JP2017190554A - Semi-aromatic polyamide fiber, semi-aromatic polyamide unwoven fabric and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sei-aromatic polyamide fiber consisting of semi-aromatic polyamide high in heat resistance and excellent in crystallinity and excellent in heat resistance and mechanical strength, the nonwoven fabric and a manufacturing method therefor.SOLUTION: Thee is provided a semi-aromatic polyamide fiber or a semi-aromatic polyamide unwoven fabric consisting of semi-aromatic polyamide containing a terephthalic acid component and a diamine component, the diamine component is one or 1,8-octane diamine, 1,10-decane diamine, 1,12-dodecane diamine and a triamine unit to a diamine unit in polyamide is 0.3 mol% or less.SELECTED DRAWING: None

Description

  The present invention relates to a semi-aromatic polyamide fiber and a semi-aromatic polyamide nonwoven fabric made of a semi-aromatic polyamide including a terephthalic component and a linear diamine component having an even number of carbon atoms.

  Conventionally, nylon 6 fiber and nylon 66 fiber are known as polyamide fiber and non-woven fabric, and they have been used for various industrial applications because of high strength, toughness and excellent durability. However, since these polyamide-based fibers and nonwoven fabrics are aliphatic polyamides, they have the disadvantage of poor dimensional stability due to heat and water absorption.

  Fibers and non-woven fabrics made of nylon 46, which is a high melting point, high crystalline polyamide, have also been proposed, and are being considered for use in industrial materials as fibers and non-woven fabrics with excellent heat resistance and dimensional stability. No. 46 has a defect that it is easy to absorb moisture and the physical property change due to moisture absorption is large.

  In order to solve problems such as insufficient heat resistance of these aliphatic polyamides and poor dimensional stability due to water absorption, various semi-aromatic polyamides containing terephthalic acid units as dicarboxylic acid units have been proposed and partially put into practical use. Has reached. For example, as an industrialized semi-aromatic polyamide, polyamide 6T composed of a terephthalic acid component and a 1,6-hexamethylenediamine component and polyamide 9T composed of a terephthalic acid component and a 1,9-nonanediamine component are known.

  The semi-aromatic polyamide has higher heat resistance and lower water absorption than aliphatic polyamides such as nylon 6 and nylon 66, so it has excellent dimensional stability and molding for electric / electronic parts and automobile parts. Widely used in the field of goods.

  However, since the semi-aromatic polyamide has a melting point close to the thermal decomposition temperature of the polymer, coloring due to thermal decomposition at the time of melt processing and deterioration of product performance may be problematic. Therefore, the same problem arises in the manufacturing stage of the fiber and nonwoven fabric which consist of these semi-aromatic polyamides.

  For example, in the case of polyamide 6T, since the melting point of the homopolymer is as high as 370 ° C., it becomes impossible to suppress the thermal decomposition of polyamide 6T during melt processing, and to obtain the desired fiber and nonwoven fabric with excellent heat resistance. It becomes difficult. Therefore, the polyamide 6T improves the melt moldability by lowering the melting point by introducing a copolymer component, and obtains the intended semi-aromatic polyamide fiber and nonwoven fabric. However, in the copolymerized polyamide 6T, the crystallinity is impaired, and there arises a problem that mechanical properties and various physical properties, particularly heat resistance is lowered.

  In fiber applications, semi-aromatic polyamide fibers (for example, Patent Documents 1 to 3) mainly composed of a semi-aromatic polyamide (hereinafter abbreviated as polyamide 6T) composed of terephthalic acid units and 1,6-hexanediamine units. And semi-aromatic polyamide fibers mainly composed of semi-aromatic polyamide (hereinafter abbreviated as polyamide 12T) composed of terephthalic acid units and 1,12-dodecanediamine units (for example, Patent Documents 4 to 6). Reference)), a semi-aromatic polyamide comprising a terephthalic acid unit and a saturated aliphatic diamine unit having 6 to 8 carbon atoms in the main chain and having 1 to 2 methyl side chains at the 2-5 positions of the main chain. A semi-aromatic polyamide fiber (see, for example, Patent Document 7), a semi-aromatic polyamide comprising a terephthalic acid unit and a 5-methyl-1,9-nonanediamine unit. Semi-aromatic polyamide fibers (for example, see Patent Document 8), semi-aromatic polyamide fibers composed of a semi-aromatic polyamide composed of terephthalic acid units and 1,9-nonanediamine units (for example, see Patent Document 9), and the like. Various melt-spinnable semi-aromatic polyamide fibers and nonwoven fabrics have been proposed, but none has been put into practical use.

  Furthermore, 60-100 mol% of the dicarboxylic acid unit is composed of a terephthalic acid unit, 60-100 mol% of the diamine unit is composed of a polyamide composed of 1,9-nonanediamine unit, and 60-100 mol of the dicarboxylic acid unit. % Of terephthalic acid units, 60 to 100 mol% of diamine units are composed of 1,9-nonanediamine units and 2-methyl-1,8-octanediamine units, and 1,9-nonanediamine units and 2-methyl- A semi-aromatic polyamide fiber composed of a polyamide having a molar ratio of 1,8-octanediamine units of 40:60 to 99: 1 has been proposed (for example, see Patent Document 10). Since this polyamide 9T has a diamine having a carbon number longer than that of the polyamide 6T, the melting point is lower than that of the polyamide 6T, and the problem at the time of melt processing is small. However, since polyamide 9T has an odd number of carbon atoms in its constituent diamine, the chemical structure of the polyamide is asymmetric and the crystallinity is impaired, so that it can be used as a semi-aromatic polyamide that requires high crystallinity. It was not enough.

  Examples of polyamides that solve the above-mentioned problems of polyamide 6T and polyamide 9T include polyamide 10T composed of terephthalic acid and 1,10-decanediamine, and a molded article in which polyamide 10T resin has high crystallinity and excellent heat resistance. (For example, refer to Patent Document 13). However, in semi-aromatic polyamides such as polyamide 10T, as a problem in molding processing, it is known that gels are generated in the polyamide due to the condensation of the diamine component as a raw material and the physical properties are impaired. ing.

  For example, it is disclosed that a semi-aromatic polyamide (for example, polyamide 6T) composed of an aliphatic diamine composed of hexamethylene diamine and adipic acid and terephthalic acid is gelled by the generation of triamine as a by-product. (For example, refer nonpatent literature 1). Furthermore, it is disclosed that when such a semi-aromatic polyamide is obtained, the amount of triamine in the polyamide is reduced if polymerization is performed without adding water.

