JP2002515949A - Method for producing high-strength aramid fiber - Google Patents

Abstract

Abstract: A method is disclosed for producing extra-high strength para-aramid filaments by extruding a solution of para-aramid through a microcapillary and drying the resulting filaments under high tension.

Description

FIELD The present invention certain spinneret capillary dimensions DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION production method invention high strength aramid fiber, special high by a combination of steps elements including specific coagulation conditions, and the particular drying tension The present invention relates to a method for producing tenacity aramid fiber. DESCRIPTION OF THE PRIOR ART U.S. Pat. No. 4,965,033, issued Oct. 23, 1990 to Chiou's application, discloses an aromatic polyamide fiber using a high mass injected coagulating liquid stream. Is disclosed. U.S. Pat. No. 3,767,756, issued Oct. 23, 1973 to the Blades application, and U.S. Pat. No. 3,767,756 issued Dec. 22, 1992 to the Yang application. No. 173,236 discloses aromatic polyamide fibers using a spinneret having a capillary of 0.025 to 0.25 millimeters (1 to 10 mils) and a capillary of less than 0.064 millimeters (2.5 mils). It discloses spinning and drying of the fibers under tension near 0.3 grams / denier (gpd). U.S. Pat. No. 4,726,922, issued Feb. 23, 1988 to the Cochran and Young applications, discloses a method for spinning aromatic polyamide fibers to increase the strength of the fibers and the use of 3. Disclose their drying under a tension of ７7 grams / denier (gpd). SUMMARY OF THE INVENTION (a) Filaments of an acid solution containing at least 30 grams of poly (p-phenylene terephthalamide) having an inherent viscosity of at least 4 per 100 milliliters of acid are drawn from a spinneret and into an inert non-coagulating fluid. Extruding together with coagulating liquid overflowing through the layer into the coagulating bath and then through the spinning tube, (b) forming another coagulating liquid at an angle of 0 ° to 85 ° with respect to the filament symmetrically around the filament In a downward direction, the filament is jetted within about 2.0 milliseconds from the time it enters the spinning tube, and (i) the mass flow rate of the combined overflowing and jetted coagulating liquid greater than about 250 versus the mass of the filament. Maintaining the flow rate ratio, and (ii) the combined overflowing and injected coagulation in the spinning tube that is less than the speed of the filament exiting the spinning tube Maintaining a mean linear velocity of the liquid, and (iii) maintaining a constant flow rate of both the injected and overflowing coagulation liquid, and (c) having a strength of at least 28 gpd, comprising the step of drying the filament. Use of a spinneret having a capillary diameter of up to 0.051 millimeters (2 mils) and a filament under tension of at least 3.0 grams / denier (gpd) in a process for producing yarns of poly (p-phenylene terephthalate). An improvement comprising drying is provided. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an apparatus that can be used in the practice of the method for producing fibers that can be used in the present invention. DETAILED DESCRIPTION OF THE INVENTION Great efforts have been devoted to the development of yarns and fabrics having increased strength. Each improvement has been painstakingly won and very significant to provide significant benefits even with small increases. The yarn of the present invention has a tenacity of at least 28 gpd and can be produced using the apparatus shown in FIG. These yarns generally have a polyherenic viscosity of at least 4.0 dissolved in sulfuric acid having a concentration of at least 98% according to the method disclosed in U.S. Pat. No. 3,767,756. Manufactured using (p-phenylene terephthalamide) (PPD-T). The PPD-T solution is extruded from the spinneret through an air gap and into a coagulation bath. The spinneret has a capillary diameter of 0.051 millimeters (2.0 mils) or less. Capillaries larger than 0.051 millimeters (2.0 mils) produce fiber filaments that are believed to have relatively poor molecular orientation resulting in reduced strength, and therefore use relatively small diameter capillaries. Not as strong as those manufactured. As a practical matter, capillaries smaller than about 1 mil may be difficult to use and may not produce fibers of acceptable properties. FIG. 1 is a sectional view of a preferred coagulation bath 1. The bath 1 is an annular structure consisting of an insertion disc 2 fitted in a support structure 3. The support structure 3 includes an inlet 4 for introducing a cooling liquid 5 under pressure into a distribution ring 6, the ring of which is suitable for promoting a uniform distribution of the cooling liquid around the coagulation bath 1. 