KR100393509B1 - Electrically conductive fiber - Google Patents

Abstract

High strength poly (p-phenylene derephthalamide) fibers are electrically conductive by polyaniline ring-substituted with sulfonic acid groups.

Description

Electrically conductive fibers

<Related application>

This application is a partial continuing application of US Patent Application No. 07 / 227,785, filed August 3, 1988.

Yue, Epstein and Mac Diarmid in Proc. As reported in Symposium on Electroresponsive Molecular and Polymeric Systems, Brookhaven National Laboratory Oct, 1989, sulfonic acid ring-substituted polyaniline has a "self-doped" conductivity of about 0.03 S / cm without external doping. Polymer. Synthesis of such materials is also described in J.A.C.S. 1991, V. 113, N. 7 pp. 2665-2671, which indicates that the measured conductivity for pressurized pellets is about 0.1 S / cm.

Fibers from blends of polyaniline and poly (p-phenylene terephthalamide) prepared from homogeneous solutions in concentrated sulfuric acid are described in Polymer Commun 31, 275 (1990). These fibers are described as having improved mechanical properties while retaining the conductivity of pure polyaniline. The concentration of poly (p-phenylene terephthalamide) in the spinning solution used by the experimenter was lower than that of the lyotropi phase production initiator, so that the fibers were spun from the isotropic solution.

1 is an enlarged 1200 times view of a fiber transverse longitudinal micrograph of the present invention.

<Summary of invention>

The present invention includes, as main components, poly (p-phenylene terephthalamide) and sulfonic acid group ring-substituted polyaniline in an amount that makes the fiber electrically conductive, and has an as-spun stiffness of 10 g / denier ( gpd) or more and a sulfur content of at least 9% by weight, based on the weight of sulfonated polyaniline, to provide a high strength, high modulus, electrically conductive fiber. Preferably, the ratio of sulfonated polyaniline to poly (p-phenylene terephthalamide) in the fiber is 10/90 to 30/70 by weight.

Sulfonated in concentrated sulfuric acid (> 100%), wherein the ratio of sulfonated polyaniline to pulley (p-phenylene terephthalamide) is 10/90 to 30/70 based on weight percent and the total polymer content in the solution is at least 15% by weight. Forming a two-liquid of polyaniline and poly (p-phenylene terephthalamide) and extruding the solution into a coagulation bath through an air gap to form a fiber Methods of making the fibers are also included in the present invention.

The spinning dope used in the process of the invention is obtained by combining polyaniline with a solution of poly (p-phenylene terephthalamide) (PPD-T) in concentrated sulfuric acid (> 100%) at a temperature above 45 ° C. Can be prepared. Under these conditions, sulfonation of polyaniline occurs, and the temperature and sulfuric acid concentration increase and the reaction accelerates over time. The individual method used for sulfonation of polyaniline is not critical. The sulfonation method is disclosed in the references described in the background paragraph above. The sulfur content of sulfonated polyaniline should be at least 9% by weight for high conductivity. The molecular weight of the polyaniline used in the present invention is not critical. Low molecular weights result in lower solution viscosity and easier processing, but can be more easily removed from the fiber during processing or use. PPD-T is used in polymer form with an intrinsic viscosity of at least 5. In order to obtain the desired high strength, a certain concentration of PPD-T is used, which provides a constant dilution, as described in US Pat. No. 3,767,756. Spinning liquids with a total polymer content of sulphonated polyaniline and PPD-T of at least 15% by weight fulfill this requirement.

The ratio of sulfonated polyaniline to PPD-T in the spinning solution and consequently the spinning fiber has a significant effect on the fiber properties. When the content of sulfonated polyaniline exceeds 30% by weight of the polymer mixture, the tensile strength of the composite fibers is undesirably reduced and at the same time no increase in electrical conductivity is involved. In order to provide an electrical conductivity of at least about 0.03 S / cm, the sulfonated polyaniline should comprise at least 10% by weight of the polymer mixture. Preferably, the sulfonated polyaniline should comprise 20 to 30% by weight, based on the polymer mixture. Surprisingly, the fibers of the present invention comprising such mixtures exhibit much higher electrical conductivity than the fibers of 100% sulfonated polyaniline. The spinning process of the present invention is believed to increase conductivity.

