MXPA99008304A - Procedure to treat with heat filaments of crystalline liquid polymer thermotropic dealto number of deniers, directly on the bob - Google Patents

Abstract

The present invention describes and claims a novel process for the heat treatment of denier high number filaments of a thermotropic liquid crystalline polymer, preferred embodiments include a process for the formation of heat-treated filaments, a few totally polyesters and polyesteramides. aromatics, the method involves: heating a thermotropic liquid crystalline polymer above its melt transition temperature, passing said molten polymer through an extrusion chamber equipped with an extrusion capillary having an aspect ratio greater than 1 and less than about 15 to form a filament, wind the filament on a coil with a low tension a with a stretch ratio of at least 4, and heat treat the filament directly on the coil under suitable temperature and pressure conditions for a sufficient period, the filaments so formed are at least 50 deniers per filament, and exhibits essentially uniform molecular orientation through its cross-section, the heat-treated filaments show remarkably good tensile properties while retaining at least 80 to 90% of the expected properties of conventional number filaments low deniers (5 to 1 0 denier per filament

Description

PROCEDURE TO TREAT HEAT FILAMENTS OF HEAT HIGH-THERMOPROPIC CRYSTALLINE LIQUID POLYMERS NUMBER OF DENIERS. DIRECTLY ON THE COIL BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a process for heat treating filaments of a thermotropic liquid crystalline polymer of high denier number. Specifically, the present invention provides a method for heat treating high denier filaments, made from a variety of fully aromatic thermotropic liquid crystalline polyesteramides and polyesters directly on the coil in which the filaments are wound.

DESCRIPTION OF THE PREVIOUS TECHNIQUE Thermotropic liquid crystalline polymers (LCP) are an important group of polymers, which are usually fully aromatic molecules that contain a variety of heterogeneous atom bonds including ester and / or esteramide bonds. After heating at sufficiently high temperature, the PCLs melt to form a phase of liquid crystalline molten material (often referred to as an "anisotropic phase"), rather than a sotropic molten material phase. Generally, the LCPs consist of linear molecules ("rigid rod") that can be aligned to produce the order of the desired liquid crystalline material. As a result, the LCPs exhibit low melt viscosity and therefore improved performance and process capabilities. Because LCPs are oriented to form linear "rigid rod" molecules, LCPs exhibit extremely high mechanical properties. In this way, it is well known in the art that PCLs can be formed into shaped articles, such as films, rods, tubes, fibers, and various other molded articles. In addition, it is also known in the art that PCLs, particularly in the form of fiber, exhibit exceptionally high mechanical properties after a heat treatment process. However, all methods known in the art describe the formation of only fibers of low number of deniers, for example, of about 10 deniers per filament (dpf), which exhibit high mechanical properties in their heat treated forms and such as they are spun It is an object of the present invention to provide a method for forming LCP filaments of high number of uniformly oriented deniers. A filament with a high number of deniers means a filament of more than 50 dpf.

It is also an object of the present invention to provide a method for forming LCP filaments of high number of deniers of more than 50 dpf, which exhibit improved mechanical, thermal and chemical resistance properties in the heat treated and spinning forms . It is further an object of the present invention to provide a method for forming LCP filaments of high number of deniers, which exhibit properties comparable to those of the LCP filaments of low number of deniers (ie, filaments of less than 10 dpf) in its conditions treated with heat and as they are spun. It is also an object of the present invention to provide LCP filaments of high number of deniers of more than 50 dpf having properties comparable to those of LCP filaments of low number of deniers of less than 10 dpf. Finally, an object of the present invention is to provide an industrially economical and cost effective way to heat treat the high denier filaments of this invention, directly on the coil so as to produce filaments of high denier number. superior mechanical and physical properties. There is great convenience in forming LCP filaments of high number of uniformly oriented deniers, which exhibit improved mechanical, thermal and chemical resistance properties in the heat-treated and as-spun form. For example, such high-denier LCP filaments can replace steel cords in steel belt tires. In addition, since the LCP filaments are of substantially lower density compared to steel cords, it is expected that the LCP filaments exhibit properties much superior in comparison to the properties exhibited by the steel cords. It is also obvious from the prior art that there is a real need for LCP filaments of high denier number that exhibit improved mechanical, thermal and chemical resistance properties.

PREVIOUS TECHNIQUE The following references are described as background of the prior art. The patent of E.U.A. No. 4,183,895 discloses a process for treating polymeric products that form anisotropic melt material. It is claimed that a heat treatment process allowed to obtain fibers having improved mechanical properties, and the tenacity of the fiber was increased by at least 50% and up to at least 10 grams per denier. The patent of E.U.A. No. 4,468,364 discloses a process for extruding thermotropic liquid crystalline polymers (LCP). It is claimed that by extruding a LCP through the orifice of a die having a L / D ratio of less than 2 (preferably 0), and at a stretch rate of less than 4 (preferably 1), filaments can be obtained which show high mechanical properties The patent of E.U.A. No. 4,910,057 discloses a highly elongated element of substantially uniform cross-sectional configuration, which is capable of providing enhanced service as a reinforcement support in an optical fiber cable. The patent of E.U.A. No. 5,246,776 discloses an aramid monofilament and a method for obtaining same. The patent of E.U.A. No. 5,427,165 discloses a reinforcing assembly formed at least in part from continuous monofilaments of liquid crystalline organic polymer (s). The polymers used therein are mainly aramides. Japanese Patent Laid-open No. 4-333616 discloses a method for making filaments from 50 to 2000 dpf from molten liquid crystalline polymers. The mechanical properties of these heat-treated filaments were significantly lower than the properties reported for the filaments with the lowest number of deniers of 5 to 10 dpf. Reference J. Rheology 1992, Vol. 36 (p.1057-1078) reports a study of the rheology and orientation behavior of a thermotropic liquid crystalline polyester using capillary dies with different aspect ratios.

