JP3480128B2 - Method for producing high modulus polyparaphenylene benzobisoxazole multifilament - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength, high-modulus polybenzazole multifilament having excellent strength and elastic modulus, which is used as an industrial material. [0002] Polybenzazole fiber has more than twice the strength and elastic modulus of polyparaphenylene terephthalamide fiber, which is a typical super fiber currently on the market, and is expected as a next-generation super fiber. Have been. [0003] By the way, it is conventionally known to produce fibers from a polyphosphoric acid solution of a polybenzazole polymer.
For example, the spinning method is described in US Pat. No. 5,296,185.
No. 5,385,702, a washing and drying method is proposed in WO09 / 04726, and a heat treatment method is proposed in US Pat. No. 5,296,185. [0004] However, the elastic modulus of the high-strength polybenzazole fiber obtained by the above-mentioned conventional manufacturing method can be maintained even at 350 ° C. or higher as described in US Pat. No. 5,296,185. It is about 290 GPa. Labs report extremely high elastic moduli,
Elastic modulus of 290 GP with 5.0 GPa or more strength
Yarns (a collection of filaments) of a or more have not yet obtained industrial production technology. [0005] The inventors of the present invention have sought to develop a polybenzazole fiber having the ultimate elastic modulus as an organic fiber material, and have started to solve the problem. Rigid polymers such as so-called ladder polymers have been considered as a means for achieving the ultimate elastic modulus. However, such rigid polymers are not flexible and have flexibility and processability as organic fibers. It is essential that the polymer be a linear polymer. [0007] SGWierschke et al.
ciety Symposium Proceedings Vol.134, p.313 (1989)
As shown in (1), cis-type polyparaphenylenebenzobisoxazole has the highest theoretical elastic modulus among linear polymers. This result was also confirmed by Tashiro et al. (Macromolecules. Vol. 24, p. 3706 (1991)). Among polybenzazoles, cis-type polyparaphenylene benzobisoxazole has a crystal elastic modulus of 475 GPa. (P. Galen et al. Material Research Society Symposium
Proceedings Vol. 134, p. 329 (1989)), which was considered to have the ultimate primary structure. Therefore, in order to obtain the ultimate elastic modulus, the use of polyparaphenylene benzobisoxazole as the polymer was a theoretical result. The fiberization of the polymer is disclosed in US Pat.
No. 85, a method described in U.S. Pat. No. 5,385,702, and a heat treatment method is performed by a method proposed in U.S. Pat. No. 5,296,185. The elastic modulus of the yarn obtained by such a method is at most 290 GPa, It only achieves a crystal elastic modulus of 61%. Therefore, the need for research on improvement of these methods was keenly felt, and it was found that desired physical properties could be achieved by the following methods. That is, the yarn discharged from a spinneret, which is a spin dope composed of polyparaphenylene benzobisoxazole (PBO) and polyphosphoric acid, from a spinneret into a so-called air gap (draw zone) has an extremely high elongational viscosity. Rather than the concept of spinning, drawing is more representative of the reality. However, spun-doped PBO molecular chains have a very long molecular relaxation time, whereas polyphosphate molecules have a relatively short relaxation time, which is not irrelevant to the relaxation of the doped molecular chains. For this reason, by controlling the molecular relaxation in the draw zone, the structure is controlled and spun out.
Can further obtain a polybenzazole multifilaments having a high elastic modulus such as a high strength has and has not obtained so far by heat treating the fiber, and the high strength / high modulus polybenzazole Multi Filament
Found that it had microstructural features not available with previous techniques. [0010] Thus, the present invention overcomes the technical difficulties so far, and provides a high-strength high-modulus polyparaphenylene benzobisoxazole multifilament which approaches a crystal elastic modulus.
