Copolymerized aramid fiber and method of manufacturing the same

Abstract

To provide a copolymerized aramid fiber made of a meta-aramid polymer having a small amount of low molecular weight components and a small molecular weight dispersion.SOLUTION: There are provided a polymer that is obtained by co-polymerizing a specific monomer in a specific ratio, and has a small amount of low molecular weight components and a small molecular weight dispersity; and further, a high-strength meta-aramid fiber that is obtained by using the polymer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to copolyaramid fibers and a method for producing the same. More specifically, the present invention relates to copolyaramid fibers characterized by being formed from copolyaramid having a small amount of low molecular weight components and a small molecular weight dispersity, and having excellent breaking strength, and a method for producing the same.

Background Art

[0002] Conventionally, it is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy. Among such wholly aromatic polyamides, fibers of meta-type wholly aromatic polyamides (hereinafter sometimes referred to as meta-aramid) typified by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers. Exhibiting these properties, they are used, for example, in disaster prevention and safety clothing applications such as protective clothing, and industrial applications such as filters and electronic components.

[0003] In recent years, due to the sophistication of society, the needs for weight reduction and high strength have been increasing in the above-mentioned various applications. As spun yarns, those made of high-strength meta-aramid fibers with a breaking strength of more than 4.5 cN / dtex are preferably used.

[0004] Furthermore, in the above-mentioned various applications, the requirements for further processability and improvement of fatigue resistance have been increasing. In order to satisfy these requirements, it is necessary to maintain a high elongation while ensuring the breaking strength of the fiber, that is, to increase the toughness.

[0005] In particular, the elongation of the fiber is one of the important factors in clothing applications. Clothing made of high-elongation fibers exhibits flexibility, leading to an improvement in texture and comfort. Therefore, if meta-aramid fibers having sufficient elongation while satisfying the breaking strength can be obtained, their industrial value is extremely high.

[0006] Here, as methods for spinning meta-aramid, there are the following. Conventionally known dry spinning (for example, Japanese Patent Publication No. 35-14399) involves volatilizing and drying the solvent from near the surface of the fibrous polymer solution extruded from a spinneret to form fibers. On the other hand, in wet spinning, for example, (a) A method in which a meta-aramid polymer solution substantially free of salts is discharged into a coagulation bath composed of an amide solvent and water for coagulation to form a fibrous material (yarn), and then stretched in a plastic stretching bath composed of an amide solvent and water, followed by washing with water and heat treatment (Japanese Patent Laid-Open Nos. 2001-303365, 2003-301326, 2003-342832, etc.), (b) A method in which a polymer solution composed of a meta-aramid and an amide solvent containing salts is discharged into a coagulation bath composed of an amide solvent and water and substantially free of salts for coagulation as a porous linear body, and then stretched in a plastic stretching bath composed of an aqueous solution of an amide solvent, followed by washing with water and heat treatment (Japanese Patent Laid-Open No. 2005-232598), (c) A method in which a meta-aramid polymer solution obtained by solution polymerization in an amide solvent and neutralized with calcium hydroxide, calcium oxide, etc. and containing calcium chloride and water is spun into an aqueous coagulation bath substantially free of inorganic salts and having an amide solvent concentration of 45 to 60% by mass to form a fibrous material (International Publication No. 2007 / 089008, International Publication No. 2011 / 118022), (d) A wet spinning method in which meta-aramid polymer powder is redissolved in an amide solvent, and then a 15 to 25% by mass meta-type wholly aromatic polyamide solution is spun into an aqueous coagulation bath containing 35 to 45% by mass of a high-concentration inorganic salt for coagulation (Japanese Patent Publication No. 48-17551), and so on.

[0007] In the above methods, although the fiber strength finally obtained exceeds 4.5 cN / dtex in some cases, the elongation at break of the obtained fibers is often about 30%, and no example of a manufacturing method for general-purpose meta-aramid fibers having high strength and high elongation has been reported.

[0008] In addition, Japanese Patent Application Laid-Open No. 2-263829 reports a method for producing aramid fibers with a strength exceeding 6 cN / dtex by spinning a copolymer obtained by copolymerizing N,N′-bis(4-aminophenyl)isophthalamide and paraphenylenediamine at an arbitrary ratio. However, the resulting elongation was as low as 10% or less.

