MXPA97001072A - Procedure for preparing films and polyben fibers - Google Patents

Abstract

A process for preparing polybenzazole filaments, which includes, extruding the filaments from a spinner (1), having at least 100 holes, which are arranged to form an annular pattern (2) around the center of the spinner (1), the center and at least two radial sections (3) of the spinner (1) having no holes, and an average width that is at least 3 times the minimum pitch of the holes, and stretching the filaments to through an extinguishing chamber, while providing a substantially radial gas flow therein through the spinner (1) from at least two different directions

Description

/ "PROCEDURE FOR PREPARING POLYBENZAZOL FILAMENTS AND FIBERS DESCRIPTION OF THE INVENTION The present invention relates to a process for preparing filaments and fibers of polybenzoxazole or polybenzothiazole. The fibers prepared from polybenzoxazole (PBO) and from J "" "polybenzothiazole (PBT), (hereinafter referred to as polymers of PBZ or polybenzazole) can be prepared by first extruding a solution of the polybenzazole polymer in a mineral acid (a polymer "absorbent material") through a die or spinner to prepare a filament of absorbent material. The filament of absorbent material is then stretched through a air gap, is washed in a bath comprising water or a > mixture of water and a mineral acid, and then it is dried. If multiple filaments are extruded simultaneously, then they can be combined into a multi-filament fiber either before, during, or after the washing step. 20 As the filaments of the polybenzazole absorbent material are extruded, the high extensional viscosity of the absorbent material, the rapid cooling of the filaments, and the differences in the cooling rates of the extruded filaments in the center of the spinner, compared to those Extruded at the spinner's edge, they can cause frequent breakages as they are pulled through the air gap. Although this yarn stability problem can be reduced to some degree, using a slower spinning speed, and / or having a lower hole density on the yarn spinner, these methods are generally less desirable from the productivity point of view or equipment design. Since smaller diameter filaments are more desirable than filaments with larger diameters, which could be obtained normally - by using a spinner with larger holes, the twist-stretch ratio may need to be increased significantly to stretch the filaments enough to produce filaments with a smaller diameter, which can also cause ruptures in the filaments. In addition, although the stability of the spinning line can be improved by reducing the number of holes per spinner . (hereinafter referred to as hole density), it is necessary to increase the number of spinners per spinning head, or increase the size of the spinner, in order to continuously spin a greater number of filaments from an individual spinning head . However, such equipment configurations may be less desirable. U.S. Patents A 5,294,390 and 5,385,702 disclose methods for increasing the stability of a spinning line by extruding polybenzazole filaments through a partially enclosed air gap, which has gas flowing through the > .- Means to cool the filaments to a relatively uniform temperature. Although this method improves the stability of the spinning line, methods to further improve spinner stability and the number of filaments are desirable, which can be extruded by spinning head, while maintaining a relatively stable spinning line. In one aspect, this invention is a process for preparing polybenzazole filaments, which comprises: (a) extruding /, the filaments from a spinner that has at least 100 holes, which are arranged to form an annular pattern around the center of the spinner, the center and at least two radial sections of the spinner having no holes, and an average width, which is at least about 3 times the minimum passage of the holes; and (b) stretch the filaments through of an extinguishing chamber, while providing a substantially radial gas flow therethrough through the spinner from at least two different directions. In a second aspect, this invention is a process for preparing filaments of polybenzazole, which comprises: (a) Extrude the filaments from a spinner having at least 100 holes, which are arranged to form an annular pattern around the center of the spinner, the center having no holes, and an average width, which is therefore less about 3 times the minimum pitch of the holes; Y (B) stretching the filaments through an extinguishing chamber, while providing a substantially radial gas flow therethrough, through the filaments from at least two directions. It has been found that the process of the invention provides means for preparing polybenzazole filaments and fibers, which allows them to be spun from spinning dies having a relatively high orifice density, but they maintain relatively stable spinning conditions. The stability of the spinning conditions creates a more efficient spinning process, minimizing the number of line breaks, ensures the uniformity of the filament being stretched, which allows to optimize the cooling conditions of the filaments, which can improve the tensile strength and the filament tension 'module. The penetration capacity of the air flow between the filaments immediately below the spinner is improved, the cooling of the strands and the thinning profile become more uniform, and the spinning process is stabilized by using the method of the invention . These and other advantages