The fibers of the present invention have good strength, radial stiffness above 10 gpd, and moderate conductivity. The term "spinning state" means that the fibers formed in the spinning step followed by the winding have not been subjected to any stretching or heat treatment action that changes the molecular alignment or arrangement of the polymer molecules. The washing and drying actions necessary to remove solvents or impurities are acceptable. The conductivity of the fibers of the present invention remains stable under the conditions of use and the fibers do not require doping. Sulfonated polyaniline is dispersed within the fiber as an elongated amorphous structure parallel to the fiber axis. From this, it can be explained that a high degree of conductivity appears even at low concentration of sulfonated polyaniline in the composite fiber.

Test Methods

Electrical conductivity:

The electrical resistance of the fiber at ambient conditions is measured by a four probe method that calculates electrical conductivity. The fiber specimen to be tested is about 1.5 cm in length. Four electrodes were fabricated on fiber specimens using room temperature curable silver paste. The two internal voltage measurement electrodes are spaced about 8 mm apart. A current is applied to the two external electrodes and the voltage corresponding to the known current is measured with an electrometer. Calculate the resistance according to Ohm's law. Conductivity is calculated in S / cm by standardizing based on fiber cross section and distance between voltage electrodes.

Tensile test:

The stiffness / elongation / modulus (T / E / M (Tenacity / Elongation / Mondulus)) of a single filament of 2.54 cm (1 ") gauge length is measured in g / denier (gpd) for T and M The tensile test is carried out in accordance with ASTM 2101. The filament denia is measured according to ASTM D1577 using a vibrometer.

Elemental sulfur analysis:

The fiber sample is first burned with oxygen in the flask. The resulting SO ₂ and SO ₃ gases are absorbed in water. Hydrogen peroxide is added to ensure that all sulfur is converted to sulfates. Boil together with platinum black to remove any excess H ₂ O ₂ , then adjust the pH. The solution is then added to water with isopropanol in a ratio of 50/50. The solution is then titrated with a standardized BaCl ₂ solution to determine the sulfate concentration. The amount of sulfur is determined based on the sulfate concentration.

The following examples are intended to illustrate the invention and are not to be considered in a limiting sense.

<Example 1>

This example illustrates the formation of conductive fibers by air gap spinning a polyaniline / poly (p-phenylene terephthalamide) solution having a high polymer concentration.

Polyaniline was prepared according to the following method. A solution consisting of 134.3 g of aniline, 194.4 g of 37 wt% HCl solution and 1350 g of deionized water was introduced into a 2 L jacketed glass reaction vessel under a nitrogen environment. The solution was continuously stirred using a 7.62 cm (3 inch) diameter wing wheel with twin-blade. The coolant supplied by the cooling device was circulated around the reaction vessel jacket to cool the aniline / HCl solution to -3 ° C. An oxidant solution consisting of 155 g of ammonium persulfate in 270 g of water was added to the reaction vessel at a rate of 1.95 mL / min using a syringe pump. After addition of the oxidant solution, the reaction mixture was stirred at about −3 ° C. for 3.5 days. The reactor contents were then filtered, slurried repeatedly in water and filtered to wash the collected powder, and then neutralized by vacuum re-slurrying twice in 0.15 M ammonium hydroxide solution for 24 hours each time. The neutralized polymer was then dried and washed twice with 1.5 liters of methanol and finally with acetone. The polymer was dried and the dry box stored until just before use. The polymer had an intrinsic viscosity of 1.29 measured at 30 ° C. in a 0.5% by weight solution in H ₂ SO ₄ (concentration: 96.7%) and the polymer was electrically nonconductive because the polyaniline was removed by neutralization with ammonium hydroxide. This is because the conversion from the conductive type (emerald salt) to the insulating base type.

