JP5707161B2 - Method for producing meta-aramid fiber - Google Patents

Description

  The present invention relates to a method for producing meta-aramid fibers. More specifically, the present invention relates to a method for producing meta-aramid fiber by melt spinning unlike conventional solution spinning.

  Meta-aramid fibers are widely used as heat-resistant fibers in electrical insulating paper such as motors and transformers, bag filters for incinerators, honeycomb structures, and heat-resistant work clothes. Conventionally, a polymer was obtained by an acid chromatography method in which a diamine and an acid chloride of an aromatic dicarboxylic acid were reacted in a solution, and this was solution-spun using an organic solvent to obtain a meta-aramid fiber. However, in the acid chromatography method, a salt is inevitably generated for neutralization of alkali, and it is necessary to remove the salt, and the manufacturing process is complicated. Furthermore, since solution spinning using an organic solvent is performed, there is a problem that the cost of solution recovery and the like is high, and the environmental load is large (Patent Document 1). Normally, meta-aramid used as heat-resistant fiber has no thermoplastic property, so it has characteristics suitable for heat-resistant work clothes that are infusible. On the contrary, melt spinning is impossible and solution spinning is unavoidable. Met.

  For this reason, attempts have been made in the past to develop thermoplasticity by allowing lactam to coexist with meta-aramid and to melt-spin meta-aramid (Patent Document 2), but synthesis of meta-aramid involves reacting acid chloride of dicarboxylic acid with lactam. This was an extension of the acid chromatography method and did not solve the problem of polymer synthesis. Furthermore, there was a concern that harmful lactams may be generated from the polymer as a gas during melt spinning, causing safety and environmental problems.

  On the other hand, there is a disclosure of a direct polymerization method that does not use acid chloride in the synthesis of meta-aramid (Patent Document 3). However, no knowledge about melt spinnability is disclosed.

  If it is possible to melt-spin meta-aramid obtained by a synthesis method that does not produce salt as a by-product, it is possible to simplify not only the safety and the environment but also the production equipment, which is very useful industrially.

Japanese Patent Publication No. 48-17551 Japanese Patent Laid-Open No. 2-145620 JP 2009-256610 A

  The subject of this invention is providing the manufacturing method of the meta aramid fiber which melt-spins the meta aramid obtained by the synthesis method which does not byproduce salt.

The manufacturing method according to the present invention for solving the above-described problems is as follows.
(1) Using 3,4'-diaminodiphenyl ether and metaphenylene diamine as the diamine component in a ratio of 30 mol% / 70 mol% to 70 mol% / 30 mol% with respect to the total diamine component, isophthalic acid as the acid component, and heating them Thus, a meta-aramid fiber having a solution logarithmic viscosity of 0.1 to 0.4 dL / g measured in N-methyl-2-pyrrolidone is obtained, and this is melt-fabricated, thereby producing a meta-aramid fiber.
(2) The method for producing meta-aramid fiber according to (1), wherein the melt viscosity of the meta-aramid oligomer is 100 to 2000 Pa · s.
(3) The method for producing metaaramid fibers according to (1) or (2), wherein 40% or more of the terminals of the metaaramid oligomer are amine terminals.
(4) A method for producing meta-aramid fibers, wherein solid-phase polymerization is performed on meta-aramid fibers obtained by any one of the methods (1) to (3).

  According to the method for producing meta-aramid fibers according to the present invention, not only safety and environment but also production facilities can be simplified, and the total cost of meta-aramid fibers can be reduced.

It is a side view photograph of the meta-aramid fiber obtained by the present invention. It is an example of the meta-aramid fiber obtained by this invention. It is a figure which shows the time dependence of the melt viscosity of the metaaramid oligomer used by this invention. It is a spectrum figure which shows the example of the < ¹ > H NMR spectrum measured in the Example and comparative example of this invention.

Hereinafter, the present invention will be described in detail together with preferred embodiments.
The meta-aramid referred to in the present invention is a wholly aromatic polyamide composed of an aromatic diamine and an aromatic dicarboxylic acid, in which an amine and a carboxylic acid are bonded to the meta position in both the diamine component and the dicarboxylic acid component. In the present invention, unlike the prior art, it is important to obtain meta-aramid by direct polymerization of diamine and dicarboxylic acid without using acid chloride. Therefore, it is possible to simplify the equipment and contribute to the cost reduction.