will be apparent from the description that follows. Figure 1 shows an example of a spinner hole pattern for use in the method of the first aspect of the invention, as described below. Referring now to Figure 1, there is shown a spinner (1), which is part of a group of holes (2), three groups of which are separated from each other by radial sections of the spinner (3), which have no holes, having a width (W). Figure 2 shows an example of a spinner hole pattern useful in the method of the second aspect of the invention. The polybenzazole filaments used in the process of the invention can be obtained by spinning an absorbent material containing a polybenzazole polymer. As used herein, "polybenzazole" refers to polybenzoxazole homopolymers (PBO), polybenzothiazole homopolymers (PBT), and copolymerized, randomized, sequential, or block PBO and PBT polymer. Polybenzoxazole, polybenzothiazole, and randomized, sequential, or block copolymerized polymers thereof are described, for example, in "Liquid Crystalline Polymer Compositions, Process and Products" ("Compositions, Process and Products of Crystalline Polymer, Liquid "), by Wolfe et al., US Patent 4,703,103 (October 27, 1987);" Liquid Crystalline Polymer Compositions, Process and Products "(" Compositions, Processes and Products of Crystalline Polymer, Liquid "), US Patent 4,533,692 (August 6, 1985);" Liquid Crystalline Poly (2,6-benzothiazole) Composition, Process and Products "(" Composition, Process and Products of Poly (2,6-benzothiazole) Crystalline, Liquid "), U.S. Patent 4,533,724 (August 6, 1985);" Liquid Crystalline Polymer Compositions, Process and Products "(" Crystalline Polymer Compositions, Processes and Products, "), US Patent 4,533,693 (August 6, 1985). 1985), "Thermooxidatively Stable Articulated p-Benzobisoxazole and p-Benzobisthiazole Polymers" ("Thermo-oxidatively Stable, Articulated p-Benzobisoxazole and p-Benzobistiazole Polymers"), by Evers, US Patent 4,539,567 (November 16, 1982); Y "Method for Making Heterocyclic Block Copolymer" ("Method for Making a Block Copolymer, Heterocyclic"), by Tsai, patent of E.U.A. 4,578,432 (March 25, 1986). The structural units present in the PBZ polymer are preferably selected, so that the polymer is a liquid, lyotropic crystalline. Preferred monomer units are illustrated below in formulas I-VIII. The polymer most preferably consists of monomer units selected from those illustrated below, and preferably consists essentially of cis-polybenzoxazole, trans-polybenzoxazole, or trans-polybenzothiazole. -fcasO- ©; . cis-polybenzoxazole Poly [benzo (1,2-d: 5,4-d ') bisoxazole-2,6-diyl-1,4-phenylene] trans-pol i benzoxazole Poly [benzo (1) 2-d: 4,5-d ') bisoxazole-2,6-diyl-1,4-phenylene] 0 trans-polybenzothiazole / > 0 cis-polybenzothiazole AB-PBO Poly (2,5-benzoxazole) Poly (2,5-benzothiazole) AB-PBO 20 Poly (2,6-benzoxazole) Poly (2,6-benzothiazole). Suitable polymers or copolymers of polybenzazole and absorbent materials can be synthesized by known methods, such as those described by Wolfe and other patents of E.U.A. 4,533,693 (August 6, 1985); Sybert et al., Patent of E.U.A. 4,772,678 (September 20, 1988); Harris, patent of E.U.A. 4,847,350 (July 11, 1989); and Gregory et al., U.S. Patent. 5,089,591 (February 18, 1992). In summary, the appropriate f "monomers are reacted in a solution of non-oxidizing and dehydrating acid (the acidic solvent) under a non-oxidizing atmosphere, with vigorous mixing and high shear, at a temperature which is increased in a stepwise manner. or ramp of not more than about 120 ° C to at least about 190 ° C. Suitable solvents for the The PBZ polymer absorbent material preparation includes cresols and non-oxidizing acids. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid, and highly concentrated sulfuric acid, or mixtures thereof. Preferably, the acidic solvent is polyphosphoric acid or the acid Sulfonic methane, but polyphosphoric acid is very preferred. The concentration of polymer in the solvent is preferably at least about 7% by weight, preferably at least about 10% by weight, and most preferably at least about 14% by weight. The maximum concentration is limited by the practical factors of handling, such as the solubility of the polymer and the viscosity of the absorbent material. The concentration of the polymer normally does not exceed 30% by weight, and is preferably not more than about 20% by weight. Oxidation inhibitors, tarnish agents, coloring agents, and antistatic agents can also be added to the absorbent material. These polibenzazoles are directly or separately spun by a method of wet spinning of dry jet, made to measure / that the absorbent material dissolves in the polyphosphoric acid. He The polybenzazole material is preferably filtered by passing it through a porous plate having a number of holes with a diameter of 1 to 5 mm. Then, it is preferably passed through a space called a melting bath, formed by a porous plate surface and the rear surface of the nozzle spinner, and through a woven material or non-woven fabric of metal fibers contained therein. The absorbent material is then spun through a spinner having a number of holes arranged in a circular, crystal-like or trefoil-shaped pattern. The arrangement of the holes of the yarn on the spinner and the hole density will affect the gas's ability to flow past the filaments closest to the gas source and reach the filaments. Figure 1 shows an example of a spinner, which can be used in the process of the first aspect of the invention.