The reference J. Appl. Polym. Sci. 1995, Vol 55 (p.1489-1493) reports the distribution in rod orientation exempted from thermotropic liquid crystalline polyesters. The orientation function increases with the increasing apparent shear rate of 166 to 270 sec "1, but decreases with the apparent apparent shear rate of 566 to 780 sec." All references described herein are incorporated in their entirety in the same as reference.

BRIEF DESCRIPTION OF THE INVENTION It has now been unexpectedly and surprisingly found that filaments of high denier number, heat treated and as spun, of at least 50 denier per filament can be obtained which show essentially uniform molecular orientation through its cross section. In addition, these high denier filaments show remarkably good tensile properties which retain at least 80 to 90% of the expected properties of the filaments of low number of conventional deniers (5 to 10 dpf), which was hitherto unattainable by any of the known references of the prior art, as briefly described above.

Thus, in accordance with this invention, a method is provided for forming a filament of a thermotropic liquid crystalline polymer having the following properties: (i) deniers of at least about 50 deniers per filament; (ii) tenacity of at least about 8 grams per denier; (iii) module of at least about 450 grams per denier; and (iv) elongation of at least about 2%. The process of the present invention is formed of the following steps: (a) heating a thermotropic liquid crystalline polymer at a temperature of at least about 15 ° C above its transition to melting to form a fluid stream of said thermotropic polymer; (b) passing said current through a heated extrusion chamber, wherein said chamber is disposed with a suitable cylindrical orifice to form the filament of said polymer, and wherein said cylindrical orifice has an aspect ratio of length to diameter (L / D) greater than about 1 and less than about 15; and (c) winding said filament at a winding speed of at least about 200 meters per minute and with a draw ratio (D / D) of at least about 4; and with the proviso that when L / D is between 0 and 2, the DD is at least 4 so that the filament of essentially uniform molecular orientation is formed through its cross section, and having a value of deniers. of at least about 50 deniers per filament. In another aspect of the invention, there is also provided a method for forming a heat-treated filament of a thermotropic liquid crystalline polymer having the following properties: (i) deniers of at least about 50 deniers per filament; (I) tenacity of at least about 20 grams per denier; (iii) module of at least about 600 grams per denier; and (iv) elongation of at least about 3%. Thus, in accordance with this aspect of the present invention, the method is comprised of the following steps: (a) heating a thermotropic liquid crystalline polymer at a temperature of about 15 ° C to about 50 ° C above its transition to the melt to form a fluid stream of said polymer; (b) extruding said polymer stream through a heated cylindrical spinner having at least one extrusion capillary to form a filament, wherein said capillary has an aspect ratio of length to diameter (L / D) on the scale from about 1 to about 10; (c) winding said filament at a winding speed of at least about 200 meters per minute and with a stretch ratio of about 5 to about 40, so that a filament of essentially uniform molecular orientation is formed through the cross section, and having a denier value on the scale of about 50 to about 1000 denier per filament; and (d) heat treating said filament under suitable conditions of temperature and pressure for a sufficient period, optionally in the presence of an inert atmosphere, to form the heat treated filament. In yet another aspect of this invention, a filament such as is spun, of a thermotropic liquid crystalline polymer is also provided. In a further aspect of this invention, there is also provided a heat-treated filament of a thermotropic liquid crystalline polymer. In another embodiment of this invention, a method is also provided to heat treat the high denier filaments of this invention directly on the coil on which they were wound while rotating. Other aspects and advantages of the present invention are further described in the following detailed description of the preferred embodiments thereof. Examples of the aromatic-aliphatic polyesters and polyesteramides that can be used to practice the invention, can include those having the following structures: II is lll is IV is V is V I is I saw him DETAILED DESCRIPTION OF THE INVENTION In accordance with this invention, there is provided a process for forming a filament of a thermotropic liquid crystalline polymer having the following properties: (i) deniers of at least about 50 deniers per filament; (ii) tenacity of at least about 8 grams per denier; (iii) module of at least about 450 grams per denier; and (v) elongation of at least about 2%. The process of the present invention is formed of the following steps: (a) heating a thermotropic liquid crystalline polymer at a temperature of at least about 15 ° C above its transition to melting to form a fluid stream of said thermotropic polymer; (b) passing said current through a heated extrusion chamber, wherein said chamber is disposed with a suitable cylindrical orifice to form the filament of said polymer, and wherein said cylindrical orifice has an aspect ratio of length to diameter (L / D) greater than about 1 and less than about 15; and (c) winding said filament at a winding speed of at least about 200 meters per minute and with a draw ratio (D / D) of at least about 4; and with the proviso that when L / D is between 0 and 2, the DD is at least 4 so that the filament of essentially uniform molecular orientation is formed through its cross section, and having a value of deniers. of at least about 50 deniers per filament. As described above, the references of the prior art describe various methods for the manufacture of filaments of thermotropic polymers, including filaments of high number of deniers. A specific example of a method for preparing filaments of high number of deniers is described in the patent of E.U.A. No. 4,468,364, which is incorporated herein by reference in its entirety. In this work, the thermotropic polymers were extruded from jets of greater diameter to low stretches, which automatically gave thicker filaments. The molten material of the polymer was also extruded at low yields, ie at low polymer velocity in the jet, and winding the filaments at low speed. This means that most of the orientation of the filament is obtained from the convergent flow in the jet itself, which explains why the increase in the length of the capillary causes the orientation to decrease, that is, the orientation or filament module. The passage of the polymer through the capillary before leaving the jet will cause disorientation of the flow, which had been induced by the converging part of the jet above the capillary. Unlike the conditions of the prior art process discussed hereinabove, the method of the present invention operates at greater stretches, with the result that the filament undergoes elongation to decrease the diameter thereof once it emerges from the orifice of the filament. jet. This elongation flow locates most of the orientation in the filament, thus providing a filament having essentially uniform cross-sectional orientation. In addition, the present invention also provides a commercially practical process in which the performance of the polymer can be increased. Because the pressure on the jet will increase linearly with the performance, the pressure will reach non-practical levels for small jets. In accordance with the process of the present invention, the preferred