JP2023020354A - Copolymer aramid fiber, method for producing the same, and textile product containing the same - Google Patents

Abstract

To provide a copolymer aramid fiber having high heat resistance, well-balanced strength and elongation, and high knot strength.SOLUTION: There is provided a copolymer aramid fiber that has a breaking strength of 7.0 to 15.0 cN/dtex, a knot strength of 4.4 to 5.6 cN/dtex, a breaking elongation of 10 to 30%, and a melting point of 290°C or higher.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a copolymer aramid fiber having heat resistance and high knot strength, a method for producing the same, and textile products containing the same. More specifically, the present invention relates to a copolymer aramid fiber characterized by having an excellent balance of physical properties such as strength, elongation, knot strength and heat resistance, and a method for producing the same.

With the development of spinning technology, various fibers have been industrialized, and by selecting the chemical structure and spinning conditions that make up the fiber, fibers with physical properties according to the required performance and use are developed and manufactured. High-strength, high-modulus fibers can provide a high-strength structure, but if the elongation is low, they will break without being able to absorb large deformations. The strength and elongation of these fibers are in a trade-off relationship, and it has been difficult to develop a copolymer aramid fiber that satisfies both strength and elongation.

Furthermore, in recent years, the applications of chemical fibers have become more complicated, and there are increasing cases where not only high strength and elongation but also high knot strength of fibers is required. Therefore, a fiber having high strength and elongation and knot strength while having heat resistance is required.

In addition to strength, heat resistance is also required in material development. For example, fibers made of wholly aromatic polyamide (sometimes referred to as aramid fibers) are particularly useful as high-strength, heat-resistant, and flame-retardant fibers.

For example, para-type wholly aromatic polyamide fibers composed of paraphenylene terephthalamide have high strength and high elastic modulus, and thus are widely used as reinforcing materials for various matrices and industrial materials such as ropes. In addition, meta-type wholly aromatic polyamide fiber composed of metaphenylene isophthalamide is a flexible fiber in addition to heat resistance. Used for industrial purposes.

The mechanical properties of these aramid fibers are para-type breaking strength of 15 to 20 cN/dtex, breaking elongation of 1 to 5% ("Kevlar" (registered trademark) manufactured by DuPont, "Twaron" (registered trademark) manufactured by Teijin Limited. Trademark)), etc., and the meta type has a breaking strength of 3 to 6 cN / dtex and a breaking elongation of 30 to 60% (“Nomex” (registered trademark) manufactured by DuPont Co., Ltd., “Conex” manufactured by Teijin Ltd. (registered trademark)), and applications have been developed in consideration of the physical properties of these fibers.

On the other hand, there are the following examples of reports on high knot strength fibers. For example, in Japanese Patent Application Laid-Open No. 63-235521 (Patent Document 1), para-oriented aramid fibers are subjected to low-temperature predrying and steam treatment to achieve a strength of 21.4 g/de and a knot strength of 7.5 to 8.4 g/de. (36-39%) high toughness para-aramid fibers. In addition, in Japanese Patent Laid-Open No. 5-9867 (Patent Document 2), the strength is 22.5 to 23.4 g/de and the knot strength is 7.1 to 8.2 g/de by attaching silicon fine particles to the surface of the para-aramid fiber. reported a method to obtain fibers with de (30-36%). In addition, in JP-A-2019-157285 (Patent Document 3), by using a fiber treatment agent, the strength is 20.2 cN / de and the knot strength is 7.8 cN / de (39%) or more. All of the fibers reported are para-aramid fibers, which have heat resistance but relatively low elastic modulus.

However, when aramid fibers are used, para-type fibers are generally used in fields where heat resistance is required and when higher strength is required, but this is limited to applications that are less likely to be deformed during use. On the other hand, in fields where heat resistance is required, when flexibility is required, the meta type is used, but strength must be sacrificed.
Therefore, it has not been possible to obtain a synthetic fiber having heat resistance equivalent to that of aramid fiber, a good balance between strength and elongation, and high knot strength in the prior art.

