JP2010116663A - Method for producing molded body from polyphosphoric acid solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve maintenance cycle of an apparatus in industrial production of a high performance polybenzazole molded product and suppress metal ion contamination of a polyphosphoric acid solvent. <P>SOLUTION: The method for producing the molded product from the phosphate solution, uses a production apparatus which is made of a highly corrosive resistant material in at least a dope-contacted part of a device for agitating the dope to be uniformly dispersed and/or a pump device for transferring the uniformly dispersed dope, and in addition, a filter material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing a molded body comprising a high-performance polymer, particularly a polymer excellent in mechanical strength and heat resistance.

  A polymer having a rigid unit such as a para bond of an aromatic ring in the main chain has high heat resistance and excellent mechanical properties. Among these polymers, polybenzazoles are high-performance polymers with extremely high heat resistance. The polymerization and molding processes for these polymers are known to use polyphosphoric acid as a solvent (Wolfe et al. Macromolecules, 1981, pages 909 and 915). Although the performance evaluation of the polymer using these polyphosphoric acid solvents has been made on a laboratory scale, it has not been industrially produced until recently, and problems associated with industrial implementation have not been discussed.

  When these high-performance polymers are polymerized or processed into fibers, films, etc., with a reactor that applies shear, a pump that transports the polymer solution, and a pump that dispenses a fixed amount from the base, the viscosity that makes it easy to process the polymer solution In order to lower the coefficient, the process temperature often exceeds 160 ° C. In addition, the temperature may be higher due to shear heat generation in the apparatus. At this time, with conventional corrosion resistant materials such as SUS316L and stellite steel (Mitsubishi Materials), polyphosphoric acid corrodes the metal, so part of the equipment melts, making it difficult to recycle the solvent, The problem of shortening occurred.

  In the present invention, when polymerizing and molding a high-performance polymer using a polyphosphoric acid solvent, it is intended to improve the material of a conventional apparatus, improve the life of a reactor and a pump, and reduce the concentration of metal ions in a recycling solvent. .

That is, the first invention according to the present invention is a device for stirring and uniformly dispersing a dope and / or a uniformly dispersed dope when a molded body is produced from a polyphosphoric acid solvent and a dope comprising a polymer soluble in polyphosphoric acid. At least a portion of the wetted portion of the pump device that transports the material is a corrosion-resistant material having a material elution rate of 0.1 (mm / year) or less at 116% polyphosphoric acid 175 ° C. immersion evaluation , and the corrosion-resistant material is a nickel-based alloy The second invention is a method for producing a molded body from a polyphosphoric acid solution , characterized in that the filter medium according to the first invention is used. The present invention relates to a method for manufacturing a body .

  When processing high-performance polymers using a highly corrosive solvent such as polyphosphoric acid, materials with a high degree of corrosion resistance must be used, resulting in problems of equipment corrosion and metal elution into the recovery solvent. . According to the present invention, the maintenance frequency due to corrosion of production facilities and the elution of metal into the recovered solvent are reduced, and the product manufacturing cost can be reduced.

The present invention is described in detail below.
The present invention is disclosed in Wolf et al., “Liquid Crystalline Polymer Compositions, Process and Products” U.S. Pat. S. Patent 4,703,103 (October 27, 1987); Wolfe et al., “Liquid Crystalline Polymer Compositions, Process and Products” U.S. Pat. S. Patent 4,533,692 (August 6, 1985); Wolfe et al., “Liquid Crystalline Poly (2,6-Benzothiazole) Compositions, Process and Products” U.S. Pat. S. Patent 4,533,724 (August 6, 1985); Wolfe et al., “Liquid Crystalline Polymer Compositions, Process and Products”, U.S. Pat. S. Patent 4,533,693 (August 6, 1985); Evers, “Thermoxatively Stable Articulated p-Benzobisazole p-Benzobisimidazole Polymers”, U.S. Pat. S. Patent 4,359,567 (November 16, 1982); Tsai et al., “Method for Making Heterocyclic Block Polymer Compositions, Process and Products” U.S. Pat. S. Patent 4,578,432 (March 25, 1986); 11 Ency. Poly. Sci. & Eng. , “Polybenzothazoles and Polybenzoxazoles”, 601 (J. Wiley & Sons 1988) and W. W. PAM, PBT, and homopolymers of these polymers, as described in Adams et al., “The Materials Science and Engineering of Rigid-Rod Polymers” (Materials Research Society 1989); The present invention relates to a production method of processing a polymer containing a part of the polymer in a main chain through a polyphosphoric acid solvent.

