JP3367080B2 - High tensile strength aramid - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention provides an aramid polymer in which fibers and thin films can be drawn and, after drawing, has a combination of extremely high tensile strength, tensile elongation and tensile elastic modulus.

[0002]

BACKGROUND OF THE INVENTION The essence of high tensile strength and tensile modulus of a fiber is that it has a suitable high molecular weight and a well-drawn "rod-like" conformation about the fiber axis. It is well known in the art that it is the ability of polymeric materials to have good parallel "orientation". When using a fairly hard chain para-aramid, typically poly (p-phenylene terephthalamide) (PPD-T), the spinning liquid coagulates due to the good alignment ability of the precursor liquid crystal spinning liquid. Excellent orientation is obtained if extruded from the spinneret before. The fibers thus formed have improved elastic modulus and sometimes toughness, albeit slightly, by heat treatment under tension carried out in the crystallization process, but lack the important stretch orientation capability. Another way to obtain oriented aramid fibers with high tensile strength and tensile modulus is that it is initially amorphous, although it is not possible to make a neat liquid crystal solution by choosing the appropriate semi-flexible composite. As-spun (as-spu
There is a method in which the fiber of n) is sufficiently drawn at a high temperature to arrange the chains in a preferable arrangement. These are typically random copolymers that are non-crystalline in the stretched state. Random copolymers based on the corresponding dibasic acid, 3,4'-oxydibenzoic acid (3,4'-ODB) are generally described, for example, in combination of certain cited monomers ( As part of a number of possibilities for Japanese patent application 78-143726) or in a generalized official statement (H. Sasaki et al. U.S. Pat. No. 4,507,467),
It was disclosed. Such stretchable copolymers generally have the essential crystalline ability to enhance orientation, which is a major prerequisite for maximizing fiber strength, as described above. Absent. Copolymers based on 3,4'-oxydibenzoic acid and selected substituted bibenzoic acids, and p-phenylenediamine, herein described, which provide significant improvements in tensile strength and tensile modulus. Disclosed are essentially crystalline that can be sufficiently stretched to obtain and have a very high level of orientation. This crystalline region is novel both in that the dibasic acid units are incorporated isomorphously, but also as shown by the unique copolymer diffraction.

HW Schmitt (HWSc
hmidt) and D. Gou, Makromol. Chem.
Volume 189 (1988), pp. 2029-2037, reports the utility of units of 2,2'-dimethyl-4,4'-bibenzoic acid in aromatic polyesters.

US Pat. Nos. 4,384,107 and 4,461,886 disclose aramids having stilbinyle and / or biphenylyl units. Among the possible biphenylyl-type units are those derived from 2,2'-disubstituted-4,4'-bibenzoic acid, with the noted substituents including chlorine, bromine, nitro and methyl groups. . There is no mention of the utility of the other units claimed herein for random copolymers.

US Pat. No. 4,843,141 discloses 2,2'-disubstituted-4.4'-bibenzoic acid, aromatic aminophenols, and optionally aromatic dibasic acids such as tetraphthalic acid, and also optionally. Disclosed are polyester aramids having units derived from aromatic hydroxy acids or amino acids. Substituents noted include chlorine, bromine, nitro groups and methyl groups. As opposed to polyester aramids, there is no description of the utility of these bibenzoic acids in aramids.

[0006]

SUMMARY OF THE INVENTION Up to about 10 mol% of the first unit derived from p-phenylenediamine (PPD) and terephthalic acid (T), 2,2'-disubstituted-bibenzoic acid and PPD.
About 30 to about 70 mol% of a second unit derived from oxydibenzoic acid (ODB) and about 70 to about 30 mol% of a unit derived from PPD (herein referred to as "third unit") There is provided a stretchable aramid essentially comprising: High tensile strength and tensile modulus (te
Such polymers are drawn, especially in the form of fibers or films, in order to obtain highly oriented crystalline materials with a nsile modulus.

The present invention is a stretchable aramid having the chemical formula

[Chemical 4] A first unit having up to about 10 mol% and a chemical formula

[Chemical 5] A second unit having about 30 to about 70 mol% and a chemical formula

[Chemical 6] And a third unit having about 70 to about 30 mole% of aramid. However, in the above formula, X ¹ and X ² are independently selected from the group consisting of chlorine, bromine, a nitro group and a methyl group.