polymers are thermotropic liquid crystalline polymers. Thermotropic liquid crystal polymers are polymers that are crystalline and liquid (ie, anisotropic) in the molten material phase. Thermotropic crystalline polymers include fully aromatic polyesters, aromatic-aliphatic polyesters, aromatic polyazomethines, aromatic polyesteramides, aromatic polyamides and aromatic polyester carbonates. The aromatic polyesters are considered to be "fully" aromatic in the sense that each portion present in the polyester contributes at least one aromatic ring to the base structure of the polymer. Specific examples of suitable aromatic-aliphatic polyesters are copolymers of polyethylene terephthalate and hydroxybenzoic acid, as described in Polyester X7G-A Self Reinforced Thermoplastic, by WJ Jackson son, HF Kuhfuss and TF Gray son, 30th Anniversary Technical Conference, 1975 Reinforced Plastics / Composites Institute, The Society of the Plastics Industry, Inc., Section 17-D, p. 1-4. A further description of said copolymer can be found in "Liquid Crystal Polymers: I. Preparation and Properties of p-Hydroxybenzoic Acid Copoiymers", Journal of Polymer Science, Polymer Chemistry Edition, Vol 14, pp. 2043-58 (1976), by W. J. Jackson Jr. and H. F. Kuhfuss. The references cited above are incorporated herein by reference in their entirety. The aromatic polyazomethines and processes for preparing them are described in the U.S. Patents. Nos. 3,493,522; 3,493,524; 3,503,739; 3,516,970; 3,516,971; 3,526,611; 4,048,148 and 4,122,070. Each of these patents is hereby incorporated by reference in its entirety. Specific examples of such polymers include poly (nitrile-2-methyl-1,4-phenylene-nitrimethyl-diene-1,4-phenylenethylidine); poly (nitrile-2-methyl-1,4-phenylene-nitrilomethylidin-1,4-phenylenemethylidine); and poly (nitrile-2-chloro-1,4-phenylene-nitrilomethylidin-1,4-phenylenemethylidine). The aromatic polyesteramides are described in the patents of E.U.A. Nos. 5,204,443, 4,330,457, 4,966,956, 4,355,132, 4,339,375, 4,351, 917 and 4,351, 918. Each of these patents is hereby incorporated by reference in its entirety. Specific examples of such polymers include polymers formed from the monomers comprising 4-hydroxybenzoic acid, 2,6-hydroxynaphthoic acid, terephthalic acid, 4,4'-biphenol and 4-aminophenol; and polymers formed from the monomers comprising 4-hydroxybenzoic acid, 2,6-naphthalenedicarboxylic acid, terephthalic acid, isophthalic acid, hydroquinone and 4-aminophenol. Preferred aromatic polyamides are those that can be processed in the molten state and form thermotropic melt phase, as described above. Specific examples of such polymers include polymers formed from monomers comprising terephthalic acid, soft-gel acid, and 2,2'-bis (4-aminophenol) propane. Aromatic polyester carbonates are described in the U.S.A. No. 4,107,143, which is incorporated herein by reference in its entirety. Examples of such polymers include those consisting essentially of hydroxybenzoic acid units, hydroquinone units, carbonate units and aromatic carboxylic acid units. Preferred liquid crystal polymers for use in the process of the present invention are fully aromatic thermotropic polyesters. Specific examples of said polymers can be found in the patents of E.U.A. Nos. 3,991,013; 3,991, 014; 4,057,597; 4,066,620; 4,075,262; 4,118,372; 4,146,702; 4,153,779; 4,156,070; 4,159,365; 4,169,933; 4,181, 792; and 4,188,476, and UK application No. 2,002,404. Each of these patents is hereby incorporated by reference in its entirety. The fully aromatic polyesters that are preferred for use in the present invention are described in the U.S. Patents. commonly assigned Nos. 4,067,852; 4,083,829; 4,130,545; 4,161, 470; 4,184,996; 4,238,599; 4,238,598; 4,230,817; 4,224,433; 4,219,461; and 4,256,624. The descriptions of all patents and applications of E.U.A. commonly assigned identifiers, are hereby incorporated by reference in their entirety. The fully aromatic polyesters described herein are typically capable of forming an anisotropic melt phase at a temperature of less than about 350 ° C. The fully aromatic polyesters which are suitable for use in the process of the present invention can be formed by various ester formation techniques, whereby organic monomeric compounds having functional groups which after condensation form the required recurring portions are reacted. For example, the functional groups of the organic monomeric compounds can be carboxylic acid groups, hydroxyl groups, ester groups, acyloxy groups, acid halides, etc. The organic monomeric compounds can be reacted in the absence of a heat exchange fluid by a process of acidolysis of molten material. Accordingly, they can be initially heated to form a solution of molten material from the reactants, the reaction continuing as the solid polymer particles are suspended therein. A vacuum can be applied to facilitate the removal of volatile compounds formed during the final stage of condensation (for example, acetic acid or water). In the patent of E.U.A. commonly assigned No. 4,083,829, entitled "Melt Processable Thermotropic Wholly Aromatic Polyester", describes a suspension polymerization process, which can be used to form the fully aromatic polyesters that are preferred for use in the present invention. According to said method, the solid product is suspended in a heat exchange medium. The description of this patent has previously been incorporated herein in its entirety as a reference. When the process of acidolysis of molten material or the suspension procedure of the patent of E.U.A. No. 4,083,829, the organic monomer reagents from which the fully aromatic polyesters are derived can be initially provided in a modified form, whereby the usual hydroxy groups of said monomers are esterified (ie, they are provided as acyl esters) lower). The lower acyl groups preferably have from about two to about four carbon atoms. Preferably, the acetate esters of organic monomer reagents are provided. Representative catalysts which may optionally be used in the process of acidolysis of molten material or in the suspension process of the patent of E.U.A. No. 4,083,829, include dialkyl tin oxide (for example, dibutyl tin oxide), diaryl tin oxide, titanium dioxide, antimony trioxide, alkoxy titanium silicates, titanium alkoxides, alkali metal and alkali metal salts of carboxylic acids (e.g., zinc acetate), gaseous acid catalysts such as Lewis acids (e.g., BF3), hydrogen halides (e.g., HCl), and similar catalysts known to those skilled in the art. The amount of catalyst used is typically from about 0.001 to about 1% by weight based on the total weight of the monomer, and more commonly from about 0.01 to about 0.2% by weight. The fully aromatic polyesters that are preferred for use in the present invention commonly show a weight average molecular weight of from about 10,000 to about 200,000, and preferably about 20,000 to about 50,000 (eg, about 30,000 to about 40,000). Said molecular weight can be determined by commonly used techniques, such as measurements of gel permeation chromatography or solution viscosity. Other methods include the determination of the end group by infrared spectroscopy in compression molded films or spectroscopic measurements of nuclear magnetic resonance (NMR) of polymer solutions or solid phase NMR of powder or polymer films. Alternatively, light scattering techniques in a pentafluorophenol solution can be used to determine molecular weight. The fully aromatic polyesters or polyesteramides additionally commonly exhibit an inherent viscosity (ie, IV) of at least 2.0 dL / g for example, about 2.0 to about 10.0 dL / g, when dissolved in a concentration of 0.1% in Weight in a mixture of 1: 1 hexafluoroisopropanol solvents (HFIPypentafluorophenol (PFP) (v / v) at 25 ° C.

