JP2006169686A - Method for producing polybenzazole fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial method for producing a polybenzazole fiber with a compact drying apparatus by developing a technique to quickly drying a polybenzazole fiber. <P>SOLUTION: A polybenzazole fiber is produced by using a spinning dope obtained by dissolving a polybenzazole polymer in an acid solvent. The spinning dope contains 2-15 mass% substance left in the form of solid at normal temperature in the spun polybenzazole fiber. The substance is preferably a pigment soluble in the solvent of polybenzazole and having a thermal decomposition temperature of ≥300°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing polybenzazole fibers. More particularly, the present invention relates to a production method capable of efficiently drying polybenzoxazole fibers in a short time.

  Polybenzazole fiber is solidified by extruding a dope containing polybenzoxazole or polybenzothiazole polymer and an acid solvent from a spinneret, and then dipping in a coagulating fluid (water or a mixture of water and inorganic acid). Then, in order to 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).

However, in order to reduce the residual inorganic acid solvent in the yarn, it is necessary to wash at a high temperature for a long time (for example, Patent Document 2), and the washed fiber is continuously dried as efficiently as possible. For example, a method in which drying is performed stepwise at two or more temperatures is employed (Patent Document 3).
JP-A-8-170222 JP-A-8-60437 JP-A-7-197307

  Polybenzazole fibers can be produced by the above-described method, but since the residence time in the drying process is required for a long time, there is a problem that the equipment becomes very large in high-speed spinning. An object of the present invention is to solve such technical and industrial problems, so that polybenzazole fibers can be dried at a high speed, and the polybenzazole fibers are industrially produced in a compact drying facility. It is to provide a method of manufacturing.

That is, the present invention employs the following configuration.
1. In the method for producing a polybenzazole fiber using a spinning dope in which a polybenzazole polymer is dissolved in an acid solvent, 2 to 15% by mass of a substance remaining as a solid at room temperature in the spun polybenzazole fiber in the spinning dope A method for producing a polybenzazole fiber, characterized in that the polybenzazole fiber is contained.
2. 2. The method for producing a polybenzazole fiber according to 1 above, wherein a content of a substance remaining as a solid at room temperature in the spun polybenzazole fiber is 2 to 8% by mass.
3. 3. The poly (1) or (2) above, wherein the substance remaining as a solid at room temperature in the polybenzazole fiber after spinning is a pigment that is soluble in a polybenzazole solvent and has a thermal decomposition temperature of 300 ° C. or higher. A method for producing benzazole fiber.
That is, the present inventors include a substance that remains as a solid at room temperature in the spinning dope in the polybenzazole fiber after spinning, and the content of this substance is 2 mass in the polybenzazole fiber after spinning. In addition, the substance remaining as a solid in the polybenzazole fiber after spinning is soluble in a polybenzazole solvent such as polyphosphoric acid and has a thermal decomposition temperature of 300 ° C. or higher. In the process of producing polybenzazole fibers, the drying rate when the polybenzazole coagulating liquid is removed by drying from the polybenzazole fibers is improved, and as a result, it is found that the pigment can be dried in a short time. The present invention has been completed.

  According to the production method of the present invention, a substance remaining as a solid at room temperature in the polybenzazole fiber after spinning is present in the specific amount of polybenzazole fiber, so that the coagulating liquid comes out of the fiber. Since the route is secured, the drying speed can be improved as compared with the conventional method. For this reason, it is possible to produce polybenzazole fibers with a drying equipment that is compact compared to conventional drying equipment.

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. Furthermore, PBO widely includes polymers composed of units of a plurality of oxazole rings bonded to poly (p-phenylenebenzobisoxazole) and aromatic groups. Similar considerations apply to PBT and PBI. Also included are mixtures, copolymers, block polymers of two or more polybenzazole polymers such as PBO, PBT and / or mixtures of PBI, block or random copolymers of PBO, PBT and PBI, and the like.

  The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers that form liquid crystals at a specific concentration in polyphosphoric acid. The polymer consists of monomer units described in structural formulas (a) to (f).

