ANISOTROPIC MELT PROCESSABLE POLYESTER COMPRISING RELATIVELY LOW CONCENTRATION OF 6-OXY-2-NAPHTHOYL MOIETY

Abstract: A melt processable polyester capable of forming an anisotropic melt phase below 400°C comprising recurring 6-oxy-2-naphthoyl, 4-oxybenzoyl, symmetrical dioxyaryl and symmetrical dicarboxyaryl moieties wherein the 6-oxy-2-­ naphthoyl moiety is present at a concentration of 3 to 15 mole percent. The polyester can be prepared on a relatively economical basis and has been found to undergo melt extrusion at a sufficiently low temperature to form high quality fibres, films and three-dimensional shaped articles.

Description: ANISOTROPIC MELT PROCESSABLE POLYESTER COMPRISING RELATIVELY LOW CONCENTRATION OF 6-OXY-2-NAPHTHOYL MOIETY This invention relates to a melt processable polyester capable of forming an anisotropic melt. Although many aromatic polyesters are intractable materials aromatic polyesters which are capable of forming an an isotropic melt have been extensively described in the literature and in patents. Representative disclosures of anisotropic melt forming polyesters, poly(ester-amides), or poly(ester carbonates) which may include 6-oxy-2-naphthoyl moiety are present in US Patent Nos 4 161 470; 4 219 461; 4 256 624; 4 279 803; 4 299 756; 4 318 841; 4 318 842; 4 330 457 and 4 337 190; and commonly assigned US Serial Nos. 251 625, filed April 6, 1981; 251 629, filed April 6, 1981; 287 345, filed July 27, 1981 and 319 024, filed November 6, 1981. In US Patent No. 4 219 461 a polyester is disclosed which comprises substantial concentrations of 6-oxy-2naphthoyl and 4-oxybenzoyl moieties and symmetrical dioxyaryl and symmetrical dicarboxyaryl moieties. In US Patent No. 4 299 756 a polyester is disclosed which comprises 6-oxy-2-naphthoyl moiety, 3-phenyl-4oxybenzoyl or 2-phenyl-4-oxybenzoyl moiety, 1,3dioxyphenylene moiety and terephthaloyl moiety. In US Patent No. 4 318 841 a polyester is disclosed which comprises 6-oxy-2-naphthoyl moiety, 4-oxybenzoyl moiety, the non-symmetrical 1,3-dioxyphenylene moiety, and terephthaloyl moiety. The present invention provides a novel melt processable polyester which forms a highly tractable anisotropic melt phase below approximately 4000C in the substantial absence of polymer degradation unlike many polymers which include a relatively high concentration of 4-oxybenzoyl moiety. The polyester can be prepared on a more economical basis than that claimed in US Patent No. 4 219 461 since it includes 6-oxy-2-naphthoyl moiety in a relatively low concentration. According to the present invention there is provided a melt processable polyester capable of forming an anisotropic melt phase at a temperature below approximately 4000C comprising the recurring moieties I, II, III and IV wherein: I is EMI2.1 II is EMI2.2 III is a symmetrical dioxyaryl moiety of the formula: -O-Ar-Owhere Ar is a divalent radical comprising at least one aromatic ring which optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foregoing, and IV is dicarboxyaryl moiety of the formula: : EMI2.3 where Ar' is a divalent radical comprising at least one aromatic ring which optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foregoing, wherein the polyester comprises approximately 3 to 15 mole percent of moiety I, approximately 20 to 70 mole percent of moiety II, approximately 7.5 to 38.5 mole percent of moiety III, and approximately 7.5 to 38.5 mole percent of moiety IV. The melt processable polyester of the present invention comprises at least four recurring moieties which when combined ih the polyester have been found to form an atypical highly tractable anisotropic melt phase at a temperature below approximately 4000C, and preferably below approximately 3700C (e.g. below approximately 3500C in a particularly preferred embodiment). In those instances when the polyester is sufficiently crystalline the polymer melting temperature may be confirmed by the use of a differential scanning calorimeter (i.e. DSC) employing repeat scans at a 200C per minute heat-up rate and observing the peak of the DSC melt transition. In those instances when the polyester is substantially amorphous it exhibits no melting peak which is readily discernible by differential scanning calorimetry. Because of its ability to exhibit anisotropic properties (i.e. liquid crystalline properties) in the melt, the polyester readily can form a product having a highly oriented molecular structure upon melt processing. Preferred polyesters are capable of undergoing melt processing at a temperature in the range of