(Hereinafter, the fiber of the present invention refers to this multifilament
And to enable its industrial production. [0011] Means for Solving the Problems That is, the present invention for adapting the above object relates to a method of frenzy of manufacturing the above SL multifilament, consisting essentially of poly para-phenylene benzobisoxazole The polymer dope is as follows (1)
- (3) [0012] [number 2] ^{(0.000167 / C × V) 0} . 5 ≦ Q ≦ 0.00022 / C × V
(1) (S × V) /Q≧0.3 (2) 40 × Q 0. 5 ≦ L ≦ 80
× Q ^0.5 (3) (where Q is the single-hole discharge amount (g /
Min), V is the spinning speed (m / min), C is the polymer concentration (weight ratio), S is the orifice outlet cross-sectional area (cm ² ), and L is the length of the draw zone (cm). ) Is introduced into a non-coagulable gas from a spinneret so as to satisfy the conditions shown in (1), the spun yarn obtained is introduced into an extraction bath to extract the phosphoric acid contained in the yarn, and then dried, Winding then 600 ° C
The heat treatment is performed under the above-mentioned temperature under tension. Hereinafter, the present invention will be described in more detail. The polyparaphenylene benzobisoxazole fiber in the present invention refers to a PBO homopolymer and a random, sequential or block copolymer with a polybenzazole (PBZ) containing substantially 85% or more of a PBO component. Here, the polybenzazole (PBZ) polymer is, for example, a “Liquid Crystalline Polymer C” by Wolfe et al.
ompositions, Process and Products "U.S. Patent No. 4
No. 703103 (October 27, 1987), "Liquid
Crystalline PolymerCompositions, Process and Prod
Ucts, U.S. Patent No. 4,533,692 (August 6, 1985), Liquid Crystalline Poly (2.6-Benzothiazol
e) Compositions, Process and Products "U.S. Patent No. 4,533,724 (August 6, 1985)," Liquid C
rystalline Polymer Compositions, Process and Produ
cts "U.S. Pat. No. 4,533,693 (August 6, 1985)
Sun), Evers "Thermooxidative-ly Stable Articula
ted p-Benzobisoxazole and p-Benzobisoxazole Polyme
rs "U.S. Pat. No. 4,539,567 (November 1, 1982)
6) Tasi et al., “Method for making Heterocyclic Bl
ock Copolymer "U.S. Pat. No. 4,578,432 (198
March 25, 2006). The structural unit contained in the PBZ polymer is preferably selected from a lyotropic liquid crystal polymer. The monomer units consist of the monomer units described in structural formulas (a) to (h), and more preferably consist essentially of the monomer units selected from structural formulas (a) to (c). The following margins are used. Embedded image The following margins are used. Embedded image Embedded image Embedded image Embedded image Embedded image Suitable solvents for forming the polymer dope consisting essentially of PBO include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid. The concentration of the polymer in the solvent is preferably at least about 7% by weight, more preferably at least 1%.
0% by weight, most preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as, for example, the solubility and dope viscosity of polyno. Due to their limiting factors, the polymer concentration is usually 20% by weight
Never exceed. A suitable polymer, copolymer or dope is synthesized by a known method. See, for example, Wolfe et al., US Pat. No. 4,533,693 (August 6, 1985);
U.S. Pat. No. 4,772,678 to S. bert et al. (September 20, 1988); U.S. Pat.