  The polybenzazole fiber is manufactured from a dope containing polybenzazole, and a suitable solvent for preparing the dope includes cresol and a non-oxidizing acid capable of dissolving the polymer. Examples of suitable non-oxidizing acids include inorganic acids such as polyphosphoric acid, methanesulfonic acid and high concentrations of sulfuric acid or mixtures thereof. Of these, polyphosphoric acid and methanesulfonic acid are particularly preferred. Further, after completion of the polymerization, the benzazole copolymer can be used as it is as a dope for spinning without isolation.

  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 thus obtained is extruded from a spinneret and stretched in a space to be formed into a filament. Suitable manufacturing methods are described in the aforementioned references and US Pat. No. 5,034,250. The dope filament exiting the spinneret enters the space between the spinneret and the washing bath. This space is commonly referred to as an air gap, but need not be air. This space needs to be filled with a solvent that does not react with the dope without removing the solvent, and examples thereof include air, nitrogen, argon, helium, and carbon dioxide.

The spun dope filament is introduced into a polybenzazole polymer coagulating liquid, washed, neutralized with an inorganic base such as sodium hydroxide, calcium hydroxide, potassium hydroxide, etc., and most of the solvent is removed. Is done.
The solidifying liquid here is a liquid that is compatible with an inorganic acid such as polyphosphoric acid in which a polybenzazole polymer is dissolved, and does not serve as a solvent for the polybenzazole polymer. It is a mixed solution of water and inorganic acid.
Washing is compatible with an inorganic acid such as polyphosphoric acid in which a polybenzazole polymer is dissolved, and the fiber or filament is brought into contact with a liquid that does not serve as a solvent for the polybenzazole polymer. Or to remove the solvent from the filament. The cleaning liquid is not particularly limited as long as it is a liquid capable of removing the solvent of polybenzazole, and suitable cleaning liquid includes water and a mixture of water and an acid solvent. When the acid is polyphosphoric acid, the residual phosphorus concentration in the filament is preferably washed to 8000 ppm or less, more preferably 5000 ppm or less. Thereafter, the filament is subjected to drying, heat treatment, winding and the like as necessary.

  The substance that remains as a solid at room temperature in the polybenzazole fiber after spinning in the present invention is not particularly limited, but is resistant to an acid solvent in which the polybenzazole polymer is dissolved, and the thermal decomposition temperature is 300 ° C. The above substances are preferred. Examples include carbon blacks such as pigments, thermal black, acetylene black, channel black, furnace black and lamp black, carbons such as fullerene and carbon nanotubes, and inorganic fine particles atomized to the nano level. A pigment that is soluble in an acid solvent is preferable because it is more difficult to reduce spinnability and yarn strength if it is soluble.

  Examples of the pigment that is soluble in the polybenzazole solvent (preferably polyphosphoric acid) and has a thermal decomposition temperature of 300 ° C. or higher in the present invention include insoluble azo pigments, condensed azo pigments, dye lakes, isoindolinones, and isoindolines. , Dioxazines, perinones and / or perylenes, phthalocyanines, quinacridones, etc. Of course, the technical content of the present invention is not limited to these. One or more of these pigments can be used in combination.

  In the present invention, the spinning dope contains a substance remaining as a solid at room temperature in the spun polybenzazole fiber as long as the substance can be uniformly dispersed or dissolved in the dope. However, it can be mixed at any stage during the polymerization of polybenzazole or at the stage of polymer dope at the end of the polymerization. For example, a method of charging polybenzazole at the same time when charging a raw material, a method of adding at a stage where the reaction is carried out by raising the temperature stepwise or at an arbitrary heating rate, and adding to the reaction system at the end of the polymerization reaction A method of stirring and mixing can be recommended.

