JP2021031790A - Method for producing nylon 4 fiber and nylon 4 fiber - Google Patents

Abstract

To provide a method for producing a nylon 4 fiber capable of producing the nylon 4 fiber having high strength.SOLUTION: The method for producing the nylon 4 fiber includes: a dissolution step of dissolving nylon 4 in a solvent to obtain a spinning solution; a spinning step of subjecting the spinning solution to dry spinning to obtain an undrawn fiber; and a drawing step of drawing the undrawn fiber to obtain the nylon 4 fiber, wherein the nylon 4 has a weight-average molecular weight of 1,300,000 or more, the spinning solution has a concentration of 15 mass% or more in terms of dissolved nylon, and in the drawing step, a drawing temperature is 270°C or higher, and a stretching magnification is 4.5 times or more.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for producing nylon 4 fibers and nylon 4 fibers.

Nylon 4, which is one of the polyamide resins, is expected as a resin which has a higher amide bond density and exhibits excellent thermal and mechanical properties as compared with nylon 6 and nylon 66, which are more general-purpose polyamide resins. There is. In this regard, for example, Non-Patent Document 1 predicts that the elastic modulus of the crystal of nylon 4 is superior to that of other existing nylons.

Nylon 6 and Nylon 66 are generally made into fibers by melt spinning. On the other hand, fibers made from nylon 4 (nylon 4 fibers) have been known for their excellent property potential for a long time, but since the melting point and decomposition temperature of nylon 4 are close to each other, they are made into fibers by melt spinning. Has been considered difficult.

Here, it is considered preferable to improve the strength of the nylon fiber because it leads to a reduction in the amount used and a weight reduction in the product, particularly in industrial applications such as tire cords. It has been reported that nylon 4 is synthesized by bio-derived (Non-Patent Document 2 and Patent Document 1), and in the future, it is possible to produce nylon 4 and fibers using it by bio-derived. Therefore, the adoption of nylon 4 is preferable in terms of consideration for the environment.

Under these circumstances, studies have been conducted to spin nylon 4 fibers with high strength in order to use nylon 4 instead of nylon 6 and nylon 66 to make fibers for reinforcing rubber centered on tires. It has been.

For example, Patent Documents 2 to 4 disclose that nylon 4 is fibrated by melt spinning by mixing a drug that acts like a plasticizer that weakens the hydrogen bond of nylon. Further, Patent Document 5 discloses a technique of lowering the melting point of nylon 4 by adding a salt to perform melt spinning without decomposition.

On the other hand, in addition to melt spinning, the production of nylon 4 fibers by wet spinning, dry wet spinning, dry spinning and the like has also been studied so far.

For example, Patent Document 6 discloses a technique of dissolving nylon 4 in formic acid and methylene chloride for wet spinning, and Patent Document 7 discloses a technique of dissolving nylon 4 in an aqueous solution containing zinc chloride for wet spinning. .. Further, Patent Document 8 discloses that nylon 4 fibers are obtained by wet or dry wet spinning or gel spinning using an ionic liquid as a solvent.

Patent Documents 9 and 10 disclose that nylon 4 is fibrated by dry spinning.

Anik Peeters et al., Int. J. Quantam Chem., 87, 307-310 (2002) Norioki Kawasaki et al., Polymer, 46, 9987-9993 (2005)

JP-A-2009-159840 U.S. Patent Application Publication No. 3,009,893 Japanese Unexamined Patent Publication No. 50-6817 Japanese Unexamined Patent Publication No. 50-12325 International Publication No. 2012/157576 U.S. Patent Application Publication No. 4,094,945 Tokukousho 36-5165 Gazette International Publication No. 2015/186364 U.S. Patent Application Publication No. 3,076,774 U.S. Patent Application Publication No. 3,324,061

However, with respect to the above-mentioned prior art of melt spinning, the strength of the fibers disclosed in Patent Documents 2 to 4 remains at about 3 g / d (331 MPa), 2.7 g / d, and 2.8 g / d, respectively, which are sufficient. Not expensive. Further, in the technique disclosed in Patent Document 5, it is difficult to add salt to the resin, and it is necessary to wash the fibers after melt spinning to remove the salt, and the orientation is relaxed due to the washing. It is difficult to increase the strength of the fiber because the removed portion becomes a void.

Further, regarding the above-mentioned prior art of wet spinning or dry wet spinning, the strength of the fibers disclosed in Patent Documents 6 and 7 remains at 4.21 g / d and 3.44 g / d, respectively, although they are both sufficiently high. Absent. Further, although the technique disclosed in Patent Document 8 can obtain nylon 4 fiber having relatively high strength, it is difficult to industrialize because it uses a very expensive ionic liquid.