JP-A-63-235521 JP-A-5-9867 JP 2019-157285 A

An object of the present invention is to provide a copolymer aramid fiber having high heat resistance, well-balanced strength and elongation, and high knot strength.

The inventors of the present invention, as a result of intensive studies in order to solve the above problems, have achieved high heat resistance by using a polymer obtained by copolymerizing a plurality of specific monomers in a specific ratio as a fiber. The present inventors have found that it is possible to obtain a copolymer aramid fiber having a good balance between strength and elongation, and a high binding strength, and have completed the present invention.

That is, according to the present invention,
1. A copolymer aramid fiber having a breaking strength of 7.0 to 15.0 cN/dtex, a knot strength of 4.4 to 5.6 cN/dtex, a breaking elongation of 10 to 30%, and a melting point of 290° C. or higher. ,
2. The copolymer aramid fiber according to 1 above, which has a dry heat dimensional change rate of less than 2% at 250°C;
3. From a copolymer aramid polymer in which the copolymer aramid fibers are composed of a structure containing metaphenylene terephthalamide units and/or metaphenylene isophthalamide units and paraphenylene terephthalamide units and/or paraphenylene isophthalamide units The copolymer aramid fiber according to 1 or 2 above,
4. The copolymer aramid fiber contains at least three structures selected from the group of metaphenylenediamine, paraphenylenediamine, isophthaloyl, and terephthaloyl, metaphenylenediamine and/or isophthaloyl monomer units, paraphenylenediamine and/or 4. The copolymer aramid fiber according to any one of 1 to 3 above, wherein the molar ratio of terephthaloyl monomer units is in the range of 50 or more and less than 68:50 or less and more than 32;
5. 5. The copolymer aramid fiber according to any one of 1 to 4 above, which has a weight average molecular weight of 400,000 to 1,000,000, and
6. A method for producing a copolymer aramid fiber, comprising:
A structure containing a metaphenylene terephthalamide unit and/or a metaphenylene isophthalamide unit and a paraphenylene terephthalamide unit and/or a paraphenylene isophthalamide unit, wherein each of the amide units is metaphenylene diamine and paraphenylene containing at least three structures selected from the group of diamine, isophthaloyl, and terephthaloyl, and having a molar ratio of meta-phenylenediamine and/or isophthaloyl monomer units and para-phenylenediamine and/or terephthaloyl monomer units of 50 or more and less than 68 : Produced in the following steps (1) to (5) using a copolymer aramid polymer having a weight average molecular weight of 400,000 to 1,000,000 in the range of 50 or less and greater than 32, and production of (6) A method for producing a copolymer aramid fiber that satisfies the conditions,
(1). The copolymerized aramid polymer is dissolved in an amide solvent in the range of 10 to 30% by mass to prepare a dope for spinning, passed through a spinneret,
(2). coagulated by spinning in an aqueous coagulation bath containing 1 to 20% by mass of an amide solvent;
(3). The film is washed in an aqueous washing bath, then stretched in a boiling water stretching bath in a range of 1.1 to 5.0 times,
(4). Perform dry heat treatment in the range of 100 to 250 ° C,
(5). While applying heat treatment in the range of 290 to 380 ° C., hot drawing is performed at a draw ratio of 2.0 to 10.0 times,
(6). The total draw ratio of the boiling water draw ratio and the hot draw ratio is 7 times or more. and,
7. A textile product selected from the group consisting of fall prevention materials, safety ropes, and safety nets, comprising the copolymer aramid fiber according to any one of 1 to 5 above.

The copolymer aramid fiber obtained in the present invention has heat resistance that can withstand use environments of 250 ° C. or higher, breaking strength of 7.0 to 15.0 cN / dtex, knot strength of 4.4 to 5.6 cN / dtex. , the elongation at break is 10 to 30% and the balance of physical properties is excellent, so it can be suitably used in safety ropes, fall prevention materials, and the like.