  The polymer can be AB type as represented by chemical structural formulas (c) and (d) and / or AA / BB type units as represented by chemical structural formulas (a) and (b).

In the formula, each Ar represents various aromatic groups. The aromatic group may be a heterocycle such as a pyridinylene group, provided that a ring is formed of carbon. The aromatic group may be a condensed polycyclic group ring or a non-condensed polycyclic group, with one 6-membered ring being preferred. Without limitation on the size, aromatic Shokumoto preferably be containing up to 18 carbon atoms, more preferably preferably contains up to 12 carbon atoms, more preferably containing up to 6 carbon atoms Things are preferable. Ar1 in the AA / BB type unit preferably has a 1,2,4,5-phenylene structure or an analogue thereof. AB in the AB type unit is preferably a 1,3,4-phenylene structure or an analog thereof. Each Z is independently an oxygen atom, a sulfur atom, or a nitrogen and hydrogen atom. Each DM is a direct bond or a divalent organic structure independently of each other. As the divalent structural unit, the aforementioned aromatic group (Ar) is preferable. In particular, a 1,4-phenylene structure or an analog thereof is preferable. The nitrogen atom and the Z structure of each azole ring are bonded to the carbon atom of the adjacent aromatic group, and the 5-membered azole ring and the aromatic group are condensed. The azole ring of AA / BB type unit is described in 11 Ency. Poly. Sci. & Eng. , “Polybenzothazoles and Polybenzoxazoles”, 601 (J. Wiley & Sons 1988).

  The polymer is preferably composed of AB-PBZ repeating units or AA / BB-PBZ repeating units, more preferably essentially consisting of AA / BB-PBZ repeating units. In the azole ring in the polymer, Z is preferably an oxygen atom, a sulfur atom, or nitrogen and hydrogen.

  The repeating units used in the present invention are preferably those represented by structural formulas (a) to (h). More preferred are those represented by structural formulas (a)-(f), and even more preferred are those represented by structural formulas (a)-(d).

  The PBZ polymer preferably has an average of at least about 25 or more repeating units, more preferably at least about 50 or more repeating units, and more preferably at least about 100 or more repeating units. The intrinsic viscosity of the AA / BB-PBZ rigid straight chain is preferably at least about 10 dl / g or more, more preferably at least about 15 dl / g or more as measured by 25 ° C. methanesulfonic acid, Preferably it is at least about 20 dl / g or more. For some applications, the intrinsic viscosity is optimally at least approximately 25 or 30 dl / g. The intrinsic viscosity number may be 60 dl / g, but is preferably 40 dl / g. The intrinsic viscosity of the semi-rigid AB-PBZ polymer is preferably at least about 5 dl / g or more, more preferably at least about 10 dl / g or more, and even more preferably at least about 15 dl / g or more. Something is preferable.

  This polymer or copolymer can be polymerized to a preferred repeating unit by reacting a monomer or oligomer in a polyphosphoric acid solvent.

  Eliminating unevenness in the concentration of the polymer polyphosphate solvent and micro-dispersion are extremely important in reducing defects of the molded article and stabilizing the quality. As the reactor that can be used in the present invention, a twin screw kneader, a single screw reactor, a single screw extruder using a dispersion element, and a twin screw extruder can be used. It is particularly preferable to select a model that can handle high viscosity.

  As a pump that can be used in the present invention, a gear pump, a Mono pump (Hyojin equipment), a screw feeder, and the like are possible. A gear pump that can set the discharge pressure high is particularly useful. In particular, in a large-scale facility, it is necessary to have a pressure increasing capability commensurate with viscous resistance when a long polymer line is transferred.

  In order to reduce the amount of phosphoric acid-dissolved metal generated from the equipment, in addition to making the equipment sliding parts lubricated with polyphosphoric acid solution resistant to phosphoric acid corrosion resistance, select a material with high material hardness and resistance to wear. There is a need. There are cases where parts are processed from a base material and thermal spray materials, but it is important to select a thermal spraying method that has a dense structure as well as a composition.

  Examples of phosphoric acid corrosion resistant materials include nickel alloys such as Hastelloy, tantalum / niobium alloys, cobalt alloys such as stellite, stainless steels such as SUS317, and ceramics such as graphite and alumina. Of these, nickel alloys are particularly excellent. Further, a nickel-based tungsten carbide alloy or nickel-based alloy HIP (hot isostatic pressing) processing base material having excellent wear resistance is preferable. Coatings such as cermet and carbon nitride are also useful, but it is necessary to devise so as not to cause performance degradation due to pinholes by making the base material corrosion resistance and coating thickness appropriate. Needless to say, in order to use a combination of different types of materials, consideration should be given to thermal expansion and residual stress at the joint.

