JP4929922B2 - Method for producing polybenzazole fiber and polybenzazole fiber - Google Patents

Description

  The present invention relates to a polybenzazole fiber, and more specifically, is superior in post-processability such as fiber cutting and felting compared to conventional polybenzazole fibers, and not only industrial materials but also polybenzazole. The present invention relates to a method for producing a polybenzazole fiber that can be used in various applications utilizing the heat resistance and flame retardancy of the fiber.

The polybenzazole fiber is extruded from a spinneret by a dope containing a polybenzoxazole or polybenzothiazole polymer and an acid solvent, and then immersed in a solidifying liquid (for example, water or a mixture of water and an inorganic acid). In order to solidify and then remove the acid solvent, it is produced by a method of washing in a water washing bath, further neutralizing the acid remaining in the yarn through an aqueous bath of an inorganic base, and then drying (for example, Patent Document 1).
Japanese Patent No. 3564822

  Polybenzazole fiber has the highest level of performance among organic fibers in all respects, such as strength, elastic modulus, heat resistance, flame retardancy, and has been developed for various applications that take advantage of these characteristics. Yes. However, in applications that make use of heat resistance and flame retardancy, because of the high strength and high elastic modulus of polybenzazole fiber, it is not easy to cut the fiber, so post-processability is poor and post-processability is improved. It is desired.

  As a method for improving the post-processability, a method for significantly reducing the strength of the fiber can be considered. As a method for significantly reducing the strength of the polybenzazole fiber, a method of reducing the concentration and molecular weight of the polymer or heat-treating the fiber at a high temperature for a long time can be considered. However, if the polymer concentration or molecular weight is reduced, yarn breakage is likely to occur during spinning, loss of switching from normal brand production occurs, and the viscosity behavior of the dope changes greatly, so the spinning conditions are also changed. There is a problem that operability deteriorates. On the other hand, in order to heat treat the fiber at a high temperature for a long time, a high-temperature furnace is required, which is a problem because a large amount of energy is required.

  There is a need for polybenzazole fibers that have greatly reduced strength while maintaining the excellent heat resistance and flame retardancy of polybenzazole fibers. There has been a demand for a polybenzazole fiber excellent in post-processability and a method for producing the same, which suppresses generation as much as possible and does not have a problem of deterioration in operability.

  The present invention has been made in view of the above circumstances, and provides a method for producing a polybenzazole fiber with improved post-processability while maintaining the excellent heat resistance and flame retardancy of the polybenzazole fiber. A method for producing polybenzazole fibers that does not require significant changes in production process conditions, suppresses switching loss as much as possible, and does not require long-time heat treatment at high temperatures. Is to provide.

The present invention employs the following configuration. That is,
(1) A polybenzazole dope in which polybenzazole is dissolved in a solvent is spun from a spinneret, and the spun dope filament is immersed in a liquid (coagulation bath) containing a polybenzazole coagulant to coagulate. A method for producing a polybenzazole fiber, wherein the spun dope filament is brought into contact with a vapor of a polybenzazole coagulant and then immersed in a coagulation bath.
(2) The method for producing a polybenzazole fiber as described in the first item, wherein the polybenzazole coagulant is water.
(3) The method for producing a polybenzazole fiber according to the first or second aspect, wherein the polybenzazole solvent is polyphosphoric acid or methanesulfonic acid.
(4) Obtained by the method for producing a polybenzazole fiber according to any one of (1) to (3), wherein the cross section of the polybenzazole fiber is identified by an optical microscope as a sheath layer and a core layer, and the average diameter of the core layer A polybenzazole fiber, wherein a ratio R (%) of r ₂ to fiber cross-sectional diameter r ₁ is 90% or less.

According to the production method of the present invention, it is necessary to significantly change the process conditions of the polybenzazole fiber whose strength is greatly reduced while maintaining the excellent heat resistance and flame retardancy of the polybenzazole fiber. Therefore, it is possible to manufacture with the occurrence of switching loss as much as possible.
The obtained fiber is excellent in post-processing properties such as fiber cutting and felting, and it can be used in various applications requiring heat resistance and flame retardancy.