Polyaniline (base) prepared as described above in 49.8 g of H ₂ SO ₄ (100.15%) in a nitrogen purged glove bag, cooled in a pre-dried glass bottle using a dry ice / acetone bath located outside the glove bag. Form) 10.2 g was added to prepare a 17 wt% polyaniline / H ₂ SO ₄ solution. The mixture was vigorously stirred with a spatula while cooling in a dry ice / acetone bath. The mixture was then transferred to a pre-dried twin cell with a cross plate for mixing (see US Pat. No. 3,767,756 to Blades). The mixture was pressed back and forth using a crossover plate at approximately 45 ° C. for 2 hours to obtain a uniform solution. The solution in the twin cell was transferred to three pre-dried glass bottles in amounts of 3.32, 7.83 and 9.3 g. The polyaniline solution was mixed with poly (p-phenyleneterephthalamide) (PPD-T) and concentrated sulfuric acid (> 100%) to give 18.6 weight with a polyaniline: PPD-T weight ratio of 10:90, 20:80 and 30:70 A% spin dope solution was prepared. For example, 3.32 g of 17 weight percent polyaniline solution at room temperature under nitrogen was added to 0.81 g H ₂ SO ₄ (100.15 weight%) and 19.4 weight% poly (p-phenylene terephthalamide) in H ₂ SO ₄ (> 100 weight%). ) Was mixed with 26.19 g of a solution to prepare a 10:90 solution. The mixture was then stirred at about 65 ° C. for 30 minutes, transferred to a 2.54 cm (1 inch) diameter twin cell, left at 70 ° C. for 30 minutes, and passed further through the cross plate between cells for 30 minutes at 65 ° C. To ensure uniformity. By the same procedure, spinning dope with polyaniline: PPD-T ratios of 20:80 and 30:70 was prepared by adjusting the amount of poly (p-phenylene terephthalamide) solution and polyaniline solution.

Spinning dope containing 18.6 wt% polymer was spun through the air gap according to the following procedure. The spinning dope solution prepared above was transferred to one side of the twin cell, and the filter pack and dynalloy disc, consisting of 200 and 325 mesh stainless steel screens, were twin cell and 0.076 mm (3 mil) in diameter, Inserted between single hole spinnerets of 0.23 mm (9 mils). The spinneret was placed at 6.35 mm (0.25 inch) above a 3.79 liter (1 gallon) glass vessel containing ice-cooled deionized water. Solid guides were placed in deionized water at a distance of 7.62 cm (3 inches) below the spinneret. After the solid line was further passed by 20.32 cm (8 inches) in water, the solid line was wound on a bobbin partially impregnated in a tray containing deionized water. The extrusion pressure, spinneret temperature (same as the spinning cell), and fiber take-up rate in atm (lbs / in ² (psi)) for samples spun from three polyaniline / PPD-T solutions are summarized in Table 1 .

Immediately after spinning, continuous filaments of typically less than 0.3 g on each bobbin were impregnated in 900 mL deionized water for one day. During this time, the water was replaced three times with fresh deionized water. The filament sample was then dried and the denier (D) / stiffness (T) / elongation (E) / modulus (M), electrical conductivity and elemental sulfur analysis values were measured. The results in Table 1 show that the fibers are electrically conductive after sufficient washing with deionized water. This is an unexpected result, since doped polyaniline typically loses conductivity when contacted with aqueous solutions having a pH above about 4. The fiber samples all contain sulfur, and by this sulfur the sulfonic acid group will be covalently bound to the polyaniline at the ortho position relative to the imide group. Sulfonation of polyaniline occurred in situ as it was processed in concentrated H ₂ SO ₄ (> 100%) at elevated temperature. The sulfonic acid group acts as an internal dopant that conducts the polyaniline polymer. This hypothesis is supported by the fact that sulfur is not easily removed, as recorded for samples 10 and 12 in Table 1. These two samples were impregnated in 900 mL of 0.1 M ammonium hydroxide for 4 hours. The fibers treated with ammonium hydroxide were then washed sufficiently with deionized water. After neutralization and washing with water, the two fiber samples contained 3.24 and 3.21 wt% sulfur. The fact that sulfur is not removed by neutralization is evidence that sulfur is present as a sulfonated acid group covalently bound to polyaniline.