  Further, as a method for producing a semi-aromatic polyamide having a reduced triamine amount, a method of appropriately adjusting mainly the conditions of solid-phase polymerization in the latter half of the polymerization step is disclosed (for example, see Patent Document 11). Furthermore, a production method for obtaining a condensed polyamide by adjusting a molar balance without adding water by using a slurry composed of a molten xylylenediamine and a dicarboxylic acid solid is disclosed (see, for example, Patent Document 12). ).

Japanese Patent Laid-Open No. 44-22210 JP-A 46-00846 Japanese Patent Publication No. 3-56576 JP 47-29451 A JP 48-08531 A JP-A-48-32611 U.S. Pat. No. 2,752,328 Japanese Examined Patent Publication No. 52-43757 British Patent No. 1070416 JP 9-13222 A JP 2008-239908 A JP 2001-200053 A JP-A-6-239990

Polymer Chemistry Vol. 25, No. 277, page 318 (1968)

  An object of the present invention is to provide a semi-aromatic polyamide fiber and a nonwoven fabric having high heat resistance and mechanical strength, which are made of a semi-aromatic polyamide having high heat resistance and excellent crystallinity, which solves the above problems. .

  As a result of intensive studies to solve such problems, the present inventors have found that semi-aromatic polyamides using a specific diamine component and having a sufficiently reduced amount of triamine have high crystallinity and heat resistance. The present inventors have found that fibers and nonwoven fabrics excellent in heat resistance and mechanical strength can be obtained by spinning this semi-aromatic polyamide.

That is, the gist of the present invention is as follows.
(1) A terephthalic acid component and a diamine component, wherein the diamine component is 1,8-octanediamine, 1,10-decanediamine, or 1,12-dodecanediamine, and is a triamine unit relative to the diamine unit in the polyamide. Is a semi-aromatic polyamide fiber or a semi-aromatic polyamide non-woven fabric comprising a semi-aromatic polyamide, wherein the non-aromatic polyamide fiber is 0.3 mol% or less.
(2) The copolymer component other than the terephthalic acid component and the diamine component, which are the main components of the semi-aromatic polyamide, is contained in a proportion of 0 to 5 mol% with respect to the total number of moles of the raw material monomers. The semi-aromatic polyamide fiber or semi-aromatic polyamide nonwoven fabric according to (1).
(3) The semi-aromatic polyamide fiber or the semi-aromatic polyamide nonwoven fabric according to (1) or (2), wherein the melting point measured using a differential scanning calorimeter is 280 ° C to 340 ° C.
(4) The semi-aromatic polyamide fiber or the semi-fragrance according to any one of (1) to (3), wherein the degree of supercooling ΔT measured using a differential scanning calorimeter is 40 ° C. or less. Family nonwoven fabric.
(5) The method for producing a semi-aromatic polyamide fiber according to any one of (1) to (4), wherein the following steps (a) to (d) are sequentially performed.
(A) A suspension of diamine and solid terephthalic acid in a molten state at 80 ° C. or more and 150 ° C. or less under the condition that the blending amount of water is 5 parts by mass or less with respect to a total of 100 parts by mass of terephthalic acid and diamine. Step of stirring and mixing to obtain a mixture.
(B) In the mixture obtained in step (a), at a temperature lower than the melting point of the semiaromatic polyamide to be finally produced, a salt is formed by the reaction of terephthalic acid and diamine, and a low weight is obtained by the polymerization of the salt. A step of performing a coalescence formation reaction to obtain a mixture of a salt and a low polymer.
(C) A step of polymerizing the mixture of the salt and low polymer obtained in step (b) to obtain a semi-aromatic polyamide having a melting point of 280 ° C. to 340 ° C. measured using a differential scanning calorimeter. .
(D) A step of melt-spinning the semi-aromatic polyamide obtained in step (c) and drawing and heat-treating the obtained yarn.
(6) The method for producing a semi-aromatic polyamide fiber according to any one of (1) to (4), wherein the following steps (a) to (d) are sequentially performed.
(A) The terephthalic acid powder is heated in advance to a temperature not lower than the melting point of diamine and not higher than the melting point of terephthalic acid, so that the terephthalic acid powder is substantially maintained at a temperature not lower than the melting point of diamine and not higher than the melting point of terephthalic acid. Adding diamine to terephthalic acid powder without containing water.
(B) In the mixture obtained in step (a), at a temperature lower than the melting point of the semiaromatic polyamide to be finally produced, a salt is formed by the reaction of terephthalic acid and diamine, and a low weight is obtained by the polymerization of the salt. A step of performing a coalescence formation reaction to obtain a mixture of a salt and a low polymer.
(C) A step of polymerizing the mixture of the salt and low polymer obtained in step (b) to obtain a semi-aromatic polyamide having a melting point of 280 ° C. to 340 ° C. measured using a differential scanning calorimeter. .
(D) A step of melt-spinning the semi-aromatic polyamide obtained in step (c) and drawing and heat-treating the obtained yarn.
(7) The polymerization step of step (c) is a step of subjecting the mixture obtained in step (b) to solid phase polymerization while maintaining a temperature below the melting point of the produced polyamide (5) or ( 6) The manufacturing method of the semi-aromatic polyamide fiber of description.
(8) In step (d), after melting the semi-aromatic polyamide at the melting point to 360 ° C., melt spinning from the spinneret nozzle with a melt residence time of 30 minutes or less, and cooling the resulting yarn, the temperature 120 C. to 250.degree. C. After stretching at a draw ratio of 2 times or more, constant length heat treatment, tension heat treatment or relaxation heat treatment is performed at 120 to 270.degree. C. Method for producing semi-aromatic polyamide fiber.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber and nonwoven fabric which are excellent in heat resistance and mechanical strength which consist of semi-aromatic polyamide with high heat resistance and high crystallinity can be obtained. Therefore, air bag base fabric use, heat resistant filter use, radiator hose reinforcing fiber use, tarpaulin use, brush bristle use, fishing line use, tire cord use, artificial turf use, carpet use, fish net use, rope use, filter use It can be suitably used for various industrial material applications such as fiber applications, fiber applications for seat sheets, and filter applications.

