitrogen atmosphere in a batch-type box-type furnace using two types of heat sources, a heated nitrogen flow and a wall electric heater. At this time, the temperature is raised from 20 ° C. to 230 ° C. in 60 minutes (average 3.5 ° C./min), held at 230 ° C. for 60 minutes, and raised from 230 ° C. to 260 ° C. in 30 minutes (average 1 ° C./min). Warm and hold at 260 ° C. for 60 minutes, raise the temperature from 260 ° C. to 290 ° C. for 30 minutes (1 ° C./min on average), hold at 290 ° C. for 720 minutes, then stop using the heat source and keep the inside of the furnace in the outside air. It was cooled by leaving it open for 3 hours to obtain 15 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Comparative Example 2]
15 kg of the spun yarn obtained in the same manner as in Example 6 was rewound in the same manner as in Comparative Example 1 to obtain a bobbin package for heat treatment. This was heat-treated in a batch format in the same manner as in Comparative Example 1 to obtain 15 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Comparative Example 3]
15 kg of spun yarn made of liquid crystal polyester (β) obtained in the same manner as in Example 11 was rewound in the same manner as in Comparative Example 1 to obtain a bobbin package for heat treatment. This was heat-treated in a nitrogen atmosphere in a batch-type box-type furnace using two types of heat sources, a heated nitrogen flow and a wall electric heater. At this time, the temperature is raised from 20 ° C. to 280 ° C. in 60 minutes (average 4.3 ° C./min), held at 280 ° C. for 60 minutes, and rises from 280 ° C. to 310 ° C. in 30 minutes (average 1 ° C./min). The mixture was warmed and held at 310 ° C. for 810 minutes, after which the use of the heat source was stopped, the inside of the furnace was opened to the outside air, and the mixture was left to stand for 3 hours to cool the mixture to obtain 15 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Comparative Example 4]
15 kg of a spinning yarn made of liquid crystal polyester (γ) obtained in the same manner as in Example 12 was rewound in the same manner as in Comparative Example 1 to obtain a bobbin package for heat treatment. This was heat-treated in a nitrogen atmosphere in a batch-type box-type furnace using two types of heat sources, a heated nitrogen flow and a wall electric heater. At this time, the temperature is raised from 20 ° C. to 280 ° C. in 60 minutes (average 4.3 ° C./min), held at 280 ° C. for 60 minutes, and rises from 280 ° C. to 310 ° C. in 30 minutes (average 1 ° C./min). The mixture was warmed and held at 310 ° C. for 810 minutes, after which the use of the heat source was stopped, the inside of the furnace was opened to the outside air, and the mixture was left to stand for 3 hours to cool the mixture to obtain 15 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Comparative Example 5]
15 kg of spun yarn made of liquid crystal polyester (δ) obtained in the same manner as in Example 13 was rewound in the same manner as in Comparative Example 1 to obtain a bobbin package for heat treatment. This was heat-treated in a nitrogen atmosphere in a batch-type box-type furnace using two types of heat sources, a heated nitrogen flow and a wall electric heater. At this time, the temperature is raised from 20 ° C. to 300 ° C. for 60 minutes (average 4.7 ° C./min), held at 300 ° C. for 60 minutes, and raised from 300 ° C. to 330 ° C. in 30 minutes (average 1 ° C./min). The mixture was warmed and held at 330 ° C. for 810 minutes, after which the use of the heat source was stopped, the inside of the furnace was opened to the outside air, and the mixture was left to stand for 3 hours to cool the mixture to obtain 15 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

[Reference example 1]
5 kg of the spun yarn obtained in the same manner as in Example 1 was rewound in the same manner as in Comparative Example 1 ^{to obtain a bobbin package for heat treatment having an average winding density of 0.60 g / cm 3} and a yarn layer thickness of 75 mm. This was heat-treated in a batch format in the same manner as in Comparative Example 1 to obtain 5 kg of heat-treated yarn. The analysis results of the obtained liquid crystal polyester fiber (heat-treated yarn) are shown in Table 5.

As shown in Table 5, in Examples 1 to 10, since the liquid crystal polyester fiber was produced by performing continuous heat treatment by transporting under a control to a specific elongation ratio, the liquid crystal polyester fiber was produced over the entire length of the fiber even though it was long. It is possible to suppress the variation in strength. In particular, in Examples 1 to 9 in which the elongation ratio is set to 1.001 times or more, the strength variation is 3.0% or less, and the strength variation can be suppressed to a higher degree.

In Examples 11 to 13, a liquid crystal polyester different from that in Example 1 is used, but since the liquid crystal polyester fiber is produced by performing continuous heat treatment by transporting under a control to a specific elongation ratio, it is related to the type of liquid crystal polyester. It is possible to suppress the variation in strength over the entire length of the fiber.

On the other hand, in Comparative Examples 1 to 5, since the heavy-duty spun yarn was heat-treated by the batch method, the heat and airflow became uneven in the package to be heat-treated, and the heat-treated yarn had a great variation in strength over the entire length of the fiber. It is occurring greatly in.

In Reference Example 1, the spinning yarn is heat-treated by a batch method to suppress the strength variation, but this is because the spinning yarn has a low weight, so that heat in the package to be subjected to the heat treatment is generated. This is probably because the airflow has little unevenness.

The liquid crystal polyester fiber of the present invention can be suitably used as general industrial materials such as ropes, cords and slings, and higher-order processed products such as tension members of submarine telegraph cables and optical cables.

As described above, a preferred embodiment of the present invention has been described, but various additions, changes or deletions can be made without departing from the spirit of the present invention, and such additions, changes or deletions are also included in the scope of the present invention. Is done.

1 ... Unwinder 2 ... First roller 3 ... Heat treatment furnace 4 ... Second roller 5 ... Winder 6, 7, 8 ... Heating zone 9 ... Spinning source Thread 10 ... Furnace pipe 11 ... Control unit 12 ... Heat-treated thread

Claims (6)

It is a continuous fiber having a weight of 10 kg or more, the total length of the continuous fiber is divided into 50 equal parts in the longitudinal direction, and the average value (A ₁ ) obtained from the strength measurement data of these 50 points is 18 cN / dtex or more, and the strength is concerned. A liquid crystal polyester fiber having a strength variation of 8.0% or less calculated according to the following formula based on the average value (A ₁ ) and standard deviation (σ _{1) obtained from the measurement data.}
Strength variation = (σ ₁ / A ₁ ) x 100 The liquid crystal polyester fiber according to claim 1, wherein the total fineness is 220 dtex or more. A high-order processed product using at least a part of the liquid crystal polyester fiber according to claim 1 or 2. The method for producing a liquid crystal polyester fiber according to claim 1 or 2.
A method for producing a liquid crystal polyester fiber, which comprises at least a step of heat-treating the spun yarn of the liquid crystal polyester fiber, and in the heat treatment step, the spun yarn is conveyed at an elongation ratio of 1.00 to 1.200 and the heat treatment is performed. The production method according to claim 4, wherein the strength ratio before and after the heat treatment is 1.5 times or more. The production method according to claim 4 or 5, wherein in the heat treatment step, the heat treatment is performed while transporting the spun yarn in a roll-to-roll manner.

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