As shown in this Figure, the holes of the spinning nozzle are divided into groups, which are separated from each other by sections of the spinner, which do not have spinning holes. The hole density on the spinner, in both methods of the invention, is preferably less than above 2.0 holes / cm2, preferably at least about 4.0 holes / cm2, and most preferably at least about 6.0 holes / cm2, but preferably it is less than about 10.0 holes / cm2, (based on the area of the spinner covered by the holes, which is also referred to herein as the "active" area). In general, higher hole densities are preferred from the productivity point of view, although, as the hole density increases, it becomes more difficult to conduct the cooling gas through the filaments that are extruded, in a sufficient form to cool them at a uniform speed. In the process of the first aspect of the invention, the spinner is constructed in such a way that the holes are divided into at least two groups, most preferably at least three groups. The number of groups is preferably less than ten, since the space on the spinner, required for the sections, which do not have holes, will reduce the space available on the spinner for the holes. The patterns of the spinning hole groups, divided, are not especially limited, but are preferably radially symmetrical, with respect to the center of the spinner. Preferably, the width of r? the radial section (s) and the center of the spinner section having no holes, in the procedures of both aspects of the invention, is at least about 5 mm, and less than about 50 mm. mm, most preferably less than about 10 mm; or preferably it is at least about 3 times the minimum pitch of the holes, and less than about 30 times the minimum pitch of the holes. Figure 2 shows a spinner, which is useful in the r-procedure of the second aspect of the invention. In a second aspect of the invention, there is a space in the middle of the spinner that has no holes, and the holes do not need to be divided into sections. An advantage of this aspect of the invention is that once the spinning conditions are optimized for a given radial width of filaments (the distance between the outside of the active area into the active area, defined in part by the width of the space in the middle of the spinner) at a given distance of passage, spinners of different sizes can be designed, having a different number of holes, and can be used under substantially equal spinning conditions, provided that the holes, in the spinner, are configured to maintain the same radial width. The term "annular pattern", as used herein, means that the spinning holes are arranged on the spinner to leave a space at the center of the arrangement, which has no holes. Figure 2 illustrates a reticular, annular pattern.