  In the present invention, 3,4′-diaminodiphenyl ether (3,4′-DPE) and metaphenylenediamine (mPDA) are used in a ratio of 30 mol% / 70 mol% to 70 mol% / 30 mol%, and isophthalic acid (IPA) is used as the dicarboxylic acid component. ) Meta-aramid is made into a melt fiber, which is based on three important findings different from the prior art. The first is that the meta-aramid exhibits thermoplasticity by copolymerizing 3,4'-DPE with meta-aramid as a diamine component. Secondly, meta-aramid copolymerized with 3,4'-DPE exhibits melt spinnability even in the case of an oligomer (low molecular weight) having a logarithmic viscosity of 0.1 to 0.4 dL / g. It is. Third, although 3,4′-DPE / mPDA / IPA-based metaaramid oligomers have melt spinnability, thermoplasticity is increased when the solution logarithmic viscosity is a polymer (high molecular weight) of 1.0 dL / g or more. It is lost and infusible.

  From these, 3,4'-DPE / mPDA / IPA meta-aramid can be made into an infusible fiber by performing melt spinning in the oligomer state and then increasing the molecular weight, and can be handled in the same way as conventional mPDA / IPA-based meta-aramid. There is a big merit that you can.

  In order to maximize such merits, it is important that the meta-aramid has the following composition. That is, 3,4'-DPE and mPDA are used in a ratio of 30 mol% / 70 mol% to 70 mol% / 30 mol% with respect to the total diamine component, and IPA is used as the dicarboxylic acid component. The higher the 3,4′-DPE ratio in the diamine component, the more the thermoplasticity of metaaramid becomes more prominent. However, by setting it to 30 mol% or more, sufficient thermoplasticity to melt the metaaramid oligomer is imparted. Can do. Preferably it is 40 mol% or more. On the other hand, if the 3,4'-DPE ratio is too high, it is difficult to make it infusible even when the meta-aramid is made to have a high molecular weight. By setting the mPDA ratio to 30 mol% or more, sufficient infusibility can be imparted when meta-aramid is increased in molecular weight. The mPDA ratio is preferably 40 mol% or more. Further, it is preferable to increase the mPDA ratio because the glass transition temperature when the molecular weight of meta-aramid is increased can be increased. From this viewpoint, the mPDA ratio is preferably 30 mol% or more. According to the study by the inventors, the glass transition temperature of the high molecular weight meta-aramid was 276 ° C. for mPDA 100 mol%, 264 ° C. for 75 mol%, 253 ° C. for 50 mol%, 244 ° C. for 30 mol%, and 240 ° C. for 20 mol%. It was. In addition, the measuring method of glass transition temperature was as follows. That is, using a DSC RDC 6220 manufactured by Seiko Instruments Inc., the sample weight was set to 5.0 mg ± 0.4 mg, and the temperature raising condition was 25 ° C. → 350 ° C. → 25 ° C. → 350 ° C. (temperature raising rate 10 ° C./min) As a result, the glass transition temperature was determined at 2nd run.

  The molecular weight of the metaaramid oligomer is defined by the solution viscosity. In the present invention, metaaramid is dissolved in N-methyl-2-pyrrolidone at a concentration of 0.5 g / dL, and a metaaramid oligomer having a solution log viscosity measured at 30 ° C. of 0.1 to 0.4 dL / g is used. is important. By setting the solution logarithmic viscosity within this range, sufficient melt spinnability can be exhibited. Preferably, if it is 0.10 to 0.20 dL / g, the melt viscosity of the metaaramid oligomer can be made the same as that of ordinary polyester (polyethylene terephthalate), and there is a possibility that an existing polyester melt spinning apparatus can be diverted. Industrial significance is great.