Preferably the polymer is about 35 to about 2 second units.
65 mol% and about 65 to about 35 mol% of the third unit. More preferably, the polymer comprises about 45 to about 55 mol% second units and about 55 to about 45 mol% third units. It is also preferred that the first unit does not exceed about 5 mol%.

Preferably, X ¹ and X ² are the same. More preferably X ¹ and X ² are chlorine or a methyl group, and particularly preferably X ¹ and X ² are chlorine.

2,2'-Disubstituted-4,4'-bibenzoic acid (or halides of these acids, especially chlorides, which are often used in the polymerization process to form aramids)
Are produced by methods known in the art. The synthesis of acyl chlorides of 2,2'-dibromo- and 2,2'-dinitro-4,4'-bibenzoic acid is taught in US Pat. No. 4,384,107. For the synthesis of the corresponding 2,2′-dimethyl compound, see “Makromol. Chem.” Vol. 189 (1988), 2
This is taught in the HW Schmidt and D. Gwar reports on pages 020-2037. 2,2'-dichloro-4,4'-dicyanobiphenyl was produced by the method disclosed in U.S. Pat. No. 3,872,2037, followed by reflux (atmospheric pressure) 20% Na.
When hydrolyzed in aqueous OH and then neutralized with acid,
2,2'-dichloro-4,4'-bibenzoic acid is obtained. 3,
4'-Oxydibenzoic acid is described in J. Polym. Sci. Part A: Poly.
Chem. 28, pages 75-87, M.H.B.
It is generated by a method such as MHBSkovby.

The polymer is produced by techniques known in the prior art for producing aramids (see, for example, British Patent 1,547,802 and US Pat. No. 3,673,143). The polymer produced should have sufficient molecular weight to form fibers or thin films. The polymer has an inherent viscosity of about 2 or more.
osity). Such polymers can be spun into fibers or formed into other shapes by methods known in the art for aramids (eg, US Pat. No. 3,673,143 for thin film formation, Example 2 and US for fiber spinning). See Japanese Patent No. 3,767,756).

The polymer of the present invention is stretchable, and when stretched, it exhibits improved properties, especially tensile elastic modulus, than unstretched polymer. Applicants are not willing to stick to this hypothesis in order for the aramid polymer to be stretchable and to exhibit optimal physical properties upon stretching, but the aramid polymer must have the following properties: That is, it is soluble in the solvent for fiber spinning; stable to the drawing conditions (especially high temperature); in the as-spun fiber (unstretched) state Amorphous; and preferably exhibiting considerable crystallinity and high orientation in the stretched state. The elongation of the thin film strip is an indicator that the polymer meets these criteria. This polymer is soluble in N-alkylamide solvents such as N-methyl-pyrrolidone. Although many aramids satisfy some of these conditions, applicants believe that satisfying all of these conditions are only some of the theoretically possible total aramid polymers.

The stretchable polymers of the present invention are useful for fibers and thin films where high tensile strength and tensile modulus are important, as well as cords and composites. Suitable temperatures for stretching are preferably from about 350 ° C to about 5735 ° C, most preferably about 400 ° C.
℃ to about 520 ℃. The temperature required for any particular aramid can be readily determined by heating the aramid (eg, thin film or fiber) to a given temperature and attempting to manually stretch it (see Example 1). . Without elongation, obviously higher temperatures are required.

The force required to draw the fiber is determined by relatively easy experimentation. If the aramid does not break at a certain elongation, the aramid can be stretched to its specified elongation value. In other words, the aramid can be stretched with some force (but less than the force required to break the aramid). This force can be easily determined for any aramid and temperature by heating the aramid to the stretching temperature and stretching with sufficient force while measuring the force with a tensiometer.

The expression "extension of at least X%" shall mean the value calculated by the following equation:

## EQU1 ## (final length)-(initial length) / initial length × 100 It is preferable that the aramid is extended by at least 3%, and it is more preferable that the aramid is extended by at least about 4%, and further,
Most preferably, the aramid extends at least about 6%.
Also preferably, the aramid is at least 400% elongated. The tensile strength of the stretched aramid is preferably at least 1.25 times the tensile strength of unstretched aramid.