The filaments of the absorbent material, extruded through the spinner, are cooled to a temperature lower than the solidification temperature of the absorbent material, by passing them through an air gap and into a wash bath containing a suitable washing fluid. . Initially, as the filaments are extruded from the spinner, they preferably pass through an extinguishing chamber, which surrounds the filaments, as they leave the spinner. Since the length of the extinguishing chamber is optional, it is preferably long enough to provide a relatively constant temperature atmosphere under the initial extrusion from the spinner, such as with an inert gas flow through the filaments to maintain a temperature from 0 ° C to 100 ° C in the extinguishing chamber. Once the filament leaves the extinguishing chamber, it can be exposed to atmospheric conditions until it coagulates. The length of the extinguishing chamber is preferably between 2 and 120 cm, but may be longer. The flow of gas through the filaments is directed from at least two different directions. Preferably, a number of gas jets are used to direct the flow of gas through radial portions of the filaments, from as many directions as practical. Alternatively, a series of deflectors can be used within the extinguishing chamber to help direct the flow of gas therein, or a pressurized device can also be used, surrounding the filaments, having a screen or filter allowing a flow of gas uniformly distributed through the radial sections of filaments. The gas can originate either from outside the filament arrangement, or from a source located in the middle of the arrangement. It is believed that, without being bound by theory, a radial extinction of the filaments, by means of a gas coming from a number of directions around the filaments, is highly desirable in terms of cooling all the filaments at a uniform rate, allowing the cooling temperature is more easily optimized for all the filaments, and improving the stability of the spinning line. As the gas travels through the radial portion of the filament arrangement, it is continuously expelled down between the filaments. The temperature of the gas is preferably at least about 30 ° C, preferably at least about 40 ° C, and most preferably at least about 50 ° C, but preferably not more than about 100 ° C, preferably not greater than about 90 ° C, and most preferably not greater than about 80 ° C. Convenient means for washing the filaments, as an initial washing step, in a multi-step washing process, is to run the filaments through a solidification bath, funnel-shaped, a water aspirator, multi-step, or other vertical bath. Then, the filaments can be further washed in a bath, using washing rollers. After the filaments pass through the first wash bath, they travel on at least one drive roller. The maximum ratio of twist / stretch in the air gap, which will allow stable, continuous spinning, is reduced as the filament deniers become thinner. Stable yarn spinning of 1.5 denier, at a speed greater than 200 m / minute, is possible by the method of this invention. The average denier per filament (dpf) is preferably at least about 1.5, and less than about 3.5. The filaments are subsequently washed under conditions sufficient to preferably remove at least about 98.0% by weight of the acidic solvent present in the filaments, preferably at least about 99% by weight, and most preferably at least about 99.5% by weight. Suitable washing fluids include any liquid, which is non-solvent for the polymer, but which will dilute the acidic solvent in the filament of absorbent material. Examples of washing fluids include water, methanol, acetone, and mixtures of water and the solvent, from which the polybenzazole absorbent material is composed, either in liquid or vapor form. Preferably, the absorbent material is prepared using polyphosphoric acid and the wash fluid is a mixture of water and phosphoric acid. In addition, the washing of the filaments can be carried out as a multi-step process. The washed filaments may be subsequently dried in a suitable drying process. In addition, it may also be desirable to apply a spin finish to the filaments, before or after being dried, in order to help protect the filaments from mechanical damage. To increase the filament tension module, these can be treated with heat, at a temperature greater than 300 ° C, or very preferably at a temperature higher than 450 ° C, but lower than 650 ° C is preferred. The process of the invention is preferably carried out at a terminal velocity of at least about 200 m / minute, preferably at least about 400 m / minute, and most preferably at least about 600 m / minute. The filament used in the process of the invention can be combined with other filaments to form a multi-filament fiber at any point, during the process of the invention. Preferably, however, the filaments are combined just before, or during, the first wash bath. In addition, when a large number of filaments are spun simultaneously, the filaments can be divided into several groups, by a guide, then the initial washing step, as a means to prepare more than one multi-filament fiber from the same spinner. The tensile strength of the filaments produced by the process of the invention is preferably at least about 600 Ksi, and most preferably at least about 800 Ksi. The modulus of nionsion of the filaments produced by the process of the invention is preferably at least about 20 Msi, most preferably at least about 30 Msi.