In the present invention, the melt viscosity of the meta-aramid oligomer is preferably 100 to 2000 Pa · s. A low melt viscosity is preferred for smoothly progressing melt fiber formation and thinning of the fiber, and the melt viscosity is preferably 400 Pa · s or less. On the other hand, if the melt viscosity is too low, on the contrary, the spinnability may be lowered, so that it is preferably 100 Pa · s or more. The melt viscosity referred to in the present invention is a strain of 0.5 deg. At a melt fiberizing temperature using a parallel plate rheometer. Η ^* measured at a strain rate of 62.8 rad / sec is taken as the melt viscosity. For example, a 3,4′-DPE / mPDA / IPA = 0.5 / 0.5 / 1.0 oligomer having a logarithmic viscosity of 0.17 and having an end group of amine and carboxylic acid (1: 1) in a nitrogen atmosphere Η ^* when stored at 300 ° C. for 12 minutes is 300 Pa · s, which is close to η ^* (220 Pa · s) at 300 ° C. of homopolyethylene terephthalate having an intrinsic viscosity of 0.63 used for polyester fibers for clothing. . The meta-aramid oligomer used in the present invention is recognized to increase in viscosity in the process of measuring the melt viscosity with a rheometer, and it is preferable to investigate the relationship between the melt residence time, melt viscosity, and melt spinnability.

  Further, the end group of the meta-aramid oligomer may have a carboxylic acid end and an amine end. However, the rich end of the amine end reduces the melt viscosity and is suitable for melt spinning. From this viewpoint, it is preferable that 40% or more of the end groups are amine ends. The amount of terminal groups can be determined by titration, nuclear magnetic resonance (NMR) or the like.

  It is preferable from the viewpoint of heat resistance that the meta-aramid fiber obtained in the present invention has a high degree of polymerization and a glass transition temperature of 240 ° C. or higher.

  The composition of meta-aramid used in the present invention has been described above. The method for producing meta-aramid fiber of the present invention will be described in detail below.

  First, the synthesis of the meta-aramid oligomer is basically performed by the method described in Patent Document 3. A desired amount of 3,4'-DPE, mPDA, and IPA is weighed and heated under an inert gas stream. At this time, since mPDA has sublimation properties, it is preferable that mPDA is slightly excessive (about 10 mol% excess) when synthesis is performed in an open system or a vacuum system. In order to suppress sublimation of mPDA, all may be equimolar when the synthesis is performed in a pressure system. Further, the molecular chain terminal can be controlled by the charging ratio of the diamine component and the dicarboxylic acid component. If the diamine component and the dicarboxylic acid component are equimolar, the amine terminal and the carboxylic acid terminal are approximately 1: 1, but the dicarboxylic acid component is In the case of excess, carboxylic acid end groups increase, and in the case of excess of the diamine component, amine end groups increase. In the present invention, it is preferable from the viewpoint of simplification of equipment that the synthesis from oligomer synthesis to fiberization is performed in a melt system and no purification step using a solution is included. For this reason, it is preferable to adjust the preparation amounts of the amine component and the dicarboxylic acid component so that the diamine component and the dicarboxylic acid component are all reacted.

  Next, the synthesis temperature is preferably higher than the melting point of 3,4'-DPE, mPDA, and IPA, and more preferably 240 ° C. or higher from the viewpoint of being higher than the melting point of the synthesized oligomer. In this way, the monomer or oligomer that is the raw material can be stirred and then stirred, and the synthesis reaction can be advanced efficiently. What is necessary is just to determine reaction time suitably so that it may become a desired solution relative viscosity.

  Next, the meta-aramid oligomer obtained in this way is melted, and at this time, the melt fiberization method is not particularly limited, and known methods and apparatuses can be used. For example, it can be melted by a single screw extrusion kneader or a twin screw extrusion kneader from a quantitative feeder and discharged from a known spinneret. At this time, degassing may be performed by venting with a kneader in order to prevent gut breakage. In addition to the round hole, a deformed base such as a Y hole or a C hole can be used as the shape of the base. However, as described above, a lower melt viscosity is advantageous for spinnability, so the molecular weight of the meta-aramid oligomer, that is, the solution logarithmic viscosity and molecular chain end group composition is appropriately selected, and the spinning temperature is increased. Is effective. However, since a new high-temperature spinning device may be used to increase the spinning temperature, the cost may be increased. Therefore, it is preferable to appropriately select the solution logarithmic viscosity and molecular chain end group composition.