TABLE 1

<Example 2>

This example illustrates air gap spinning of a 15.2 wt% polymer solution in H ₂ SO ₄ containing sulfonated polyaniline / PPD-T in a weight ratio of 30/70. A 10 wt% polyaniline / H ₂ SO ₄ solution was prepared by mixing 8 g of polyaniline prepared in Example 1 and 72 g of H ₂ SO ₄ (100.15%) while cooling with a dry ice / acetone mixture under a dry nitrogen environment. The mixture was then transferred to twin cells under nitrogen and further mixed at room temperature for 2 hours to obtain a homogeneous solution. 15.2 wt% of spinning dope was prepared by mixing 22.66 g of 10 wt% polyaniline solution and 27.30 g of PPD-T / H ₂ SO ₄ (> 100%) in a twin cell at 65 ° C. in a dry nitrogen environment. The mixture was further mixed at about 65 ° C. for 1 hour to obtain a homogeneous solution. The solution was then spun at 80 ° C., extrusion pressure of 23.1 atm (340 psi) and winding speed of 59.45 m (195 feet) / minute by the procedure described in Example 1. After washing with deionized water as described in Example 1, the f / ment's D / T / E / M was 2.0 / 7.9 / 4.1 / 265 and the electrical conductivity was 0.09 S / cm. The comparison results show that with 15.2 wt% polyaniline / PPD-T solution, fibers with lower tensile strength, modulus and electrical conductivity are obtained than with 18.6 wt% solution.

<Example 3>

(Comparative Example)

This example describes air gap spinning of a 13.2 wt% polymer solution in H ₂ SO ₄ containing sulfonated polyaniline / PPD-T in a weight ratio of 30/70.

At room temperature for 2 hours twin-cell H ₂ SO ₄ (concentration: 100.15%) in _{5.91 g PPD-T / H 2} SO 4 (> 100%) and Example 2, 10 wt% polyaniline / H ₂ SO ₄ solution of Spinning dope was prepared by mixing 18.16 g. The twin cell was then heated to 45 ° C. and further mixed for 1 hour to obtain a homogeneous 13.2 wt% polyaniline / PPD-T (30/70) solution. The solution was then spun at 70 ° C., extrusion pressure of 27.2 atm (400 psi) and winding speed of 59.45 m (195 feet) / minute by the procedure described in Example 1. After washing with deionized water as described in Example 1, the D / T / E / M of the filaments was 3.4 / 5.5 / 4.7 / 206 and the electrical conductivity was 0.03 S / cm. A comparison of Samples 9 and 10 in Table 1 shows that fibers with a 13.2 wt% polyaniline / PPD-T (30/70) solution had lower tensile strength, tensile modulus and electrical conductivity than with an 18.6 wt% solution. Indicates that is obtained.

<Example 4>

This example describes the formation of conductive fibers by air gap spinning a sulfonated polyaniline / PPD-T solution containing 18.6% by weight of polymer.

Spinning solutions containing 18.6 wt% polymer in concentrated H ₂ SO ₄ and having a polyaniline / PPD-T ratio of 10/90, 20/80, 30/70 and 40/60 were prepared according to the following procedure. PPD-T (19.4 wt% in H ₂ SO ₄ ), the polyaniline polymer (base type) prepared in Example 1, and sulfuric acid (100.15 wt%) with 18.6 wt% polymer and the desired polyaniline / PPD-T ratio Placed in a pre-dried glass bottle in the required amount to form a solution. The bottle was then placed in an oven purged with nitrogen at 70 ° C. for 1 hour, after which the mixture was stirred and transferred to a hot (70 ° C.) twin cell. The twin cells were heated to 70 ° C. in an oven purged with nitrogen for 1 hour and then the mixture was mixed with a cross plate for 1.5 hours to obtain a homogeneous solution.

The polyaniline / PPD-T solution was spun according to the procedure described in Example 1. The extrusion pressure, spinneret temperature, and winding speed for each spinning run are summarized in Table 2.

Immediately after spinning, bobbins containing continuous filaments (approximately 0.3 g of each fiber) were impregnated in 900 mL deionized water for one day. During this time, the water was replaced three times with fresh deionized water. The D / T / E / M, electrical conductivity of the flush fibers is summarized in Table 2. Even if the fibers were washed sufficiently with deionized water, they were still electrically conductive. The results in Table 2 also show that the tensile strength and modulus decrease as the polyaniline / PPD-T ratio increases. The preferred ratio is 30/70, since in this case the fibers have the highest conductivity and high strength and modulus.