Hereinafter, the present invention will be described in detail.
The polybenzazole fiber according to the present invention refers to a fiber made of a polybenzazole polymer, and the polybenzazole (hereinafter also referred to as PBZ) refers to polybenzoxazole (hereinafter also referred to as PBO) or polybenzothiazole (hereinafter referred to as PBOZ). , PBT), or polybenzimidazole (hereinafter also referred to as PBI). In the present invention, PBO refers to a polymer containing an oxazole ring bonded to an aromatic group, and the aromatic group is not necessarily a benzene ring, and may be a biphenylene group, a naphthylene group, or the like. PBO refers to a polymer containing an oxazole ring bonded to an aromatic group, but the aromatic group is not necessarily a benzene ring. Furthermore, PBO is not only a homopolymer of poly (p-phenylenebenzobisoxazole) but also a copolymer or aromatic in which a part of the phenylene group of poly (p-phenylenebenzobisoxazole) is substituted with a heterocyclic ring such as a pyridine ring. Polymers consisting of a plurality of oxazole ring units bonded to a group are widely included. The same applies to PBT and PBI. Also included are two or more mixtures of PBO, PBT and PBI, two or more block or random copolymers of PBO, PBT and PBI, and mixtures of these polybenzazole polymers, copolymers, block polymers, etc. .

  The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers that form liquid crystals at a specific concentration. The polymer consists of monomer units described in structural formulas (a) to (h), and preferably consists essentially of monomer units selected from structural formulas (a) to (d). In addition, these monomer units may partially include monomer units having a substituent such as an alkyl group or a halogen group.

  Suitable solvents for forming the polymer dope include cresol and non-oxidizing acids that can dissolve the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and high concentrations of sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

  The polymer concentration in the dope is preferably at least about 7% by weight, more preferably at least 10% by weight, particularly preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration usually does not exceed 20% by weight.

  In the present invention, suitable polymers or copolymers and dopes are synthesized by known methods. For example, Wolfe et al. US Pat. No. 4,533,693 (1985.8.6), Sybert et al. US Pat. No. 4,772,678 (1988.9.22), Harris US Pat. No. 4,847,350 (1989.7.11) or Gregory et al. U.S. Pat. No. 5,089,591 (1992.2.18). In summary, suitable monomers are heated in a non-oxidizing, dehydrating acid solution at a stepwise or constant rate of heating from about 60 ° C. to 230 ° C. under high-speed stirring and high shear conditions in a non-oxidizing atmosphere. It is made to react by raising.

  The dope polymerized in this way is supplied to the spinning section and discharged from the spinneret at a temperature of usually 100 ° C. or higher. A plurality of base pores are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of nozzle holes is not particularly limited, but it is important that the arrangement of the spinning holes on the spinneret surface has a hole density that does not cause fusion between the spun yarns (dope filaments).

  In order to obtain a sufficient draw ratio (SDR), the spun yarn needs a sufficiently long draw zone length as described in US Pat. No. 5,296,185, and has a relatively high temperature (above the solidification temperature of the dope). It is desirable that the air is uniformly cooled with a rectified cooling air having a temperature equal to or lower than the spinning temperature. The length (L) of the draw zone is required to be a length that completes solidification in a non-solidifying gas, and is roughly determined by the single-hole discharge amount (Q). In order to obtain good fiber properties, it is desirable that the draw zone take-out stress is 2.2 g / dtex or more in terms of polymer (assuming that only the polymer is stressed).

The greatest feature of the method for producing the polybenzazole fiber according to the present invention is that the dope filament obtained by extruding the polybenzazole dope containing the solvent from the spinneret into the coagulating liquid-containing liquid is solidified. Is passed through the atmosphere of the coagulating liquid vapor, or the coagulating liquid vapor is sprayed on the dope filament, etc., and a steam treatment for positively contacting with the coagulant vapor is performed.
As a coagulant for polybenzazole, at least one of water, methanol, ethanol, acetone, and ethylene glycol is preferable, and water is more preferable in terms of simplicity.

Although the steam treatment method is not particularly limited, for example, in the case of water, as a method of passing through a steam atmosphere, a polybenzazole dope containing an acid solvent is extruded from a spinneret and then passed through a tube filled with steam. Examples of the method for spraying water vapor include a method for spraying steam using a slit nozzle onto a polybenzazole dope containing an acid solvent extruded from a spinneret.
This steam treatment can reduce the fiber strength. The reason why the fiber strength decreases is not clear, but it is considered that the change in the crystal structure of the fiber is the main reason. When the coagulation liquid is water, the hydrolysis of the polymer may be accelerated.