7 The introduction of coagulation liquid into the bath is from a surrounding manifold containing baffles or packings to provide a uniform distribution of coagulation liquid to the orifice and non-turbulence. In the case of an annular bath, the manifold can surround the bath. Even in the case of rectangular baths with slot orifices, the manifold can surround the bath, but the coagulating liquid is supplied only to the side of the bath parallel to the slots. It is only necessary that the coagulating liquid flow to the orifice be non-turbulent near the orifice. Therefore, the filter 7 may be glass beads, a series of screens, a honeycomb structure, a dipped metal plate, or other similar device. After passing through the filter 7, the coolant passes through a perforated plate or screen 8 and flows horizontally towards the center of the bath 1 without discernible turbulence or backmixing, where the coolant 5 is removed from the stop cap 10 It comes into contact with the protruding filaments 9, whereby both the coolant 5 and the filaments 9 pass through the orifice 11 in a downward direction into the spinning tube 14. To promote uniform non-turbulent flow towards the opening 11, the bottom of the bath can be contoured as described by the areas indicated by A and B. The area around the orifice may be tapered toward the orifice. Preferably, the depth of the coagulation bath is no greater than 20% of the bath depth in the non-turbulent region. A suitable bath depth for spinning a small scale, for example, 20 filaments, is about 2.5 inches (3.15 cm) and 3.1 mm with a diminishing penetration having an initial diameter of about 12 mm. With an orifice having a diameter of Suitable bath depths for larger scale spinning, for example, 1,000 filaments, are about 23 cm and are combined with a 9 mm diameter orifice with a decreasing entrance having an initial diameter of about 28 mm. . Insert disc 2 includes an annular injector 12 that operates in a manner similar to the injector disclosed in U.S. Pat. No. 4,298,565. The orifice 11 preferably has a spout 13, that is, the orifice 11 has a slightly smaller diameter than the spinning tube 14 to ensure that the filament 9 adheres to the orifice 11 and the wall of the spinning tube 14. Help prevent. The coolant 5 is introduced from the opening 15 through the passage 16 into one or more jet openings 17, whereby the coolant 5 together with the filaments 9 and the other coolant 5 moves the spinning tube in a downward direction. It is directed through a delivery device (not shown) through an outlet 18. According to known procedures, the filaments are washed and / or neutralized and dried before winding the yarn produced by this method. Preferably, the angle of the liquid directed by the jet opening 17 to the filament forms an angle (θ) in the range of 0 to 85 degrees. Although satisfactory results can be obtained with θ-90 degrees, the choice of the data requires very tight adjustment of the method and is therefore undesirable in commercial operation. Thirty degrees is an angle particularly suitable for use in commercial manufacturing methods. The jet opening 17 is located adjacent the orifice 11 and directs the jetted coagulating liquid downward toward the filament within about 2 milliseconds from the time the filament enters the spinning tube. When the spinneret, spinning orifice, jet and the extension of the spinning tube are carefully aligned on the same axis and when the jetting parts are carefully designed and aligned to give a perfectly symmetric jet around the yarn row. The method gives the greatest improvement. Misalignment of the injection parts or blockage of solid particles in the injection openings that breaks symmetry can reduce or eliminate the improvement. Such symmetry may be provided by two or more injection orifices or by slots which are symmetrically spaced with respect to the yarn row. According to this method, the flow of overflowing coagulating liquid (Q ₁ ) and injected coagulating liquid (Q ₂ ) is regulated and kept constant in order to obtain the improvement according to the invention. The mass-flow rate ratio (R) of the filament mass-flow rate is adjusted to be greater than about 250. Preferably, the mass-flow ratio (R) is greater than about 300. In the practice of the present invention, the flow rate of the overflowing coagulation fluid (Q ₁ ) is adjusted by adjusting the bath depth (dimension h) above the orifice 11 by measuring the inflow into the bath. It also depends on the diameter of the spinning tube 14. Dimension h is generally less than 1 inch (2.5 cm) and preferably less than about 0.5 inch (1.3 cm). If