approximately 3200 to 3900C. The usual difficulties incurred when one attempts to melt process many aromatic polyesters by conventional melt processing techniques effectively are eliminated. The first essential unit (i.e. moiety I) of the polyester, of the present invention is a 6-oxy-2-naphthoyl moiety of the structural formula: EMI4.1 Such moiety is free of aromatic ring substitution and is present in a relatively low concentration as discussed hereafter. As will be apparent to those skilled in the art, moiety I can be derived from unsubstituted 6-hydroxy-2naphthoic acid and the derivatives thereof. A convenient laboratory preparation for forming 6-hydroxy-2-naphthoic acid is described in Berichte, Vol. 58, 2835-45 (1925) by K Fries and K Schimmelschmidt which is herein incorporated by reference. Also, US Patent No. 1 593 816 is concerned with a process for synthesizing 6-hydroxy-2-naphthoic acid by reacting carbon dioxide with the potassium salt of beta-naphthol. Moiety I comprises approximately 3 to 15 mole percent of the polyester. In a preferred embodiment moiety I is present in a concentration of approximately 5 to 10 mole percent (e.g. 5 or 10 mole percent). The presence of moiety I in the polyester of the present invention even in such low concentrations has been found to significantly lower the melting or softening temperature of the resulting polyester thereby making possible the use of more conventional melt extrusion equipment and processing conditions than would otherwise be required. For instance, if moiety I were eliminated and the concentrations of the other moieties correspondingly increased, the melting temperature of the resulting polyester commonly would be approximately 300 to 800C higher. Such lowering of the melting temperature in the polyester of the present invention is accomplished in combination with the ability to form a highly tractable anisotropic melt. The relatively low concentration of moiety I makes it possible to obtain a polyester with these attractive properties at minimum cost. The second essential moiety (i.e. moiety II) of the polyester of the present invention is a 4-oxybenozyl moiety of the structural formula: EMI5.1 Such moiety is free of ring substitution and is present in a substantial concentration. For instance, moiety II is present in a concentration of 20 to 70 mole percent. In a preferred embodiment moiety II is present in a concentration of approximately 50 to 65 mole percent (e.g. 50 or 60 mole percent). The third essential moiety (i.e. moiety III) of the polyester of the present invention is a symmetrical dioxyaryl moiety of the formula: -O-Ar-Owhere Ar is a divalent radical comprising at least one aromatic ring. Moiety III is symmetrical in the sense that the divalent bonds which join this moiety to other moieties in the main polymer chain are symmetrically disposed on one or more aromatic rings (e.g. are para to each other or diagonally disposed when present on a naphthalene ring). Moiety III optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foregoing. However in a preferred embodiment moiety III is free of ring substitution and the concomitant expense associated therewith. Preferred moieties which may serve as the symmetrical dioxyaryl moiety in the polyester of the present invention include: EMI6.1 and and mixtures of the foregoing. Particularly preferred symmetrical dixoyaryl moieties are: EMI6.2 which may be derived from hydroquinone and its derivatives, and EMI6.3 which may be derived from p,p'-biphenol and its derivatives. Representative examples of ring substituted compounds from which moiety III may be derived include methyl hydroquinone, chloro-hydroquinone, and bromohydroquinone. Moiety III is present in the polyester of the present invention in a concentration of approximately 7.5 to 38.5 mole percent, and preferably in a concentration of approximately 12.5 to 22.5 mole percent (e.g. 17.5 or 20 mole percent). The fourth essential moiety (i.e. moiety IV) of the polyester of the present invention is a dicarboxyaryl moiety of the formula: EMI7.1 where Ar' is a divalent radical comprising at least one aromatic ring. The Ar' of moiety IV may be: EMI7.2 wherein the divalent bonds are meta and/or para disposed which join this moiety to other moieties in the main polymer chain. Moiety IV optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foreging. However, in a preferred embodiment moiety IV is free of ring substitution and the concomitant expense associated therewith. Preferred moieties which may serve as the dicarboxyaryl