[0009] On the other hand, controlling the molecular weight of the polymer is a method that can stably exhibit high strength and high elongation for various spinning methods as described above. Meta-aramid is a polymer obtained by polycondensation reaction of aromatic diamine and aromatic dicarboxylic acid dichloride, and very strict control of monomer composition and by-products is required. In addition, due to the characteristics of polymerization, generation of oligomers with low molecular weight easily occurs, not only increasing the low molecular weight components but also broadening the molecular weight distribution.

[0010] Such excessive low molecular weight components and broad molecular weight distribution in the raw material polymer can cause structural defects and fracture factors during fiber formation, which are problems to be noted for exhibiting high strength and high elongation. In response to such problems, Japanese Patent Application Laid-Open No. 2007-154356 reports a method for producing meta-aramid fibers with a molecular weight distribution of less than 5 by sealing amine terminals at the end of polymerization, having few flyings and excellent wet spinning properties. However, there has been no reported example of improving the mechanical properties of fibers by controlling the molecular weight distribution of the polymer.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Summary of the Invention

Problems to be Solved by the Invention

[0012] An object of the present invention is to provide a high-strength and high-elongation copolymerized aramid fiber mainly composed of a meta-aramid polymer having few low-molecular-weight components and a small molecular weight distribution, as described in the background above.

Means for Solving the Problems

[0013] As a result of intensive studies to solve the above problems, the present inventor has found that by copolymerizing specific monomers at a specific ratio, the resulting polymer has few low-molecular-weight components and a small molecular weight distribution, and further, by using this polymer, a high-strength and high-elongation copolymerized aramid fiber can be obtained, thus completing the present invention.

[0014] That is, according to the present invention, 1. A fiber comprising an aramid copolymer containing a metaphenylene isophthalamide unit and a metaphenylene terephthalamide unit, wherein the weight average molecular weight of the aramid copolymer is 400,000 to 1,000,000, the molecular weight distribution is 2.0 to 5.0, the breaking strength of the fiber is 4.5 to 7.0 cN / dtex, and the breaking elongation is 30 to 60%, characterized in that it is a copolymerized aramid fiber. 2. The copolyaramid fiber according to 1 above, wherein the aramid copolymer contains structural units composed of metaphenylenediamine, isophthaloyl, and terephthaloyl, and the molar ratio of metaphenylenediamine and isophthaloyl units to terephthaloyl units is 70:30 to 99:1. 3. A method for producing a copolyaramid fiber, characterized in that the following steps (1) to (5) are sequentially carried out using an aramid copolymer containing metaphenylenediamine isophthalamide units and metaphenylenediamine terephthalamide units, having a weight average molecular weight of 400,000 to 1,000,000 and a molecular weight dispersity of 2.0 to 5.0, which is the method for producing the copolyaramid fiber according to 1 above. (1) Dissolving the aramid copolymer in an amide-based solvent in the range of 10 to 30% by mass to obtain a spinning dope, and discharging the dope from a spinneret. (2) Spinning and coagulating in an aqueous coagulation bath containing 1 to 20% by mass of an amide-based solvent. (3) Washing with water in an aqueous washing bath, and subsequently stretching in a boiling water stretching bath in the range of 1.1 to 5.0 times. (4) Performing dry heat treatment in the range of 100 to 250°C. (5) While applying heat treatment in the range of 290 to 380°C, performing hot stretching at a stretching ratio in the range of 1.5 to 5.0 times. And, 4. The method for producing a copolyaramid fiber according to claim 3, wherein the aramid copolymer contains structural units composed of metaphenylenediamine, isophthaloyl, and terephthaloyl, and the molar ratio of metaphenylenediamine and isophthaloyl units to terephthaloyl units is 70:30 to 99:1. is provided.

Advantages of the Invention

[0015] The copolyaramid fiber obtained in the present invention has heat resistance capable of withstanding a use environment of 250°C or higher, a breaking strength of 4.5 to 7.0 cN / dtex, and an elongation at break of 30 to 60%. Since the balance of physical properties is excellent, it can be suitably used in applications such as protective clothing and rubber reinforcement.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail. The copolymerized aramid fiber of the present invention is characterized in that its breaking strength is 4.5 to 7.0 cN / dtex and its breaking elongation is 30 to 60%. Examples of the polymer constituting such copolymerized aramid fiber include wholly aromatic polyamides (hereinafter sometimes referred to as aramids), specifically, those composed of a meta-type aromatic diamine component, a meta-type aromatic dicarboxylic acid component, and a para-type aromatic dicarboxylic acid component, and are synthesized by copolymerization.