EXAMPLES The following examples are presented to illustrate the invention, and should not be interpreted, in any way, as limiting.

* "* * The following methods to measure the physical properties of the filaments and the fibers and the stability of the yarn were used to obtain the data reported in Table I.

Method for Measuring Intrinsic Viscosity The reduced viscosity at 30 ° C was obtained by dissolving the polybenzazole in methanesulfonic acid at various concentrations and then extrapolating the concentration to zero.

Monofilament Denier A sample of fiber was maintained at a temperature of 20 + 2 ° C 20 and at a relative humidity of 65 + _2% for 18 hours, a 90 m portion of the sample was taken, its weight was measured, and the The measured weight was converted to a weight of 9000 m to obtain fiber denier. The denier of the monofilament was calculated from the denier of the fiber group, dividing by the number of monofilaments in 25 the group Method for Determining the Maximum Rotation / Stretch Ratio The fiber strand was taken by a traction roller (group) without put it in contact with a washing fluid, the circumferential speed of said roller was increased by a certain rate of increase, and the maximum ratio of spin / stretch was defined as the ratio of the maximum spinning speed, at which the break occurred of the fiber (Vw) at the speed of the line of expulsion within a hole (Vo) obtained from an amount of ejection of individual hole and the diameter of the hole, or Vw / Vo.

Method for Evaluating Stability of Yarn Spinning was performed at a speed of 200 m / minute, until a statistically significant rate of fiber rupture was obtained, which was then converted to represent the number of ruptures during a period of 8 hours.

Method for Measuring Lint (Filament Rupture) A roll washer washes and dry fibers were unrolled at a speed of 100 m / minute, and the lint was counted by a lint detector, photoelectric tube type, until it was obtained a statistically significant number, which was then converted to a filament breaking speed per 10,000 m.

Method for Measuring Stress Resistance, Stress Modulus, and Elongation at Rupture Averages of tensile strength, tensile modulus, and elongation at break were obtained from measurements at a grip interval of 5 cm, a stretch speed of 100% per minute and n = 30 using a Tensilon ™ machine from Orientech (Inc.) Company, in accordance with Test Method No. JIS L 1013 (1981).

EXAMPLE 1 A portion of 4,6-diamino-1,3-benzene diol dihydrochloride (50.0 g, 0.235 mole) was stirred with 200 g of polyphosphoric acid (with a phosphorus pentoxide content of 83.3% by weight) under a flow of Nitrogen gas at 40 ° C for 12 hours. The temperature of the mixture was raised to 60 ° C, and the hydrochloric acid was removed under a reduced pressure of about 50 mm Hg. Terephthalic acid (39.0 g, 0.236 mole) and phosphorus pentoxide (103 g) were added to the above, and the mixture was polymerized under a flow of nitrogen gas at 60 ° C for 8 hours and at 120 ° C for 9 hours. , at 150 ° C for 15 hours, and at 180 ° C for 24 hours. The polybenzazole polymer solution thus obtained was used as an absorbent material for spinning. The intrinsic viscosity of the polymer was obtained by mixing a sample of the solution with water in a mixer to obtain a washed sample of the polymer particles. The polymer particles were redissolved in methanesulfonic acid, the viscosity was measured at 215 ° C, and the intrinsic viscosity [I] was 30.5 dl / g. The concentration of the polymer of the absorbent material was 14.0% by weight, and the concentration of the solvent, in the case of using phosphorus pentoxide as the polyphosphoric composition, was 86.0% by weight. After kneading the absorbent material using a twin screw extruder, and degassing the absorbent material, it was transferred to the spinning head by means of a gear pump. It was passed through a particle filling layer with a layer width of 50 mm (with a varied ratio of average particle diameter and average appearance) composed of inorganic substances in the spinning head, was passed through a plate of dispersion with a multiple number of holes of a diameter 2 mm punched in a frame shape, and then passed through a lamination layer with a particle penetration rate of above 15 mm of 2.5%, constructed of a metal fiber cloth with a diameter of 10 mm. The absorbent material was spun at a temperature of 160 ° C and an ejection speed of 64.2 g / minute, passing it through a spinner having a hole density of 4.8 holes / cm2, with 284 fine holes of a diameter of 0.20 mm, a hole length of 0.20 m, and an entry angle of 20 degrees, divided into groups by a section width (W) of 8.6"" '' mm, as shown in Figure 1. The number of Orifice holes was preferably at least about 500, preferably at least about 1,000, and most preferably at least about 2,500. The spun filaments were then guided through an extinguishing chamber to provide an air flow through the filaments from at least two directions towards a funnel-shaped coagulation apparatus, circulating 20% of the solution ~ "Aqueous polyphosphoric acid maintained at a temperature of 22 + _2 ° C, installed 35 cm below the surface of the spinning nozzle.In addition, the extraction and washing of phosphoric acid in the fiber strand were carried out by rolling the fiber spun on a roller (group) installed on the lower external part of said extraction bath to change the running direction of the fiber strand, releasing the tension of the yarn by winding the fiber strand on a roller (group), while water was sprayed onto the fiber strand running by a spray apparatus installed near said roller, and then the fiber was passed through a hot air circulation dryer to reduce its water content to less than 2.0% by weight. weight, and then it was wound at a speed of 200 m / minute.The results are shown in Table I.