moiety in the polyester of the present invention include: EMI8.1 and and mixtures of the foregoing. In a particularly preferred embodiment moiety IV is approximately 40 to 90 mole percent (e.g. approximately 50 mole percent) of isophthaloyl moiety and approximately 10 to 60 mole percent of terephthaloyl moiety (e.g. approximately 50 mole percent). In another particularly preferred embodiment moiety IV is all terephthaloyl moiety and is incorporated in conjunction with a 4,4'dioxybiphenyl moiety of moiety III. In a further particularly preferred embodiment moiety IV is all isophthaloyl moiety and is incorporated in conjunction with 1,4-dioxyphenylene moiety. Moiety IV is present in the polyester of the present invention in a concentration of approximately 7.5 to 38.5 mole percent, and preferably in a concentration of approximately 12.5 to 22.5 mole percent (e.g. 17.5 or 20 mole percent). When isophthaloyl moiety is present as all or as a portion of moiety IV in the polyester of the present invention, it is preferred that the total molar concentration of moiety I plus the molar concentration of isophthaloyl moiety does not substantially exceed approximately 25 mole percent of the polyester. Other ester-forming moieties (e.g. dioxy units, dicarboxy units and/or other combined oxy and carboxy units) than those specified for moieties I, II, III and IV additionally may be included in-the polyester of the present invention in a minor concentration. Representative additional ester-forming moieties may be derived from substituted hydroxynaphthoic acids, mhydroxybenzoic acid, substituted hydroxybenzoic acids, cycloaliphatic dicarboxylic acids, etc. Amide-forming moieties also may be included in the polyester of the present invention in a minor concentration. Representative reactants which may form such amide-forming moieties include m-aminophenol, p-aminophenol, maminobenzoic acid, p-aminobenzoic acid, mphenylenediamine, p-phenylenediamide, etc. The additional ester-forming moieties and/or amide-forming moieties optionally may be included in the polyester of the present invention so long as such moieties do not raise the melting temperature of the resulting polymer above that spcified, or do not otherwise interfere with the exhibition of the desired anisotropic properties in the melt. The total minor concentration of such additional ester-forming and amide-forming moieties if present generally will be less than 10 mole percent of the total polymer. The polyester of the present invention is preferably "wholly aromatic" in the sense that each moiety present contributes at least one aromatic ring to the main polymer chain. The polyester of the present invention commonly exhibits: EMI10.1 or EMI10.2 end groups depending upon the synthesis route selected. As will be apparent to those skilled in the art, the end groups optionally may be capped, e.g. acidic end groups may be capped with a variety of alcohols, and hydroxyl end groups may be capped with a variety of organic acids. For instance, end capping units such as phenylester: EMI10.3 and methylester: EMI10.4 optionally may be included at the end of the polymer chains. The polymer also may be oxidatively cross-linked to at least some degree, if desired, by heating in an oxygen-containing atmosphere (e.g. in air) while in bulk form or as a previously shaped article at a temperature below its melting point for a limited period of time (e.g. for a few minutes). The polyester of the present invention tends to be substantially insoluble in all common polyester solvents, such as hexafluoroisopropanol and o-chloropehnol, and accordingly is not susceptible to solution processing. It can surprisingly be readily processed by common melt processing techniques as discussed hereafter. Most compositions are soluble in pentafluorophenol. The wholly aromatic polyester of the present invention commonly exhibits a weight average molecular weight of about 2000 to 200,000, and preferably about 10,000 to 50,000, e.g. about 20,000 to 25,000. Such molecular weight may be determined by standard techniques not involving the solutioning of the polymer, e.g. by end group determination via infra-red spectroscopy on compression moulded films. Alternatively, light scattering techniques in a pentafluorophenol solution may be employed to determine the molecular weight. The polyester prior to heat treatment additionally commonly exhibits an inherent viscosity (i.e. IV) of at least 0.6, and preferably at least 1.0 (e.g. approximately 2 to 8) when dissolved in a concentration of 0.1 