  The solution processed in the present invention is a polyphosphoric acid solution and has a property of dissolving even a corrosion-resistant metal such as stainless steel at a temperature exceeding 160 ° C. Therefore, the clearance of the reactor and the pump is changed, and the dispersion capacity and the liquid feeding capacity are appropriately reduced over time. In addition, since metal ions are eluted in the phosphoric acid solvent, a change in solvent quality is unavoidable when the solvent is recycled. It is extremely difficult to adsorb metal ions once dissolved in a solvent and purify the solvent, and it is important to minimize metal elution in the polymer molding process.

  Although it is effective to reduce the temperature of the process to reduce corrosion of equipment and piping due to polyphosphoric acid, the higher the degree of polymerization of the polymer used, the higher the viscosity coefficient of the solution, so there is a limit to lowering the temperature. There is. In addition, it is desired that the temperature in the reactor can be used even at a high temperature because the apparatus size can be reduced by increasing the temperature to shorten the reaction time and the equipment cost can be reduced.

  The present invention will be described by taking as an example a high performance polymer material polybenzbisoxazole processed via a polyphosphoric acid solvent. A preferred temperature for producing fibers from a polyphosphoric acid solution having a polymer concentration of about 200 weight percent of a polybenzbisoxazole polymer having a degree of polymerization of about 200 is 165 ° C or higher, more preferably 170 ° C or higher. However, since the viscosity at 170 ° C. of this solution is as high as 1000 Pa · s (shear rate 10 per second), the heat dissipation of the shear energy in the reactor and the pump is large, and the solution temperature increases remarkably. For this reason, corrosion progresses with normal corrosion resistant materials, and wear of the device and elution of undesirable metal ions into the solvent progress. There arises a problem that the replacement period of the device parts is shortened to several months, and the concentration of metal ions in the solution is increased.

  As a material for an apparatus for processing polyphosphoric acid at a high temperature, it is necessary to use a material particularly excellent in phosphoric acid corrosion resistance. The evaluation of phosphoric acid corrosion resistance is easier as it is confirmed at a higher temperature. Therefore, in some cases, the evaluation is performed at a temperature higher than the actual processing temperature, but industrial production can be stably performed by using a material having excellent corrosion resistance. The evaluation of the present invention is carried out by a method of measuring weight loss by immersing the material in a polyphosphoric acid solution at 210 ° C. for 40 hours. When the evaluation temperature is lower than 210 ° C., the elution amount of the material is small and measurement is difficult. Further, when the temperature is 230 ° C. or higher, the glass used as an evaluation container is often eluted and is difficult to implement. Although there is no restriction | limiting in particular in polyphosphoric acid density | concentration, it evaluates by 116% which is easy to acquire commercially. The soaking time is 40 hours as a standard, and the elution amount per 24 hours is calculated. Even if the evaluation time is shortened to about 100 hours for a material having high corrosion resistance and about 4 hours for a material having insufficient corrosion resistance, there is no problem as long as it can be determined whether it exceeds 1 (mm / year).

  The corrosion-resistant material used when processing a 14% solution of polybenzbisoxazole having a polymerization degree of 200 at 180 ° C. is 1 (mm / year) or less, more preferably 0.5 (mm / year) or less, more preferably 0. .1 (mm / year) or less.

  Reactors and pumps that process polyphosphoric acid solutions are lubricated with polyphosphoric acid solutions, but wear due to part rubbing and dissolution by phosphoric acid occur simultaneously. Increasing the hardness of the material is essential to extend the life of twin screw extruders and gear pumps. As a metallurgical material suitable for such applications, stellite has been used, but phosphoric acid corrosion resistance is insufficient and it cannot withstand long-term use. Suitable materials for the present invention include nickel-based alloys such as Plasthard (manufactured by Mitsubishi Materials) and nickel-based tungsten carbide-containing alloys. The hardness of the material having sufficient wear resistance due to sliding is HRC20 or more, more preferably HRC40 or more, and further preferably HRC50 or more. As materials having excellent corrosion resistance and high hardness, there are materials suitable for the above-mentioned WC-containing materials and nickel-based alloys.