[0017] Particularly preferably used in the present invention is a wholly aromatic polyamide composed of a copolymerized aramid polymer having a structure containing a metaphenylene isophthalamide unit and a metaphenylene terephthalamide unit from the viewpoints of mechanical properties, heat resistance, and flame retardancy.

[0018] In the copolymerized aramid fiber of the present invention, the wholly aromatic polyamide composed of the above copolymerized aramid polymer is randomly copolymerized. Examples of the aromatic diamine component as a raw material thereof include metaphenylenediamine, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone, etc., and derivatives having substituents such as halogen and alkyl groups having 1 to 3 carbon atoms on these aromatic rings.

[0019] Examples of the raw material of the aromatic dicarboxylic acid component constituting the wholly aromatic polyamide of the present invention include aromatic dicarboxylic acid halides. Examples of the meta-type aromatic dicarboxylic acid halides include isophthalic acid chlorides, isophthalic acid bromides, etc., and derivatives having substituents such as halogen and alkoxy groups having 1 to 3 carbon atoms on these aromatic rings.

[0020] Similarly, examples of the para-type aromatic dicarboxylic acid halides include terephthalic acid halides such as terephthalic acid chloride and terephthalic acid bromide, and derivatives having substituents such as halogen and alkoxy groups having 1 to 3 carbon atoms on these aromatic rings.

[0021] In the present invention, using the above aromatic diamine component and aromatic dicarboxylic acid component, a copolyaramid polymer containing a metaphenylene isophthalamide unit and a metaphenylene terephthalamide unit is obtained.

[0022] Further, in the present invention, the aromatic diamine component includes metaphenylenediamine, and the aromatic dicarboxylic acid component includes structural units composed of isophthaloyl and terephthaloyl. Preferably, the molar% of the above metaphenylenediamine and / or isophthaloyl structural unit is 70 to 99% of the whole, and the molar% of the terephthaloyl structural unit is 1 to 30% of the whole.

[0023] When the molar% of the metaphenylenediamine and / or isophthaloyl structural unit is less than 70%, the target elongation may not be achieved. Further, when the molar% of the metaphenylenediamine and / or isophthaloyl structural unit is greater than 99%, the target strength may not be achieved.

[0024] Examples of the polymerization method of the wholly aromatic polyamide of the present invention include a method of isolating a polymetaphenylene isophthalamide polymer powder by bringing an organic solvent system (for example, tetrahydrofuran), which is not a good solvent for the produced polyamide containing metaphenylenediamine and isophthalic acid chloride, into contact with an inorganic acid acceptor and an aqueous solution system containing a soluble neutral salt (interfacial polymerization, Japanese Patent Publication No. 47-10863), or a method of solution-polymerizing the above diamine and acid chloride in an amide solvent and then neutralizing with calcium hydroxide, calcium oxide, etc. (solution polymerization, Japanese Unexamined Patent Application Publication No. 8-074121, Japanese Unexamined Patent Application Publication No. 10-88421), etc., but the method is not limited thereto.

[0025] In addition, from the perspective of forming fibers with breaking strength and elongation at break that can withstand practical use, the weight average molecular weight of the wholly aromatic polyamide copolymer (also referred to as an aramid copolymer) used in the present invention needs to be 400,000 to 1,000,000 according to the analysis method described later. Further, 500,000 to 900,000 is preferable, and 550,000 to 800,000 is more preferable. When the weight average molecular weight is less than 400,000, not only does the breaking strength significantly decrease, but stable spinning cannot be performed. Also, when the molecular weight exceeds 1,000,000, when preparing and spinning the wholly aromatic polyamide solution described later, the viscosity is too high, making it difficult to handle and requiring dedicated equipment.