Especially preferred polymers for the process of the present invention are fully aromatic polyesters and polyesteramides. In the preferred embodiments of the present invention, the specifically preferred polyesters are listed below: a) The fully aromatic polyester capable of forming an anisotropic phase in the molten state at a temperature below about 350 ° C consists essentially of recurring portions I and 11 where: I is is The fully aromatic polyester as described above is described in U.S. Patent No. 4,161,470. The polyester consists of about 10 to about 90% by mole of the portion I, and about 10 to about 90% by mole of the portion II. In one embodiment, portion II is present at a concentration of about 65 to about 85 mole%, and preferably at a concentration of about 70 to about 80 mole%; for example, approximately 75% in moles. In another embodiment, portion II is present in a minor proportion of about 15 to about 35 mole%, and preferably at a concentration of about 20 to about 30 mole%. b) The fully aromatic polyester capable of forming an anisotropic phase in the molten state at a temperature below 400 ° C consists essentially of the recurring portions I, II, III, and VII wherein: I is I I is l l l is and Vi l is The polyester comprises from about 40 to about 60 mole% of portion I, from about 2 to about 30% of portion II, and from about 19 to about 29 mole% of each of portions III and VII. In one of the preferred embodiments, the polyester comprises from about 60 to about 70% by mole of the portion I, from about 3 to about 5% by mole of the portion II, and from about 12.5 to about 18.5% by mole of each one of the portions III and VII. Preferred polyesteramides of the process of the present invention are summarized below: a) The fully aromatic polyesteramide capable of forming an anisotropic phase in the molten state at a temperature below 360 ° C consists essentially of the recurring portions II, I and VI where: II is I is and V I is The fully aromatic polyesteramide as described above is described in U.S. Patent No. 4,330,457, which is incorporated herein by reference in its entirety. The polyesteramide consists of about 25 to about 75 mole% of portion II, about 37.5 to about 12.5 mole% of each of portions I and VI. The polyesteramide preferably comprises from about 40 to about 70 mole% of the portion II, and about 15 to about 30 mole% of each of the portions I and VI. In one of the preferred embodiments of the invention, the polyesteramide comprises from about 60 to about 65 mole% of the portion II, and from about 17.5 to about 20 mole% of each of the portions I and VI. b) The fully aromatic polyesteramide capable of forming an anisotropic phase in the molten state at a temperature below about 380 ° C consists essentially of the recurring portions I, II, III, VII and VI where: is is l l l is I saw him V I is The fully aromatic polyesteramide as described above is described in U.S. Patent No. 5,204,443, which is incorporated herein by reference in its entirety. The polyesteramide consists of about 40 to about 70% by mole of the portion I, from about 1 to about 20% by mole of the portion II, from about 14.5 to about 30% by mole of the portion III, from about 7 to about 27.5 mole% of the VII portion, and from about 2.5 to about 7.5 mole% of the VI portion. c) The fully aromatic polyesteramide capable of forming an anisotropic phase in the molten state at a temperature below about 350 ° C consists essentially of the recurring portions 1, 11, III, IV, V, and VI where: is I I is I V is You see and V I is The polyesteramide as described above, consists of about 40 to about 70% by mole of the portion I, from about 10 to about 20% by mole of the portion II, from about 2.5 to about 20% by mole of the portion III, from about 0 to about 3 mol% of the IV portion, from about 12.5 to about 27.5 mol% of the V portion and from about 2.5 to about 7.5 mol% of the VI portion.