Regarding the above-mentioned prior art of dry spinning, Patent Documents 9 and 10 do not show any specific procedure for dry spinning using nylon 4 and specific physical properties of the obtained fiber.

From the above, the development of a technique for producing nylon 4 fiber having high strength is strongly desired.

Therefore, an object of the present invention is to provide a method for producing nylon 4 fibers capable of producing nylon 4 fibers having high strength. Another object of the present invention is to provide nylon 4 fibers having high strength.

That is, the method for producing nylon 4 fibers of the present invention is:
A dissolution step of dissolving nylon 4 in a solvent to obtain a spinning solution,
A spinning process of obtaining undrawn fibers by dry spinning using the spinning solution, and
A drawing step of drawing the undrawn fibers to obtain nylon 4 fibers, and the like.
The nylon 4 has a weight average molecular weight of 1,300,000 or more.
The spinning solution has a dissolved nylon 4 having a concentration of 15% by mass or more.
In the stretching step, the stretching temperature is 270 ° C. or lower and the stretching ratio is 4.5 times or more.
It is characterized by that. According to the method for producing nylon 4 fibers of the present invention, nylon 4 fibers having high strength can be produced.

In the method for producing nylon 4 fibers of the present invention, when the weight average molecular weight of the nylon 4 is x and the concentration of nylon 4 in the spinning solution is y (mass%), the following formula (1):
-7.20 x 10 ^-6 x + 33.02 ≤ y ≤ -1.61 x 10 ^-6 x + 24.46 (1)
It is preferable to satisfy. In this case, higher strength nylon 4 fibers can be prepared.

In the method for producing nylon 4 fiber of the present invention, it is preferable that the solvent contains formic acid from the viewpoint of availability and high solubility in nylon 4.

The nylon 4 fiber of the present invention is characterized by being produced by the above-mentioned method for producing nylon 4 fiber. The nylon 4 fiber of the present invention has high strength.

According to the present invention, it is possible to provide a method for producing nylon 4 fibers, which can produce nylon 4 fibers having high strength. Further, according to the present invention, it is possible to provide nylon 4 fibers having high strength.

It is a figure which shows the preferable relational expression of the weight average molecular weight of nylon 4 and the concentration of nylon 4 in a spinning solution in the manufacturing method of nylon 4 fiber of this invention. It is the schematic of the dry spinning apparatus of an example which can be used in the manufacturing method of nylon 4 fiber of this invention. It is a schematic diagram of an example stretching apparatus (one-step stretching) that can be used in the method for producing nylon 4 fibers of the present invention. It is a schematic diagram of an example stretching apparatus (two-stage stretching) that can be used in the method for producing nylon 4 fibers of the present invention. It is a figure which shows the molecular weight distribution of an example nylon 4 which can be used in the manufacturing method of the nylon 4 fiber of this invention.

(Manufacturing method of nylon 4 fiber)
The method for producing nylon 4 fibers according to an embodiment of the present invention (hereinafter, may be referred to as "the method for producing the present embodiment") is a step of dissolving nylon 4 as a resin in a solvent to obtain a spinning solution. (Dissolving step), dry spinning using the above-mentioned spinning solution to obtain undrawn fibers (spinning step), and stretching the above-mentioned undrawn fibers to obtain nylon 4 fibers (drawing step). It is characterized by containing at least one feature, and if necessary, other steps such as a step of drying the undrawn fibers before the drawing step (drying step) can be included. Further, in the production method of the present embodiment, the weight average molecular weight of the nylon 4 is 1,300,000 or more, and the concentration of the dissolved nylon 4 in the spinning solution is 15% by mass or more. One of the features is that there is.

The manufacturing method of the present embodiment has been found by the present inventors focusing on dry spinning of nylon 4 fibers and after diligent studies. Then, according to the production method of the present embodiment, nylon 4 fibers having high strength can be produced.

In addition, in this specification, "nylon 4 fiber" means the fiber of the linear polymer containing nylon 4.
Further, in the present specification, "dry spinning" means that the raw material is discharged from a mouthpiece (nozzle) in a state of being dissolved in a solvent, and the solvent is evaporated in a hot atmosphere to form fibers.

Hereinafter, the raw materials used in the production method of the present embodiment will be specifically described.

<Nylon 4>
As described above, in the production method of the present embodiment, nylon 4 having a weight average molecular weight of 1,300,000 or more is used. Generally, in order to achieve high fiber strength, a high degree of molecular orientation is required, but in the conventional dry spinning example, nylon 4 fiber with sufficiently high strength cannot be obtained. It was. Under such circumstances, the present inventors have found that nylon 4 used for ordinary spinning has a low molecular weight, and therefore the molecular entanglement is insufficient even if it is made into fibers, and repeated diligent studies.