h is too small, the air is drawn into the spinning tube 14 by the pumping action of the advancing filament, which is detrimental to both the tensile and mechanical properties of the yarn being produced. Therefore, h should be large enough to ensure that no air bubbles are carried. From the above considerations, a calculation of the appropriate diameter of the spinning tube 14 is made. The rate of overflow of the cooling liquid (Q ₁ ) through the orifice is greatly affected by the moving yarn train through the same orifice, and this effect should be taken into account. For example, the overflow velocity through a 9.5 mm (0.375 inch) diameter orifice under a 15.9 mm (0.625 inch) hydrostatic head is about 1.5 liters / l in the absence of a moving yarn train. Minutes (0.4 gallons / minute) and 8.7 liters / minute (2.3 gallons / minute) in the presence of a 1,000 filament line of 1.5 denier / filament traveling at 686 m / min. ). This is generally due to the pumping effect of the filament moving through the liquid layer due to boundary layer phenomena. To counteract this effect, the orifice size, ie the diameter of the cross-sectional area, is appropriately chosen. The flow rate of the injected coagulation liquid (Q ₂ ) is preferably adjusted by metered pumping through a selected size injection opening. The smaller cross-sectional dimension of the jet (e.g., the hole diameter of the flow width) is generally in the range of 0.05 to 2.5 mm (2 to 100 mils). It is desirable that the flow velocity and the jet opening be such that the axial velocity of the injected coagulating liquid is at least about 50% of that of the yarn being treated and preferably prevents pulling up of the yarn row resulting in a reduction in breaking stress. Should exceed at least about 80% of the yarn speed. However, the axial velocity of the injected coagulating liquid must not exceed 200% of that of the yarn being treated and preferably to prevent yarn striking which may result in a reduction in the measured yarn strength. Does not exceed about 150% of speed. Thus, a mass flow rate ratio of the combined coagulation liquid to filament mass of greater than about 250, preferably greater than about 300, as well as a yarn velocity of greater than about 6.0 which also provides a suitable velocity for the injected coagulation liquid. It is necessary to use a suitable injected liquid flow rate and injection openings or slots that provide a momentum ratio of injected to overflowing coagulation liquid. In the method of the present invention, the average linear velocity of the combined coagulation liquid in the spinning tube is maintained at a speed less than the speed of the filament exiting the spinning tube. This prevents strong loss of the yarn due to "looping" of the filaments in the yarn and possible process discontinuity problems due to the absence of sufficient tension before the feed roll. The present invention can be used for a wide range of spinning speeds and especially for spinning speeds of at least 300 m / min and preferably at least about 350 m / min, although higher spinning speeds may be used when compared to lower spinning speeds. Causes a reduction in power. These advantages are the strengths produced by the process of the present invention while increasing both the mass-flow rate ratio (R) and the momentum ratio (φ), and thus can offset the loss of strength due to a continuous increase in spinning speed, Mass-flow ratios (R) above 5000 and momentum ratios (φ) above 50 do not provide any further significant improvement and are economically attractive for industrial production, especially large deniers such as, for example, 1500 denier. It is believed that it will not be targeted. After the fibers have been spun and passed through a coagulation bath, they are washed and dried to complete production. The fiber must be thoroughly washed to remove any traces of acid and eliminate acid-related fiber degradation. Water alone or a combination of water and an alkaline solution can be used for textile cleaning. A common cleaning method is to spray an alkaline aqueous solution (eg, saturated NaHCO ₃ or 0.05 N NaOH) onto a roll as the yarn row exits the coagulation bath to reduce the acid content to about 0.01% (dry fiber). Standard). The fibers can be conveniently dried on a heated roll (eg, 160 ° C.). A preferred washing method for the present invention is to wash the fibers with a spray liquid and send them continuously to a dryer roll maintained at about 150 ° C. One important element of the method of the present invention involves drying the fiber under high tension of about 3.0-7.0 grams / denier (gpd). Drying tensions less than 3.0 gpd produce fibers with reduced molecular orientation resulting in