The greatest feature of the method for producing a polybenzazole fiber according to the present invention is that a substance that can remain as a solid at room temperature in the polybenzazole fiber after spinning is contained in the spinning dope, and the content of this substance is By mass%, the amount becomes 2% or more in the polybenzazole fiber after spinning, whereby the drying rate can be improved.
The reason for this is that when the solidifying liquid is removed from the spun polybenzazole fiber by drying, the solidifying liquid passes through the voids between the microfibrils of the polybenzazole fiber and out of the fiber. A path that passes out of the fiber is temporarily formed, but this path (path) is easily clogged by drying, but there is a substance that can remain as a solid at room temperature in the fiber of the present invention. This is because the presence of the solidifying liquid ensures a path through which the solidifying liquid exits the fiber. If the substance remaining as a solid at room temperature in the polybenzazole fiber after spinning is present in an amount of 2% by mass or more, it becomes easy to secure a path by the substance, and as a result, the drying speed is increased. It is considered that the drying time can be shortened. When the polybenzazole fiber after spinning contains less than 2% of a solid substance at room temperature, the drying rate is not improved so much. On the other hand, if the polybenzazole fiber after spinning contains too much material remaining as a solid at room temperature, it is not preferable because the yarn properties are deteriorated. Preferably it is 8% or less, More preferably, it is 6% or less.

  The higher the drying temperature, the shorter the drying time of the polybenzazole fiber can be shortened. The drying temperature is preferably 290 ° C. or lower, more preferably 280 ° C. or lower, from the viewpoint of the decrease in yarn physical properties. As the heating zone in the drying step, radiation such as an electric furnace or flame, a heating roller or heating air, a heating inert gas, heating steam, or oil can be used.

  In the present invention, the substance remaining as a solid at room temperature in the spun polybenzazole fiber is preferably a pigment that is soluble in a polybenzazole solvent and has a thermal decomposition temperature of 300 ° C. or higher. As described above, if the substance remaining as a solid in the polybenzazole fiber after spinning is 2% or more, the drying rate is improved, but the substance is soluble in a polybenzazole solvent (preferably polyphosphoric acid). Otherwise, the yarn breakage immediately after the spinning dope is pushed out from the spinneret frequently occurs, the spinnability is lowered, and the yarn strength may be lowered. Further, as described above, since the temperature of the heating zone in the drying step may be close to 300 ° C., the thermal decomposition temperature is preferably 300 ° C. or higher. This is because if the thermal decomposition temperature is less than 300 ° C., it will be decomposed during drying and will not remain as a solid in the polybenzazole fiber, and it will be difficult to secure a path (path) that goes out of the fiber. The thermal decomposition temperature of the substance remaining as a solid at normal temperature is preferably 350 ° C. or higher, more preferably 400 ° C. or higher.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. Of course, it is also possible, and they are all included in the technical scope of the present invention.

(Residual acid concentration in the fiber)
The concentration of residual phosphorus atoms was measured using a scanning X-ray fluorescence analyzer (Rigaku ZSX 100e) after solidifying the sample into a pellet.
(Fiber diameter)
The single yarn diameter was measured at a magnification of 5000 using a scanning electron microscope (SEM).

(Drying speed evaluation method)
Using a sample that has never given a history of moisture content of 40% or less (yarn in the middle of drying), the moisture content is 40% to 1% at a drying temperature of 250 ° C. under a tension of 0.3 g / dtex. The time required to reach was measured. The moisture content was calculated from the weight before drying: W0 (g) and the weight after drying: W1 (g) according to the following formula. In addition, drying at the time of measuring weight after drying: W1 (g) was implemented on 250 degreeC and the conditions for 30 minutes.
(Formula) Moisture content (%) = (W0−W1) / W1 × 100