When focusing on the metal elution in the manufacturing process, the filtering member has a large effect of changing to a corrosion-resistant material because of its large liquid contact area. Generally, the filter member is composed of fine wires of 100 microns or less. Even if SUS316 is used, the strength of the member is lost in a short period of time and the filtration function cannot be performed. The elution rate of SUS316L is 0.09 (mm / year) at 170 ° C., but doubles to 0.19 (mm / year) at 180 ° C. When the 100 × 800 mesh SUS316L wire mesh with a 100 × 800 mesh was used, what was usable for one month at 170 ° C. became unusable because fragments of the wire mesh flowed out in two weeks at 180 ° C. It is preferable that the elution rate is slow, and if the continuous use period is not long, problems such as an increase in polymer waste due to exchange loss occur. In particular, preferred filtering material, SUS316 and SUS317 and super stainless Les scan steel NAS354N (Nippon Yakin Kogyo), further Hastelloy C-22 are preferred.

  Filtration is performed to prevent foreign matter from entering the molded product. The required filtration accuracy differs depending on the type of molded product, and in film applications, it captures objects that are larger than the size that becomes a foreign matter protrusion. In the fiber, it is necessary to capture solids having a size larger than that affecting the yarn breakage during spinning. It is necessary to replace the filter medium before the filter medium is eluted and the opening becomes large and the desired filtration accuracy cannot be maintained. In addition, when using a thin wire non-woven fabric, elution progresses and the wire itself breaks away and enters the product as a defect. If the exchange period of the filter medium is made very short in order to prevent such a problem, not only will the loss associated with the exchange increase, but the amount of metal ions dissolved in the solvent will increase. As the corrosion resistance of the filter medium, the material elution rate by phosphoric acid at the filtration temperature (175 ° C.) is preferably 0.1 (mm / year) or less, more preferably 0.05 (mm / year) or less, and still more preferably 0.8. 02 (mm / year).

  The following examples are for illustrative purposes only and are not intended to limit either the specification or the claims of the invention. Unless otherwise noted, all quantities and percentages are given by weight.

<Method for Evaluating Material Elution Rate with Phosphoric Acid Solvent> A material having a thickness of 2 mm, a width of 10 mm, and a length of 30 mm was washed with methyl alcohol, air-dried, weighed with an electronic balance, and 150 cc in a Pyrex beaker having a diameter of 50 mm at room temperature. Of 116%. It puts into a 210 degreeC hot-air circulation type dryer (Yamato Scientific Co., Ltd. DS-64), and takes out a beaker 40 hours after including a predetermined temperature (about 10 minutes). After slow cooling at room temperature, the phosphoric acid around the sample is wiped off, washed in running water for 5 minutes, then immersed in purified water for 1 hour and air dried. The weight reduction rate is obtained from the data obtained by weighing the sample with an electronic balance and measuring the weight loss, the surface area of the sample, and the material density data. Corrosion resistance evaluation under flow was not performed due to the nature of the solution to be handled, and the elution rate of the material into phosphoric acid was evaluated by the evaluation in the above-mentioned stationary place (only natural convection).
<Hardness value> Rockwell hardness and C scale value described in JIS Z2245 (1998) were obtained from a material provider.

Reference example 1
A polyphosphoric acid solution in which 14% by weight of a cis-polybenzoxazole polymer having an intrinsic viscosity of 30 dl / g was dissolved was kneaded with a twin screw extruder having a nominal diameter of 90 mm and L / D = 30 at 200 ° C., and placed at the tip. The pressure was increased to 20 MPa with a 150 cc / rev gear pump, and the flow rate was supplied at 400 kg / hour. The polymer dope temperature at the biaxial extruder outlet at this time was 205 ° C., the material of the apparatus was Hastelloy C-276 for the screw and barrel of the biaxial extruder, and the wetted part of the gear pump was M23S manufactured by Sumitomo Electric. Although the device was operated continuously for 5 months, it was possible to continue production with no decrease in the discharge efficiency of the gear pump.

  The elution rates of Hastelloy C-276 and Igetalloy M23S into 116% phosphoric acid at 210 ° C. were 0.07 mm / year and 0.08 mm / year, respectively.

Comparative Example 1
In Reference Example 1 , when the gear pump was manufactured with Stellite # 3, the discharge efficiency of the gear pump decreased from 95% to 76% in 3 months under the condition of the polymer solution temperature of 205 ° C., so it was necessary to replace it with a new gear pump. .

  The dissolution rate of Stellite # 3 into 116% phosphoric acid at 210 ° C. was 4.1 mm / year.

Reference example 2
In Reference Example 1 , the Hastelloy C-276 cylinder in the barrel of the biaxial extruder had many scratches with a depth of 0.12 mm at the contact portion with the screw kneader after operation for 3 months. When all cylinders were made of Mitsubishi Plastics MA Plasthard-S, the cylinder inner wall was not damaged by 0.05 mm or more after 6 months of operation.