  In the steam treatment in the present invention, since the dope filament is positively brought into contact with the gas (air) containing the above-mentioned liquid vapor, the coagulant rapidly penetrates and diffuses throughout the fiber inside the dope filament, and the solidification nucleus It is thought that such a thing may be formed in the fiber center part direction. Surprisingly, when the fiber cross-section is observed after fiber formation, a boundary line that appears to be generated based on the difference in the timing of the start of structure formation is recognized, and so-called two-layer expression that can be expressed as a sheath core is recognized It is done. The better the coagulant penetrates to the center, the smaller the core layer and eventually the borderline will not be recognized. In addition, in the conventional fiber which is not subjected to steam treatment, a two-layer structure of the sheath / core is not recognized.

  A simple discrimination between the sheath layer and the core layer in the polybenzazole fiber can be made by observing the fiber cross section with an optical microscope. That is, when the fiber cross section is cut to a thickness that can be observed with an optical microscope, and magnified about 40 times with an optical microscope, the boundary between the sheath layer and the core layer is recognized as a circular line. The outer side of the circular line is a sheath layer, and the inner side is a core layer.

When the sheath layer is formed due to the penetration of the coagulant vapor, it is preferable that the thickness of the sheath layer is as large as possible and the diameter of the core layer is as small as possible. The ratio of the core layer in the polybenzazole fiber of the present invention, that is, the ratio of the average diameter (r ₂ ) of the core layer in the fiber cross-sectional direction to the fiber cross-sectional diameter (r ₁ ) R (%) = (r ₂ / r ₁ ) × 100 is preferably 90% or less, more preferably 80% or less, still more preferably 60% or less, and most preferably close to 0%.

The temperature of the steam treatment varies depending on the type of coagulant, but in the case of water, the temperature of the steam atmosphere or the temperature of the sprayed steam is preferably 50 to 200 ° C, more preferably 60 to 160 ° C, and even more preferably 70. ~ 130 ° C. If it is less than 50 degreeC, the effect of reducing an intensity | strength will become small. On the other hand, when the temperature exceeds 200 ° C., yarn breakage frequently occurs and the productivity tends to be remarkably lowered. If the coagulant has a lower boiling point than water, the temperature may be lower, and if the coagulant has a higher boiling point than water, the temperature may be higher, and can be appropriately selected in consideration of the boiling point and the vapor pressure.
The content of the vapor component with respect to the total gas components in the vapor phase is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more for short-time treatment. .

If the vapor phase temperature is too low, the thickness of the sheath layer will not develop, and conversely if the temperature is too high, the sheath / core structure will appear, but the temperature of the passing filament will rise and the yarn will tend to break frequently. is there. If the vapor content is too low, the sheath / core structure is difficult to develop.
The apparatus for performing the steam treatment is not particularly limited as long as the dope filament is in contact with the steam and can at least solidify the surface layer, and is not particularly limited to a continuous type, a non-continuous type, a sealed type, and a non-sealed type.

  The filament after passing through the vapor phase is then directed to a coagulation (extraction) bath for polybenzazole solvent extraction and complete coagulation of the filament. The coagulation bath is not particularly limited, and any type of coagulation bath may be used. For example, funnel type, water tank type, aspirator type or waterfall type can be used. Finally, extraction is performed so that the solvent remaining in the filament in the coagulation bath is 1% by mass or less, preferably 0.5% by mass or less. There is no particular limitation on the liquid used as the extraction medium in the present invention, but water, methanol, ethanol, acetone, ethylene glycol and the like that are substantially incompatible with polybenzazole are preferable. As the extract, an aqueous phosphoric acid solution or water is simple and desirable. Further, a method of separating the coagulation (extraction) bath in multiple stages, gradually decreasing the concentration of the phosphoric acid aqueous solution, and finally washing with water can be adopted. In the coagulation (extraction) step, it is a preferred method to neutralize the filament bundle with an aqueous sodium hydroxide solution and then wash with water. Thereafter, drying and heat treatment can be applied to form a fiber that can be distinguished into two layers of a sheath and a core.