Example 1
In a nitrogen stream, 2,509 g of 4,6-diaminoresorcinol dihydrochloride and 1895 g of terephthalic acid were added to 16241 g of 122% polyphosphoric acid and stirred for 30 minutes at 60 ° C., then slowly heated to 120 ° C. for 5 hours. The reaction was carried out at 135 ° C. for 20 hours and at 150 ° C. for 5 hours. Further, after adding a dispersion obtained by adding 42 g of terephthalic acid and 146.3 g of copper phthalocyanine (thermal decomposition temperature 550 ° C.) to 558 g of 116% polyphosphoric acid, this oligomer dope was reacted at 170 ° C. for 4 hours and at 200 ° C. for 12 hours. A poly (p-phenylenebenzobisoxazole) dope having an intrinsic viscosity of 29 dL / g measured with a methanesulfonic acid solution at 30 ° C. was obtained.
Thereafter, spinning was carried out under conditions such that the single yarn filament diameter was 11.5 μm and 1.5 denier. A spinning dope is extruded from a nozzle having a hole diameter of 0.20 mm and a hole number of 166 at a spinning temperature of 175 ° C. to form a filament, and then immersed in a first washing bath arranged to converge at an appropriate position to form a multifilament. And solidified. A quench chamber having a quench temperature of 60 ° C. was installed in the air gap between the spinning nozzle and the first cleaning bath so that the filaments were stretched at a more uniform temperature.
Then, it washed with water until the residual phosphorus density | concentration in a polybenzazole fiber became 5000 ppm or less, neutralized with 1% NaOH aqueous solution for 5 seconds, and then washed with water for 10 seconds. Then, it was dried until the moisture content reached 40%, and was wound at a winding speed of 200 m / min in the middle of drying.
The result of measuring the time required for the moisture content to reach from 1% to 40% by the above-described drying rate evaluation method using the wound intermediate yarn having a moisture content of 40% was 39 seconds. . The amount of copper in the obtained yarn was measured by chemical analysis, and the result of calculating the amount of copper phthalocyanine in the yarn from the ratio between the molecular weight of copper phthalocyanine and the atomic weight of copper as the central metal was 5% by mass.

(Example 2)
Under a nitrogen stream, 2,509 g of 4,6-diaminoresorcinol dihydrochloride, 1956 g of terephthalic acid, and 15587 g of 122% polyphosphoric acid were stirred at 60 ° C. for 30 minutes, and then slowly heated to 135 ° C. for 20 hours and at 150 ° C. for 5 hours. The reaction was allowed to proceed at 170 ° C. for 15 hours. 100.6 g of carbon black was added to 17 kg of the poly (p-phenylenebenzobisoxazole) dope having an intrinsic viscosity of 29 dL / g measured with the obtained methanesulfonic acid solution at 30 ° C., and mixed with stirring.
Thereafter, spinning was carried out under conditions such that the single yarn filament diameter was 11.5 μm and 1.5 denier. A spinning dope is extruded from a nozzle having a hole diameter of 0.20 mm and a hole number of 166 at a spinning temperature of 175 ° C. to form a filament, and then immersed in a first washing bath arranged to converge at an appropriate position to form a multifilament. And solidified. A quench chamber having a quench temperature of 60 ° C. was installed in the air gap between the spinning nozzle and the first cleaning bath so that the filaments were stretched at a more uniform temperature.
Then, it washed with water until the residual phosphorus density | concentration in a polybenzazole fiber became 5000 ppm or less, neutralized with 1% NaOH aqueous solution for 5 seconds, and then washed with water for 10 seconds. Thereafter, the film was dried until the moisture content reached 40%, and was wound at a winding speed of 200 m / min in the middle of drying.
The result of measuring the time required for the moisture content to reach 1% from 40% by the above-described drying speed evaluation method using the wound intermediate yarn having a moisture content of 40% was 44 seconds. The amount of carbon black in the obtained yarn was 4% by mass.