[0026] For the polymer within the molecular weight range defined in the present invention, a mixture of a low molecular weight polymer and a high molecular weight polymer can be used, and as long as the overall molecular weight is a value within the molecular weight range defined by adjusting the mixing ratio. For example, when a polymer with a weight average molecular weight of 200,000 and a polymer with a weight average molecular weight of 800,000 are mixed, and the weight average molecular weight of this mixed polymer is 600,000, there is no problem in using it because it is within the molecular weight range defined in the present invention.

[0027] From the perspective of forming fibers with breaking strength and elongation at break that can withstand practical use, the molecular weight distribution of the aramid polymer used in the present invention needs to be 2.0 to 5.0 according to the analysis method described later. Further, 2.5 to 4.8 is preferable, and 2.5 to 4.5 is more preferable. Since it is a polymer formed by a polycondensation reaction, it is not practically preferable to be less than 2.0 because it cannot be achieved without using a special polymerization method. Also, when it is greater than 5.0, it becomes difficult to achieve the target strength and elongation.

[0028] The wholly aromatic polyamide fiber of the present invention is produced through the spinning solution preparation process, spinning and coagulation process, washing process, boiling water drawing process, dry heat treatment process, and heat drawing process described below using the wholly aromatic polyamide obtained by the above production method.

[0029] [Spinning Solution Preparation Process] In the spinning solution preparation process, the wholly aromatic polyamide of the present invention is dissolved in a solvent to prepare a spinning solution (dope). When preparing the spinning solution, an amide-based solvent is usually used, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), etc. Among these, from the viewpoints of solubility and handling safety, it is preferable to use NMP or DMAc.

[0030] As for the solution concentration, an appropriate concentration may be appropriately selected from the viewpoints of the coagulation rate in the subsequent spinning and coagulation process and the solubility of the polymer, and usually it is necessary to be in the range of 10 to 30% by mass. In order to achieve stable spinning, it is more preferable to be in the range of 15 to 25% by mass.

[0031] In the present invention, an inorganic salt may be introduced into the dope, and it is preferable to contain 0 to 20% by mass of the inorganic salt with respect to the dope, and 0 to 10% by mass of the inorganic salt is more preferable in order to obtain stable spinnability.

[0032] Here, if the inorganic salt content exceeds 20% by mass, the coagulation rate becomes too fast and a large number of voids are formed in the fiber, so that fibers having the desired physical properties cannot be obtained. As the inorganic salt, it is preferable to use chloride salts such as calcium chloride, magnesium chloride, and lithium chloride.

[0033] [Spinning and Coagulation Process] In the spinning and coagulation process, the dope obtained above is spun into a coagulation liquid and coagulated. The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. As long as stable wet spinning can be performed, the number of spinning holes, the spinning hole diameter, the arrangement state, etc. of the spinneret do not need to be particularly limited. For example, a multi-hole spinneret for staple fibers with 10 to 30,000 spinning holes and a spinning hole diameter of 0.03 to 0.2 mm can be used.

[0034] Also, the temperature of the dope when spinning from the spinneret is preferably in the range of 20 to 90°C, and more preferably 70 to 90°C.

[0035] As the coagulation bath used for obtaining the fiber of the present invention, an aqueous solution containing 1 to 20% by mass of an amide-based solvent, preferably an aqueous solution containing 3 to 15% by mass, is used. The temperature of this aqueous solution preferably ranges from 50 to 90°C.

[0036] In addition, the coagulation bath can contain an inorganic salt such as calcium chloride or magnesium chloride, preferably 30% by mass or more, more preferably 35 to 45% by mass. As described above, the dope is spun from the spinneret into the coagulating liquid and passed through the coagulation bath to obtain a coagulated fiber.

[0037] [Washing step, boiling water stretching step] The coagulated fiber thus obtained is sufficiently washed in an aqueous washing bath and sent to the boiling water stretching step. The draw ratio in the boiling water stretching bath needs to be in the range of 1.1 to 5.0 times, and more preferably in the range of 1.1 to 3.0 times. Here, "boiling water" is a concept that also includes "heated water" with a temperature of 90°C or higher. By performing the stretching within the range of the said magnification and raising the molecular chain orientation, the strength of the finally obtained fiber can be ensured.