(July 11, 1989). According to Gregory et al., U.S. Pat. No. 5,089,959 (February 18, 1992), polymers consisting essentially of PBO can be produced at high reaction rates under relatively high temperature, high shear conditions in a dehydrating acid solvent. High molecular weight is possible. The dope polymerized in this manner is supplied to the spinning section and discharged from the spinneret at a temperature of usually 100 ° C. or higher. The arrangement of the base pores is usually plural in a circumferential or lattice shape, but other arrangements are also possible. Although the number of spinneret pores is particularly limited, the arrangement of the spinneret pores on the spinneret face must maintain a pore density that does not cause fusion between the discharge yarns. The spun yarn needs a sufficient draw zone length as described in US Pat. No. 5,296,185 in order to obtain a sufficient draw ratio (SDR), and requires a relatively high temperature (solidification of the dope). It is preferable that the cooling air is uniformly cooled by a rectified cooling air having a temperature not lower than the spinning temperature. The length (L) of the draw zone needs to be a length that completes solidification in a non-coagulating gas, and is roughly determined by the single hole discharge amount (Q). In order to obtain good fiber properties, the draw-out stress of the draw zone needs to be 2 g / d or more in terms of polymer (assuming that stress is applied only to the polymer). On the other hand, if the yarn residence time in the draw zone becomes longer, the polybenzazole molecular chain has an extremely long relaxation time, but polyphosphoric acid has a relatively short relaxation time. Relaxation has progressed slightly. Since the yarn has an extremely high molecular orientation and a high elastic modulus, a slight relaxation appears as a decrease in the elastic modulus. It has been found that preventing this is a decisive factor in improving physical properties. That is, when the spun yarn obtained by satisfying the following formula is heat-treated, a fiber having physical properties and structure which has not existed conventionally can be obtained. [0029] [number 3] ^{(0.000167 / C × V) 0} . 5 ≦ Q ≦ 0.00022 / C × V
(1) (S × V) /Q≧0.3 (2) 40 × Q 0. 5 ≦ L ≦ 80
× Q ^{0. 5} (3) [0030] Here Q is the single-hole discharge rate (g / min), V is the spinning rate (m / min), C is the polymer concentration (weight ratio), S is the orifice outlet cross-sectional area (Cm ² ), L is the length (cm) of the draw zone. The yarn drawn in the draw zone is then led to a coagulation bath (extraction bath). Since the spinning tension is high, there is no need to consider the disturbance of the extraction bath, and the following type of extraction bath may be used. For example, a funnel type, a water tank type, an aspirator type, a waterfall type, or the like can be used. The extract is desirably an aqueous phosphoric acid solution or water. Finally, 99.0% or more, preferably 99.5% or more of the phosphoric acid contained in the yarn is extracted in the extraction bath. There is no particular limitation on the liquid used as the extraction medium in the present invention, but water, methanol, and methanol having substantially no compatibility with polybenzoxazole are preferred.
And so on. Alternatively, the extraction bath may be separated into multiple stages, the concentration of the aqueous phosphoric acid solution may be gradually reduced, and finally, the aqueous solution may be washed with water. Further, the fiber bundle is desirably neutralized with an aqueous sodium hydroxide solution or the like and washed with water. The extracted yarn is dried immediately or separately and wound up. By subjecting the obtained dried fiber to a heat treatment at a temperature of 600 ° C. or higher under tension, an elastic modulus (290 GPa or higher) which has not been obtained before can be obtained. The fiber has a density of 1.55 or more. Surprisingly, a fiber having such a high elastic modulus can obtain a two-point interference image as shown in FIG. 1 in a small-angle X-ray scattering image. Until now, the spun yarn of the PBO fiber shows only equatorial streak but no regulation in the meridian direction, and the small-angle X-ray scattering image of the fiber (heat-treated yarn) showing a high elastic modulus of PBO is shown in FIG. It has been reported that a four-point interference image is obtained as shown in (SJBai et al., Polymer, vol. 33, p. 2136 (1
992) or S. Kumar et al. Polymer, vol. 35, p. 5408 (1
991)), it is scientifically clear that the fine structure obtained by the present invention is a novel fine structure. The method for measuring the small-angle X-ray scattering and the method for measuring the density were based on the following methods. <Method of measuring small-angle X-ray scattering> A small-angle X-ray scattering image was recorded by the following method. The X-ray to be used for the measurement was a rotor flex RU-200 manufactured by Rigaku Electric Co., Ltd., using a copper counter electrode and an output of 40 kV × 1.
It was generated by driving at 00 mA. The optical system used was a three-slit pinhole small-angle camera. At this time, the nickel foil was placed between the camera and the X-ray generator to monochromatic X-rays.