percent by weight in pentafluorophenol at 600C. In some embodiments the polyester of the present invention may be considered crystalline in the sense that fibres melt extruded therefrom exhibit x-ray diffraction patterns using Ni-filtered CuKss radiation and flat plate cameras characteristic of polymeric crystalline materials. In other embodiments the polyester of the present invention is substantially amorphous. The aromatic polyester of the present invention in all instances may be easily melt processed. Unlike the aromatic polyesters commonly encountered in much of the prior art, the polyester of the present invention is not intractable and forms an an isotropic melt phase whereby an atypical degree of order is manifest in the molten polymer. The subject polyester readily forms liquid crystals in the melt phase and accordingly exhibits a high tendency for the polymer chains to orient in the shear direction. Such anisotropic properties are manifest at a temperature which is amenable for melt processing to form shaped articles. Such order in the melt may be confirmed by conventional polarized light techniques whereby crossed polarizers are utilized. More specifically, the an isotropic melt phase may conveniently be confirmed by the use of a Leitz polarizing microscope at a magnification of 40X with the sample on a Leitz hot stage and under a nitrogen atmosphere. The polymer melt is optically anisotropic, i.e. it transmits light when examined between crossed polarizers. The amount of light transmitted increases when the sample is sheared (i.e. is made to flow); however, the sample is optically anisotropic even in the static state. The polyester of the present invention may be formed by a variety of ester-forming techniques whereby organic monomer compounds possessing functional groups which upon condensation form the requisite recurring moieties are reacted. For instance, the functional groups of the organic monomer compounds may be carboxylic acid groups, hydroxyl groups, ester groups, acyloxy groups, acid halides, etc. The organic monomer compounds may be reacted in the absence of a heat exchange fluid via a melt acidolysis procedure. They, accordingly, may be heated initially to form a largely melt solution of the reactants wherein some reactants such as terephthalic acid initially are present to some degree as solids. Low levels of terephthalic acid may dissolve under such circumstances. The polymer sometimes is suspended therein as solid polymer particles. A vacuum may be applied to facilitate removal of volatiles formed during the final stage of the condensation (e.g. acetic acid or water). In US Patent No. 4 067 852 there is described another slurry polymerisation process which may be employed to form the polyester of the present invention wherein the solid product is suspended in a heat exchange medium. The disclosure of this patent is herein incorporated by reference. When employing either the melt acidolysis procedure or the slurry procedure of US Patent No. 4 067 852 the organic monomer reactants from which moieties I, II and III are derived may be initially provided in a modified form whereby the hydroxyl groups of these monomers are esterified (i.e. they are provided as acyl esters). The lower acyl groups preferably have from about 2 to about 4 carbon atoms. Preferably the acetate esters of the organic compounds which form moieties I, II and III are provided. Accordingly, particularly preferred reactants for the condensation reaction are 6-acetoxy-2-naphthoic acid, 4-acetoxybenzoic acid, and hydroquinone diacetate or 4,4'-diacetoxybiphenyl. Representative catalysts which optionally may be employed in either the melt acidolysis procedure or in the procedure of US Patent No. 4 067 852 include dialkyl tin dioxide (e.g. dibutyl tin oxide), diaryl tin oxide, titanium dioxide, alkoxy titanium silicates, titanium alkoxides, alkali and alkaline earth metal salts of carboxylic acids, the gaseous acid catalysts such as Lewis acids (e..g BF3), hydrogen halides (e.g. HC1), etc. The quantity of catalyst utilized typically is about 0.001 to 1 percent by weight based upon the total monomer weight, and most commonly about 0.01 to 0.2 percent by weight. The molecular weight of a previously formed polyester may be further increased via a solid state polymerisation procedure wherein the particulate polymer is heated in an inert atmosphere (e.g. in a nitrogen atmosphere) at a temperature of about 2400C for 10 to 12 hours. The polyester of the present invention readily can be melt processed in the