The present invention will be described in detail below.
The copolymer aramid fiber of the present invention has a breaking strength of 7.0 to 15.0 cN/dtex, a knot strength of 4.4 to 5.6 cN/dtex (42.3% to 50%), and a breaking elongation of 10 to 30. % and a melting point of 290° C. or higher. Polymers constituting such copolymer aramid fibers include wholly aromatic polyamides (hereinafter sometimes referred to as aramids), specifically meta-type and / or para-type aromatic diamine components and meta-type and / or It is composed of a para-type aromatic dicarboxylic acid component and is synthesized by copolymerization.

In the present invention, meta-phenylene terephthalamide units and/or meta-phenylene isophthalamide units and para-phenylene terephthalamide units and/or para-phenylene isophthalamide units are particularly preferably used from the viewpoint of mechanical properties, heat resistance and flame retardancy. It is a wholly aromatic polyamide mainly composed of a copolymer composed of a structure containing an amide unit.

In the copolymer aramid fiber of the present invention, the wholly aromatic polyamide comprising the copolymer aramid polymer is randomly copolymerized, and preferably at least three selected from the group consisting of meta-phenylenediamine, para-phenylenediamine, isophthaloyl and terephthaloyl. 50 or more and less than 68 mol% of meta-phenylenediamine and/or isophthaloyl monomer units, and 50 or less and more than 32 mol% of para-phenylenediamine and/or terephthaloyl monomer units. Preferably, the mol% of meta-phenylenediamine and/or isophthaloyl monomer units is 55 or more and less than 63, and the mol% of paraphenylenediamine and/or terephthaloyl monomer units is 45 or less and more than 37 of the whole. More preferably, the meta-phenylenediamine and/or isophthaloyl monomer unit mol% is 55 or more and less than 60, and the paraphenylenediamine and/or terephthaloyl monomer unit mol% is 45 or less and exceeds 40. is particularly preferred.

When the mole % of metaphenylenediamine and/or isophthaloyl monomer units exceeds 68, the desired knot strength cannot be obtained. Further, when the mol % of metaphenylenediamine and/or isophthaloyl monomer units is less than 50, the resulting polymer cannot be spun because it does not dissolve in the amide solvent described later.

Table 1 shows combinations of meta-phenylenediamine, para-phenylenediamine, isophthaloyl and terephthaloyl.
The present invention preferably includes at least three structures, such as those shown in Examples 1-4, and particularly preferably four structures, such as Example 5.

Aromatic diamine components that are raw materials for the copolymer aramid fiber of the present invention include meta- or para-phenylenediamine, 3,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl sulfone, etc., and halogen in these aromatic rings, Derivatives having a substituent such as an alkyl group having 1 to 3 carbon atoms can be exemplified.

Examples of raw materials for the aromatic dicarboxylic acid component constituting the copolymer aramid of the present invention include aromatic dicarboxylic acid halides. Examples of meta-type aromatic dicarboxylic acid halides include isophthalic acid halides such as isophthalic acid chloride and isophthalic acid bromide, and derivatives having substituents such as halogens and alkoxy groups having 1 to 3 carbon atoms on the aromatic ring thereof. can be done. Similarly, 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 halogens and alkoxy groups having 1 to 3 carbon atoms on the aromatic ring thereof. can be exemplified.

As a method for polymerizing the copolymerized aramid of the present invention, an organic solvent system (e.g., tetrahydrofuran) that is not a good solvent for the resulting polyamide containing metaphenylenediamine and isophthalic chloride and an aqueous solution containing an inorganic acid acceptor and a soluble neutral salt A method of isolating a powder of polymetaphenylene isophthalamide polymer by contacting a system (interfacial polymerization, JP-B-47-10863), or solution polymerization of the above diamine and acid chloride in an amide solvent, followed by Method of neutralizing with calcium hydroxide, calcium oxide, etc. (solution polymerization, JP-A-8-074121, JP-A-10-88421) and the like, but not limited thereto. .

The weight-average molecular weight of the copolymerized aramid polymer of the present invention is preferably 400,000 to 1,000,000 according to the analysis method described later, from the viewpoint of forming fibers having practically durable breaking strength. If the weight-average molecular weight of the copolymerized aramid polymer is less than 400,000, not only the strength at break is remarkably reduced, but also stable spinning may not be possible. In addition, when the molecular weight of the copolymerized aramid polymer exceeds 1,000,000, when preparing and spinning the wholly aromatic polyamide solution described later, the viscosity is too high and it is difficult to handle, and dedicated equipment may be required. .