In accordance with the process of the present invention, a fluid stream of liquid crystalline polymer is provided to any conventional extrusion apparatus. The foregoing is achieved by heating the thermotropic liquid crystalline polymer of the present invention to form a molten material. Any of the known methods for heating the polymer to form a molten material in this invention can be employed. The particular apparatus used is not critical to the operation of the method of the present invention, and any suitable apparatus can be used herein. One such apparatus which has been found to be suitable for use with liquid thermotropic liquid polymers employs a contact fusion method so that the residence time of fusion can be kept short and constant. The apparatus includes a heated surface against which a molded liquid crystal polymer rod is pressed. The fluid stream of the polymer in the molten state is then introduced into the extrusion chamber within which a filter pack and a cylindrical orifice are arranged. After passing through the filter pack, the molten polymer is extruded through the cylindrical orifice. In a preferred embodiment, the extrusion chamber consists of a single orifice cylindrical chamber in which the polymer is heated to a temperature in the range of about 20 ° C to about 50 ° C above its melting transition point. In this preferred embodiment, the cylindrical orifice having an aspect ratio (L / D) of about 1 to about 10 is employed. As used herein, the aspect ratio is intended to define the length (L) to diameter (D) of the cylindrical hole. In a more preferred embodiment of this invention, the aspect ratio of the cylindrical orifice is in the range of about 1 to about 3. After the liquid stream of the liquid crystal polymer is extruded through the orifice, the polymer forms a elongated shaped article having the polymer molecules oriented substantially parallel to the direction of flow. The orientation of the polymer molecules can be confirmed by determining the orientation angle by X-ray analysis. The extruded articles configured in the form of filaments are then drawn and wound onto a filament spool. In accordance with the method of this invention, it is critical that the proper stretch ratio be utilized to exploit the maximum benefit of the practice of the present invention. Therefore, in a preferred embodiment, the draw ratio of from about 4 to about 20 is used. In a more preferred embodiment, the draw ratio of from about 4 to about 15 is used. The draw ratio (DD) as used in FIG. used herein is defined as the cross-sectional area ratio of the hole (Ai) to the cross-sectional area of the filament (A2). Said relationship is also frequently expressed as the winding speed ratio of the filament (V2) to the extrusion speed of the filament (Vi). In this way the stretch ratio, DD, can be expressed in terms of the following equation: DD = Ai / A2 = V2 / V1 Therefore, in accordance with the method of the present invention, liquid thermotropic liquid crystalline polymer filaments having essentially uniform molecular orientation can be made which exhibit unusually superior mechanical properties. For example, by the proper practice of the method of the present invention it is now possible to obtain a high denier number filament having unreachable properties therein. More specifically, it has now been discovered that filaments having a number of deniers on the scale of about 100 to about 1,000 denier per filament (dpf) can be easily made by the following method of this invention. In a preferred embodiment, filaments having a number of deniers on the scale at about 150 to about 500 dpf can easily be made. In a more preferred embodiment, filaments having a denier number in the range of about 180 to about 300 dpf can be easily made. Denier as used herein is defined as a weight in grams of 9,000 meters of filament. The dpf as used herein is the denier of a single continuous filament. The conditions of temperature and pressure under which the liquid crystal polymer can be extruded are not critical to the process of the present invention and can be readily determined by one skilled in the art. Typically, the thermotropic polymers are extruded at a temperature within the range of about 280 ° C to about 400 ° C and at a pressure of about 7.03 kg / cm2 to about 351.5 kg / cm2. As described hereinabove, liquid crystal polymers have very rigid, rod-like molecules. In the resting state, the polymer molecules are aligned in local regions, thus forming ordered arrays or domains. The existence of the domain texture within the microstructure of a liquid crystal polymer can be conformed by conventional polarized light techniques where a polarization microscope using crosslinked polarizers is used. The mechanical properties of the filaments produced according to the process of the present invention can be further improved by subjecting the articles to heat treatment after extrusion. The articles can be heat treated in an inert atmosphere (eg, nitrogen, argon, helium). For example, as the article can be brought to a temperature of about 10 ° C to about 30 ° C below the melting temperature of the liquid crystal polymer, temperature at which the filament remains as a solid object. The periods of heat treatment commonly vary from a few minutes to a number of days, for example, from 0.5 to 200 hours, or more. Preferably, the heat treatment is conducted for a period of from about 1 to about 48 hours (eg, from about 24 to about 30 hours). The heat treatment improves the properties of the article by increasing the molecular weight of the liquid crystalline polymer and increasing the degree of crystallinity. Therefore, according to one of the preferred embodiments of the present invention, there is also provided a method for forming a heat-treated filament of a thermotropic liquid crystalline polymer having the following properties: (i) denier of at least about 50 deniers per filament; (ii) tenacity of at least about 20 g per denier; (iii) module of at least about 600 g per denier; (iv) elongation of at least about 3%. The process for forming said filament is comprised of the following steps: a) heating a thermotropic liquid crystalline polymer at a temperature from about 15 ° C to about 50 ° C above its melting transition to form a fluid stream of said polymer; b) extruding said polymer stream through a heated cylindrical spinner having at least one extrusion capillary to form a filament, wherein said capillary has an aspect ratio of length to diameter (L / D) on the scale of about 1 to about 10; c) winding said filament at a winding speed of at least about 200 meters per minute and stretching ratio of about 5 to about 40 so as to form a filament of essentially uniform molecular orientation through the cross section and having a denier on the scale of about 50 to about 1000 denier per filament; and d) heat treating said filament at suitable temperature and pressure conditions for a sufficient period, optionally in the presence of an inert atmosphere, to form the heat treated filament. Any of the preferred thermotropic polyesters or polyesteramides described above can be used in this preferred embodiment. In addition, as described herein, the heat treatment can be carried out in stages at a final temperature of about ° C below the melting transition of the thermotropic polymer. In a preferred embodiment of the present invention there is also provided a filament such as is spun from a thermotropic liquid crystalline polymer having the following properties: (a) denier of at least about 50 deniers per filament; (b) tenacity of at least about 8 grams per denier; (c) module of at least about 450 grams per denier; and (d) elongation of at least about 2%. In another preferred embodiment of the present invention, the filament denier as it is spun is on the scale of about 100 to about 1000 dpf. In another more particularly preferred embodiment of the invention, the filament denier as it is spun is on the scale of about 150 to about 500 dpf. In another more particularly preferred embodiment of the present invention, the filament denier as it is spun is on the scale of about 180 to about 300 dpf. In yet another preferred embodiment of the present invention, there is also provided a heat treated filament of a thermotropic liquid crystalline polymer having the following properties: (a) denier of at least about 50 denier per filament; (b) tenacity of at least about 20 grams per denier; (c) module of at least about 600 grams per denier; and (d) elongation of at least about 3%. In a further aspect of the invention there is also provided a method for heat treatment of the high denier filaments produced in accordance with the method of the present invention described above. In this aspect of the invention, the filaments wound on the coil are heat treated directly to obtain the heat treated filaments, thereby offering significant cost savings. Therefore, according to this aspect of the invention, the method is comprised of the following steps: (a) heating a thermotropic liquid crystalline polymer at a temperature of at least about 15 ° C above its melting transition to form a fluid stream of said thermotropic polymer; (b) passing said current through a heated extrusion chamber wherein said chamber is disposed with a suitable cylindrical orifice to form the filament of said polymer, and wherein said cylindrical orifice has an aspect ratio of length to diameter (L / D) greater than about 1 and less than about 15; and (c) winding said filament in a coil at a low tension of at least about 5 grams and winding speed of at least about 200 meters per minute and draw ratio (DD) of at least about 4 so that it forms the filament of essentially uniform molecular orientation through its cross section and having a denier of at least about 50 deniers per filament; and (d) heat treating said filament directly in said coil at suitable temperature and pressure conditions for a sufficient period, optionally in the presence of an inert atmosphere, to form the heat treated filament. Therefore, by practicing said aspect of the present invention, it is currently possible to obtain a heat-treated filament having the following properties: (i) denier of at least about 50 deniers per filament; (ii) tenacity of at least about 20 grams per denier; (iii) module of at least about 600 grams per denier; and (iv) elongation of at least about 3%. Any of the polymers described above can be used in this aspect of the invention. Preferred thermotropic polymers are polyesters and polyesteramides as described above. Surprisingly, it has been found that applying low tension while winding the filament in the coil considerably improves the tensile properties of the filaments after heat treatment. For example, tensions of approximately 5 grams to 30 grams appear to be essential. It is preferred that said tensions of about 10 grams are applied to obtain the maximum benefit of the practice of the present invention. The present invention is further illustrated by the following examples, which are provided for purposes of illustration and not to limit the scope of the present invention.