In general, it is necessary to highly orient the molecules in order to increase the strength and elastic modulus of the fiber. Such molecular orientation occurs when the molecular chains dissolved in the solution are stretched in an appropriately entangled state. Then, in order to achieve such a high degree of orientation in the process of spinning and drawing, it is necessary to consider both the molecular weight and the concentration of the spinning solution (the concentration of nylon 4 dissolved in the spinning solution) at the same time. It was found that there is. If the molecular weight is too small, the molecular chains are less entangled and cannot be stretched, and in some cases, the molecules may slip through during stretching. On the other hand, if the molecular weight is too large, the molecular chains are entangled too much, making it difficult to draw well, and the viscosity of the spinning solution increases, resulting in extreme handleability in each process of dissolution, spinning and drawing. It gets worse. Therefore, there is an optimum region for the molecular weight.
Further, the concentration of the spinning solution also has an optimum region from the same viewpoint. That is, if the concentration of the spinning solution is too low, the molecular chains tend to be less entangled, while if the concentration of the spinning solution is too high, the molecular chains tend to be entangled too much.

However, both the molecular weight and the concentration of the spinning solution are preferably large or high within the optimum range. The reason why a large molecular weight is preferable is that the end of the molecular chain is considered to be equivalent to a defect, and it is said that the end of the molecular chain should be as small as possible in order to increase the strength. Is. Further, the reason why the concentration of the spinning solution is preferable is that the solvent in the spinning solution escapes from the fiber in the process of dry spinning, and the portion becomes a void (void) that can inhibit high strength. Therefore, the higher the polymer concentration and the smaller the amount of solvent that escapes, the smaller the voids.

In consideration of the above, as a result of investigating the optimization of the molecular weight of nylon 4 and the concentration of the spinning solution, the present inventors investigated the concentration of the spinning solution using nylon 4 having a weight average molecular weight of 1,300,000 or more. It has been found that high strength of the fiber can be achieved by adjusting the content to 15% by mass or more.
The weight average molecular weight of nylon 4 is measured by size exclusion chromatography (SEC) using polymethylmethacrylate as a standard substance.

The method for preparing nylon 4 used in the present embodiment is not particularly limited as long as a predetermined weight average molecular weight is achieved. For example, nylon 4 can be prepared by the ring-opening polymerization method of 2-pyrrolidinone described in Polymer, 46, p9987-9993 (2005). Further, the high molecular weight nylon 4 can be prepared from 2-pyrrolidinone as a monomer with reference to the production method described in JP-A-5-0201.

As the raw material 2-pyrrolidinone, for example, those produced from petroleum, those produced from bio-derived resources such as γ-aminobutyric acid using a microorganism-derived enzyme, and the like can also be used.

<Other polyamide resins>
In the production method of the present embodiment, nylon 4 having a weight average molecular weight of 1,300,000 or more as described above may be used as a raw material, and other polyamide resin may be used as a raw material. Examples of other polyamide resins include nylon 4 having a weight average molecular weight of less than 1,300,000, aliphatic polyamides other than nylon 4 (nylon 6, nylon 66, etc.), total aromatic polyamide (aramid, etc.), and semi-fragrance. Group polyamide (nylon 6T / 66, nylon 6T / 6I, etc.) and the like can be mentioned. However, from the viewpoint of surely obtaining the desired effect and considering the environment, it is preferable not to use the above-mentioned other polyamide resin in the production method of the present embodiment.

Next, each step included in the manufacturing method of the present embodiment will be specifically described.

<Melting process>
The dissolution step is a step of dissolving the nylon 4 in a solvent to obtain a spinning solution. Further, in the spinning solution obtained in this dissolution step, the concentration of the dissolved nylon 4 is 15% by mass or more. In other words, in this dissolution step, the nylon 4 is dissolved in a solvent so that the concentration in the spinning solution is 15% by mass or more. If the concentration of nylon 4 in the obtained spinning solution is less than 15% by mass, the amount of solvent to be evaporated is too large, making dry spinning difficult, or the obtained fibers have many voids. It occurs and it is not possible to finally obtain high-strength nylon 4 fibers.

The solubility of nylon 4 having a weight average molecular weight within the above range depends on the solvent used, but generally has an upper limit of about 30% by mass. The concentration of nylon 4 in the spinning solution is preferably 22% by mass or less from the viewpoint of optimization.