  The meta-aramid fiber obtained by the present invention can be used in the same manner as a conventionally known meta-aramid fiber, and can be designed to have a desired fiber shape (polygonal, flat, hollow, etc.) for melt spinning. Various functional improvements can be expected by shape control. In addition, the fiber diameter can be controlled freely, and microfibers or nanofibers can be formed. Furthermore, if spunbonding, meltblowing, or the like is performed, a nonwoven fabric can be formed with a single spinning, and it is expected that the cost can be greatly reduced as compared with conventional papermaking and electrospinning methods.

  Hereinafter, the present invention will be described in detail based on examples. In addition, the measuring method in an Example used the following method.

A. Solution logarithmic viscosity (η)
Meta-aramid was dissolved in N-methyl-2-pyrrolidone at a concentration of 0.5 g / dL and measured with an Ostwald viscometer at 30 ° C.

B. Melt Viscosity RHEOSOL-G3000, a rheometer manufactured by UBM, used a parallel plate to measure dynamic viscoelasticity, and η ^* at a strain rate of 62.8 rad / sec was taken as melt viscosity. The measurement conditions are as follows.
Distance between parallel disks 0.5mm
Distortion 0.5 deg.
The strain rate was repeatedly measured from 0.628 to 62.8 rad / sec.
Note that, after reaching the desired temperature for 3 minutes, data acquisition was started, and this time was set to 0 minutes.

C. Melt spinnability Melt spinnability was judged by whether the heater block was opened immediately after completion of the melt viscosity measurement, the parallel discs were pulled apart, and the yarn was drawn. More specifically, those having a spinnability of 4 cm or more over the entire surface of the parallel disk have good spinnability (◎), only the edge of the parallel disk is threaded, and the length is 2 cm or more. With spinnability (○), only the edge of the parallel disk is twisted, and the length is less than 2 cm, there is no spinnability (△), and the melt viscosity cannot be measured. Was not thermoplastic (x). That is, ◎ and ○ evaluations were considered to have spinnability.

D. Polymer end group content Model substances A, B, and C shown in FIG. 4 were prepared, and 1H NMR spectra were measured. Here, the signal a corresponds to the amide hydrogen inside the oligomer, the signal a 'corresponds to the amide hydrogen at the carboxylic acid terminal, and the signal a "corresponds to the amide hydrogen at the amine terminal. The signal integration ratio (integral value of a ′) / (integral value of a ′ + integral value of a ″) × 100 (%) was defined as the amount of amine end groups.

[Example 1]
2.5 mmol of 3,4'-DPE, 2.75 mmol of mPDA, and 5 mmol of IPA were weighed and put into a test tube substituted with argon. While stirring with a magnetic stirrer, the temperature was raised from room temperature to 260 ° C. with a mantle heater, and further maintained at 260 ° C. for 1 hour, and 3,4′-DPE / mPDA / IPA = 0.5 / 0.5 / 1. 0.0 metaaramid oligomers were obtained. This was cooled, dissolved in N-methyl-2-pyrrolidone, methanol was added to precipitate, this was filtered off, dried and purified. The η of this oligomer was measured and found to be 0.17 dL / g. The ratio of the number of amine end groups to the number of carboxylic acid end groups was 1: 1 (amount of amine end groups = 50%).

Then, about 0.2 g of this was weighed, the melt viscosity was measured at 300 ° C. with a rheometer, and immediately after the measurement was completed, the measurement disk was raised and the melt spinnability was examined. A whiskered molten meta-aramid fiber could be obtained (FIG. 2). The time from the start of data acquisition to the last measurement at a strain rate of 62.8 rad / sec was 1035 seconds (17 minutes 15 seconds), and η ^* was 353 Pa · s (Table 1). Further, after cooling this, the solution relative viscosity was measured and found to be 0.23 dL / g (Table 1). Table 1 shows η ^* and η in the state where the melt spinning test was performed. Further, when the change in melt viscosity with time was examined, as shown in FIG. 3, it showed a tendency to increase in viscosity with the heating time, corresponding to an increase in η.