  After that, the fiber is dried and further subjected to a heat treatment step as necessary. The drying temperature is not particularly limited as long as the coagulant or solvent of polybenzazole can easily fly, but specifically 150 to 400 ° C, preferably 200 to 300 ° C, more preferably 220 to 270 ° C. In order to improve the elastic modulus, heat treatment may be performed under tension as necessary. About heat processing temperature, it is 400-700 degreeC, Preferably it is 500-680 degreeC, More preferably, you may be 550-630 degreeC. The tension applied is 0.3 to 1.2 g / dtex, preferably 0.5 to 1.1 g / dtex, more preferably 0.6 to 1.0 g / dtex.

  The polybenzazole fiber obtained by the production method of the present invention has a diffraction peak derived from the crystal (200) plane in the equatorial profile in the electron beam diffraction diagram of the polybenzazole crystal obtained from the surface layer portion (surface to 1 μm). When the area is S1, and the diffraction peak area derived from the crystal (010) plane and the (−210) plane is S2, S2 / S1 is preferably 0.1 to 0.8, more preferably 0.2 to 0.7. If it is less than 0.1, the strength of the fiber is insufficiently reduced. On the other hand, if it exceeds 0.8, the strength of the fiber is excessively reduced even if the post-processability is high, and the operability and processability are deteriorated. Sometimes.

In addition, in the azimuth angle profile of electron diffraction of the (200) plane of the polybenzazole crystal obtained from the surface portion (1 μm from the surface) and the center portion of the polybenzazole fiber, the half width of the diffraction peak obtained from the surface layer portion Is preferably 0.75 to 1.25, divided by the half width of the diffraction peak obtained from the center.
T is more preferably 0.85 to 1.15. If it is less than 0.75, the strength reduction of the fiber may be insufficient. Conversely, if it exceeds 1.25, the strength reduction of the fiber becomes too large, and the operability and process passability may deteriorate.

In addition, regarding the apparent crystal size of the (200) plane of the polybenzazole crystal calculated from the electron beam diffraction profile in the equator direction obtained from the surface layer part (surface to 1 μm) and the center part of the polybenzazole fiber, A value U obtained by dividing the apparent crystal size by the apparent crystal size at the center is preferably 0.75 to 1.25.
U is more preferably 0.85 to 1.15. If it exceeds 1.25, the strength reduction of the fiber may be insufficient, and conversely if it exceeds 1.25, the strength reduction of the fiber becomes too large, and the operability and process passability may deteriorate. .

Furthermore, regarding the apparent crystal size of the (010) plane of the polybenzazole crystal calculated from the electron diffraction profile in the equatorial direction obtained from the surface portion (1 μm from the surface) and the central portion of the polybenzazole fiber, A value V obtained by dividing the apparent crystal size by the apparent crystal size at the center is preferably 0.75 to 1.25.
V is more preferably 0.85 to 1.15. If it exceeds 1.25, the strength reduction of the fiber may be insufficient, and conversely if it exceeds 1.25, the strength reduction of the fiber becomes too large, and the operability and process passability may deteriorate. .

In the present invention, a polybenzazole fiber is analyzed by an electron diffraction method, and in order to obtain a diffraction diagram and an analysis result, a known method can be adopted, and the measurement fiber is in the fiber axis (length) direction, and What was obtained by cutting into an ultra-thin section having a thickness of about 70 nm so as to include the surface layer portion and the center portion of the fiber is used.
That is, single fibers are embedded in an epoxy resin prepared according to the Luft method (J. Biophys. Biochem. Cytol., 9, 409 (1961)), and left in a 60 ° C. oven overnight to solidify and fix to embed the fibers. A resin block is obtained. Next, the resin block is attached to an ultra microtome manufactured by Reichert, and is polished using a glass knife until the embedded fibers appear in the vicinity of the block surface, and then a single fiber using a diamond knife manufactured by Diatom Cut in a direction parallel to the axial direction.
For example, when the diameter of a single fiber is 10 μm, when an ultrathin section having a thickness of about 70 nm is continuously cut from the fiber surface, it can be cut into about 140 sections. All cut sections were selectively collected on a copper grid as a group of every 10 sheets in the cutting order. The first to tenth sheets from the start of cutting are defined as group 1, and are sequentially defined as group 1, group 2... Group n. Among these groups, when n is an even number, the (n / 2) th group is used for the limited-field electron diffraction measurement when the nth group is odd, and when the n is an odd number, the (n / 2-0.5) th group is used. When one single fiber is all cut into ultrathin sections having substantially the same thickness, the above-described group of fiber sections includes both the surface layer portion (surface) and the center portion of the fibers.
After making an ultra-thin slice with a thickness of about 70 nm and including both the surface layer (surface) and the center of the fiber, the resulting ultra-thin slice was collected on a 300-mesh copper grid and thinly deposited with carbon. Apply. The central part in the present invention is a place including a part that can be regarded as a central point when the cross section of the fiber is regarded as a circle, and means a core part having a diameter of up to several microns. , The middle part of both surfaces.
Next, an ultrathin section was introduced into the electron microscope, and a limited-field electron diffraction image was taken for both the surface layer and the center of the fiber (in this case, the diameter of the limited field-of-view (aperture) was 1 μm or less, An electron beam diffractogram is obtained in which a portion free from artifacts (for example, wrinkles, blurring of the slice, etc.) generated in the cutting of the thin slice is selected as a diffraction image photographing site.