In the production method of the present embodiment, when the weight average molecular weight of nylon 4 used is x and the concentration of nylon 4 in the spinning solution is y (mass%), the following formula (1):
-7.20 x 10 ^-6 x + 33.02 ≤ y ≤ -1.61 x 10 ^-6 x + 24.46 (1)
It is preferable to satisfy (the hatched portion in FIG. 1). By making the weight average molecular weight of nylon 4 and the concentration of nylon 4 in the spinning solution satisfy the above relational expression, a higher strength nylon 4 fiber (for example, a fiber strength of 900 MPa, particularly 1000 MPa or more) can be obtained. Can be prepared.

The solvent is not particularly limited as long as nylon 4 dissolves in 15% by mass or more at 25 ° C., but formic acid is preferably used from the viewpoint of availability and high solubility in nylon 4. In other words, the solvent used in the dissolution step preferably contains formic acid. In addition to formic acid, examples of the solvent include hexafluoroisopropanol (HFIP) and trifluoroacetic acid (TFA), which can be used in combination with formic acid. In other words, the solvent used in the dissolution step can further contain one or more selected from hexafluoroisopropanol and trifluoroacetic acid in addition to formic acid.

<Spinning process>
The spinning step is a step of obtaining undrawn fibers by dry spinning using the spinning solution obtained in the melting step. The operation of dry spinning is not particularly limited, and dry spinning can be performed by a conventionally used dry spinning device.

As an example, FIG. 2 shows a schematic view of a dry spinning apparatus that can be used in the manufacturing method of the present embodiment. In the dry spinning apparatus 100 shown in FIG. 2, the syringe 11 is first filled with a spinning solution. The syringe 11 is provided with a heater 117, and the spinning solution can be appropriately heated. The spinning solution filled in the syringe 11 is discharged into the air from the nozzle 116 attached to the lower end of the syringe 11 by applying pressure from above by the plunger 115. A heater 12 is provided directly below the nozzle 116 to form a thermal atmosphere that can be adjusted to a predetermined temperature. Then, fibers are formed from the solution after discharge, and the above-mentioned thermal atmosphere promotes evaporation of the solvent from the fibers. After that, the fibers are sequentially fed through one or more feed rollers including a feed roller 13 provided vertically below the nozzle, and the fibers (undrawn fibers) are wound by the take-up roller 15.

As shown in FIG. 2, the fibers from the heater 12 to the feed roller 13 vertically downward may be surrounded by a cylinder 16 (for example, a polycarbonate cylinder) provided with the solvent trap 17. Further, as shown in FIG. 2, an outer diameter measuring instrument 18 is provided between the rollers (for example, between the feed roller 13 and the feed roller 14 or between the feed roller 14 and the take-up roller 15), and dry spinning is performed. The diameter of the fiber obtained in 1 may be measured regularly. Further, as shown in FIG. 2, a series of spinning steps may be performed by the dry spinning apparatus 100 covered with the protective cover 19.

<Drying process>
In the production method of the present embodiment, the undrawn fibers obtained in the spinning step may be dried as a drying step after the spinning step described above and before the drawing step described later. The drying method is not particularly limited, and examples thereof include a method of leaving the fibers in a chamber adjusted to a predetermined temperature and humidity.

<Stretching process>
The drawing step is a step of drawing the undrawn fibers after the spinning step or the drying step to obtain nylon 4 fibers. In the production method of the present embodiment, nylon 4 fibers having high strength can be finally obtained through this drawing step.

The drawing operation is not particularly limited, and the undrawn fibers can be drawn by a conventionally used drawing device.
As an example, FIG. 3A shows a schematic view of a stretching device (one-stage stretching) that can be used in the manufacturing method of the present embodiment. In the drawing apparatus 200 shown in FIG. 3A, the fibers pass through a heating chamber 22 that can be adjusted to a predetermined temperature (drawing temperature) while being sequentially fed by the feeding roller 21, the yarn guides 23, 26, and the take-up roller 25. It is heated by doing. At this time, the fibers are stretched by increasing the take-up speed of the take-up roller 25 to be higher than the take-up speed of the take-out roller 21.

The stretching ratio in the stretching device 200 is adjusted by changing the winding speed of the winding roller 25 and the feeding speed of the feeding roller 21, respectively.