As the polymer within the molecular weight range defined by the copolymerized aramid polymer of the present invention, a mixture of a low molecular weight polymer and a high molecular weight polymer can be used. good. For example, when a polymer having a weight average molecular weight of 200,000 and a polymer having a weight average molecular weight of 800,000 are mixed, and the weight average molecular weight of the mixed polymer is 600,000, there is no problem in using the molecular weight range defined in the present invention. do not have.

The copolymer aramid fiber of the present invention uses the copolymer aramid polymer obtained by the above production method, and the spinning solution preparation step, spinning/coagulation step, washing step, boiling water drawing step, and dry heat treatment step described below. , manufactured through a hot drawing process.

[Spinning solution preparation step]
In the spinning solution preparation step, the copolymerized aramid polymer of the present invention is dissolved in a solvent to prepare a spinning solution (dope). In preparing the spinning solution, an amide-based solvent is usually used, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). Among these, it is preferable to use NMP or DMAc from the viewpoint of solubility and handling safety.

As the solution concentration, an appropriate concentration may be appropriately selected from the viewpoint of the coagulation rate and polymer solubility in the spinning/coagulation step, which is the next step, and is usually in the range of 10 to 30% by mass. is necessary. In order to achieve stable spinning, the range of 15 to 25% by mass is more preferable.

In the present invention, an inorganic salt may be introduced into the dope, preferably 0 to 20% by mass of the inorganic salt relative to the dope, and 0 to 10% by mass of the inorganic salt to obtain stable spinnability. is more preferred.

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, making it impossible to obtain a fiber having the desired physical properties. As inorganic salts, chloride salts such as calcium chloride, magnesium chloride and lithium chloride are preferably used.

[Spinning/coagulation process]
In the spinning/coagulating step, the dope obtained above is spun into a coagulating liquid and coagulated. The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. The number of spinning holes in the spinneret, the diameter of the spinning holes, the state of arrangement, etc. of the spinneret are not particularly limited as long as they can be stably wet-spun. A multi-hole spinneret for 0.2 mm staple fibers or the like can be used.
The temperature of the dope during spinning from the spinneret is preferably 20 to 90°C, more preferably 70 to 90°C.

The coagulation bath used to obtain the fiber of the present invention is an aqueous solution containing 1 to 20% by mass, preferably 3 to 15% by mass, of an amide solvent. The temperature of this aqueous solution is preferably in the range of 50-90°C.
In addition, the coagulation bath can contain an inorganic salt such as calcium chloride or magnesium chloride in an amount of preferably 30% by mass or more, more preferably 35 to 45% by mass.
As described above, the dope is spun from a spinneret into a coagulation liquid and passed through a coagulation bath to obtain a coagulation thread.

[Washing process, boiling water drawing process]
The coagulated yarn thus obtained is thoroughly washed in an aqueous washing bath and sent to a boiling water drawing step.
The draw ratio in the boiling water drawing bath should be in the range of 1.1 to 5.0 times, more preferably in the range of 1.1 to 3.0 times. The strength of the finally obtained fiber can be ensured by performing the drawing within the range of the draw ratio and increasing the molecular chain orientation.

[Dry heat treatment process]
A dry heat treatment step is preferably performed on the fibers that have undergone the washing and drawing steps. In the dry heat treatment step, the fibers that have been washed in the above washing step are subjected to a dry heat treatment at 100 to 250°C. Dry heat treatment is preferably carried out in the range of 100 to 200°C. Moreover, it is preferable to carry out the dry heat treatment under a constant length. The temperature of the dry heat treatment mentioned above refers to the set temperature of fiber heating means such as a hot plate and a heating roller.