The profile in the equator direction of the obtained electron diffraction pattern is approximated using a Lorentz function, and the integrated intensity (area) and half-value width of diffraction peaks derived from (200), (010) and (-210) are approximated. And the area derived from (200) is S1, and the sum of the areas derived from (010) and (-210) is S2, and S2 / S1 is calculated.
The apparent crystal size (ACS) is calculated using the following equation.
ACS = 0.9λ / βcosθ
Here, λ is the wavelength of the electron beam, β is the full width at half maximum (in radians), and θ is the half value of the diffraction angle 2θ.
Further, for (200) diffraction, the half-value width is calculated by approximating the diffraction profile in the azimuth angle direction with a Lorentz function.

  The reason why the polybenzazole fiber of the present invention is moderately reduced in strength and improved in post-processability is not clear, but when estimated from the electron diffraction pattern of the polybenzazole crystal by the electron beam diffraction method as described above, The selective orientation in the a and b axis directions of at least the fiber surface layer crystal is randomized compared to the conventional one, and the difference in crystal orientation between the surface layer portion and the center portion of the fiber is reduced. It is considered that the orientation is randomized as compared with the conventional one, and this reduces the fiber strength and improves the post-processability of the polybenzazole fiber. In addition, the selective orientation of crystals is moderately disturbed, stress concentration in a specific direction is relaxed, and latent strain inside the fiber is reduced, so that fibrillation can be suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In addition, the following method was employ | adopted for various measurements.

·Measuring method:
(Intrinsic viscosity)
Using methanesulfonic acid as a solvent, the viscosity of the polymer solution prepared to a concentration of 0.5 g / l was measured in an oven at 30 ° C. using an Ostwald viscometer.

(Measurement method of fiber strength and elastic modulus)
It measured with the tensile tester according to JISL1013.

(Measurement method of heat resistance of fiber)
Using a thermogravimetric analyzer (TA Instrument's TGA Q50), when the temperature was increased from room temperature at a temperature increase rate of 20 ° C./min in the air, the weight retention rate [(at a certain temperature The sample weight / original sample weight) × 100] was evaluated at a temperature of 90%.

(Measurement method of flame retardancy of fiber)
According to JIS K7201, it evaluated by the limiting oxygen index (Limiting Oxygen Index: LOI).
(Fiber cross-section observation method)
A fiber for measurement was embedded in an epoxy resin (G-2 manufactured by Gatan) and subjected to argon ion etching with a cross section polisher (SM-09010 manufactured by JEOL Ltd.) to obtain a cross section for observation. It was. Next, the boundary line between the core layer and the sheath layer is observed with an optical microscope, the average diameter (r ₂ ) of the core layer and the fiber cross-sectional diameter (r ₁ ) are measured, and the average diameter (r ₂ ) of the core layer is measured. The ratio R (%) to the fiber cross-sectional diameter (r ₁ ) was determined.
R (%) = (r ₂ / r ₁ ) × 100