reduced strength, and drying tensions greater than 7.0 gpd cause excessive yarn breakage and associated handling difficulties. Drying tensions of about 3.5-6.0 gpd are particularly preferred. Test Method Tensile Properties Strength is reported as the breaking stress divided by the linear density. Modulus is reported as the slope of the initial stress / strain curve converted to the same units as strength. Elongation is the percentage increase in length at break. Both strength and modulus are initially calculated in g / denier, giving a dN / tex unit when it is multiplied by 0.8826. Each reported measurement is the average of 10 breaks. Denier is the weight in grams of 9000 meters of yarn or filament and dtex is the weight in grams of 10,000 meters. Tensile properties for the yarn are measured after conditioning for a minimum of 14 hours under test conditions at 24 ° C. and 55% relative humidity. Prior to testing, each yarn is twisted to a 1.1 twist multiplier (eg, a nominal 1500 denier yarn is twisted by about 0.8 turns / centimeter). Each twisted specimen has a test length of 25.4 cm and is stretched 50% per minute (based on the original unstretched length) using a typical stress / strain recorder. Is done. The yarn yarn multiplier (TM) is Where tpi = turns / inch and tpc = turns / centimeter. The tensile properties for yarns are different and lower than the tensile properties for individual filaments, and their values for yarn cannot be successfully and accurately estimated from filament values. Momentum Ratio (φ) The momentum ratio is defined as the ratio of the momentum (M ₂ ) of the injected coagulation liquid along the yarn row direction to the momentum of the overflowing coagulation liquid (M ₁ ), ie, φ = M ₂ / M _Is one. Momentum is defined as the product of mass velocity and flow velocity. The calculation of the momentum ratio is described in the aforementioned U.S. Pat. No. 4,298,565, and in the examples [Wherein Q ₁ is the flow velocity of the overflowing liquid, Q ₂ is the flow velocity of the injected liquid, d ₁ is the inner diameter of the spinning tube, and d ₂ is the smaller dimension of the injection opening. Where θ is the acute angle between the injected liquid and the thread array]. As long as d ₁ and d ₂ and Q ₁ and Q ₂ are in the same unit, the ratio φ is independent of the unit selected. Mass-flow rate ratio (R) This is the ratio of the mass-flow rate of the total coagulation liquid to the mass-flow rate of the filament (dry basis). The basic unit of the liquid flow rate Q is gal / min here. Q × 3899 = mass-flow rate, g / min For yarn, the basic units are speed (Y) in yd / min and denier (D) in g / 9000 m 2. YD × (0.9144 / 9000) = mass−flow rate, g / min The mass−flow rate is now Q / YD × 3.8376 × 10 ⁷ . In this equation, it is assumed that the density of the coagulation liquid is about 1.03 g / ml. EXAMPLES In the following examples, poly (para-phenylene terephthalamide) (PPD-T) having an inherent viscosity of about 6.3 dL / g before dissolution and about 5.5 dL / g in fiber form is disclosed in U.S. Pat. No. 4,340,559 was spun using tray G. The diameter of the spinning tube is 0.3 inches, and jets of 0.21 and 0.42 millimeters (8 and 16 mils) are used with a 30 degree angle between jet and yarn row. did. The solvent used in making the spinning dope was about 100.1% sulfuric acid and the concentration of polymer in the spinning dope was about 19.4% by weight. As shown in Tables I and II, 0.051 and 0.064 millimeter (2.0 and 2.5 mil) spinnerets were used. The number of spinneret capillaries used included 133, 266, 400, 500, 560 and 666 capillaries. The air gap, the filament travel from the exit face of the spinneret to the first contact with the coagulating liquid, was about 0.235 inches (0.635 cm). The coagulation liquid was kept at about 3 ° C. For all of the following examples, a yarn tension of about 1.0 gpd was used during washing and neutralization. Examples of the present invention used a mass flow ratio (R) of 325 to 1680 with a spinneret having a 0.051 millimeter capillary. The yarn was dried under a tension greater than 2 grams / denier and the yarn had a linear density of 60-1500 denier. The comparative example used the same polymer and the same spinneret under the same conditions, except that the mass flow ratio, momentum ratio, dry tension, and spinneret capillary dimensions were different as shown in Table I. . In the following examples, a PPD-T of the same properties as used above was used, except that different spinnerets were used as shown in Table II and some other conditions were changed. The spinning was performed using the same equipment and spinning conditions as used in. Table II also shows the yarn properties of these examples.