substantial absence of polymer degradation to form a variety of relatively stiff shaped articles, e.g. moulded three-dimensional articles, fibres, films, tapes, etc. The polyester of the present invention is suited for moulding applications and may be moulded via standard injection moulding techniques commonly utilized when forming moulded articles. Unlike the polyesters commonly encountered in the prior art it is not essential that more severe injection moulding conditions (e.g. higher temperatures), compression moulding, impact moulding, or plasma spraying techniques be utilized. Fibres or films may be melt extruded. A moulding compound may be formed from the polyester of the present invention which incorporates approximately 1 to 60 percent by weight of a solid filler (e.g. talc) and/or reinforcing agent (e.g. glass fibres). The polyester of the present invention also may be employed as a coating material which is applied as a powder or from a liquid dispersion. Fibres formed from the polyester of the invention may be used with particular advantage as tire cords and in other industrial applications, such as conveyor belts, hose, cabling, resin reinforcement, etc. Films formed of the polyester of the present invention may be used as strapping tape, cable wrap, magnetic tape, electric motor dielectric film, etc. The fibres and films exhibit an inherent resistance to burning. The following examples are presented as specific illustrations of the claimed invention. EXAMPLE 1 To a 300 ml three-neck round bottom flask equipped with a sealed paddle stirrer, gas inlet tube, and a distillation head connected to a condenser were added the following: (a) 11.51 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 49.54 grams of 4-acetoxybenzoic acid (0.275 mole); (c) 16.99 grams of hydroquinone diacetate (0.0875 mole); (d) 7.27 grams of isophthalic acid (0.04375 mole); (e) 7.27 grams of terephthalic acid (0.04375 mole); (f) 0.0046 gram of potassium acetate catalyst. The flask was thoroughly purged of oxygen by evacuation and refilling with dry argon three times, and was heated in a fluidized sand bath under a slow stream of argon. The contents of the flask were initially heated to 2400C over a period of one hour, from 240C to 3000C over a period of two hours, from 3000 to 3600C over a period of one hour, and were finally evacuated to 0.1 Torr at 3600C for 15 minutes. The vacuum was released with dry argon, and the contents of the flask were allowed to cool. The inherent viscosity (IV) of the polymer was approximately 4.93 as determined in pentafluorophenol solution of 0.1 percent by weight concentration at 600C in accordance with the equation: IV = ln 4 rel) c where c = concentration of solution (0.1 percent by weight), and t rel = relative viscosity. When the polymer was subjected to differential scanning calorimetry (200C/min heating rate), it exhibited a second order glass transition temperature at 1100C and a slight melt endotherm at 3100C, The polymer melt was optically anisotropic. The powdered polymer was dried in a vacuum oven, and while molten and at a temperature of 3600C was extruded through a single hole spinneret (0.127 mm diameter x 0.178 mm) at a throughput rate of 0.44 (gram/minute). The as-spun filament was quenched in ambient air (i.e. at 720F and 65 percent relative humidity) prior to windup at a speed of 1234 metres/minutes. A section of the resulting as-spun polyester fibre had a denier of 4.5 and exhibited the following average single filament properties: Tenacity (grams per denier) 7.2 Initial modulus (grams per denier) 479 Elongation (percent) 1.8 Following thermal treatment in a dry nitrogen flow at 2800C for 15 hours the fibre exhibited the following average single filament properties. Tenacity (grams per denier) 17.1 Initial modulus (grams per denier) 514 Elongation (percent) 3.3 EXAMPLE 2 To a 300 ml three-neck round bottom -flask equipped with a sealed paddle stirrer, gas inlet tube, and a distillation head connected to a condenser were added the following: (-a) 5.8 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 54.0 grams of 4-acetoxybenzoic acid (0.25 mole); (c) 17.3 grams of hydroquinone diacetate (0.089 mole); (d) 14.5 grams of isophthalic acid (0.0875 mole); and (e) 0.02 gram of sodium acetate catalyst. The flask was thoroughly purged of oxygen by evacuation and refilling with dry argon three times, and was heated in a fluidised sand bath under a slow stream of argon. The contents of the flask were initially heated with stirring to 2500C over a period of one