[0038] [Dry heat treatment step] Preferably, a dry heat treatment step is performed on the fiber that has undergone the above washing and stretching steps. In the dry heat treatment step, the fiber washed in the above washing step is dry heat treated in the range of 100 to 250°C, preferably in the range of 100 to 200°C. Also, the dry heat treatment is preferably performed under a fixed length. The temperature of the above dry heat treatment refers to the set temperature of fiber heating means such as a hot plate or a heating roller.

[0039] [Thermal stretching step] In the present invention, a heat drawing process is performed on the fibers that have undergone the above dry heat treatment process. In the heat drawing process, drawing is carried out while applying heat treatment in the range of 290 to 380 °C. The treatment temperature is preferably in the range of 290 to 350 °C. If it is less than 290 °C, it is unsuitable because high magnification drawing cannot be performed, and if it exceeds 380 °C, discoloration or breakage of the fibers may occur. In the heat drawing process, the draw ratio needs to be in the range of 1.5 to 5.0 times, preferably in the range of 1.8 to 3.0 times. Note that the temperature of the heat drawing treatment refers to the set temperature of fiber heating means such as a hot plate or a heating roller.

[0040] And, the total draw ratio of the boiling water draw ratio and the heat draw ratio in the present invention needs to be 7 times or more. If the total draw ratio is less than 7 times, the target strength cannot be achieved. Therefore, the boiling water draw ratio and the heat draw ratio need to be appropriately adjusted in view of the process conditions. The breaking strength of the copolyaramid fiber obtained by the above method is 4.5 to 7.0 cN / dtex.

[0041] When the breaking strength is less than 4.5 cN / dtex, it is insufficient as the strength of the copolyaramid fiber targeted by the present invention. Also, the elongation at break needs to be 30% to 60%, preferably 35% to 55% or more. When the elongation at break is less than 30%, the flexibility is not sufficiently exhibited because the elongation is not sufficient. When the elongation at break exceeds 60%, it becomes difficult to obtain sufficient strength.

Examples

[0042] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples and Comparative Examples. In addition, each physical property value in the Examples and Comparative Examples was measured by the following method.

[0043] [Weight average molecular weight Mw and molecular weight distribution] Analysis was performed using a high-performance liquid chromatography apparatus equipped with a size exclusion chromatography column in accordance with JIS-K-7252. The eluent used was dimethylformamide (containing 0.01 mol% lithium chloride), and measurements were taken. As the standard molecular weight sample, a polystyrene set manufactured by Sigma-Aldrich (peak top molecular weight Mp = 400 to 2,000,000) was used. The molecular weight distribution was calculated as the weight average molecular weight Mw / number average molecular weight Mn.

[0044] [Single fiber fineness] In accordance with JIS-L-1015, measurements were carried out according to Method A for the linear density, and the apparent fineness was indicated.

[0045] [Breaking strength, elongation at break] Using a tensile testing machine (manufactured by Instron, model: 5565), measurements were taken in accordance with JIS-L-1015 under the following conditions. (Measurement conditions) Grip interval: 20 mm Initial load: 0.044 cN (1 / 20 g / dtex) Tensile speed: 20 mm / min

[0046] [Dry heat dimensional change rate] In accordance with JIS-L-1013, measurements were carried out according to Method B, and the dimensional change rate at 250 °C was determined.

[0047] [Melting point of fiber] The melting point of the fiber was determined by thermomechanical analysis in accordance with JIS-K-7197. Among the peaks of the obtained samples, the peak top temperature of the peak detected on the high temperature side or the temperature at which peak detection became impossible due to fiber melting was taken as the melting point.

[0048] [Example 1] By interfacial polymerization according to Japanese Patent Publication No. 47-10863, a copolymerized aramid polymer powder was synthesized in which the meta-phenylenediamine and isophthaloyl monomer units were 90 mol% of the total and the terephthaloyl monomer units were 10 mol%. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers, and the weight ratio was set to 4:1. The weight average molecular weight was 710,000 and the molecular weight dispersity was 4.1.

[0049] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the copolymerized aramid polymer was adjusted to 20% with respect to the polymer solution.

[0050] This polymer solution was heated to 85 °C to obtain a spinning dope, and was extruded and spun from a spinneret with a circular discharge hole having a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 85 °C. The composition of this coagulation bath was 43 mass% calcium chloride, 3 mass% NMP, and the remaining water was 54 mass%. After passing through at a yarn speed of 5.0 m / min at an immersion length (effective coagulation bath length) of 100 cm, it was once drawn out into the air.