EXAMPLES (GENERAL) The following abbreviations are used in the examples: HBA = 4-hydroxybenzoic acid HNA = 2,6-hydroxynaphthoic acid TA = terephthalic acid IA = isophthalic acid NDA = 2,6-naphthalenedicarboxylic acid BP = 4,4'-Biphenol HQ = Hydroquinone AA = 1-Acetoxy-4-acetamidobenzene IV = Inherent viscosity dL / g = Deciliters per gram; a unit of measurement of IV% by weight = Percent by weight; generally used to represent the concentration of a solution to measure IV = average grams of polymer in 100 mL of a mixture of solvents.

MV = Viscosity of molten material DSC = Differential Scanning Calorimetry T = Tenacity M = Module E = Elongation gpd = Grams per denier General analytical techniques used for characterization of the polymer: A variety of analytical techniques were used to characterize the polymer used and the filaments formed according to the present invention, which includes the following:] V: the viscosity of the solution of the samples of polymer, IV, was measured at 25 ° C in a concentration of 0.1% by weight of solution in equal parts by volume of pentafluorophenol and hexafluoroisopropanol. MV: The MV of the polymer samples was measured using a model 2052 Kayeness melt rheometer equipped with a Hastalloy barrel and a plunger tip. The radius of the die hole was 0.0381 cm and the length was 2.54 cm. For the purpose of determining the viscosity of molten material, a viscosity versus shear velocity plot was generated by measuring viscosities at shear rates of 56, 166, 944, 2388 and 8333 sec "1, and viscosities were interpolated to 100 and 1000 sec "1.

DSC: the DSC of the polymer samples is carried out in a Perkin Elmer 7700 Thermal Analysis System. In all the tests, the samples, sealed in aluminum trays, were heated or cooled at a speed of 20 ° C / min under a nitrogen atmosphere. The DSC curves obtained from the second heating run were taken for the analysis. Optical microscopy: Samples were prepared for microscopic analysis by thin sectioning using a glass knife microtome. The sections were examined by polarized optical microscopy to observe the morphological behavior at room temperature. Traction properties: The mechanical properties of the monofilament samples were measured in accordance with ASTM D 387.2. All samples were tested at a gauge length of 25.4 cm, 20% strain rate and filament break 10.

EXAMPLE 1 This example demonstrates the general increase in the mechanical properties of a denier high number filament as spun from a fully crystalline liquid crystalline polyester produced in accordance with the present invention; that is, filaments formed by a die that has an aspect ratio (L / D) greater than 2 and a stretch ratio (DD) equal to or greater than 4.

The filaments were formed from a fully liquid crystalline aromatic polyester consisting of HBA units and HNA units. (Vectra ™ A, commercially available from HNA Holdings, Inc., Charlotte, NC). This polymer had a melting temperature of 280 ° C and an inherent viscosity of 6.30 dL / g when measured in a solution with a concentration of 0.1% by weight in equal parts by volume of pentaf Iorofol and hexafluoroisopropanol at 25 ° C. A sample of the polymer was dried overnight at 130 ° C under vacuum. The polymer was melted in an extruder with a diameter of 2.54 cm, and the extruded material was metered using a conventional polymer metering pump into the spin pack where it was filtered through 50/80 chipped metal. The molten material was extruded through a single-hole spinner with various aspect ratios (L / D) as listed in Table 1. Cross-flow cooling was applied to the emerging filament to provide a drop in temperature and a stable spinning environment. The cooling was placed 4 cm below the surface of the spinner, and it was 120 cm long and 15 cm wide. The cooling flow velocity in the highest part was 30 mpm (O.dmps). The monofilament was coated either with water or with a spinning finish before passing around a pulley system that controlled the winding speed. This finally wound up on a Sahm reel winder.

The mechanical properties of the monofilaments produced in accordance with this example 1 were measured according to ASTM D387.2, and the results are listed in table I. For comparison purposes, the monofilaments were also extruded in the manner described above with the except that DD ratios were kept below 4. In a few of these comparative runs, spinners with low aspect ratios (L / D less than 2) were used, as shown in the quad. The mechanical properties of these monofilaments were measured using the same procedures as described above and are also shown in table 1. The data given in table 1 indicate a dramatic improvement in the properties of extruded monofilaments with spinners having aspect ratios (L / D) greater than 1 and DD ratio greater than 4 compared to those monofilaments that were extruded with spinners that have LD aspect ratio less than 2 and DD ratios less than 4. Thus, this example demonstrates the beneficial effects which are achieved by extruding liquid crystal polymer through spinners having L / D greater than 2 at a draw ratio greater than 4 in accordance with the process of the present invention.