(Comparative Example 1)
Under a nitrogen stream, 2,509 g of 4,6-diaminoresorcinol dihydrochloride, 1956 g of terephthalic acid, and 15587 g of 122% polyphosphoric acid were stirred at 60 ° C. for 30 minutes, and then slowly heated to 135 ° C. for 20 hours and at 150 ° C. for 5 hours. The mixture was reacted for 15 hours at 170 ° C. to obtain a poly (p-phenylenebenzobisoxazole) dope having an intrinsic viscosity of 31 dL / g measured with a methanesulfonic acid solution at 30 ° C.
Thereafter, spinning was carried out under conditions such that the single yarn filament diameter was 11.5 μm and 1.5 denier. A spinning dope is extruded from a nozzle having a hole diameter of 0.20 mm and a hole number of 166 at a spinning temperature of 175 ° C. to form a filament, and then immersed in a first washing bath arranged to converge at an appropriate position to form a multifilament. And solidified. A quench chamber having a quench temperature of 60 ° C. was installed in the air gap between the spinning nozzle and the first cleaning bath so that the filaments were stretched at a more uniform temperature.
Then, it washed with water until the residual phosphorus density | concentration in a polybenzazole fiber became 5000 ppm or less, neutralized with 1% NaOH aqueous solution for 5 seconds, and then washed with water for 10 seconds. Thereafter, the film was dried until the moisture content reached 40%, and was wound at a winding speed of 200 m / min in the middle of drying.
The result of measuring the time required for the moisture content to reach 1% from 40% by the above-described drying rate evaluation method using a wound intermediate yarn having a moisture content of 40% was 64 seconds.

(Comparative Example 2)
Under a nitrogen stream, 2,509 g of 4,6-diaminoresorcinol dihydrochloride, 1956 g of terephthalic acid, and 15587 g of 122% polyphosphoric acid were stirred at 60 ° C. for 30 minutes, and then slowly heated to 135 ° C. for 20 hours and at 150 ° C. for 5 hours. The reaction was allowed to proceed at 170 ° C. for 15 hours. 25.2 g of copper phthalocyanine (thermal decomposition temperature 550 ° C.) was added to 17 kg of poly (p-phenylenebenzobisoxazole) dope having an intrinsic viscosity of 30 dL / g measured with the obtained methanesulfonic acid solution at 30 ° C., and mixed by stirring. did.
Thereafter, spinning was carried out under conditions such that the single yarn filament diameter was 11.5 μm and 1.5 denier. A spinning dope is extruded from a nozzle having a hole diameter of 0.20 mm and a hole number of 166 at a spinning temperature of 175 ° C. to form a filament, and then immersed in a first washing bath arranged to converge at an appropriate position to form a multifilament. And solidified. A quench chamber having a quench temperature of 60 ° C. was installed in the air gap between the spinning nozzle and the first cleaning bath so that the filaments were stretched at a more uniform temperature.
Then, it washed with water until the residual phosphorus density | concentration in a polybenzazole fiber became 5000 ppm or less, neutralized with 1% NaOH aqueous solution for 5 seconds, and then washed with water for 10 seconds. Thereafter, the film was dried until the moisture content reached 40%, and was wound at a winding speed of 200 m / min in the middle of drying.
The result of measuring the time required for the moisture content to reach 1% from 40% using the drying rate evaluation method described above using a wound intermediate yarn having a moisture content of 40% was 59 seconds. It was. The amount of copper in the obtained yarn was measured by chemical analysis, and the result of calculating the amount of copper phthalocyanine in the yarn from the ratio of the molecular weight of copper phthalocyanine to the atomic weight of copper as the central metal was 1% by mass.

以上の結果から、本発明の製造方法により、従来に比べて大幅に乾燥速度が向上し、短時間で乾燥させることができることがわかる。

From the above results, it can be seen that the production method of the present invention significantly improves the drying rate compared to the conventional method and can be dried in a short time.

  According to the method for producing polybenzazole fiber of the present invention, since the drying rate can be greatly improved as compared with the conventional method, it becomes possible to produce polybenzazole fiber with a compact facility compared to the conventional facility, Industrial applicability is great.

Claims (3)

  In the method for producing a polybenzazole fiber using a spinning dope in which a polybenzazole polymer is dissolved in an acid solvent, 2 to 15% by mass of a substance remaining as a solid at room temperature in the spun polybenzazole fiber in the spinning dope A method for producing a polybenzazole fiber, characterized in that the polybenzazole fiber is contained.   The method for producing a polybenzazole fiber, wherein a content of a substance remaining as a solid at room temperature in the spun polybenzazole fiber is 2 to 8% by mass.   The substance remaining as a solid at room temperature in the polybenzazole fiber after spinning is a pigment that is soluble in a polybenzazole solvent and has a thermal decomposition temperature of 300 ° C or higher. Production method of polybenzazole fiber.