[0051] This coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20 °C and 30 °C water, respectively. This washed yarn was stretched 2.4 times in boiling water at 90 °C, and then immersed in warm water at 90 °C for 40 seconds and washed.

[0052] Next, it was wound around a roller with a surface temperature of 170 °C for dry heat treatment, and then stretched 1.8 times on a hot plate with a surface temperature of 325 °C to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.1 dtex, a breaking strength of 5.5 cN / dtex, and an elongation at break of 42%.

[0053] [Example 2] By interfacial polymerization according to Example 1, a copolymerized aramid polymer powder in which the meta-phenylenediamine and isophthaloyl monomer units are 80 mol% of the whole and the terephthaloyl monomer unit is 20 mol% was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as acid chloride monomers so that the weight ratio was 3:2. The weight average molecular weight was 650,000 and the molecular weight dispersity was 3.8.

[0054] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the copolymerized aramid polymer was adjusted to 22% with respect to the polymer solution.

[0055] This polymer solution was heated to 85 °C to obtain a spinning dope, and was extruded and spun from a spinneret with a circular discharge hole having a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 85 °C. The composition of this coagulation bath was 43 mass% calcium chloride, 3 mass% NMP, and the remaining water was 54 mass%. After passing through at a yarn speed of 5.0 m / min with an immersion length (effective coagulation bath length) of 100 cm, it was once pulled out into the air.

[0056] This coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20 °C and 30 °C water, respectively. This washed yarn was stretched 2.2 times in boiling water at 90 °C, and then immersed in warm water at 90 °C for 40 seconds and washed.

[0057] Next, after winding around a roller with a surface temperature of 170 °C for dry heat treatment, it was stretched 1.9 times on a hot plate with a surface temperature of 325 °C to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.1 dtex, a breaking strength of 6.0 cN / dtex, and an elongation at break of 39%.

[0058] [Example 3] By interfacial polymerization according to Example 1, a copolymerized aramid polymer powder in which the m-phenylenediamine and isophthaloyl monomer units are 70 mol% of the whole and the terephthaloyl monomer unit is 30 mol% was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers so that the weight ratio was 2:3. The weight average molecular weight was 750,000 and the molecular weight dispersity was 3.2.

[0059] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the copolymerized aramid polymer was adjusted to 21% with respect to the polymer solution.

[0060] This polymer solution was heated to 85°C to obtain a spinning dope, and was discharged from a spinneret having a circular discharge hole with a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 90°C for spinning. The composition of this coagulation bath was 41% by mass of calcium chloride, 1% by mass of NMP, and the remaining water was 58% by mass. After passing through at a yarn speed of 5.0 m / min with an immersion length (effective coagulation bath length) of 100 cm, it was once drawn out into the air.

[0061] This coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20°C and 30°C water, respectively. This washed yarn was stretched 2.5 times in boiling water at 90°C, and then immersed in warm water at 90°C for 40 seconds and washed.

[0062] Next, it was wound around a roller with a surface temperature of 170°C for dry heat treatment, and then stretched 1.8 times on a hot plate with a surface temperature of 325°C to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.0 dtex, a breaking strength of 6.5 cN / dtex, and an elongation at break of 35%.

[0063] [Example 4] By interfacial polymerization according to Example 1, a copolymerized aramid polymer powder in which the meta-phenylenediamine and isophthaloyl monomer units were 95 mol% of the whole and the terephthaloyl monomer unit was 5 mol% was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers so that the weight ratio was 9:1. The weight average molecular weight was 690,000 and the molecular weight dispersity was 4.8.

[0064] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the copolymerized aramid polymer was adjusted to 22% with respect to the polymer solution.

[0065] This polymer solution was heated to 85 °C to obtain a spinning dope, and was extruded and spun from a spinneret having a circular discharge hole with a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 87 °C. The composition of this coagulation bath was 41% by mass of calcium chloride, 1% by mass of NMP, and the remaining water was 58% by mass. After passing through at a yarn speed of 5.0 m / min at an immersion length (effective coagulation bath length) of 100 cm, it was once pulled out into the air.