Hereinafter, the present invention will be described in detail. The fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention are semi-aromatic polyamide fibers made of a dicarboxylic acid component and a diamine component. In the present invention, it is necessary to use a dicarboxylic acid component and a diamine component having a specific chemical structure from the viewpoint of high crystallinity.
In the present invention, it is necessary to use terephthalic acid as the dicarboxylic acid component. The reason for this is that terephthalic acid is most preferable for obtaining fibers and nonwoven fabrics made of semi-aromatic polyamide having high crystallinity and high crystallinity among aromatic dicarboxylic acids.

  In the present invention, the diamine component constituting the fiber and nonwoven fabric made of semi-aromatic polyamide is 1,8-octanediamine, 1,10-decanediamine, or 1,12-dodecanediamine. Diamine. Straight chain aliphatic diamines are preferred for obtaining fibers and non-woven fabrics made of semi-aromatic polyamides having high crystallinity because of their high chemical structure symmetry.

  The reason why the diamine used must have an even number of carbon atoms will be described below. In general, a so-called even-odd effect appears in polyamide. That is, when the number of carbon atoms in the monomer unit of the diamine component used is an even number, a more stable crystal structure is formed as compared with the case where the number is an odd number, so that the effect of improving crystallinity is exhibited. Therefore, from the viewpoint of high crystallinity, the linear aliphatic diamine needs to have an even number of carbon atoms.

  When the number of carbon atoms of the diamine is less than 8, the melting point of the resulting semi-aromatic polyamide exceeds 340 ° C. and exceeds the decomposition temperature, which is not preferable. On the other hand, when the number of carbon atoms of the diamine exceeds 12, the melting point of the obtained semi-aromatic polyamide is less than 280 ° C., which is not preferable because the heat resistance is insufficient in practical use. A diamine having 9 or 11 carbon atoms is not preferable because of insufficient crystallinity due to the even-odd effect of polyamide.

  The fiber and non-woven fabric made of the semi-aromatic polyamide of the present invention include a dicarboxylic acid component other than the terephthalic acid component as a main component and / or a type other than a linear aliphatic diamine component having 8, 10 or 12 carbon atoms. The diamine component (hereinafter sometimes referred to as “copolymerization component”) may be copolymerized. The copolymerization component is preferably 5 mol% or less, more preferably 3 mol% or less, and even more preferably substantially free of the copolymerization component, based on the total number of moles of raw material monomers (100 mol%). . This is because, from the viewpoint of high crystallinity, it is preferable to have a structure close to a homopolymer having high regularity rather than a copolymer having an irregular chemical structure. In other words, if the copolymerization component exceeds 5 mol%, the crystallinity is lowered and the melting point is also lowered, so that fibers and nonwoven fabrics made of semi-aromatic polyamide having high crystallinity and heat resistance cannot be obtained. There is.

  Examples of dicarboxylic acid components other than terephthalic acid that can be used as a copolymer component for fibers and nonwoven fabrics made of the semi-aromatic polyamide of the present invention include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, Aliphatic dicarboxylic acids such as suberic acid, azelaic acid, sebacic acid, undecanedioic acid and dodecanedioic acid, cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and naphthalenedicarboxylic acid Can be mentioned.

  Examples of other diamine components that can be used as a copolymer component for fibers and nonwoven fabrics made of the semi-aromatic polyamide of the present invention include 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1, Examples include aliphatic diamines such as 12-dodecanediamine, alicyclic diamines such as cyclohexanediamine, and aromatic diamines such as xylylenediamine. In addition, any of the 1,8-octanediamine, 1,10-decanediamine, and 1,12-octanediamine listed above is an essential diamine component for the fiber and nonwoven fabric made of the aromatic polyamide of the present invention. . When any one of 1,8-octanediamine, 1,10-decanediamine, and 1,12-dodecanediamine is used as an essential diamine component, the other diamine components are used as copolymerization components. For example, when 1,8-octanediamine is used as an essential diamine component, 1,10-decanediamine and 1,12-dodecanediamine are used as copolymerization components.

  The fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention may be copolymerized with lactams such as caprolactam, if necessary.

  In the present invention, the molar ratio of the main component terephthalic acid component to the diamine component is preferably terephthalic acid component / diamine component = 45/55 to 55/45, and 47.5 / 52.5 to 52.5. More preferably, it is /47.5. By setting the molar ratio of the terephthalic acid component to the diamine component in the range of 45/55 to 55/45, fibers and non-woven fabrics made of high molecular weight semi-aromatic polyamide can be obtained.

  The fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention are required to have a sufficiently reduced amount of triamine. Semi-aromatic polyamides tend to have a triamine structure as a by-product due to a condensation reaction between diamines during polymerization. When the amount of triamine is large, a crosslinked structure is formed in the molecular chain, and the crosslinked structure restricts the movement and arrangement of the molecular chain, so that the crystallinity is lowered. In addition, if the amount of triamine is large, a large amount of gel is generated. Therefore, when fibers and nonwoven fabrics are produced, the upstream pressure change of the filter becomes large in the filtration process with the filter, and it cannot be continuously produced. Or the like, or cause a decrease in mechanical properties of the resulting fiber and nonwoven fabric.

  Therefore, the triamine unit contained in the fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention needs to be 0.3 mol% or less of the diamine unit, and preferably 0.2 mol% or less. More preferably, it is 0.15 mol% or less. In order to obtain such a semi-aromatic polyamide fiber and non-woven fabric, the amount of triamine contained in the semi-aromatic polyamide used as a raw material must be 0.3 mol% or less of the diamine unit. It is preferably 2 mol% or less, and more preferably 0.15 mol% or less. When the amount of triamine contained in the raw material polymer exceeds 0.3 mol%, a gel-like material is generated and the continuous productivity is lowered, or the triamine structure in the fiber made of polyamide is 0. When it exceeds 3 mol%, problems arise that the crystallinity of the resulting fiber and the nonwoven fabric is lowered, the color tone is lowered, and the mechanical properties are lowered.

  In order to make the above triamine unit 0.3 mol% or less of the diamine unit, when the salt is formed from the terephthalic acid component and the diamine component, the blending amount of water is based on 100 parts by mass of the raw material monomers in total. The amount is preferably 5 parts by mass or less.