(Measurement of electron diffraction)
The sample for electron diffraction measurement is an ultrathin slice having a thickness of about 70 nm so that the measurement fiber is in the fiber axis (length) direction and includes the surface layer portion and the center portion of the fiber by the method described below. What was used was used.
That is, single fibers are embedded in an epoxy resin prepared according to the Luft method (J. Biophys. Biochem. Cytol., 9, 409 (1961)), and left in a 60 ° C. oven overnight to solidify and fix to embed the fibers. A resin block was obtained. Next, the resin block is attached to an ultra microtome manufactured by Reichert, and is polished using a glass knife until the embedded fibers appear in the vicinity of the block surface, and then a single fiber using a diamond knife manufactured by Diatom Cutting was performed in a direction parallel to the axial direction, and an ultrathin section having a thickness of about 70 nm and including both the surface portion (surface) and the center portion of the fiber was prepared. The obtained ultrathin slices were collected on a 300 mesh copper grid, thinly deposited with carbon, and then introduced into an electron microscope, and limited-field electron diffraction was performed on both the surface layer and the center of the fiber. An image is taken (in this case, the diameter of the limited field of view (aperture) is 1 μm or less, and an ultrathin section of the fiber is free from artifacts (for example, wrinkles and blurring of the section) that occur during cutting. A selected electron diffraction pattern was obtained.
The profile in the equator direction of the obtained electron diffraction pattern is approximated using a Lorentz function, and the integrated intensity (area) and half-value width of diffraction peaks derived from (200), (010) and (-210) are approximated. Was calculated. The area derived from (200) was S1, and the sum of the areas derived from (010) and (-210) was S2, and S2 / S1 was determined.
The apparent crystal size (ACS) was calculated using the following formula.
ACS = 0.9λ / βcosθ
Here, λ is the wavelength of the electron beam, β is the full width at half maximum (in radians), and θ is the half value of the diffraction angle 2θ.
Further, for (200) diffraction, the FWHM was calculated by approximating the diffraction profile in the azimuth direction with a Lorentz function.

(Post-processability evaluation method)
The evaluation fiber which gave buckling crimp by the indentation crimping method was cut into a cut length of 44 mm to obtain a staple. The obtained staple was opened with an opener, and then a web having a basis weight of 450 g / m ² was produced with a roller card. Nine sheets of the obtained webs were laminated in sequence, using a Foster needle (product number: 15 × 18 × 40 × 3.5 PB-A F20 2-18-3B / LI / CC / CONICAL) at a needle depth of 7 mm. A felt was obtained by needle punching only from one side of the felt until the needle punching number reached 2000 / cm ² . The number of needles (converted to the number per 1 m ^{2 of} finished felt) was examined until the felt was obtained by sequentially laminating the webs. The smaller the number of broken wires, the better the post-processability.
(Process passability)
Process passability was judged based on the occurrence of production troubles in the process from spinning to fiber web production.

(Comparative Example 1)
Using a spinning dope (PBO concentration of 14% by mass) in which poly (p-phenylenebenzobisoxazole) (hereinafter abbreviated as PBO) having an intrinsic viscosity [η] of 29 dl / g was dissolved in polyphosphoric acid, a single filament diameter Was spun under the conditions of 11.5 μm and 1.65 dtex.
That is, the spinning dope was spun from a nozzle with a spinning temperature of 175 ° C. and a pore diameter of 0.20 mm and a number of holes of 166, and the spun dope filament was cooled by passing through a quench chamber having a quench temperature of 60 ° C. and passed through the quench chamber. Then, it was immersed in the 1st coagulation | cleaning bath, making it converge on a multifilament, and the filament was coagulated. Thereafter, the filament was washed with water until the residual phosphorus concentration in the filament became 5000 ppm or less, neutralized with a 1% NaOH aqueous solution for 5 seconds, and further washed with water for 10 seconds. Then, it was dried until the moisture content became 2% and wound up to obtain a fiber for evaluation. In addition, for the evaluation of the post-processability, the above-described staple having buckling crimp was used.

Example 1
In the manufacturing apparatus of Comparative Example 1, a cylinder having an inner diameter of 5 mm and a length of 1 m was installed at the exit of the quench chamber, water vapor was introduced into the cylinder to fill the cylinder with a steam atmosphere, and the multifilament was allowed to pass through the cylinder. Except for this difference, evaluation fibers and staples were obtained in the same manner as in Comparative Example 1. In addition, the circumference | surroundings of the pipe | tube were heated with the heater and the water vapor | steam temperature was controlled. The temperature of the filled water vapor was saturated water vapor at 120 ° C., and the time for the multifilament to pass through the portion of the water vapor atmosphere was 0.6 seconds.