[Hot drawing process]
In the present invention, the fiber subjected to the dry heat treatment is subjected to a hot drawing process. In the hot-stretching step, stretching is performed while heat-treating in the range of 290 to 380°C. The treatment temperature is preferably in the range of 290-350°C. If the temperature is less than 290°C, high-ratio drawing cannot be performed, and if it exceeds 380°C, discoloration or breakage of the fiber may occur. In the hot drawing step, the draw ratio should be in the range of 2.0 to 10.0 times, preferably 3.0 to 10.0 times. The temperature of the hot drawing treatment refers to the set temperature of fiber heating means such as a hot plate and a heating roller.

The total draw ratio of the boiling water draw ratio and the hot draw ratio in the present invention must be 7 times or more. If the total draw ratio is less than 7 times, the target strength cannot be obtained. Therefore, it is necessary to appropriately adjust the boiling water draw ratio and the hot draw ratio in consideration of the condition of the process.

The knot strength of the copolymer aramid fiber obtained by the above method is 4.4 to 5.6 cN/dtex (42.3% to 50%), preferably 4.9 to 5.6 cN/dtex (45% to 50%). If the knot strength is less than 4.4 cN/dtex, it is difficult to obtain sufficient strength, which is insufficient for the purpose of the present invention. If the knot strength exceeds 5.6 cN/dtex, it is difficult to obtain sufficient elongation at break, which is not preferred.

The percentage (%) in parentheses for knot strength described herein indicates the ratio of knot strength to breaking strength, and the higher the knot strength ratio, the more flexible and flexible the fiber. Good balance of strength.

Further, the breaking strength of the copolymer aramid fiber of the present invention is 7.0 to 15.0 cN/dtex, and the lower limit is more preferably 8.0 cN/dtex or more. If the breaking strength is less than 7.0 cN/dtex, the strength aimed at by the present invention is insufficient.

The breaking elongation of the copolymer aramid fiber of the present invention must be 10% to 30%, preferably 15% to 25%, more preferably 20% to 25%. If the elongation at break is less than 10%, the physical properties are not well balanced, which is the object of the present invention. When the elongation at break exceeds 30%, it becomes difficult to obtain sufficient strength.

The melting point of the copolymer aramid fiber of the present invention must be 290° C. or higher, preferably 300° C. or higher. If the melting point is lower than 290°C, the performance as a heat-resistant fiber cannot be exhibited.

In the copolymer aramid fiber of the present invention, the dry heat dimensional change rate at 250 ° C. is preferably less than 2%, more preferably 1.5% or less, further preferably 1.0% or less, and 0.5% or less. Especially preferred. If the dry heat dimensional change rate is 2% or more, the performance as a heat-resistant fiber cannot be exhibited.

The weight average molecular weight of the copolymerized aramid polymerized fiber of the present invention is preferably 400,000 to 1,000,000 according to the analysis method described later. If the weight average molecular weight of the copolymer aramid fiber is less than 400,000, the breaking strength may be significantly reduced. Further, when the molecular weight of the copolymerized aramid fiber exceeds 1,000,000, when the wholly aromatic polyamide solution is spun from the spinneret, the viscosity is too high, making it difficult to handle, and dedicated equipment may be required.

The copolymer aramid fiber obtained by the above method has not only strength but also excellent knot strength and well-balanced physical properties, and has heat resistance and flame resistance. It can be effectively used for fall prevention materials for falling prevention measures for receiving structures such as snow, etc., and textile products such as safety ropes and safety nets for ensuring the safety of workers working at heights.

The copolymer aramid fiber of the present invention contained in applications such as the fall prevention material, safety rope, and safety net is preferably 30 to 100% by weight, more preferably 50 to 100% by weight, more preferably 80 to 80% by weight, based on the total weight. 100% by weight is more preferred, and 100% is most preferred. If the content of the copolymer aramid fiber is less than 50%, the characteristics of the copolymer aramid fiber of the present invention cannot be exhibited sufficiently.

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples and Comparative Examples. Each physical property value in Examples and Comparative Examples was measured by the following methods.