hour. The contents of the flask melted to an opaque slurry and agitation began. Acetic acid began to distill over, and after heating to 2500C for 50 minutes, 16 ml of acetic acid had been collected. The contents of the flask were heated to 2800C and were maintained at 2800C for 30 minutes. At the end of such heating a total of 25 ml of acetic acid had been collected. The temperature was next raised to 3200C and was maintained at 3200C for 10 minutes, and was raised to 3400C and maintained at 3400C for 20 minutes. At the end of such heating a total of 28 ml of acetic acid (98 percent of theory) had been collected. Finally the flask was evacuated to a pressure of 0.4 Torr for 10 minutes at 3600 C. The vacuum was released with dry argon, and the contents of the flask were allowed to cool. The inherent viscosity (IV) of the polymer was approximately 2.13 as determined in a pentafluorophenol solution of 0.1 percent by weight concentration at 600C. When the polymer was subjected to differential scanning calorimetry (200C/min heating rate), it exhibited a second order glass transition temperature of 1100C and no observable melt endotherm since it was largely amorphous. The polymer melt was optically anisotropic. The powdered polymer was dried in a vacuum oven, and while molten and at a temperature of 3300C was extruded through a single hole spinneret (0.127 mm diameter x 0.178 mm) at a throughput rate of 0.14 gram/minute. The as-spun filament was quenched in ambient air (i.e. at 720F and 65 percent relative humidity) prior to windup at a speed of 423 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 3.8 and exhibited the following average single filament properties: Tenacity (grams per denier) 6.2 Initial modulus (grams per denier) 423 Elongation (percent) 1.8 Following thermal treatment in a dry nitrogen flow at 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 14.8 Initial modulus (grams per denier) 475 Elongation (percent) 3.0 The physical properties were determined in accordance with the standard ASTM testing procedure D3822. EXAMPLE 3 To a 300 ml three-neck round bottom flask equipped with a sealed paddle stirrer, gas inlet tube, and a distillation head connected to a condenser were added the following: (a) 11.5 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 45.0 grams of 4-acetoxybenzoic acid (0.25 mole); (c) 27.3 grams of 4,4'-diacetoxybiphenyl (0.10 mole); (d) 16.6 grams of terephthalic acid (0.10 mole); and (e) 0.02 gram of sodium acetate catalyst. The flask was thoroughly purged of oxygen by evacuation and refilling with dry argon three times, and was heated in a fluidised sand bath under a slow stream of argon. The contents of the flask were initially heated with stirring to 2400C over a period of 45 minutes, and to 2500C over a period -of 5 minutes, and were maintained at 2500C for 50 minutes. Next the contents were heated from 250 CC to 3400C over a period of 75 minutes and from 3400 to 3800C over a period of 15 minutes. Finally the flask was evacuated to a pressure of 0.95 Torr and 15 minutes at 3800 C. The vacuum was released with dry argon, and the contents of the flask were allowed to cool. The inherent viscosity (IV) of the polymer was approximately 5.53 as determined in a pentafluorophenol solution of 0.1 percent by weight concentration at 600C. When the polymer was subjected to differential scanning calorimetry (200C/minute heating rate), it exhibited a melt endotherm at about 3120C. The polymer melt was optically anisotropic. The powdered polymer was dried in a vacuum oven, and while molten and at a temperature of 3300C was extruded through a single hole spinneret (0.127 mm diameter x 0.178 mm) at a throughput rate of 0.39 gram/minute. The as-spun filament was quenched in ambient air (i.e. at 720F and 65 percent relative humidity) prior to windup at a speed of 800 metres/minutes. A section of the resulting as-spun polyester fibres had a denier of 4.4 and exhibited the following average single filament properties: Tenacity (grams per denier) 7.9 Initial modulus (grams per denier) 605 Elongation (percent) 1.5 Following thermal treatment in a dry nitrogen flow at 2800C for 15hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 22.5 Initial modulus (grams per denier) 758 Elongation (percent) 3.1 The physical properties were determined in accordance with the standard ASTM testing procedure D3822. EXAMPLE 4 To a 300 ml three-neck round bottom flask equipped with a sealed paddle stirrer, gas inlet tube, four inch Vigreaux column with distilling head, condenser and graduated