  In general, in order to allow the heat polymerization reaction of polyamide to proceed uniformly, a method is used in which raw materials are mixed in the presence of water and heated to advance the dehydration reaction. However, in such a method, if the amount of water during polymerization exceeds 5 parts by mass with respect to 100 parts by mass of the raw material monomers, there is a problem that an increase in the degree of polymerization is suppressed. In that case, the residence time in the polymerization apparatus in a state where there are many amine ends becomes longer, and the amount of triamine by-produced by the condensation reaction between diamines increases. As a result, a part of the polyamide has a cross-linked structure, crystallinity is lowered, gelation is promoted, and color tone is lowered. And as shown also in nonpatent literature 1, in semi-aromatic polyamide, generation of triamine is more remarkable than aliphatic polyamide. Therefore, in order to obtain a fiber made of a semi-aromatic polyamide in which the triamine unit is 0.3 mol% or less of the diamine unit, such as a fiber and a non-woven fabric made of the semi-aromatic polyamide of the present invention, The total amount of raw material monomers is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and most preferably no water is added.

In the present invention, since it is intended to obtain fibers and nonwoven fabrics made of semi-aromatic polyamide having high crystallinity, the crystallinity is preferably controlled within a specific range. As an index of crystallinity in the present invention, the degree of supercooling ΔT measured using a differential scanning calorimeter (DSC) can be used. The degree of supercooling ΔT preferably satisfies the range of ΔT ≦ 40 ° C., and more preferably satisfies the range of ΔT ≦ 35 ° C. If ΔT exceeds 40 ° C., the crystallinity is insufficient and the effect of improving the heat resistance is insufficient, which is not preferable.
In the present invention, as shown in the following formula, the degree of supercooling ΔT is the melting point of the polyamide (hereinafter sometimes abbreviated as Tm) and the cooling crystallization temperature (hereinafter sometimes abbreviated as Tcc). Defined as the difference between

ΔT = Tm (melting point) −Tcc (cooling temperature crystallization temperature)
In the above formula, a fiber made of the polyamide is lowered from the molten state to 25 ° C. at a temperature lowering rate of 20 ° C./min in an inert gas atmosphere using a differential scanning calorimeter (DSC), and then 20 ° C./min. The temperature of the endothermic peak that appears when the temperature is raised at the rate of temperature rise is defined as the melting point (Tm). Similarly, the temperature of the exothermic peak that appears when the temperature is lowered from the molten state to 25 ° C. at a temperature lowering rate of 20 ° C./min is defined as the temperature-falling crystallization temperature (Tcc). The smaller the degree of supercooling ΔT, the faster the crystallization from the polymer melted state, indicating that the polymer has high crystallinity.

  In addition, the fiber and nonwoven fabric which consist of a semi-aromatic polyamide using the diamine component which has an even number of carbon atoms have high crystallinity in the first place. In order to achieve further high crystallinity, as described above, a method in which the copolymerization component in the fiber made of the semi-aromatic polyamide of the present invention is 0 to 5 mol% can be used. In order to achieve further high crystallinity, as described above, a method of setting the triamine unit to 0.3 mol% or less with respect to the diamine unit in the fiber and the nonwoven fabric made of semi-aromatic polyamide may be used.

  The present invention is intended to obtain a fiber and a nonwoven fabric made of a semi-aromatic polyamide having high crystallinity and at the same time having high heat resistance. Therefore, when the melting point of the resulting semi-aromatic polyamide fiber and nonwoven fabric is less than 280 ° C., the heat resistance is insufficient. Therefore, the melting point needs to be controlled to 280 ° C. or higher. On the other hand, when the melting point is higher than 340 ° C., the decomposition of the polyamide is accelerated, and melt molding such as melt spinning becomes difficult. Therefore, the melting point needs to be controlled to 340 ° C. or lower.

  The fiber and nonwoven raw material polymer comprising the semi-aromatic polyamide of the present invention can be produced by a conventionally known method such as a heat polymerization method or a solution polymerization method as a method for producing a polyamide. Of these, the heat polymerization method is preferably used because it is industrially advantageous. Examples of the heat polymerization method include a melt polymerization method, a melt extrusion method, and a solid phase polymerization method. The fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention have a high melting point of 280 ° C. to 340 ° C. and are close to the decomposition temperature. Therefore, a solid phase polymerization method in which the reaction is performed at a temperature lower than the melting point of the generated polymer is preferable as compared with the melt polymerization method or the melt extrusion method in which the reaction is performed at a temperature higher than the melting point of the generated polymer.

  In general, the production of a raw material polymer for fibers and nonwoven fabric made of semi-aromatic polyamide may comprise a step (a) of obtaining a mixture from monomers, and a step (b) and (c) of polymerizing using such a mixture. In many cases, in the present invention, in order to obtain a polyamide in which the triamine unit is 0.3 mol% or less of the diamine unit, the step (a) is carried out under the condition that the water content in the polymerization system is low, that is, terephthalic acid and It is preferable that the amount of water is 5 parts by mass or less with respect to 100 parts by mass of the diamine.

As a method for carrying out the step (a) under the condition of low moisture, for example, terephthalic acid powder is heated in advance to a temperature not lower than the melting point of diamine and not higher than the melting point of terephthalic acid, and the melting point of dicarboxylic acid is not lower than the melting point of diamine. In order to keep the terephthalic acid powder state at the following temperature, a method of adding diamine to the terephthalic acid powder without containing water is preferably used.

  Alternatively, as another method for carrying out the step (a) under the condition of less moisture, 80 ° C. or higher under the condition that the blending amount of water is 5 parts by mass or less with respect to 100 parts by mass of terephthalic acid and diamine in total. The method of stirring and mixing the suspension which consists of diamine of a molten state and solid terephthalic acid at 150 degrees C or less, and obtaining a mixture is used preferably.

  The step (a) may be carried out at normal pressure, but may be carried out in a pressurized state resulting from water produced by a polyamide condensation reaction, and can be selected as appropriate.

  In the present invention, in order to ensure the reaction efficiency between solid terephthalic acid and liquid diamine, the volume average particle diameter of terephthalic acid is preferably 5 μm to 1 mm, and more preferably 20 to 200 μm. By setting the volume average particle diameter of terephthalic acid to 1 mm or less, the progress of the salt reaction can be accelerated. Further, when the thickness is 5 μm or more, there is an advantage that powder scattering is reduced and handling of the powder becomes easy.

Next, step (b) will be described.
In the step (b), the mixture obtained in the step (a) is formed at a temperature lower than the melting point of the finally produced polyamide at a temperature lower than the melting point of the polyamide by the reaction of terephthalic acid and diamine, This is a step of performing a formation reaction of a coal to obtain a mixture of a salt and a low polymer. In the step (b), crushing may be performed while the above-described production reaction is performed, or crushing may be performed after taking out the reaction once.