[Weight average molecular weight Mw]
According to JIS-K-7252, analysis was performed using a high-performance liquid chromatography device equipped with a column for size exclusion chromatography, and dimethylformamide (containing 0.01 mol% lithium chloride) was used as the developing solvent. . As a standard molecular weight sample, a Sigma-Aldrich polystyrene set (peak top molecular weight Mp=400 to 2,000,000) was used.

[Single fiber fineness]
In accordance with JIS-L-1015, measurement was carried out in accordance with the A method of regular fineness, and the apparent fineness was expressed.

[Breaking strength, breaking elongation]
Using a tensile tester (manufactured by Instron, model: 5565), measurements were made under the following conditions according to JIS-L-1015.
(Measurement condition)
Grip interval: 20mm
Initial load: 0.044cN (1/20g/dtex)
Tensile speed: 20mm/min

[Knot Strength]
Using a tensile tester (manufactured by Instron, model: 5565), it was measured according to JIS-L-1013:2010 Chemical fiber filament yarn test method 8.6.1 (standard time test).

[Dry heat dimensional change rate]
According to JIS-L-1013, measurement was carried out according to B method to obtain the dimensional change rate at 250°C.

[Melting point of fiber]
The melting point of the fiber was determined by thermomechanical analysis according to JIS-K-7197. The melting point was defined as the apex temperature of the peak detected on the high temperature side or the temperature at which peak detection became impossible due to dissolution of the fiber.

[Example 1]
Copolymerized aramid polymer containing 67 mol% of meta-phenylenediamine and isophthaloyl monomer units and 33 mol% of para-phenylenediamine and terephthaloyl monomer units by interfacial polymerization according to JP-B-47-10863. A powder was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as acid chloride monomers so that the weight ratio was 2:1. As amine monomers, both meta-phenylenediamine and para-phenylenediamine were used in a weight ratio of 2:1. The weight average molecular weight was 800,000. The polymer powder and calcium chloride were dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a clear polymer solution. At this time, the polymer solution was adjusted so that the mass concentration of the copolymerized aramid polymer was 16% and the mass concentration of calcium chloride was 3%.

This polymer solution was heated to 85° C. and spun into a coagulation bath at 85° C. through a spinneret having a hole diameter of 0.1 mm and 100 circular ejection holes. The composition of this coagulation bath is 44% by mass of calcium chloride, 3% by mass of NMP, and 53% by mass of the remaining water. After that, it was temporarily pulled out into the air.

The coagulated filaments were washed with water in the first and second water washing baths for a total immersion time of 200 seconds. The first and second aqueous washing bath temperatures used were 20° C. and 30° C., respectively. The washed yarn was stretched 2.4 times in boiling water at 90°C, then immersed in hot water at 90°C for 40 seconds and washed.

Next, after being wound around a roller having a surface temperature of 170° C. and subjected to a dry heat treatment, it was drawn 4.5 times with a hot plate having a surface temperature of 325° C. to obtain a wholly aromatic polyamide fiber.
The resulting fiber has a weight average molecular weight of 800,000, a fineness of 1.3 dtex, a breaking strength of 10.4 cN/dtex, a knot strength of 4.4 cN/dtex, a breaking elongation of 23%, a melting point of 307°C, and a dry heat dimension at 250°C. The rate of change was 1.00%.

[Example 2]
Copolymerized aramid polymer powder containing 56 mol% of meta-phenylenediamine and isophthaloyl monomer units and 44 mol% of para-phenylenediamine and terephthaloyl monomer units by interfacial polymerization according to JP-B-47-10863. was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as acid chloride monomers so that the weight ratio was 5:4. As amine monomers, both meta-phenylenediamine and para-phenylenediamine were used in a weight ratio of 5:4. The weight average molecular weight was 450,000. The polymer powder and calcium chloride were dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a clear polymer solution. At this time, the polymer solution was adjusted so that the mass concentration of the copolymerized aramid polymer was 20% and the mass concentration of calcium chloride was 2%.

This polymer solution was heated to 85° C. and spun into a coagulation bath at 85° C. through a spinneret having a hole diameter of 0.1 mm and 100 circular ejection holes. The composition of this coagulation bath is 44% by mass of calcium chloride, 3% by mass of NMP, and 53% by mass of the remaining water. After that, it was temporarily pulled out into the air.