The orientation angle is preferably 12 ° or less, more preferably 10 ° or less, further preferably 8 ° or less. The orientation angle (in fibers) is measured by the following method. A bundle of filaments about 0.5 mm in diameter is wrapped around the sample holder, taking care to keep the filaments essentially parallel. X-ray generated from a Phillips X-ray generator (12045B type) operating at 40kV 40mA using a fine adjustment long focus diffraction tube made of copper (PW2273 / 20 type) and a nickel beta filter as a filament loaded in a sample holder. Irradiate the beam.

The diffraction image from the sample filament is recorded on a Kodak DEF direct-irradiated X-ray film with a Warhas pinhole camera. The collimator of the camera is 0.64 mm in diameter.
Irradiation is continued for about 15 to 30 minutes (ie, generally long enough so that the diffraction pattern to be measured is recorded at an optical density of ˜1.0).

A digitized image of the diffracted image is recorded with a video camera. Calibrate transmission intensity using black and white standards,
Convert gray level (0-255) to optical density. The diffracted image of the fiber of the invention has two outstanding superimposed equatorial reflections at scattering angles of approximately 20 ° and 22 °, the inner (~ 20 °) reflection being used to measure the orientation angle. A sequence of data corresponding to an azimuth trace through the two selected equatorial peaks (ie, the inner reflections on both sides of the diffraction pattern) was created from the digital data file by interpolation, the sequence of data being one data point. It is configured to correspond to 1/3 radian.

The orientation angle is measured as the arc length in degrees (angle formed with respect to the 50% point of the maximum density) with respect to the half value point of the maximum optical density of the equatorial peak, and is corrected with respect to the background. It is calculated from a large number of data points (interpolation used, not integers) between the half-value points on either side of the peak.
Two peaks are measured and the orientation angle is taken as the average of the two measurements.

The apparent crystallite size of the stretched aramid may be at least 35 angstroms, preferably at least about 45 angstroms, more preferably about 55 angstroms. Apparent crystallite sizes of 35 Å and above are believed to represent significant improvements in aramid crystallinity and properties, particularly tensile modulus. The apparent crystal size was measured by the following procedure.

An X-ray diffractometer (Phillips Electronic Instruments, Inc .; Catalog No. PW1075 / 00) was operated in reflection mode and an apparent X-ray diffraction scan was performed using a diffracted beam monochromator and a scintillation detector. The crystal size was derived. Intensity data was measured using a count rate meter and recorded in a computerized data collection and editing system. In the diffraction scan, the following measuring instrument setting conditions were used. Scan rate: 1 ° 2θ per minute Step increment: 0.025 ° 2θ Scan range: 15 ° to 30 ° 2θ Wave height analyzer: Use a computer program to process the differential diffraction data, smooth the data, Determination and peak position and wave height measurements were made.

The diffraction pattern of the fibers according to the invention is characterized by two outstanding equatorial X-ray reflections. These peaks occur at about 20 ° -21 ° and 22 ° 2θ (scattering angle), and they substantially overlap and are difficult to decompose. The apparent crystal size can be calculated from the measurement of the peak half-width of the first (smaller scattering angle) equatorial diffraction peak. Since the two equatorial peaks overlap, the measurement of the peak full width at half maximum is based on the full width at half maximum at the wave height. For the peak of 20 ° -21 °, calculate the half-maximum position of the maximum peak height, and calculate 2θ corresponding to this intensity.
The value is measured on the low angle side. The difference between this 2θ value and the 2θ value at maximum peak height is doubled to give the peak half-value (ie, “line”) width.

In this measurement, only the broadening due to the measuring instrument is corrected; all other linewidth widening effects are assumed to be due to the crystal size. If the measurement line width of the sample is B, the corrected line width β is

[Number 2] ^{β = (B 2 -b 2)} 1/2 where "b" is a spread constant by the instrument.
“B” is approximately 2 in the diffraction image of the silicon crystal powder sample.
Determined by measuring the line width of the peak at the 8.5 ° 2θ position.

The apparent crystal size (ACS) is given by:

[Expression 3] ACS = (Kλ) / (β · cosθ), where K is regarded as 1 (unit), λ is the wavelength of the X-ray (here, 1.5418Å), and β is the corrected line width. (Radian unit), θ is the Bragg angle (half of the 2θ value of the selected peak obtained from the diffraction image).