Next, step (c) will be described.
In step (c), the salt or low polymer obtained in step (b) is solidified at a temperature lower than the melting point of the semi-aromatic polyamide used as a raw material for the fiber and nonwoven fabric finally produced. This is a step of obtaining a semi-aromatic polyamide by performing phase polymerization and increasing the molecular weight to a predetermined molecular weight.

  In the step (c), when the solid-state polymerization temperature is equal to or higher than the melting point of the semi-aromatic polyamide to be produced, the amount of triamine is increased. Moreover, thermal decomposition is promoted. Therefore, the color tone of the semi-aromatic polyamide may be deteriorated, which is not preferable.

  The solid phase polymerization temperature is preferably 180 to 270 ° C, more preferably 200 to 250 ° C. If the solid phase polymerization temperature is less than 180 ° C., the polymerization reaction may be insufficient. On the other hand, when it exceeds 270 ° C., thermal decomposition of the amide bond is promoted, and the amount of triamine in the obtained semi-aromatic polyamide may increase.

  The reaction time of the solid phase polymerization reaction in the step (c) is preferably in the range of 0.5 to 10 hours after reaching the reaction temperature, from the viewpoint of the balance between the finally reached molecular weight and productivity, 0.5 to 8 hours is more preferable.

  The solid phase polymerization reaction in the step (c) may be performed in an inert gas stream such as nitrogen, or may be performed under reduced pressure. Moreover, you may carry out still and may carry out stirring. Even in this case, the reaction is always carried out below the melting point of the semi-aromatic polyamide finally produced.

  Moreover, in order to manufacture the raw material of the fiber and nonwoven fabric which consist of the semi-aromatic polyamide of this invention, it is preferable to use a polymerization catalyst. Examples of the catalyst used in the present invention include phosphoric acid, phosphorous acid, hypophosphorous acid or salts thereof. Although there is no restriction | limiting in particular in the usage-amount of a catalyst in this invention, Usually, 0-2 mol% is used with respect to the total mol of a terephthalic acid and diamine.

  It is preferable to add an end-blocking agent to the fiber and non-woven fabric raw material polymer of the semi-aromatic polyamide of the present invention for the purpose of adjusting the degree of polymerization and suppressing thermal decomposition and coloring when the product is produced. As end-capping agents, aliphatic monocarboxylic acids such as acetic acid, lauric acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, isobutyric acid, With amino groups such as alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid, benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid and phenylmonoacetic acid Reactive monocarboxylic acids and aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine; cyclohexylamine Alicyclic monoamines such as benzene, dicyclohexylamine; monoamines having reactivity with carboxyl groups such as aromatic monoamines such as aniline, toluidine, diphenylamine, naphthylamine, and other acid anhydrides such as phthalic anhydride, monoisocyanates, mono Any one of acid halides, monoesters, monoalcohols, etc., or a combination thereof may be used.

  Since the addition amount of the end-blocking agent may be determined according to the purpose, it is not particularly limited, but is usually 0 to 5% by mole based on the total moles of terephthalic acid and diamine. By sealing the fibers and nonwoven fabric made of polyamide and the end groups of the semi-aromatic polyamide which is a raw material thereof, the spinnability is improved, and further, polyamide fiber and nonwoven fabric excellent in water resistance and yellowing resistance can be obtained. It is preferable that the usage-amount of terminal blocker is used in the range of 0.5-10 mol% with respect to the total number of moles of dicarboxylic acid and diamine.

  You may add additives, such as a filler and a stabilizer, to the fiber and nonwoven fabric which consist of polyamide of this invention as needed. Examples of the method of addition include addition at the time of polymerization of polyamide, or melt kneading to the obtained polyamide. Additives include talc, swellable clay minerals, fillers such as silica, alumina and graphite, pigments such as titanium oxide and carbon black, as well as antioxidants, antistatic agents, flame retardants and flame retardant aids. Well-known additives, such as an agent, are mentioned. In addition, stabilizers such as copper compounds, colorants, UV absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retarders, etc. It can also be added during or after the condensation reaction. In particular, the addition of organic stabilizers such as hindered phenols, copper halide compounds such as copper iodide, and alkali metal halide compounds such as potassium iodide as heat stabilizers, stability of melt retention during spinning, and resistance to dry heat Degradability is further improved, which is preferable.

  The relative viscosity of the raw material polymer for the fiber and nonwoven fabric made of the semi-aromatic polyamide of the present invention obtained as described above is not particularly limited, and may be appropriately set depending on the purpose. For example, in order to obtain a polyamide that can be easily melt-spun, the relative viscosity is preferably 2.0 or more.

Next, process (d) is demonstrated.
Step (d) is a step of obtaining a semi-aromatic polyamide fiber by melt-molding the semi-aromatic polyamide obtained in step (c) by melt spinning, etc., and drawing and heat-treating the obtained yarn. is there.

  Examples of the step (d) include a melt spinning method and an electrospinning method. The semi-aromatic fibers of the present invention can be obtained by these various melt molding methods.

  For melt spinning, it is usually preferable to use a screw type extruder which is a melt extruder. In order to make the triamine unit in the semi-aromatic polyamide fiber obtained by melt spinning of the semi-aromatic polyamide of the present invention 0.3 mol% or less, after melting at a melting point to 360 ° C. of the semi-aromatic polyamide, It is preferable to obtain fibers by spinning from a spinneret nozzle with a melt residence time of 30 minutes or less. Furthermore, the yarn obtained by spinning is taken up by a take-up roller or the like, and if necessary, a heating or heat retention zone is provided immediately below the nozzle, and a cooling zone is provided by a spraying chamber or the like, and further spinning is performed. An oil agent may be applied to the yarn.

  The triamine in the fiber is formed by a reaction between amino groups, which are the molecular chain end groups of the raw material diamine, and induces a three-dimensional reaction in the melt molding process such as melt spinning to form a gel or non-melt material. To do. As a result, the spinning performance in melt spinning is deteriorated and the physical properties of the yarn are lowered. Therefore, in addition to lowering the amount of triamine in the raw material polymer used for melt molding such as melt spinning, it is possible to select conditions for suppressing the amount of triamine and amino end groups in the melt molding process such as melt spinning. Specifically, it is preferable to select the melting temperature and the melting residence time.