[0066] This coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20 °C and 30 °C water, respectively. This washed yarn was stretched 2.4 times in boiling water at 90 °C, and then immersed in warm water at 90 °C for 40 seconds and washed.

[0067] Next, it was wound around a roller with a surface temperature of 170 °C for dry heat treatment, and then stretched 1.8 times on a hot plate with a surface temperature of 325 °C to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.3 dtex, a breaking strength of 5.2 cN / dtex, and an elongation at break of 49%.

[0068] [Example 5] By interfacial polymerization according to Example 1, a copolymerized aramid polymer powder was synthesized in which the meta-phenylenediamine and isophthaloyl monomer units were 98 mol% of the whole and the terephthaloyl monomer unit was 2 mol%. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers so that the weight ratio was 24:1. The weight average molecular weight was 730,000 and the molecular weight dispersity was 4.9.

[0069] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the copolymerized aramid polymer was adjusted to 21% with respect to the polymer solution.

[0070] This polymer solution was heated to 87 °C to obtain a spinning dope, and was extruded and spun from a spinneret having a circular discharge hole with a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 87 °C. The composition of this coagulation bath was 41% by mass of calcium chloride, 1% by mass of NMP, and the remaining water was 58% by mass. After passing through at a yarn speed of 5.0 m / min at an immersion length (effective coagulation bath length) of 100 cm, it was once drawn out into the air.

[0071] This coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20 °C and 30 °C water, respectively. This washed yarn was stretched 2.4 times in boiling water at 90 °C, and then immersed in warm water at 90 °C for 40 seconds and washed.

[0072] Next, it was wound around a roller with a surface temperature of 170 °C for dry heat treatment, and then stretched 1.8 times on a hot plate with a surface temperature of 335 °C to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.1 dtex, a breaking strength of 4.8 cN / dtex, and an elongation at break of 48%.

[0073] [Comparative Example 1] By interfacial polymerization according to Example 1, an aramid polymer powder consisting only of metaphenylenediamine and isophthaloyl monomer units was synthesized. At this time, isophthaloyl chloride was used as the acid chloride monomer, and metaphenylenediamine was used as the amine monomer. The weight average molecular weight was 700,000 and the molecular weight dispersity was 6.0.

[0074] This polymer powder was dissolved in NMP to obtain a transparent polymer solution. At this time, the mass concentration of the aramid polymer in the polymer solution was adjusted to 20%. This polymer solution was spun under the same conditions as in Example 1 to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.2 dtex, a breaking strength of 4.3 cN / dtex, and an elongation at break of 45%.

[0075] [Comparative Example 2] By interfacial polymerization according to Example 1, a copolymer aramid polymer powder in which metaphenylenediamine and isophthaloyl monomer units were 99.5 mol% of the whole and terephthaloyl monomer units were 0.5 mol% was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers, and the weight ratio was made 49.5:0.5. The weight average molecular weight was 660,000 and the molecular weight dispersity was 5.9.

[0076] This polymer powder was dissolved in NMP to obtain a transparent polymer solution. At this time, the mass concentration of the aramid polymer in the polymer solution was adjusted to 20%. This polymer solution was spun under the same conditions as in Example 1 to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.2 dtex, a breaking strength of 4.4 cN / dtex, and an elongation at break of 45%.

[0077] [Comparative Example 3] By interfacial polymerization according to Example 1, a copolymerized aramid polymer powder in which the m-phenylenediamine and isophthaloyl monomer units are 65 mol% of the whole and the terephthaloyl monomer units are 35 mol% was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as the acid chloride monomers, and the weight ratio was set to 3:7. The weight average molecular weight was 720,000 and the molecular weight dispersity was 3.0.

[0078] This polymer powder was dissolved in NMP to obtain a transparent polymer solution. At this time, the mass concentration of the aramid polymer was adjusted to 18% with respect to the polymer solution. This polymer solution was spun under the same conditions as in Example 1 to obtain wholly aromatic polyamide fibers. The obtained fibers had a fineness of 2.2 dtex, a breaking strength of 6.2 cN / dtex, and an elongation at break of 21%.