  The elution rates of Hastelloy C-276 and MA Plasthard-S into 116% phosphoric acid at 210 ° C. were 0.07 mm / year and 0.16 mm / year, respectively. The measured hardness was less than 20 for HASTELLOY C-276 in HRC (90 for HRB), and 40 for HRC in MA Plasthard-S. Even if the corrosion resistance is sufficient, if the material hardness is insufficient, the wear of the device is significant.

Comparative Example 2
A polyphosphoric acid solution in which 14% by weight of a cis-polybenzoxazole polymer having an intrinsic viscosity of 30 dl / g was dissolved was kneaded with a twin screw extruder having a nominal diameter of 30 mm at 197 ° C. and L / D = 35, and placed at the tip thereof. The pressure was increased to 13 MPa with a 10 cc / rev gear pump, and the flow rate was supplied at 20 kg / hour. At this time, the polymer dope temperature at the exit of the twin screw extruder was 200 ° C., and the material of the apparatus was Stellite # 6 for the screw and barrel of the twin screw extruder, and Stellite # 6 for the wetted part of the gear pump. The apparatus was operated for 3 months in intermittent operation, but the clearance increased from 0.3 mm to 1.1 mm due to the elution of the material of the biaxial extruder, and the discharge efficiency of the gear pump decreased from 95% to 77%. When the metal ion concentration in the 10% orthophosphoric acid aqueous solution recovered during this operation was measured, 10 ppm of chromium ions was detected.

  The dissolution rate of Stellite # 6 into 116% phosphoric acid at 210 ° C. was 3.5 mm / year, and the hardness value was 44 in HRC. If the corrosion resistance is poor, it cannot be used as production equipment.

Example 1
Obtained by the method shown in US Pat. No. 4,533,693, polybenzoxazole 14.0% (by weight) having an intrinsic viscosity of 28.4 dL / g measured with a methanesulfonic acid solution at 30 ° C. and a phosphorus pentoxide content of 83.2% A spinning dope comprising polyphosphoric acid was used for spinning. After kneading and defoaming with a biaxial kneader, the pressure was increased with a gear pump, and the polymer solution was transferred to a spin pack installed in the spinning head through a pipe maintained at 175 ° C. The inside of the spin pack had a structure that passed through a woven wire mesh filter medium of Hastelloy C-22 800 × 100 mesh (wire diameters: 0.065 mm and 0.1 mm). Spinning was performed from a spinneret having a number of holes of 664 at 175 ° C., and the discharged yarn was cooled using a cooling air having a temperature of 60 ° C. and then introduced into a coagulation bath. Spinning, coagulation, washing with water (neutralization), and drying were continuously carried out at a spinning speed of 350 m / min, and high-strength polybenzbisoxazole fibers having an average strength of 1112 dtex and 38 cN / dtex were obtained. This spin pack is used continuously for one month. The average thread breakage number was 0.07 / day.
(Comparative Example 3)
Instead of Hastelloy C-22 installed side by side in the same spinning head, SUS316L 800X100 mesh (wire diameters 0.065mm and 0.1mm) with a spin pack attached with a woven wire mesh filter medium, the number of holes 664 When spinning at 175 ° C. from the spinneret having the same, a high-strength polybenzbisoxazole fiber having an average of 1115 dtex and a strength of 38 cN / dtex was obtained. In this spin pack, there was no yarn breakage for the first 10 days of operation, but after that, one piece of yarn breakage occurred per day, and when the spin pack was removed on the 13th day and the inside was disassembled , the thin wire mesh was thinned. The back was transparent, and the fine lines were cut.

  The elution rates of Hastelloy C-22 and SUS316L into 116% polyphosphoric acid at 175 ° C. were 0.01 mm / year and 0.13 mm / year, respectively. SUS316L is difficult to use as a filter medium with a polybenzazole solution at 175 ° C.

Claims (2)

When producing a molded body from a polyphosphoric acid solvent and a dope comprising a polymer soluble in polyphosphoric acid, at least a dope contact of a device for stirring and uniformly dispersing the dope and / or a pump device for transferring the uniformly dispersed dope The liquid part is a corrosion-resistant material having a material elution rate of 0.1 (mm / year) or less in 116% polyphosphoric acid 175 ° C. immersion evaluation , and the corrosion-resistant material is made of a nickel-based alloy. A method for producing a molded body from a polyphosphoric acid solution. A method for producing a molded body from a polyphosphoric acid solution, wherein the filter medium according to claim 1 is used.