  Stretching is preferably performed at 270 ° C. or lower, preferably 120 ° C. to 250 ° C., using a heating bath, heated steam spray, roller heater, contact type plate heater, non-contact type plate heater, or the like. The draw ratio is preferably 2 times or more, more preferably 3 times or more. In addition, if necessary, the film is further subjected to constant-length heat treatment, tension heat treatment or relaxation heat treatment at 120 to 270 ° C., or in addition to the above-described two-stage spin-draw method, unstretched obtained by spinning. It is also possible to stretch the yarn continuously. When stretching at a temperature exceeding 270 ° C., the polyamide resin is deteriorated, melted, crystal reorganized, etc., and the strength of the resulting fiber is reduced, or a fiber having high heat resistance cannot be obtained. There is.

  The triamine in the fiber induces a three-dimensional reaction and causes poor stretchability in the fiber stretching process, so it may be difficult to obtain a highly heat-resistant fiber, or a decrease in physical properties of the yarn may occur. is there. In addition, when stretching at a temperature lower than 120 ° C., it is difficult to sufficiently open the overlap of molecular chains, the stretching ratio is low, voids and defects are formed, and fibers cannot be obtained. In some cases, the yarn physical properties may not be expressed. Therefore, it is preferable to stretch the fiber in the above stretching temperature range.

  The non-woven fabric made of the semi-aromatic polyamide of the present invention can be obtained by laminating undrawn yarn obtained under the same melting conditions as the above-described melt spinning method, or by known spunbond method, melt blow method, flash spinning method, electrospinning. And a production method such as a wet nonwoven fabric method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

<Raw material>
The raw materials used in Examples and Comparative Examples are shown below.
(1) Dicarboxylic acid component ・ Terephthalic acid (melting point: 300 ° C or higher)
・ Isophthalic acid (melting point: 343 ° C)
Adipic acid (melting point: 153 ° C)
(2) Diamine component ・ 1,8-octanediamine (melting point: 51 ° C.)
・ 1,9-nonanediamine (melting point: 36 ° C.)
・ 1,10-decanediamine (melting point: 62 ° C.)
・ 1,12-dodecanediamine (melting point: 68 ° C.)

<Measurement method>
According to the following method, the performance evaluation of the measurement of resin characteristics was performed.

(1) Average particle diameter of terephthalic acid Measurement was performed using an apparatus (“LA920” manufactured by Horiba, Ltd.) that measures the particle size distribution of the average particle diameter of fine particles, and the volume average particle diameter was evaluated.

(2) Relative viscosity of polyamide Using an Ubbelohde viscometer, 96% sulfuric acid was used as a solvent, and the measurement was performed at a concentration of 1 g / dL and 25 ° C.

(3) Decreasing crystallization temperature, melting point, and degree of supercooling of polyamide Using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, Inc., the temperature was raised to 350 ° C. at a rate of temperature increase of 20 ° C./min. Hold for a minute. Thereafter, the temperature that gives the top of the exothermic peak when the temperature is lowered to 25 ° C. at a temperature lowering rate of 20 ° C./min is maintained at the temperature of the lowering crystallization temperature (Tcc), and further at 25 ° C. for 5 minutes, The top of the endothermic peak when measuring the temperature rise was taken as the melting point (Tm). The difference between the melting point and the cooling crystallization temperature (Tm−Tcc) was defined as the degree of supercooling (ΔT).

(4) Determination of triamine in polyamide resin, semi-aromatic polyamide fiber and non-woven fabric Add 3 mL of 47% hydrobromic acid to 10 mg of polyamide (resin, fiber, non-woven fabric), heat at 130 ° C. for 16 hours, and allow to cool to room temperature did. 5 mL of 20% sodium hydroxide aqueous solution was added to make the sample solution alkaline, then transferred to a separatory funnel, 8 mL of chloroform was added and stirred, allowed to stand, and only the chloroform layer was transferred to a test tube. Concentrated with. Chloroform 1.5mL was added to the concentrated sample, and what filtered this with the membrane filter was made into the measurement sample. This measurement sample was analyzed with a gas chromatography apparatus (manufactured by Agilent Technologies, trade name “Agilent 6890N”) equipped with a mass spectrometer. Using a calibration curve prepared using diamine and triamine as standard samples, the diamine and triamine in the polyamide were quantified, and the molar ratio of triamine to diamine was calculated. The diamine used in the polymerization was used as the diamine standard substance. The triamine standard substance used was a triamine compound obtained by reacting the diamine used for polymerization in an autoclave by heating and stirring at 240 ° C. for 3 hours using palladium oxide as a catalyst.

(5) Nozzle pressurization Using an extruder type single screw extruder, melt spinning was performed under the conditions shown in Table 1. After filtration through a breaker plate and a metal non-woven filter (Naslon NF-12) having a filtration area of 68 mmφ on the back side, melt extrusion is performed from a die having a pore diameter of 0.35 mmφ24 holes at a condition of 1.45 g / min · hole. Thereafter, the film was taken up and wound up by a roller having a speed of 400 m / min. The residence time in the nozzle pack was 7 minutes. At that time, the pressure change per unit time of the filter was measured.

(6) Spinning / drawing property In the melt spinning process, the nozzle pressurization is small, there is no foreign matter such as air bubbles or gelled material contained in the filament, and there is no thread breakage in the take-up process. The state without the mark was judged as a good situation and indicated as ◯. Nozzle pressurization in the melt spinning process is remarkable, yarn breakage frequently occurs in the take-up process, yarn breakage frequently occurs in the heat drawing process, etc. It was. Although not defective, the conditions under which phenomena such as nozzle pressure increase and thread breakage occurred are indicated by Δ as problematic.