The stretched aramid preferably has the formula

[Chemical 7] A first unit having up to about 10 mol% and a chemical formula

[Chemical 8] A second unit having about 30 to about 70 mol% and a chemical formula

[Chemical 9] And a third unit having about 70 to about 30 mole percent. However, in the above formula, X ¹ and X ² are chlorine,
Independently selected from the group consisting of bromine, nitro groups and methyl groups. The preferred aramid composition of this formula is as listed above.

Stretching of the aramids of this invention results from the substantial lack of water or other solvents. Substantial lack of water or other solvent means less than 5% water or other solvent, preferably less than about 2%. The molecular weight of aramid must be large enough to be able to form fibers.

The polymer is about 2% in N-methylpyrrolidone.
It must have the above inherent viscosity. The procedure for measuring inherent viscosity is described in US Pat. No. 3,673.
No. 3,143, page 9, left column, line 10 et seq., Incorporated herein by reference.

The aramid before stretching preferably has an apparent crystallite size of 30 angstroms or less. This means that the apparent crystal size increases during the stretching process.

The equipment useful for stretching the aramid is diverse. It may be done by hand, but a more automatic and continuous process is desirable as a production method. Equipment useful in such processes is described in U.S. Pat.Nos. 3,869,430 and 4,500,278
, Which are incorporated herein by reference.

In the following example, US Pat. No. 3,869,429
Fiber properties were measured by the method taught in No. 10, right column, page 5, line 10. This is also incorporated herein.
The orientation angle and apparent crystal size were measured as described above.

[0031]

EXAMPLES Example Example 1 air intake type stirrer, slow supernatant flow of inert gas for humidity atmosphere moisture removal, solids addition instrument, and an external ice-water cooler with a glass Resin kettle with p- phenylenediamine (6.048 g; 0.058 mol) in dry N-methylpyrrolidone (NMP) containing anhydrous CaCl ₂ (6.7 g; 3%) (223 mL; 230 g)
Melted into The stirred solution was cooled to 5-10 ° C, and 2,2'-dichlorobibenzoyl chloride (9.744g;
029 mol) and 3,4'-oxydibenzoyl chloride (8.
260 g; 0.029 mol) was quantitatively added all at once. The viscosity gradually increased in about 30 minutes to reach a level (7.9% solids) suitable for casting thin films. After about 2 hours, CaO (3.14 g; 0.058 mol) was added to neutralize the by-product HCl to obtain a transparent viscous liquid. The inherent viscosity measured in 30 ° NMP was 3.88 and in 100% H ₂ SO ₄ was 2.40. Thermogravimetric analysis showed an initial weight loss at about 450 ° C;
DSC showed onset of simultaneous exotherms at the same temperature.

The polymer solution was cast into a thin film on a clean glass plate using a 0.015 inch doctor knife. In a vacuum oven flushed with nitrogen, it was dried for 5 hours at 90 ° C and then soaked overnight in room temperature water to remove CaCl ₂ , then the edges were fastened to a glass plate to fix the thin film. It was dried at 90 ° C. for 5 hours. It was then cut into 1/4 inch wide strips and hand drawn over a semi-circular hot plate with a diameter of 1 inch and a contact length of about 1.5 inches. Drawability
Changed from 400% / 400 ℃ to 600% / 440 ℃. By gradually raising the temperature to 450 ° C. and performing the stretching, a stretchability of 800% was possible. The inability to stretch above 450 ° C is due to the extreme weakening of the film in synchronization with the onset of pyrolytic degradation. Maximum tensile strength in the stretched: Toughness (T) / Elongation (E) / Elastic modulus (Mi) /Denier=8.4g
It was pd / 2.7% / 365gpd / 381 (average 8.1 / 2.8 / 300/407). The unstretched sample had T / E / Mi = 1.1 / 29/30, and was in an amorphous state with no orientation. In contrast, the drawn sample was highly crystallized and highly oriented with an apparent crystal size of 35Å and an orientation angle of 4.8 °. In the unstretched polymer, the apparent crystal size was 8Å and the orientation angle was 0.