TABLE I EXAMPLE 2 The monofilaments produced in accordance with Example I were subjected to heat treatment in stages as follows. The heat treatment of short sections of the monofilament was carried out in racks under a zero voltage in a flow of dry nitrogen using a programmed temperature profile. The programmed temperature profiles of each of the heat treatments of the monofilaments are shown in Table II. The heat treated monofilament was tested to a gauge length of 25.4 cm; 20% deformation rate and filament breakage 10. Following the heat treatment, the mechanical properties of the monofilaments were measured and listed in Table II. The measurements were made using the same tests as in Example I. The data demonstrate the increase in properties, which are obtained by subjecting the monofilaments to heat treatment conditions in stages.

TABLE II EXAMPLE 3 Examples 1 and 2 were repeated in this example 3 with the exception that filaments of high number of Vectra A polymer deniers were formed. Table III shows in summary form the properties as it is sand heat treated of the filaments TABLE III EXAMPLE 4 Examples 1 and 2 were repeated in this example 4 with the exception that thermotropic polyesteramide was used in example 4. The polyesteramide used in this example 4 consists of HNA, TA and AA units (Vectra ™ B, commercially available from HNA Holdings , Inc). Table IV shows in summary the properties as it is sand heat treated of the monofilaments of high number of deniers formed with this polymer.

TABLE IV A few samples of the VECTRA B filament were also heat treated under optimal temperature and time conditions. The results are shown in table V.

TABLE V EXAMPLE 5 Examples 1 and 2 were repeated in this example 5 except that the thermotropic polyesteramide was used. The polyesteramide used in this example consists of units HBA, HNA, TA, BP and AA. (Vectra ™ Ei, commercially available from HNA Holdings, Ing.). Table VI summarizes the properties as it is sand heat treated of the monofilaments of high number of deniers formed with this polymer.

TABLE VI EXAMPLE 6 Examples 1 and 2 were repeated in this example 6 except that the thermotropic polyesteramide was used in this example 6. The polyesteramide used in this example consists of HBA, HNA, TA, BP and AA units. (VECTRA ™ L, commercially available from HNA Holdings, Inc.). Table VII shows in summary form the properties as it is sand heat treated of the high denier monofilaments formed from this polymer.

TABLE VII EXAMPLE 7 This example 7 demonstrates the heat treatment of the filament wound directly on the coil in accordance with one of the preferred embodiments of this invention. To develop the heat treatment capabilities on the coil, a mechanism for heat treatment was constructed using a boat equipped with rubber gaskets. A programmable forced air forced oven with copper tubing running along the lower walls was used to heat the coils after it is placed and sealed in the can. Nitrogen gas was introduced into the copper pipeline between 60 and 100 SCFH, making sure that the nitrogen gas penetrates the heat treatment packaging. The purge gas heated up as it passed through the furnace pipe. The heated nitrogen was passed into the can and flowed from the center of the spool outwards. The nitrogen was then removed from the can and out of the furnace ensuring the removal of the reaction products that might otherwise inhibit the accumulation of property. The coils for heat treatment, 15.2 cm in diameter and approximately 33 cm in width, were constructed with perforated aluminum cylinders. The exterior of the cylinders was coated with fiberfrax, a porous ceramic material, to satisfy the shrinkage of the monofilaments during the heat treatment. For safety reasons (containment of glass particles), the fiberfrax was wrapped with polybenzimidazole (PBI) covers. Based on the empirical findings, a permanent layer of Vectran ™ yarn wrapped on top of the PBI wrapper provided improved heat treated properties. To improve the formation of the package (entanglement) for the processing of the individual filament, aluminum flanges were also added at each end of the coils. For the preparation of the coil, the monofilaments as they are spun were wound onto the heat treatment coils at a low voltage using a Leesona wire feeder at 50 m / minute. After the heat treatment, the fiber was rewound onto the final product spool. For coil heat treatment it was found that it is essential to wind the fiber at low tension to make the high tensile properties. Using a low rewind tension, low speed and fiber lubricant (finishing or water), monofilaments with outstanding mechanical properties were obtained. The standard heat treatment process for the monofilaments formed in accordance with the process of this invention is shown below. The initial residence time at 230 ° C was added to allow the softening point to increase and the ribbon character of the fiber to be removed.

Heat treatment cycle: (1) - Rapid increase to 230 ° C (2) - Residence time to 230 ° C for 2 hours (3) - Increase to 15 ° C / hour to 270 ° C (4) - Residence at 270 ° C for 8 hours (5) - Cooling to 100 ° C before opening the oven. Monofilaments composed of HBA and HNA units, VECTRA ™ A were spun at 3 m / minute and an appropriate stretch to make a 220 denier. For the improvement of physical properties, the filaments were heat treated on the coil to make continuous monofilaments treated with heat. The low tension during the winding and rewinding is very important in the determination of the final properties. For this experiment, it was considered that approximately 10 grams of tension were critical during the winding on the heat treatment coils to adequately achieve the optimum properties at the same time while a clean coil is made that can be heat treated and unwound without any difficulty. Tensions less than 10 grams produced coils in which the fiber exited the coil and was difficult to unwind. The physical properties of the samples rewound with 10 grams of tension at 50 m / m are as follows: Tenacity = 25.89 g / d; Elongation = 3.28% and Module = 660.1 g / d.

EXAMPLE 8 Example 7 was repeated in Example 8 except that the increased rewind tension was used at 20 grams. The physical properties of the monofilaments treated with heat are as follows: Tenacity = 18.03 g / d; Elongation = 2.50% and Module = 650.8 g / d.