EXAMPLES 2-11 5 Fibers were prepared using the method described in Example 1, with the following exceptions: For examples 2 and 3, the diameter of the holes in the spinner was 0.20 mm, the hole length was 0.20 mm, the angle of entry to the holes of the spinner was 20 °, and the density of the hole was 3. 4 and 4.0 holes / cm2, respectively, for each example. For examples 4 and 5, the width of the sections divided into groups of spinning holes (W) was changed to 6.5 mm (Example 4), and 9.9 mm (Example 5). In Examples 6-8, the spinners have 2, 6, and 8 groups of spinning holes, respectively. In Examples 9-11, the individual amount of hole ejection was 0.69 g / minute, and the filament of ejected absorbent material was cooled in the air gap area by applying a gas flow at an average flow rate of 0.7. m / second, at a temperature of 55 ° C to 95 ° C. The results are shown in Tables I and II.

TABLE I TABLE II "TO- 0

Claims (2)

1 . - A method for preparing polybenzazole filaments, which comprises: (a) extruding the filaments from a spinner having at least 100 holes, which are arranged to form an annular pattern around the center of the spinner, the center and at least two radial sections of the spinner having no holes, and an average width, which is at least about 3 times the minimum pitch of the holes; and (b) stretching the filaments through an extinguishing chamber, while providing a substantially radial gas flow therethrough through the spinner from at least two different directions.

2. The method of claim 1, wherein the spinner has at least 500 holes. 3 - The method of claim 1, wherein the spinner has at least 1,000 holes. 4 - The method of claim 1, wherein the hole density of the spinner is at least about 4.0 holes / cm 2. 5. The method of claim 1, wherein the hole density of the spinner is at least about 6.0 holes / cm2. 6 - A process for preparing polybenzazole filaments, which comprises: (a) extruding the filaments from a spinner having at least 100 holes, which are arranged to form an annular pattern around the center of the spinner, the center having no holes, and an average width, which is at least about 3 times the minimum pitch of the holes, and (b) stretching the filaments through an extinguishing chamber, while providing a flow of substantially radial gas therethrough through the filaments from at least two different directions 7. The process of claim 6, wherein the spinner has at least 500 holes. Claim 6, wherein the spinner has at least 1,000 holes 9. The method of claim 6, wherein the hole density is at least about 4.0 holes / cm 2. Claim 6, wherein the hole density is at least about 6.0 holes / cm 2. 11. A process for preparing filaments of polybenzazole, which comprises, extruding the filaments from a spinner having at least 100 holes, which are arranged to form an annular pattern around the center of the spinner, the center and at least two radial sections of the spinner having no holes, and an average width, which is at least about 3 times the minimum pitch of the holes.