Further, the stretching in the stretching step can be performed in multiple steps of two or more steps. As an example, FIG. 3B shows a schematic view of a stretching device (two-stage stretching) that can be used in the manufacturing method of the present embodiment. In the drawing device 300 shown in FIG. 3B, the fibers pass through a heating chamber 33 that can be adjusted to a predetermined temperature (drawing temperature) while being sequentially fed by the feeding roller 31, the yarn guides 32, 34, and the drawing roller 35. It is heated by. At this time, the fibers are stretched by increasing the winding speed of the drawing roller 35 to be higher than the feeding speed of the feeding roller 31 (first-stage stretching). Next, the fibers sent to the drawing roller 35 pass through a second heating chamber 37 that can be adjusted to a predetermined temperature (drawing temperature) while being sequentially fed by the yarn guides 36 and 38 and the take-up roller 40. It is heated. At this time, the fibers are stretched by increasing the take-up speed of the take-up roller 40 to be higher than the take-out speed of the draw roller 35 (substantially synonymous with the take-up speed of the draw roller 35) (second stage). Stretching).

The stretching ratio of the first stage in the stretching device 300 is adjusted by changing the winding speed of the stretching roller 35 and the feeding speed of the feeding roller 31, respectively. Further, the stretching ratio of the second stage is adjusted by changing the winding speed of the winding roller 40 and the feeding speed of the stretching roller 35, respectively. Then, the stretching ratio (total stretching ratio) in the stretching apparatus 300 is calculated as the product of the first-stage stretching ratio and the second-stage stretching ratio.

Further, as shown in FIGS. 3A and 3B, tension meters 24 and 39 may be provided in front of the take-up rollers 25 and 40 so that the tension of the drawn fibers can be continuously measured. Further, if necessary, a pre-drying furnace (not shown, for example, 125 ° C. × 1 m) may be provided in front of the heating chambers 22 and 33.

Here, the unstretched fiber used in the drawing step preferably has a solvent concentration of 0.5% by mass or less. When the concentration of the solvent is 0.5% by mass or less, the strength and elastic modulus of the finally obtained nylon 4 fiber can be further improved. From the same viewpoint, the concentration of the solvent in the undrawn fibers is more preferably 0.1% by mass or less, and further preferably 0.01% by mass or less.
The reduction of the solvent concentration in the undrawn fibers is, for example, carrying out the above-mentioned drying step, increasing the concentration of nylon 4 dissolved in the spinning solution, increasing the temperature of the hot atmosphere in the dry spinning apparatus, steam vapor. It can be achieved by hitting.

In the stretching step, the stretching temperature (in the case of performing stretching in multiple stages, the stretching temperature in the final stage) is 270 ° C. or lower. If the stretching temperature exceeds 270 ° C., the fiber may be broken. The stretching temperature is preferably 220 ° C. or higher, more preferably 240 ° C. or higher. When the stretching temperature is 220 ° C. or higher, the hydrogen bond of nylon 4 can be weakened and the molecular orientation can be promoted.
When stretching is performed in multiple stages, it is preferable that the stretching temperature in each stage becomes higher toward the latter stage.

Further, in the stretching step, the stretching ratio (the product of the stretching ratios of each stage when stretching is performed in multiple stages) is 4.5 times or more. If the draw ratio is less than 4.5 times, the strength of the obtained nylon 4 fiber may not be sufficiently increased. The draw ratio is preferably 4.8 times or more, more preferably 5.0 times or more, and 5.5 times or more, from the viewpoint of further increasing the strength of the obtained nylon 4 fibers. It is more preferable to have.

(Nylon 4 fiber)
The nylon 4 fiber of one embodiment of the present invention (hereinafter, may be referred to as “nylon 4 fiber of the present embodiment”) is characterized in that it is produced by the above-mentioned method for producing nylon 4 fiber. Since the nylon 4 fiber of the present embodiment is produced by the production method of the present embodiment described above, it has high strength. Therefore, the nylon 4 fibers of the present embodiment can be applied to a wide range of applications such as clothing, ropes, tire cords, airbags, seat belts, and parachutes.

In the nylon 4 fiber of the present embodiment, the fiber strength (tensile strength) can be 900 MPa or more. When the fiber strength of the nylon 4 fiber is 900 MPa or more, the nylon 4 fiber can be suitably used, for example, as a tire cord, particularly as a belt reinforcing layer of a tire. Further, in the nylon 4 fiber of the present embodiment, the fiber strength can be preferably 1000 MPa or more.
The fiber strength can be determined by the procedure described in the examples.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples, and can be appropriately modified without changing the gist thereof.

(Preparation of nylon 4)
Nylon 4 was prepared according to the procedure shown below.

<Purification of nylon 4>
4.0 g of sulfuric acid was added to 600 g of 2-pyrrolidinone (manufactured by Kanto Chemical Co., Inc., purity: 98.0%), and the mixture was stirred in an oil bath at 100 ° C. in an argon air stream. Then, the distillation was carried out under reduced pressure at an outside bath temperature of 150 ° C. and 1 mmHg to obtain about 10 mL of the initial distillate, and then about 570 g of the main distillate was obtained. In this way, 2-pyrrolidinone as a monomer was purified in advance.