[0079] [Comparative Example 4] By the method according to JP-A-2022-128968, a copolymerized aramid polymer powder in which the m-phenylenediamine and isophthaloyl monomer units are 83 mol% of the whole and the p-phenylenediamine and terephthaloyl monomer units are 17 mol% was synthesized. The weight average molecular weight was 570,000 and the molecular weight dispersity was 3.7.

[0080] This polymer powder and calcium chloride were dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. At this time, the mass concentration of the aramid polymer was adjusted to 22% and the mass concentration of calcium chloride was adjusted to 2.5% with respect to the polymer solution.

[0081] This polymer solution was heated to 90 °C to obtain a spinning dope, which was discharged from a spinneret with a circular discharge hole having a pore diameter of 0.1 mm and 100 holes into a coagulation bath at 85 °C for spinning. The composition of this coagulation bath was 38% by mass of calcium chloride, 5% by mass of NMP, and the remaining water was 57% by mass. The immersion length (effective coagulation bath length) was 100 cm, and after changing the yarn speed to 4.0 m / min and passing it through, it was once drawn out into the air.

[0082] The coagulated yarn was washed with water in the first to second water washing baths, and the total immersion time at this time was 200 seconds. The temperatures of the first to second aqueous washing baths were 20°C and 30°C water respectively. The washed yarn was stretched 2.5 times in boiling water at 90°C and then immersed in warm water at 90°C for 40 seconds for washing.

[0083] Next, it was wound around a roller with a surface temperature of 170°C for dry heat treatment, and then stretched 7.0 times with a hot plate at a surface temperature of 320°C to obtain aramid fibers. The obtained fibers had a fineness of 0.9 dtex, a strength of 4.6 cN / dtex, and an elongation of 25%. The physical properties of the fibers obtained in the above examples and comparative examples are shown in Table 1.

[0084]

Table 1

Industrial Applicability

[0085] The copolyaramid fibers obtained in the present invention have an excellent balance of physical properties such as strength, elongation, and heat resistance. Therefore, they can be suitably used in applications where general-purpose fibers were used at the expense of heat resistance, or in applications where the mechanical properties were compensated by a combination of multiple fibers. In particular, they can be applied to high-performance fabrics that have both appropriate strength and flexibility in protective clothing applications.

Claims

1. A fiber made of an aramid copolymer containing a m-phenylene isophthalamide unit and a m-phenylene terephthalamide unit, wherein the weight-average molecular weight of the aramid copolymer is 400,000 to 1,000,000, and the molecular weight distribution is 2.0 to 5.0, and the breaking strength of the fiber is 4.5 to 7.0 cN / dtex, and the breaking elongation is 30 to 60%. The copolymerized aramid fiber is characterized by the above.

2. The copolymerized aramid fiber according to claim 1, wherein the aramid copolymer contains structural units composed of m-phenylenediamine, isophthaloyl, and terephthaloyl, and the molar ratio of m-phenylenediamine and isophthaloyl units to terephthaloyl units is 70:30 to 99:

1.

3. A method for producing a copolymerized aramid fiber, using an aramid copolymer containing a m-phenylene isophthalamide unit and a m-phenylene terephthalamide unit, having a weight-average molecular weight of 400,000 to 1,000,000, and a molecular weight distribution of 2.0 to 5.0, and sequentially performing the steps described in the following (1) to (5). The method for producing a copolymerized aramid fiber according to claim 1 is characterized by this. (1) Dissolving the aramid copolymer in an amide-based solvent in the range of 10 to 30% by mass to obtain a spinning dope, and discharging the dope from a spinneret, (2) Spinning and coagulating in an aqueous coagulation bath containing 1 to 20% by mass of an amide-based solvent, (3) Washing with water in an aqueous washing bath, and subsequently stretching in a boiling water stretching bath in the range of 1.1 to 5.0 times, (4) Performing a dry heat treatment in the range of 100 to 250 °C, (5) While applying a heat treatment in the range of 290 to 380 °C, performing a hot stretch in the range of a draw ratio of 1.5 to 5.0 times.

4. The method for producing a copolymerized aramid fiber according to claim 3, wherein the aramid copolymer contains structural units composed of m-phenylenediamine, isophthaloyl, and terephthaloyl, and the molar ratio of m-phenylenediamine and isophthaloyl units to terephthaloyl units is 70:30 to 99:1.

Images