X-ray images of the fibers from each composition show that the sulfonated polyaniline is present in the amorphous polymer with the PPD-T polymer chains highly oriented at an orientation angle in the range of 13.6 to 14.8. Optical photograph (FIG. 1) of the first item of Table 2 shows that PPD-T and sulfonated polyaniline were separated. The sulfonated polyaniline (1) is uniformly dispersed in the cross section of the PPD-T (2) matrix and appears as stripes extending along the fiber axis in the longitudinal section. This explains the fact that high conductivity is obtained even at a 10/90 ratio.

TABLE 2

Example 5

This example illustrates the effect of neutralization of ammonium hydroxide on the conductivity of sample 2 (polyaniline / PPD-T = 10/90) of Example 4.

The conductivity of the fiber fragments of Sample 2 (Example 4), thoroughly washed with deionized water, was measured, indicating that the conductivity was 0.03 S / cm. Another sample of undried fiber was immersed in 900 mL of 0.1 M ammonium hydroxide solution for 3 hours and 900 mL of another fresh 0.1 M ammonium hydroxide solution for 4 hours. At the end of each impregnation both ammonium hydroxide solutions were colorless. However, in contact with the solution, the color of the fiber changed from green (conductive) to blue (pickled) because ammonium hydroxide neutralized the fiber's acid. The neutralized fibers were then washed with running deionized water for 6 hours to return the fibers to their initial green color. The fiber contained 1.82 wt% sulfur and had a conductivity of 0.07 S / cm. This result indicates that the conductivity is not affected by neutralization with ammonium hydroxide, and provides evidence that sulfur is present in the sulfonic acid group covalently bonded to polyaniline.

<Example 6>

This example illustrates the effect of neutralization of ammonium hydroxide on the conductivity of sample 10 (polyaniline / PPD-T = 30/70 (weight / weight)) of Example 4.

A fragment of the fiber of Sample 10 (Example 4), thoroughly washed with deionized water, had a sulfur content of 4.14% by weight and a conductivity of 0.6 S / cm. Residual pieces of undried fiber were immersed in 900 mL of 0.1 M ammonium hydroxide solution for 2 hours, and 900 mL of another fresh 0.1 M ammonium hydroxide solution for 6 hours. The color of the ammonium hydroxide solution was pale purple after each impregnation. Subsequently, even after washing the neutralized fibers with running deionized water for 16 hours, the fibers still contained 4.14 wt% sulfur and had a conductivity of 0.3 S / cm. Example 5 as well as this example shows that the polyaniline in the fiber is sulfonated and sulfonic acid groups are not readily extracted by the basic solution.

<Example 7>

(Comparative Example)

A fragment of the fiber of Sample 14 (Example 4), thoroughly washed with deionized water, had a sulfur content of 4.14% by weight and a conductivity of 0.4 S / cm. Residual pieces of undried fiber were impregnated in 900 mL of 0.1 M ammonium hydroxide solution for 2 hours, and 900 mL of another fresh 0.1 M ammonium hydroxide solution for 4 hours. The color of the ammonium hydroxide solution was dark purple after each impregnation. It was clear that some polyaniline in the fiber was extracted with ammonium hydroxide solution. The neutralized fibers were washed well for 13 hours with running deionized water. The treated fibers contained 1.67% by weight of sulfur, which was significantly lower than the sulfur content in the untreated fibers. Conductivity decreased from 0.4 S / cm to 0.04 S / cm. This example suggests that some of the sulfonated polyaniline can be extracted when the polyaniline / PPD-T ratio is significantly greater than 30/70.

Claims (1)

a) Sulfur content in concentrated sulfuric acid, wherein the ratio of sulfonated polyaniline to poly (p-phenylene derephthalamide) is 10/90 to 30/70 by weight percent and the total polymer content in the solution is at least 15% by weight. Forming a solution of sulfonated polyaniline and poly (p-phenylene derephthalamide) which is at least 9% by weight, and b) extruding the solution into a coagulation bath through an air gap to form a fiber, High-strength, high modulus, electrically conductive fibers with poly (p-phenylene derephthalamide) and sulfonic acid group-substituted polyinilines as main components and as-spun stiffness of 10 g / denier (gpd) or more Method of preparation.