Comparative Example 1 By the same polymerization as in Example 1, an inherent viscosity η = 3.
A p-phenylenediamine / 3,4'-oxydianiline (50/50) terphthalamide polymer of 01 was made, cast into a thin film and the strip stretched as before. At 400-490 ° C
Stretching properties of 450-1550% were observed. As an example, 475 ℃
The sample stretched 1500% at T / E / Mi averaged 14.7 gpd (18.4 gp
d) /4.1% (4.5%) / 384gpd (598) / 110 denier, orientation angle 11.4 °, and there is no definite diffraction spot in the X-ray diffraction record, so it is possible to judge that there is negligible three-dimensional crystallinity. Had. The apparent crystal size measured on a commercial fiber sample of this composite was 33Å, the orientation angle was 15 °,

Comparative Example 2 Similar to the method of Example 1, dry NMP (300 g) containing 2.25 g of anhydrous CaCl ₂ (0.75 wt% (w / w) solution) in which p-phenylenediamine (0.07 mol) was dissolved. Melted at 10 ° C.
7.10 g (0.035 mol) of terephthaloyl chloride and 10.33 g of 3,4'-oxybenzoyl chloride were added to this solution.
(0.035 mol). The mixture was heated to 70 ° C. and the polymerization was continued for 2 hours with stirring to give a pale yellow solution. The solution was milky and somewhat viscous. CaO (3.85 g, 0.07 mol) was mixed to neutralize the by-produced HCl to obtain a transparent viscous solution. Inherent viscosity is 25 ° C
2.00 in sulfuric acid. Dilution with NMP gave the proper viscosity for casting thin films as in Example 1. A thin film was molded in the same manner as in Example 1, heated with a hot shoe, stretched to a maximum of 700% at 400 ° C, and had a toughness (T) / elongation (E) / elastic modulus (Mi) of 11 gpd / 6.0% / 323 gpd (best Destruction 12.3 / 10.2 / 37
8) got. Orientation angle (OA) / crystal index (CT) /
The crystal size (CS) was 13 ° / 22 / 42Å. The crystal diffraction image was the same as that of PPD-T. At a low stretch ratio of 800%, OA / CT / CS was 15 ° / 20 / 35Å. The unstretched thin film had 0/12 / 10Å and T / E / Mi = 1.2 / 79/31 gpd.

While the preferred embodiments of the invention have been described above, it is clear that the invention is not intended to be limited to the precise constructions disclosed herein, but within the scope of the invention as defined by the appended claims. It is also clear that rights are reserved for all possible changes.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08G 69/32

Claims (16)

(57) [Claims] 1. A stretchable aramid / random copolymer having the chemical formula: The first unit having up to about 10 mol% has the chemical formula: A second unit having about 30 to about 70 mol% and a chemical formula: A third unit having about 70 to about 30 mol%, wherein X ¹ and X ² in the above formula are independently selected from the group consisting of chlorine, bromine, nitro and methyl groups. Aramid comprising. 2. The second unit of about 35 to about 65 mol%,
The aramid of claim 1 comprising about 65 to about 35 mole% of said third unit. 3. The second unit of about 45 to about 55 mol%,
The aramid of claim 2 comprising about 55 to about 45 mole% of said third unit. 4. The aramid according to claim ^1, wherein the X ¹ and the X ² are the same. 5. The aramid according to claim 4, wherein each of X ¹ and X ² is a chlorine or nitro group. 6. The aramid according to claim ^2, wherein the X ¹ and the X ² are the same. 7. The aramid according to claim ² , wherein each of X ¹ and X ² is chlorine or a methyl group. 8. The aramid according to claim 3, wherein each of X ¹ and X ² is chlorine or a methyl group. 9. The aramid according to claim 1, which has been stretched. 10. The aramid according to claim 2, which has been stretched. 11. The aramid according to claim 8, which has been stretched. 12. The aramid according to claim 1, which is in the form of a fiber. 13. The aramid according to claim 1, which is in the form of a thin film. 14. The aramid of claim 1 comprising up to about 5% of said first unit. 15. The aramid according to claim 4, wherein the X ¹ and the X ² are chlorine. 16. The aramid according to claim 8, wherein the X ¹ and the X ² are chlorine.