The coagulated filaments were washed with water in the first and second water washing baths for a total immersion time of 200 seconds. The first and second aqueous washing bath temperatures used were 20° C. and 30° C., respectively. The washed yarn was stretched 2.4 times in boiling water at 90°C, then immersed in hot water at 90°C for 40 seconds and washed.

Next, after being wound around a roller with a surface temperature of 170° C. and subjected to a dry heat treatment, it was drawn 4.0 times with a hot plate having a surface temperature of 315° C. to obtain a wholly aromatic polyamide fiber.
The resulting fiber has a weight average molecular weight of 450,000, a fineness of 1.54 dtex, a breaking strength of 11.1 cN/dtex, a knot strength of 4.9 cN/dtex (45%), a breaking elongation of 24%, and a melting point of 313°C and 250°C. The dry heat dimensional change rate at was 0.30%.

[Example 3]
Copolymerized aramid polymer powder containing 50 mol % of meta-phenylenediamine and isophthaloyl monomer units and 50 mol % of para-phenylenediamine and terephthaloyl monomer units by interfacial polymerization according to JP-B-47-10863. was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as acid chloride monomers so that the weight ratio was 1:1. As amine monomers, both meta-phenylenediamine and para-phenylenediamine were used so that the weight ratio was 1:1. The weight average molecular weight was 640,000. The polymer powder and calcium chloride were dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a clear polymer solution. At this time, the polymer solution was adjusted so that the mass concentration of the copolymerized aramid polymer was 16% and the mass concentration of calcium chloride was 3%.

This polymer solution was heated to 85° C. and spun into a coagulation bath at 85° C. through a spinneret having a hole diameter of 0.1 mm and 100 circular ejection holes. The composition of this coagulation bath is 44% by mass of calcium chloride, 3% by mass of NMP, and 53% by mass of the remaining water. After that, it was temporarily pulled out into the air.

The coagulated filaments were washed with water in the first and second water washing baths for a total immersion time of 200 seconds. The first and second aqueous washing bath temperatures used were 20° C. and 30° C., respectively. The washed yarn was stretched 2.5 times in boiling water at 90°C, then immersed in hot water at 90°C for 40 seconds and washed.

Next, after being wound around a roller having a surface temperature of 170° C. and subjected to a dry heat treatment, it was drawn 3.5 times with a hot plate having a surface temperature of 330° C. to obtain a wholly aromatic polyamide fiber.
The resulting fiber has a weight average molecular weight of 640,000, a fineness of 1.8 dtex, a breaking strength of 11.8 cN/dtex, a knot strength of 5.6 cN/dtex (48%), a breaking elongation of 22%, and a melting point of 301°C and 250°C. The dry heat dimensional change rate at was 0.70%.

[Comparative Example 1]
When the physical properties of a wholly aromatic copolyamide fiber ("Technora" manufactured by Teijin Limited) containing 100 mol% of paraphenylenediamine and terephthaloyl monomer units of the whole were measured, the fineness was 1.67 dtex and the breaking strength was 26.96 cN. /dtex, knot strength of 4.6 cN/dtex (16.9%), elongation at break of 6.1%, melting point of 500°C or higher, and dry heat dimensional change at 280°C of 0.30%.

[Comparative Example 2]
Copolymerized aramid polymer powder containing 33 mol% of metaphenylenediamine and isophthaloyl monomer units and 67 mol% of paraphenylenediamine and terephthaloyl monomer units by interfacial polymerization according to JP-B-47-10863. was synthesized. At this time, both isophthaloyl chloride and terephthaloyl chloride were used as acid chloride monomers so that the weight ratio was 1:2. As amine monomers, both meta-phenylenediamine and para-phenylenediamine were used in a weight ratio of 1:2. The polymer could not be spun because it did not exhibit good solubility in solvents including NMP.