Next, a three-way cock equipped with a stirring blade, a septum cap, a balloon and an argon bubbler and a distilling device were attached to a 1 L separable four-necked flask, and 500 g of the above-mentioned purified 2-pyrrolidinone was charged. After performing decompression-argon substitution three times to create an argon atmosphere, the flask was immersed in an oil bath at 40 ° C. and stirred at 100 rpm. Next, 70.4 g of potassium hydroxide as a catalyst was added, the pressure was reduced to 1 mmHg, the pressure was reduced and stirred for 30 minutes, and then the bath temperature was raised to 135 ° C. at a pace of 10 ° C. in 10 minutes. , Removed with pyrrolidone, which is azeotropically heated with the reaction. When the temperature was raised, the entire flask was covered with aluminum foil to keep it warm. Subsequently, argon substitution was performed to obtain an argon air flow, and then the oil bath temperature was set to 40 ° C., and the distilling device was removed. A PFA cannula was inserted through the septum cap, and carbon dioxide gas was bubbled at 60 mL / min (nitrogen gas equivalent: 75 mL / min) as an initiator while stirring for 93 minutes. When carbon dioxide gas is blown at a flow rate of 60 mL / min for 93 minutes, the amount of substance n corresponds to 0.228 mol according to the ideal gas law (pV = nRT) (p = 1 (atm); V = 60 × 93/1000 (L); R = 0.082; T = 298 (K)). The mass of carbon dioxide gas in this case is calculated as 0.228 × 44.01 ≈ 10.0 g because the molar mass is 44.01 g / mol. Then, after bubbling carbon dioxide gas, the stirring blade was raised from the liquid surface and left in an argon air stream at an oil bath temperature of 40 ° C. for about 40 hours for ring-opening polymerization. In this way, solids (A to H) were obtained, respectively.

About 500 g of the solid obtained as described above was finely pulverized in liquid nitrogen, stirred in 3 L of pure water at room temperature for 30 minutes, and then filtered. Stirring-filtration was repeated until the pH of the filtrate became neutral. Then, the mixture was stirred for 10 hours while being immersed in 1 L of pure water to reconfirm that the pH of the filtrate was neutral, and then the obtained solid was washed with acetone at 80 ° C. and 1 mmHg for 48 hours. It was dried under reduced pressure. Further, it was crushed using a tabletop crusher (“Mini Speed Mill MS-05” manufactured by Labnext Co., Ltd.) and classified through a 100-mesh sieve. About 100 g of the obtained classified solid was placed in 1 L of ion-exchanged water, boiled for about 5 minutes, left to cool, and then suction-filtered. The above process was repeated once again, and washing was performed twice each time. The mass after suction filtration was roughly loosened, spread appropriately, and dried in a vacuum oven at 120 ° C. for 20 minutes. In this way, nylon 4 (A to H) was obtained, respectively. Each of the obtained nylons 4 was placed in a container and stored in a desiccator (manufactured by Eclalucy Co., Ltd., "McDry MCU-201") at about 1% RH or less.

For each of the obtained nylons 4, the number average molecular weight (Mn), the weight average molecular weight (Mw), and the Z average molecular weight (Mz) were measured by size exclusion chromatography (SEC) under the following conditions. Prior to the SEC measurement, nylon 4 was discarded 5 to 10 times at a concentration of 0.05% by mass until the baseline became stable. The measurement results are shown in Table 1.
Eluent: Hexafluoroisopropanol Pretreatment: Membrane filter (Mysholidisk H-25-5, manufactured by Tosoh Corporation), filtered at 0.5 μm Additive: Sodium trifluoroacetate (10 mmol / L)
Standard substance: Polymethylmethacrylate Concentration: 0.025% by mass
Injection volume: 10 μL
Flow velocity: 0.2 mL / min
Column temperature: 40 ° C
Equipment used: HLC-8320GPC (using RI detector) (manufactured by Tosoh Corporation)
Columns: Shodex GPC HFIP 607 x 1 and Shodex GPC HFIP 606M x 1 (both manufactured by Showa Denko KK)

Further, the obtained nylon 4 was measured for shear viscosity (η) ^{at a shear rate of 0.1 s -1 under the following conditions.} The measurement results are shown in Table 1.
Dissolving device: Sealing mixer UZU (manufactured by Nakamura Kagaku Kikai Kogyo Co., Ltd.)
Melting conditions: 20 ° C x 18 hours (2 rpm)
Solvent: Formic acid Concentration: 10% by mass
Sample amount: Approximately 2-3 mL (If it sticks out, wipe it off with a spatula)
Equipment used: Rotating rheometer Kinexus pro + (manufactured by Malvern Instruments Ltd.)
Measurement mode: Steady Flow (stepwise increase in shear rate)
Shear rate range: 0.1 to 100 / s
Upper plate: 40 mmΦ (parallel plate)
Distance between plates: 0.5 mm
Measurement temperature: 60 ° C

For reference, the molecular weight distribution of the nylon 4 (A) is shown in FIG. 4, respectively.