[Procedure of Amendment] Article 184-8, Paragraph 1 of the Patent Act [Submission date] September 15, 1998 (September 15, 1998) [Correction contents]                                The scope of the claims 1. (A) at least 30 grams of at least 4 per 100 milliliters of acid Poly (p-phenylene terephthalamide) having an inherent viscosity of The filaments of the acid solution are removed from the spinneret (10) and the Coagulation overflowing through the bed into the coagulation bath (1) and then through the spinning tube (14) Extruded together with the liquid, and (b) another coagulating liquid is filled symmetrically around the filament. Filaments in a downward direction forming an angle of 0 to 85 degrees with respect to the (14) Inject within 2.0 ms after entering, (i) one greater than 250 Mass flow rate of spilled and injected coagulating liquid vs. filament mass flow (Ii) spinning at a speed lower than that of the filament exiting the spinning tube (14) Maintain the average linear velocity of the combined overflowing and injected coagulating liquid in the tube (14). And (iii) maintaining a constant flow rate of both the injected and overflowing coagulating liquid. And (c) drying the filaments. / Denier (poly (p-phenylene having a strength of 31.1 g / dtex) Terephthalamide) in the production of 0.051 millimeter (2 By using a spinneret (10) having a capillary diameter up to Under tension of at least 3.0 grams / denier (3.33 grams / dtex) And drying the filaments. 2. Mass flow rate of combined overflowing and injected coagulation liquid versus filament The method of claim 1, wherein the ratio of mass flow rates is greater than 300. 3. Spinnerets with a diameter of 0.025 mm (1 mil) to 0.051 mm 2. The method of claim 1 wherein the metric is 2 mils. 4. Filaments from 3.0 grams / denier (3.33 grams / dtex) to 7. Drying under a tension of 0 grams / denier (7.77 grams / dtex) The method of range 1.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, L U, MC, NL, PT, SE), EA (AM, AZ, BY) , KG, KZ, MD, RU, TJ, TM), CN, JP , KR (72) Inventor Mikio Ohno             44-1 Saka Tobitakacho, Konan City, Aichi Prefecture

Claims (1)

[Claims] 1. (a) at least 30 grams of at least 4 per 100 milliliters of acid; Contains poly (p-phenylene terephthalamide) having inherent viscosity The acid solution filament from the spinneret and through a layer of inert non-coagulating fluid Extruded into the coagulation bath and then with coagulating liquid overflowing through the spinning tube, (b ) Another coagulation liquid 0-85 degrees with respect to the filament symmetrically around the filament 2.0 mm from the time the filament enters the spinning tube in the downward direction forming an angle of Jetting within seconds, (i) combined overflow and jetting greater than 250 Maintaining the ratio of the mass flow rate of the solidified liquid to the mass flow rate of the filament, and The overflowing and jetting together in a spinning tube smaller than the filament speed Maintain the average linear velocity of the coagulated liquid which has been injected and Keeping both flow rates constant, and (c) drying the filaments A poly (p-phenylene) having a strength of at least 28 grams / denier 0.051 millimeter (2 mm) Use of a spinneret having a capillary diameter of up to 3.0 g / m An improvement comprising drying the filament under denier tension. 2. Mass flow rate of combined overflowing and injected coagulation liquid versus filament The method of claim 1, wherein the ratio of mass flow rates is greater than 300. 3. Spinneret diameter between 0.025 mm (1 mil) and 0.051 mm 2. The method of claim 1 wherein the pressure is 2 mils. 4. Filaments from 3.0 grams / denier to 7.0 grams / denier The method of claim 1 wherein drying under tension.