[Examples 2 and 3]
The charge ratio of 3,4′-DPE and mPDA was changed, and the composition ratio of 3,4′-DPE / mPDA was changed to 0.35 / 0.65 (Example 2) and 0 by the same operation as in Example 1. A purified meta-aramid oligomer of .65 / 0.35 (Example 3) was synthesized. Both of these oligomers had an η of 0.13 dL / g. All exhibited excellent melt spinnability, and meta-aramid oligomer fibers could be obtained (Table 1).

[Comparative Examples 1-3]
Meta-aramid oligomers having the compositions shown in Table 1 were obtained in the same manner as in Example 1, except that the charging ratio of 3,4′-DPE and mPDA was changed. However, when mPDA exceeds 70 mol%, melt spinnability was poor (Comparative Examples 1 and 2). In Comparative Example 3, although melt spinnability was recognized, it was considered that the heat resistance was insufficient even if the molecular weight was increased because the mPDA content was small.

[Comparative Example 4]
The metaaramid oligomer obtained in Example 2 was further subjected to solid phase polymerization to obtain a metaaramid oligomer having η of 0.41 dL / g. The melt spinnability was examined at 320 ° C., but the melt spinnability evaluation was poor (evaluation: Δ). Η at the time of melt spinnability evaluation was 0.44 dL / g.

[Examples 4 and 5]
The melt spinnability evaluation was performed in the same manner as in Example 1 with the temperature at which the melt spinnability evaluation was performed being 280 ° C and 320 ° C. The results are shown in Table 1, and all were excellent in melt spinnability.

[Example 6]
The meta-aramid oligomer prepared in Example 1 was put into a test tube substituted with argon, heated to 300 ° C. using a mantle heater, and held for 17 minutes. After that, after inserting a stainless steel needle into the test tube and adhering the melted meta-aramid oligomer to the test mouth, pulling the needle vigorously after once attaching the needle to the test mouth, the meta-aramid oligomer fiber was several meters away. Obtained. When the side surface of the fiber was observed with an optical microscope, it was 12 μm at the narrowest width of the fiber (FIG. 1). From the time dependency of the melt viscosity shown in FIG. 3, the melt viscosity at the time of melt spinning was estimated to be 340 Pa · s, and η was estimated to be 0.22 dL / g.

[Example 7]
The thin meta-aramid oligomer fiber obtained in Example 6 was wound around a metal reel and held at 200 ° C. under reduced pressure for 1 week for solid phase polymerization. It was confirmed that the obtained fiber was infusible and sufficiently high in molecular weight.

[Example 8]
The meta-aramid oligomer fiber obtained in Example 6 was treated in the air (normal pressure) at 200 ° C. under no load for 1000 hours, but no strength reduction was observed, and excellent long-term heat resistance was exhibited.

The method for producing meta-aramid fiber according to the present invention can be applied to all uses, and is particularly suitable for uses requiring safety and environmental considerations.

Claims (4)

  By using 3,4'-diaminodiphenyl ether and metaphenylenediamine as the diamine component in a ratio of 30 mol% / 70 mol% to 70 mol% / 30 mol% with respect to the total diamine component, using isophthalic acid as the acid component, and heating them. A method for producing meta-aramid fibers, comprising obtaining a meta-aramid oligomer having a logarithmic viscosity of 0.1 to 0.4 dL / g measured in N-methyl-2-pyrrolidone and melt-melting it.   The method for producing meta-aramid fibers according to claim 1, wherein the melt-fiber is made into a melt fiber with a melt viscosity of the meta-aramid oligomer of 100 to 2000 Pa · s.   The method for producing meta-aramid fibers according to claim 1 or 2, wherein 40% or more of the terminals of the meta-aramid oligomer are amine terminals. The manufacturing method of the metaaramid fiber which solid-phase-polymerizes the metaaramid fiber obtained by the method in any one of Claims 1-3.

Images