[Comparative Example 3]
Polymer solution of wholly aromatic polyamide fiber ("Twaron" manufactured by Teijin Limited) consisting of 100 mol% of para-phenylenediamine and terephthaloyl monomer units of the whole and 100 mol of meta-phenylenediamine and isophthaloyl monomer units of the whole % of wholly aromatic polyamide fiber ("Conex" manufactured by Teijin Limited) was mixed at a weight ratio of 5:95. This polymer solution was spun under the conditions of Example 1 to obtain a wholly aromatic polyamide fiber. When the physical properties of the obtained fiber were measured, the fineness was 1.8 dtex, the breaking strength was 22.4 cN/dtex, the knot strength was 3.7 cN/dtex (16.5%), the elongation at break was 4.6%, and the melting point could not be measured (400 ° C. or higher), and the dry heat dimensional change rate at 250° C. was 0%.
Table 1 shows the physical properties of the fibers obtained in the above examples and comparative examples.

The copolymer aramid fiber obtained by the present invention has an excellent balance of physical properties such as strength, elongation and heat resistance. It can be suitably used for applications in which mechanical properties are supplemented by In addition, it can be applied to a new heat-resistant and high-toughness material that has appropriate strength and flexibility for use as a fall prevention material, such as a material for safety ropes that are deformed frequently and require strength.

Claims (7)

A copolymer aramid fiber having a breaking strength of 7.0 to 15.0 cN/dtex, a knot strength of 4.4 to 5.6 cN/dtex, a breaking elongation of 10 to 30%, and a melting point of 290° C. or higher. . 2. The copolymer aramid fiber of claim 1, wherein the dry heat dimensional change at 250° C. is less than 2%. From a copolymer aramid polymer in which the copolymer aramid fibers are composed of a structure containing metaphenylene terephthalamide units and/or metaphenylene isophthalamide units and paraphenylene terephthalamide units and/or paraphenylene isophthalamide units The copolymer aramid fiber according to claim 1 or 2, comprising: The copolymer aramid fiber contains at least three structures selected from the group of metaphenylenediamine, paraphenylenediamine, isophthaloyl, and terephthaloyl, metaphenylenediamine and/or isophthaloyl monomer units, paraphenylenediamine and/or The copolymer aramid fiber according to any one of claims 1 to 3, wherein the molar ratio of terephthaloyl monomer units is in the range of 50 or more and less than 68:50 or less and more than 32. The copolymer aramid fiber according to any one of claims 1 to 4, which has a weight average molecular weight of 400,000 to 1,000,000. A method for producing a copolymer aramid fiber, comprising:
A structure containing a metaphenylene terephthalamide unit and/or a metaphenylene isophthalamide unit and a paraphenylene terephthalamide unit and/or a paraphenylene isophthalamide unit, wherein each of the amide units is metaphenylene diamine and paraphenylene containing at least three structures selected from the group of diamine, isophthaloyl, and terephthaloyl, and having a molar ratio of meta-phenylenediamine and/or isophthaloyl monomer units and para-phenylenediamine and/or terephthaloyl monomer units of 50 or more and less than 68 : Produced in the following steps (1) to (5) using a copolymer aramid polymer having a weight average molecular weight of 400,000 to 1,000,000 in the range of 50 or less and greater than 32, and production of (6) A method for producing a copolymer aramid fiber that satisfies the conditions.
(1). The copolymerized aramid polymer is dissolved in an amide solvent in the range of 10 to 30% by mass to prepare a dope for spinning, passed through a spinneret,
(2). coagulated by spinning in an aqueous coagulation bath containing 1 to 20% by mass of an amide solvent;
(3). The film is washed in an aqueous washing bath, then stretched in a boiling water stretching bath in a range of 1.1 to 5.0 times,
(4). Perform dry heat treatment in the range of 100 to 250 ° C,
(5). While applying heat treatment in the range of 290 to 380 ° C., hot drawing is performed at a draw ratio of 2.0 to 10.0 times,
(6). The total draw ratio of the boiling water draw ratio and the hot draw ratio is 7 times or more. A textile product selected from the group consisting of fall prevention materials, safety ropes and safety nets, comprising the copolymer aramid fiber according to any one of claims 1-5.