EXAMPLE 9 Example 7 was repeated in this example 9 with the exception that two samples of monofilaments as spun were coiled directly (during spinning at 300 m / m) on the heat treatment coils. Yarn line tensions were measured as 10 and 20 grams with the physical properties shown below. Sample No. 1: Sample as it is spun for Leesona @ 300 m / m and 10 grams of tension: Tenacity = 20.3 g / d; Elongation = 2.9%; Module = 663 g / d Sample No. 2: Sample as it is spun for Leesona @ 300 m / m and 20 grams of tension. Tenacity = 15.6 g / d; Elongation = 2.2%; Module = 652 g / d Although this invention has been illustrated by some of the relevant examples, it should not be considered that it is limited by them; if not rather, the invention encompasses the generic area as described hereinabove. Several modifications and modalities can be made without departing from the essence and field of the same.

Claims (26)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for heat treating a filament of a thermotropic liquid crystalline polymer, having the following properties: (i) denier of at least about 50 deniers per filament; (ii) tenacity of at least about 20 grams per denier; (Ii) module of at least about 600 grams per denier; and (iv) elongation of at least about 3%; said method comprises the steps of: (a) heating a thermotropic liquid crystalline polymer at a temperature of at least about 15 ° C above its transition to melting to form a fluid stream of said thermotropic polymer; (b) passing said current through a heated extrusion chamber, wherein said chamber is disposed with a suitable cylindrical orifice to form the filament of said polymer, and characterized in that said cylindrical orifice has an aspect ratio of length to diameter (L / D) greater than 1 and less than approximately 15; and (c) winding said filament on a coil at a low tension of at least 5 grams and a winding speed of at least about 200 meters per minute and with a draw ratio (DD) of at least 4 so that the filament of substantially uniform molecular orientation be formed through its cross section and having a denier value of at least about 50 deniers per filament; and (d) heat treating said filament directly on said coil under conditions of suitable temperature and pressure for a sufficient period, optionally in the presence of an inert atmosphere, to form the heat treated filament.

2. The process according to claim 1, further characterized in that said thermotropic liquid crystalline polymer is selected from the group consisting of fully aromatic polyesters, aromatic-aliphatic polyesters, aromatic polyazomethines, aromatic polyesteramides, aromatic polyamides and aromatic polyester carbonates.

3. The process according to claim 1, further characterized in that said thermotropic liquid crystalline polymer is a fully aromatic polyester.

4. The process according to claim 3, further characterized in that said polyester comprises a fully aromatic polyester processable by melting capable of forming an anisotropic phase in the molten state at a temperature below about 350 ° C, consisting essentially of the recurring portions I and II, where: I is I I is wherein said polyester comprises from about 10 to about 90 mole percent of portion I, and from about 10 to about 90 mole% of portion II.

5. The process according to claim 3, further characterized in that said polyester comprises a fully aromatic polyester processable by melting capable of forming an anisotropic phase in the molten state at a temperature below about 400 ° C, consisting essentially of the recurring portions I, II, III and VII, where: I is I is l l l is I saw him wherein said polyester comprises from about 40 to about 70 mole percent of portion I, from about 1 to about 20 mole percent of portion II, and from about 14.5 to about 30 mole percent of each of the portions III and VII.

6. The process according to claim 1, further characterized in that said thermotropic liquid crystalline polymer is a fully aromatic polyesteramide.

7. The process according to claim 6, further characterized in that said polyesteramide comprises a fully aromatic polyesteramide processable by melting capable of forming an anisotropic phase in the molten state at a temperature below about 360 ° C, consisting essentially of the recurring portions II, I and VI, where: I I is is V I is wherein said polyesteramide comprises from about 40 to about 70 mole percent of portion II, and from about 15 to about 30 mole percent of each of portions I and VI.

8. The process according to claim 6, further characterized in that said polyesteramide comprises a fully aromatic polyesteramide processable by melting capable of forming an anisotropic phase in the molten state at a temperature below about 380 ° C, consisting essentially of the recurring portions I, II, III, VII and VI, where: I is is l l l is I saw him and V I is wherein said polyesteramide comprises from about 40 to about 70 mole percent of the portion I, from about 1 to about 20 mole percent of the portion 11, from about 14.5 to about 30 mole percent of the portion III, from about 7 to about 27.5 mole percent of the VII portion, and from about 2.5 to about 7.5 mole percent of the VI portion.

9. The process according to claim 6, further characterized in that said polyesteramide comprises a fully aromatic polyesteramide processable by melting capable of forming an anisotropic phase in the molten state at a temperature below about 350 ° C, consisting essentially of the recurring portions I, II, III, IV, V and VI, where: is II is lll is IV is 15 V is VI is wherein said polyesteramide comprises from about 40 to about 70 mole percent of the portion I, from about 10 to about 20 mole percent of the portion II, from about 2.5 to about 20 percent by weight. moles of the portion III, from about 0 to about 3 mole percent of the IV portion, from about 12.5 to about 27.5 mole% of the V portion, and from about 2.5 to about 7.5 mole percent of the the VI portion.

10. The process according to claim 1, further characterized in that said thermotropic liquid crystalline polymer is heated to a temperature of about 20 ° C to about 50 ° C above its transition to melting.

11. The method according to claim 1, further characterized in that said aspect ratio (L / D) ranges from approximately 1 to approximately 10.

12. The method according to claim 1, further characterized in that said ratio of aspect (L / D) ranges from about 1 to about 3.

13. The method according to claim 1, further characterized in that said stretch ratio is from about 4 to about 20.

14. The method of compliance with Claim 1, further characterized in that said stretch ratio is from about 4 to about 15.

15. - The method according to claim 1, further characterized in that said filaments is a monofilament.

16. The method according to claim 15, further characterized in that the denier of said filament is from about 100 to about 1000 denier per filament.

17. The method according to claim 15, further characterized in that the denier of said filament is from about 150 to about 500 denier per filament.

18. The method according to claim 15, further characterized in that the denier of said filament is from about 180 to about 300 denier per filament.

19. The product produced by the process according to claim 1.

20. The product produced by the process according to claim 4.

21. The product produced by the process according to claim 5.

22. - The product produced by the process according to claim 7.

23. The product produced by the process according to claim 8.

24.- The product produced by the method according to claim 9.

25. - The product produced by the process according to claim 17. L * 26.- The product produced by the process according to claim 18.