(Example 1)
As the nylon 4, nylon 4 (D) in Table 1 was used. Nylon 4 was weighed and mixed with formic acid as a solvent (99% formic acid (special grade), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to obtain a spinning solution. The above weighing was performed so that the concentration of nylon 4 in the spinning solution was 20% by mass. In addition, the above stirring uses a sealing mixer UZU (manufactured by Nakamura Kagaku Kikai Kogyo Co., Ltd.) at an outside bath temperature of 50 ° C. and 2 rpm in order to prevent moisture absorption and formic acid scattering to reduce the weight. It took 18 hours until the nylon 4 was completely dissolved in the solvent.

The obtained spinning solution was left in an oven at 40 ° C. for about 1 hour in a closed container to remove bubbles in the solution. Then, it was transferred to the syringe of the spinning device, being careful not to let bubbles enter the solution. As the spinning device, a small spinning device manufactured by AIKI Riotec Co., Ltd. was used, and dry spinning was performed with this spinning device. The outline of this spinning apparatus is as shown in FIG. Specifically, the spinning solution was kept warm at 40 ° C., pressure was applied to the spinning solution filled in the syringe 11 from above with a plunger 115, and a nozzle 116 (single-hole nozzle, length) attached to the lower end of the syringe 11 was attached. The solution was discharged at about 0.05 mL / min from (13 mm, inner diameter: 0.26 mm). In order to dry and solidify the surface of the fluid on the spinning wire to the extent that it can withstand spinning, a heater 12 (transparent glass heater with a heating length of 10 cm) is installed directly under the nozzle 116 and set to 70 ° C. The atmosphere was heated. The distance from the nozzle 116 to the first feed roller 13 is 75 cm, the yarn is fed at a speed of almost free fall so as not to align the molecular chains as much as possible, and the yarn (undrawn fiber) is fed by the take-up roller 15 in the subsequent stage. I rolled it up.

Next, the undrawn fibers were stretched using a stretching device (one-stage stretching). The outline of the stretching device used is as shown in FIG. 3A. In this stretching apparatus 200, a ceramic electric tube furnace "AFR3-500-30KC" with a length of 30 cm and a temperature controller "AMF-10P-III" (both manufactured by Asahi Rika Seisakusho) were used as the heating chamber 22. The inside of the heating chamber 22 is divided into three zones, each of which can independently control the temperature, but only the central zone (length 15 cm) is heated, and the furnace inlet zone and outlet zone (15 cm each) are heated. Switched off and did not heat. As the stretching conditions, the temperature (stretching temperature) in the heating chamber 22 is adjusted to 260 ° C., the feeding speed of the feeding roller 21 is fixed to a constant value (0.3 m / min), and the winding speed of the winding roller 25 is adjusted. By changing, the draw ratio was adjusted to 5.0 times. In this way, nylon 4 fibers (drawn fibers) were finally obtained.

The following measurements were carried out on the obtained drawn fibers.

<Fineness>
The drawn fibers were left overnight in a constant temperature and humidity chamber adjusted to a temperature of 20 ° C. and a relative humidity of 65%, and then the fineness (dtex) was measured using a fineness measuring device "DENICON DC-21" manufactured by Search Co., Ltd. .. The results are shown in Table 2.

<Fiber strength>
After leaving the drawn fibers in a constant temperature and humidity chamber, a tensile test is performed using a small tabletop tester "EZTest EZ-SX" manufactured by Shimadzu Corporation under the conditions of a sample chuck length of 20 mm and a tensile speed of 20 mm / min. , The breaking strength (cN) in this tensile test was determined. Then, the strength (unit: cN / dtex) calculated using the fineness measured above is converted into a unit of Pa using the density of the drawn fiber, and the tensile strength (Tb, MPa) as the fiber strength is obtained. It was. Moreover, the cutting elongation (Eb,%) was determined by the same tensile test. The results are shown in Table 2.
^{Here, regarding the density of the drawn fibers, "1.25 g / cm 3} " described in the academic literature (CEBarnes, Lenzinger Berrichte, p62-66, March, 1987) was adopted as a representative value. In this example as well, as a result of measuring the densities of some drawn fibers by the floating-sink method (toluene-carbon tetrachloride system, 25 ° C.), the density is in the range of ^{1.252 to 1.255 g / cm 3.} It was confirmed.