Example 1
[Step a]
1,10-decanediamine (5050 parts by mass) as a diamine component, terephthalic acid powder (4870 parts by mass) having a volume average particle size of 80 μm, benzoic acid (72 parts by mass) as a terminal blocking agent, and sodium hypophosphite as a polymerization catalyst The monohydrate (6 parts by mass) was placed in an autoclave, heated to 100 ° C., stirred using a double helical type stirring blade at a rotation speed of 28 rpm, and heated for 1 hour. The molar ratio of the raw material monomers was 1,10-decanediamine: terephthalic acid = 50: 50.
[Step b]
The mixture obtained in step a was heated to 230 ° C. while maintaining the rotation speed at 28 rpm, and then heated at 230 ° C. for 3 hours. The formation reaction and crushing of salt and low polymer were performed simultaneously. After releasing the water vapor generated by the reaction, the resulting reaction product was taken out.
[Step c]
The reaction product obtained in the step b was polymerized by heating at 230 ° C. for 5 hours in a dryer under a normal pressure nitrogen stream to obtain a polyamide. The characteristic values of the obtained polyamide are shown in Table 1.
[Step d]
The polyamide obtained in step c was put into an extruder type single screw extruder and melt-spun under the conditions shown in Table 1. After filtration through a breaker plate and a metal non-woven filter (Naslon NF-12) having a filtration area of 68 mmφ on the back side, melt extrusion is performed from a die having a pore diameter of 0.35 mmφ24 holes at a condition of 1.45 g / min · hole. Thereafter, the film was taken up and wound up by a roller having a speed of 400 m / min. The residence time in the nozzle pack was 7 minutes. Then, it extended | stretched with the extending | stretching temperature and the draw ratio of Table 1, and obtained the polyamide fiber. Table 2 shows the characteristic values of the obtained polyamide fiber.

Example 2
[Step a and Step b]
A mixture of terephthalic acid powder having a volume average particle size of 80 μm (4870 parts by mass), sodium hypophosphite (6 parts by mass) as a polymerization catalyst, and benzoic acid (72 parts by mass) as a terminal blocking agent is obtained by a ribbon blender type. The reactor was heated to 170 ° C. with stirring at a rotation speed of 30 rpm using a double helical stirring blade under nitrogen sealing. Thereafter, decanediamine (50 parts by mass, 100% by mass) heated to 100 ° C. using a liquid injection device while maintaining the temperature at 170 ° C. and the rotation speed at 30 rpm was 28 parts by mass / min. Was added to the terephthalic acid powder continuously (continuous liquid injection method) over 3 hours to obtain a reaction product.
[Step c]
The reactant obtained in step a and step b was subsequently heated to 230 ° C. under a nitrogen stream and heated at 230 ° C. for 5 hours in the ribbon blender reactor used in step a and step b. Polymerization gave a semi-aromatic polyamide. The characteristic values of the obtained semiaromatic polyamide are shown in Table 1.
[Step d]
The semi-aromatic polyamide obtained in step c was melt-spun and heated and stretched under the conditions shown in Table 1 using an extruder type single-screw extruder to obtain semi-aromatic polyamide fibers. Table 1 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

Examples 3-6 and 9-10, Comparative Example 1
A semi-aromatic polyamide fiber was obtained by melt spinning and heat drawing after obtaining a semi-aromatic polyamide in the same manner as in Example 2 except that the type of monomer used and the production conditions were changed as shown in Table 1. . Table 2 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

Example 7
[Step a]
1,10-decanediamine (5050 parts by mass) as a diamine component, terephthalic acid powder (4870 parts by mass) having a volume average particle size of 80 μm, benzoic acid (72 parts by mass) as a terminal blocking agent, and sodium hypophosphite as a polymerization catalyst Monohydrate (6 parts by mass) and 400 parts by mass of distilled water (4 parts by mass with respect to 100 parts by mass of the raw material monomers) are put in an autoclave, heated to 100 ° C., and then stirred at a rotation speed of 28 rpm. And heated for 1 hour.
[Step b]
The mixture obtained in step a was heated to 230 ° C. while maintaining the rotation speed at 28 rpm, and then heated at 230 ° C. for 3 hours. The resulting solid was crushed while the salt and low polymer were formed. After releasing the water vapor, the obtained reaction product was taken out.
[Step c]
The reaction product obtained in the step b was polymerized by heating at 230 ° C. for 5 hours in a dryer under a normal pressure nitrogen stream to obtain a semi-aromatic polyamide. The characteristic values of the obtained semiaromatic polyamide are shown in Table 1.
[Step d]
Using the semi-aromatic polyamide obtained in step c, semi-aromatic polyamide fibers were obtained in the same manner as in Example 1 under the conditions shown in Table 1. Table 2 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

Example 8
[Step a and Step b]
A reaction product was obtained in the same manner as in Example 1.
[Step c]
The reaction product obtained in step a and step b was supplied to a twin screw extruder (30 mmφ, L / D = 45, 2 vent) and subjected to melt polymerization to obtain a pellet-like semi-aromatic polyamide. The cylinder temperature of the twin screw extruder was set to 330 ° C, and the resin temperature was adjusted to 335 ° C. The average residence time was set at 3 minutes. The hopper was sealed with nitrogen gas having an oxygen content of 50 ppm or less. The first vent was opened and sealed with the nitrogen gas, and the second vent was kept at a reduced pressure of 50 mmHg using a vacuum pump. The screw rotation speed was set to 40 rpm, and the supply amount of the low polymer from the hopper was 1 kg / hour. The characteristic values of the obtained semiaromatic polyamide are shown in Table 1.
[Step d]
Using the semi-aromatic polyamide obtained in step c, semi-aromatic polyamide fibers were obtained in the same manner as in Example 1 under the conditions shown in Table 1. Table 2 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

Comparative Example 2
[Step a, Step b and Step c]
In step a, instead of 400 parts by mass of distilled water (4 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers), 9200 parts by mass of distilled water (92 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers) A semi-aromatic polyamide was obtained in the same manner as in Example 7 except that it was changed to (part). The characteristic values of the obtained semiaromatic polyamide are shown in Table 1.
[Step d]
Semi-aromatic polyamide fibers were obtained in the same manner as in Example 1 using the semi-aromatic polyamides obtained in steps a, b and c under the conditions shown in Table 1. Table 2 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

Comparative Example 3
[Step a, Step b and Step c]
In Step a, instead of 400 parts by mass of distilled water (4 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers), 600 parts by mass of distilled water (6 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers) A semi-aromatic polyamide was obtained in the same manner as in Example 7 except that it was changed to (part). The characteristic values of the obtained semiaromatic polyamide are shown in Table 1.
[Step d]
Semi-aromatic polyamide fibers were obtained in the same manner as in Example 1 using the semi-aromatic polyamides obtained in steps a, b and c under the conditions shown in Table 1. Table 2 shows the characteristic values of the obtained semi-aromatic polyamide fiber.