The sample was obtained by winding a yarn of 3 m to 10 m around a shackle having a width of 3.8 cm, and stood in the direction perpendicular to the x-ray at the center of the goniometer. As a detector, an imaging plate (DLUR-ll) manufactured by Fuji Photo Film Co., Ltd. was used. The distance between the sample and the detector was a suitable distance between 300 mm and 400 mm. During the measurement, the space between the sample and the detector was filled with helium gas to suppress scattering and absorption of incident and scattered X-rays by air. The exposure time was 30 minutes to 2 hours. Reading of the intensity signal recorded on the imaging plate was performed using a high-precision image recording system manufactured by JEOL Ltd. At this time, the reading mode is H
S50 was specified. The resulting image was corrected for background scattering. By using the measurement method as described above, a clear small-angle scattering image could be taken. <Method for Measuring Density> The density was measured using a dry automatic densimeter Acupic (pycnometer using helium gas) manufactured by Micromeritex. The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Example 1 14.0% by weight of polybenzoxazole having an intrinsic viscosity of 24.4 dL / g and a phosphorus pentoxide content of 24.4 dL / g measured in a methanesulfonic acid solution at 30 ° C., obtained by the method shown in US Pat. No. 4,533,693. A spinning dope consisting of 83.17% polyphosphoric acid was used for spinning. The dope was passed through a metal mesh filter medium, kneaded and defoamed in a kneading device consisting of two axes, and then the pressure was increased. The temperature of the polymer solution was kept at 170 ° C.
After spinning at 70 ° C and cooling the discharged yarn using cooling air at a temperature of 60 ° C, it is wound around a godet roll to give a spinning speed, and an extraction bath consisting of a 10% phosphoric acid aqueous solution maintained at a temperature of 22 ± 2 ° C. Introduced during. Subsequently, the yarn was washed with ion-exchanged water in a second extraction bath, and then immersed in a 0.1 N sodium hydroxide solution to neutralize the yarn. After further washing in a washing bath, winding and drying in a drying oven at 80 ° C,
Further, heat treatment was performed. Table 1 shows the results. It is recognized that the fiber of the present invention has a remarkably improved elastic modulus and a unique microstructure as compared with the conventional fiber. [Table 1] Example 2 The fiber of Example 1 was washed with a washing bath, and then passed through a drying step without winding. The drying conditions are as follows. First drying oven temperature 190 ° C drying time 60 seconds, second drying oven temperature 220 ° C drying time 60
Second drying oven temperature 240 ° C Drying time 60 seconds. The moisture content of the dried fiber was 0.4% by weight. The dried fibers were further heat treated. Table 2 shows the measurement results of the heat-treated fibers.
Shown in [Table 2] From the above Tables 1 and 2, the fiber of the present invention shows a remarkable improvement in strength and elastic modulus as compared with the conventional fiber.
It is understood that the material is extremely excellent in physical properties. As described above, according to the present invention, it is possible to produce a polybenzazole fiber having a combination of high strength and a high elastic modulus and a unique fiber microstructure which could not be obtained until now. The effect of promoting industrial production and increasing the practicality as an industrial material and expanding the field of use is enormous.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a peculiar small-angle X-ray scattering image of the PBO fiber of the present invention. FIG. 2 is a small-angle X-ray scattering image observed in a conventional PBO fiber.

Claims (1)

(57) [Claims 1] The polymer dope consisting essentially of polyparaphenylenebenzobisoxazole is doped with the following (1) to
(3) Equation (1) (Where Q is the single-hole discharge amount (g / min), V is the spinning speed (m / min), C is the polymer concentration in the solvent (weight ratio), S
Is the orifice outlet cross-sectional area (cm ² ), and L is the length of the draw zone (cm). The spun yarn obtained by extruding into a non-coagulable gas from the spinneret so as to satisfy the above condition) is introduced into an extraction bath to extract the phosphoric acid contained in the yarn, followed by drying and winding. Next, a method for producing a high-modulus polyparaphenylene benzobisoxazole multifilament , which is heat-treated under tension at a temperature of 600 ° C. or higher.