(Examples 2 to 7, 9 to 13, Comparative Examples 1 to 3)
Nylon 4 fibers used, the concentration of nylon 4 in the spinning solution, the drawing temperature, and the drawing ratio were adjusted or changed as shown in Table 2 in the same manner as in Example 1 to finally obtain the nylon 4 fibers. (Stretched fiber) was obtained. Then, the obtained drawn fibers were subjected to the same measurements as in Example 1. The results are shown in Table 2.

(Example 8)
In the same manner as in Example 4, a spinning solution was obtained and undrawn fibers were obtained. Next, the undrawn fibers were stretched using a stretching device (two-stage stretching). The outline of the stretching device used is as shown in FIG. 3B. In this stretching device 300, a non-contact air heating and stretching machine (manufactured by Imoto Seisakusho Co., Ltd.) having a length of 30 cm was used as the heating chamber 33, and a self-made work having a length of 15 cm was used as the second heating chamber 37. .. The stretching temperature and stretching ratio in the first-stage stretching and the stretching temperature and stretching ratio in the second-stage stretching were adjusted and stretched as shown in Table 2, and finally nylon 4 fibers (drawn fibers) were obtained. Then, the obtained drawn fibers were subjected to the same measurements as in Example 1. The results are shown in Table 2.

(Comparative Example 4)
In the same manner as in Example 1, a spinning solution was obtained and undrawn fibers were obtained. Next, an attempt was made to draw the undrawn fibers in the same manner as in Example 1 except that the drawing temperature was adjusted to 280 ° C. However, the fibers melted during drawing (fusing), and nylon 4 fibers (drawn fibers) could not be finally obtained.

From Table 2, it can be seen that in Examples 1 to 13 according to the present invention, nylon 4 fibers having high fiber strength (tensile strength of 900 MPa or more) are obtained.
On the other hand, in Comparative Examples 1 to 3 in which the draw ratio was less than 4.5 times, the strength of the nylon 4 fiber could not be sufficiently improved as compared with the above Examples. Further, as described above, in Comparative Example 4 in which the stretching temperature was higher than 270 ° C., the fibers were broken during stretching.

Further, in the example in which the weight average molecular weight (Mw) of nylon 4 and the concentration of nylon 4 in the spinning solution satisfy the above formula (1), it can be seen that the strength of the obtained nylon 4 fibers is generally higher.

According to the present invention, it is possible to provide a method for producing nylon 4 fibers, which can produce nylon 4 fibers having high strength. Further, according to the present invention, it is possible to provide nylon 4 fibers having high strength.

100: Dry spinning device, 11: Syringe, 115: Plunger, 116: Nozzle, 117: Heater, 12: Heater, 13, 14: Feed roller, 15: Winding roller, 16: Cylinder, 17: Solvent trap, 18 : Outer diameter measuring instrument, 19: Protective cover,
200: Stretching device (1 step), 21: Feeding roller, 22: Heating chamber, 23: Thread guide, 24: Tension meter, 25: Winding roller, 26: Thread guide,
300: Stretching device (2 steps), 31: Feeding roller, 32: Thread guide, 33: Heating chamber, 34: Thread guide, 35: Stretching roller, 36: Thread guide, 37: Second heating chamber, 38: Thread guide , 39: Tension meter, 40: Winding roller

Claims (4)

A dissolution step of dissolving nylon 4 in a solvent to obtain a spinning solution,
A spinning process of obtaining undrawn fibers by dry spinning using the spinning solution, and
A drawing step of drawing the undrawn fibers to obtain nylon 4 fibers, and the like.
The nylon 4 has a weight average molecular weight of 1,300,000 or more.
The spinning solution has a dissolved nylon 4 having a concentration of 15% by mass or more.
In the stretching step, the stretching temperature is 270 ° C. or lower and the stretching ratio is 4.5 times or more.
A method for producing nylon 4 fiber, which is characterized by the above. When the weight average molecular weight of the nylon 4 is x and the concentration of nylon 4 in the spinning solution is y (mass%), the following formula (1):
-7.20 x 10 ^-6 x + 33.02 ≤ y ≤ -1.61 x 10 ^-6 x + 24.46 (1)
The method for producing a nylon 4 fiber according to claim 1. The method for producing a nylon 4 fiber according to claim 1 or 2, wherein the solvent contains formic acid. A nylon 4 fiber produced by the method for producing a nylon 4 fiber according to any one of claims 1 to 3.

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