(Example 2)
In Example 1, fibers and staples for evaluation were obtained in the same manner as in Example 1 except that the temperature of the water vapor filled in the cylinder was changed to 75 ° C. saturated water vapor.

(Example 3)
In Example 1, the size of the cylinder installed at the exit of the quench chamber was changed to a cylinder with an inner diameter of 5 mm and a length of 50 cm, and the temperature of the water vapor filled in the cylinder was saturated water vapor at 75 ° C., and the multifilament was Evaluation fibers and staples were obtained in the same manner as in Example 1 except that the time for passing through the portion of the water vapor atmosphere was 0.3 seconds.

Example 4
Following the same steam treatment as in Example 3, a goded roller and a cabinet surrounding the goded roller are installed at the outlet of the cylinder, and the steam treatment time is extended in the cabinet to obtain fibers and staples for evaluation. It was. That is, the interior of the cabinet that can be heated and controlled with a heater was filled with water vapor, and the temperature of the water vapor was 75 ° C. saturated water vapor. The total of the passage time in the cylinder installed at the exit of the quench chamber and the passage time in the cabinet was 10 seconds.

(Example 5)
Fibers and staples for evaluation were obtained in the same manner as in Example 1 except that the cylinder installed at the exit of the quench chamber had an inner diameter of 5 mm and a length of 5 cm, and the passage time in the cylinder was 0.03 seconds. .

(Example 6)
The cylinder installed at the exit of the quench chamber has a diameter of 10 cm and a length of 1 m. Further, two slit nozzles (slit width of 1 mm) are installed at the exit of the quench chamber in the facing direction, and saturated steam at a temperature of 120 ° C. is supplied to the slit nozzle. The fibers and staples for evaluation were obtained in the same manner as in Example 1 except that the multifilament was passed between the slit nozzles. The slit nozzle was installed so that saturated water vapor was sprayed from a direction of 90 ° with respect to the multifilament.

(Comparative Example 2)
Fibers and staples for evaluation were obtained in the same manner as in Example 1 except that the temperature of the water vapor filled in the cylinder was changed to 40 ° C. saturated water vapor.

(Comparative Example 3)
Fibers and staples for evaluation were obtained in the same manner as in Example 1 except that the temperature of the water vapor filled in the cylinder was changed to 200 ° C. saturated water vapor.

  Tables 1 and 2 show the evaluation results of the obtained fibers and staples for evaluation.

  The polybenzazole fiber obtained by the production method of the present invention maintains excellent heat resistance and flame retardancy, although the fiber strength decreases, and has better post-processability than conventional polybenzazole fibers. I understand that there is.

The polybenzazole fiber obtained in the present invention has improved post-processability compared to conventional fibers, and can be easily deployed in various applications that require heat resistance and flame retardancy as important characteristics. The above contribution is significant.

It is typical explanatory drawing which shows an example of the sheath core of the cross section of the polybenzazole fiber obtained by this invention. It is an example of the equatorial direction profile of the limited visual field electron diffraction pattern of the surface layer part (surface-1 micrometer) of the polybenzazole fiber obtained by this invention. It is an example of the equatorial direction profile of the limited visual field electron diffraction pattern of the surface layer part (surface-1 micrometer) of the polybenzazole fiber obtained by the comparative example.

Explanation of symbols

r ₁ : Fiber cross-sectional diameter r ₂ : Diameter of the core layer

Claims (3)

  A polybenzazole dope in which polybenzazole is dissolved in a solvent is spun from a spinneret, and the spun dope filament is immersed in a liquid containing a polybenzazole coagulant (coagulation bath) and coagulated. A method for producing a benzazole fiber, wherein the spun dope filament is brought into contact with the vapor of a polybenzazole coagulant and then immersed in a coagulation bath.   The method for producing a polybenzazole fiber according to claim 1, wherein the polybenzazole coagulant is water.   The method for producing polybenzazole fiber according to claim 1 or 2, wherein the solvent of polybenzazole is polyphosphoric acid or methanesulfonic acid.

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