The raw polymer of the semi-aromatic polyamide fiber not containing the copolymer component obtained in Examples 1, 2, 4, and 6 to 8 has a high degree of supercooling in a preferable range (ΔT is 35 ° C. or less) in the present invention. Since it has crystallinity, the obtained semi-aromatic polyamide fiber was excellent in heat resistance and moldability. Furthermore, since the triamine unit in the semi-aromatic polyamide was as low as 0.3 mol% or less of the diamine unit, gelation was suppressed, there was no nozzle pressure increase during melt spinning, and the resulting polyamide fiber was excellent Showed the characteristics. In the semiaromatic polyamides obtained in Examples 3 and 5, isophthalic acid was copolymerized as a copolymerization component, but the ratio was 5 mol% or less, so the degree of supercooling was within the range defined in the present invention ( ΔT was 40 ° C. or lower), and the heat resistance and crystallinity were excellent. Furthermore, the triamine unit in the semi-aromatic polyamide was as low as 0.3 mol% or less of the diamine unit. Therefore, gelation is suppressed, there is no nozzle pressurization at the time of melt spinning, and the resulting polyamide fiber exhibits excellent characteristics. Example 7 was polymerized in the presence of 5 parts by mass or less of water with respect to a total of 100 parts by mass of terephthalic acid and diamine, so that the triamine unit in the semi-aromatic polyamide had a gel content of 0.3 mol% or less of the diamine unit. Therefore, there was no nozzle pressure increase during melt spinning, and the resulting polyamide fiber exhibited excellent characteristics. In Examples 9 and 10, the dicarboxylic acid other than terephthalic acid was copolymerized in excess of 5% with respect to the total number of moles of the dicarboxylic acid component and the diamine component. For this reason, the polyamide fibers obtained in Examples 9 and 10 had room for improvement in mechanical properties, but could sufficiently withstand practical use.
On the other hand, in Comparative Example 1, since 1,9-nonanediamine having an odd number of carbon atoms was used as the diamine component, the degree of supercooling was high, and the obtained semi-aromatic polyamide had low crystallinity. A decrease in mechanical properties of the resulting fiber was observed. In Comparative Examples 2 and 3, polyamide was polymerized in the presence of water exceeding 5 parts by mass with respect to 100 parts by mass in total of terephthalic acid and diamine. Therefore, the triamine content in the polyamide exceeds 0.3 mol%, the gel contains a large amount of gel, the nozzle pressure increase is remarkable, and it is estimated that it is not suitable for practical use.

Claims (8)

A terephthalic acid component and a diamine component are included, and the diamine component is any one of 1,8-octanediamine, 1,10-decanediamine, and 1,12-dodecanediamine, and the triamine unit is 0. A semi-aromatic polyamide fiber or a semi-aromatic polyamide non-woven fabric comprising a semi-aromatic polyamide, characterized in that it is 3 mol% or less. The copolymer component other than the terephthalic acid component and the diamine component, which are the main components of the semi-aromatic polyamide, is contained in a proportion of 0 to 5 mol% with respect to the total number of moles of the raw material monomers. The semi-aromatic polyamide fiber or the semi-aromatic polyamide nonwoven fabric according to 1. The semi-aromatic polyamide fiber or the semi-aromatic polyamide nonwoven fabric according to claim 1 or 2, wherein the melting point measured using a differential scanning calorimeter is 280 ° C to 340 ° C. The semi-aromatic polyamide fiber or the semi-aromatic polyamide nonwoven fabric according to any one of claims 1 to 3, wherein a degree of supercooling ΔT measured using a differential scanning calorimeter is 40 ° C or less. . The method for producing a semi-aromatic polyamide fiber according to any one of claims 1 to 4, wherein the following steps (a) to (d) are sequentially performed.
(A) A suspension of diamine and solid terephthalic acid in a molten state at 80 ° C. or more and 150 ° C. or less under the condition that the amount of water is 5 parts by mass or less with respect to a total of 100 parts by mass of terephthalic acid and diamine. Step of stirring and mixing to obtain a mixture.
(B) In the mixture obtained in step (a), at a temperature lower than the melting point of the semiaromatic polyamide to be finally produced, a salt is formed by the reaction of terephthalic acid and diamine, and a low weight is obtained by the polymerization of the salt. A step of performing a coalescence formation reaction to obtain a mixture of a salt and a low polymer.
(C) A step of polymerizing the mixture of the salt and low polymer obtained in step (b) to obtain a semi-aromatic polyamide having a melting point of 280 ° C. to 340 ° C. measured using a differential scanning calorimeter. .
(D) A step of melt-spinning the semi-aromatic polyamide obtained in step (c) and drawing and heat-treating the obtained yarn. The method for producing a semi-aromatic polyamide fiber according to any one of claims 1 to 4, wherein the following steps (a) to (d) are sequentially performed.
(A) The terephthalic acid powder is heated in advance to a temperature not lower than the melting point of diamine and not higher than the melting point of terephthalic acid, so that the terephthalic acid powder is substantially maintained at a temperature not lower than the melting point of diamine and not higher than the melting point of terephthalic acid. Adding diamine to terephthalic acid powder without containing water.
(B) In the mixture obtained in step (a), at a temperature lower than the melting point of the semiaromatic polyamide to be finally produced, a salt is formed by the reaction of terephthalic acid and diamine, and a low weight is obtained by the polymerization of the salt. A step of performing a coalescence formation reaction to obtain a mixture of a salt and a low polymer.
(C) A step of polymerizing the mixture of the salt and low polymer obtained in step (b) to obtain a semi-aromatic polyamide having a melting point of 280 ° C. to 340 ° C. measured using a differential scanning calorimeter. .
(D) A step of melt-spinning the semi-aromatic polyamide obtained in step (c) and drawing and heat-treating the obtained yarn. The half of claim 5 or 6, wherein the polymerization step of step (c) is a step of solid phase polymerization of the mixture obtained in step (b) while maintaining a temperature below the melting point of the polyamide to be produced. A method for producing an aromatic polyamide fiber. In step (d), after melting the semi-aromatic polyamide at the melting point to 360 ° C., melt spinning from a spinneret nozzle with a melt residence time of 30 minutes or less, and cooling the obtained yarn, the temperature is 120 ° C. to 250 ° C. The semi-aromatic according to any one of claims 5 to 7, wherein the film is stretched at 120 ° C to 270 ° C, and then subjected to constant-length heat treatment, tension heat treatment, or relaxation heat treatment after stretching at a temperature of 2 ° C or more. A method for producing a polyamide fiber.