cylinder were added the following: (a) 58.7 grams of 6-acetoxy-2-naphthoic acid (0.025 mole); (b) 55.16 grams of 4-acetoxybenzoic acid (0.306 mole); (c) 24.13 grams of 4,4'-biphenol diacetate (0.088 mole); (d) 14.83 grams of terephthalic acid (0.089 mole); and (e) 0.0025 gram of potassium acetate catalyst. The flask was thoroughly purged of oxygen by evacuation and refilling with dry nitrogen three times, and was heated under a slow stream of nitrogen. The contents of the flask were initially heated with stirring from room temperature to 2300C over a period of 50 minutes during which time the monomers substantially melted. The contents were heated from 2300C to 3600C over a period of 210 minutes, and were heated for 15 minutes at 3600C at which temperature the flask was evacuated to a pressure of 1 Torr. The vacuum was released with dry nitrogen, and the contents of the flask were allowed to cool to room temperature. The inherent viscosity (IV) of the polymer was approximately 7.04 as determined in a 1:1 pentafluorophenol:hexafluoroisopropanol solution of 0.1 percent (W/V) concentration at 250C. Also, the melt viscosity of the resulting polymer was 400 poise at 3700C when measured in a Rheometrics mechanical spectrometer at a shear rate of 10 sex 1. When the polymer was subjected to differential scanning calorimetry (20 C/min. heating rate), it exhibited a melt endotherm peak at 3370 C. The polymer melt was optically anisotropic. The remaining polymer while molten and at a temperature of 3450C was extruded through a single hole spinneret (0.005 inch diameter x 0.007 inch) at a throughput rate of 0.42 gram/minute. The as-spun filament was quenched in ambient air (i.e. at 720F and 65 percent relative humidity) prior to windup at a speed of 800 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 5 and exhibited the following average single filament properties: Tenacity (grams per denier) 8.3 Initial modulus (grams per denier) 606 Elongation (percent) 1.48 Following heat treatment in a flowing dry nitrogen atmosphere (50 SCFH) at 3000C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 25.8 Initial modulus (grams per denier) 952 Elongation (percent) 2.6 EXAMPLES 5 TO 12 Example 4 was substantially repeated with the exceptions indicated. More specifically, the final polymerization temperature was varied (i.e. 3600C, 3700C, or 3800C), the quantity of potassium acetate catalyst was varied (i.e. 0.0025 gram, 0.0100 gram, or 0.0175 gram), and the time while heated at the final polymerization temperature under a pressure of 1 Torr was varied (i.e. 15 minutes, 37.5 minutes, or 60 minutes). The melt extrusion temperature utilized in each instance is as indicated hereafter (i.e. 3600C or 3750C). The polymerization conditions, the peak temperature by differential scanning calorimetry, the inherent viscosity, and the melt viscosity are reported below: EMI22.1 <SEP> Final <SEP> Time <SEP> at <SEP> Final <SEP> Quantity <SEP> Differential <SEP> Inherent <SEP> Melt <tb> <SEP> Polymerization <SEP> Polymerization <SEP> of <SEP> Scanning <SEP> Viscosity <SEP> Viscosity <tb> Example <SEP> Temperature <SEP> Temperature <SEP> Catalyst <SEP> Calorimetry <SEP> as <SEP> as <tb> <SEP> No. <SEP> ( C) <SEP> Under <SEP> 1 <SEP> Torr <SEP> (gram) <SEP> Peak <SEP> Determined <SEP> Determined <tb> <SEP> (minutes) <SEP> Temperature <SEP> in <SEP> Ex. <SEP> 2 <SEP> in <SEP> Ex.2 <tb> <SEP> ( C) <SEP> (poise) <tb> <SEP> 5 <SEP> 380 <SEP> 15 <SEP> 0.0025 <SEP> 335 <SEP> 10.3 <SEP> 700 <tb> <SEP> 6 <SEP> 360 <SEP> 15 <SEP> 0.0175 <SEP> 340 <SEP> 7.6 <SEP> 700 <tb> <SEP> 7 <SEP> 380 <SEP> 15 <SEP> 0.0175 <SEP> 342 <SEP> 11.4 <SEP> 18.000 <tb> <SEP> 8 <SEP> 360 <SEP> 60 <SEP> 0.0025 <SEP> 342 <SEP> 9.1 <SEP> 2.000 <tb> <SEP> 9 <SEP> 380 <SEP> 60 <SEP> 0.0025 <SEP> 347 <SEP> 16.0 <SEP> 130.000 <tb> <SEP> 10 <SEP> 360 <SEP> 60 <SEP> 0.0175 <SEP> 353 <SEP> 12.9 <SEP> 20.000 <tb> <SEP> 11 <SEP> 380 <SEP> 60 <SEP> 0.0175 <SEP> 346 <SEP> 13.5 <SEP> 100.000 <tb> <SEP> 12 <SEP> 370 <SEP> 37.5 <SEP> 0.0100 <SEP> 341 <SEP> 8.5 <SEP> 1.200 <tb> The melt extrusion temperatures, and the average single filament properties before and after heat treatment are reported below: : EMI24.1 As <SEP> Spun <SEP> Properties <tb> Example <SEP> Melt <SEP> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> No. <SEP> Extrusion <SEP> (grams <SEP> Modulus <SEP> (percent) <tb> <SEP> Temperature <SEP> per <SEP> (grams <tb> <SEP> ( C) <SEP> denier) <SEP> per <tb> <SEP> denier) <tb> <SEP> 5 <SEP> 375 <SEP> 7.8 <SEP> 570 <SEP> 1.5 <tb> <SEP> 6 <SEP> 360 <SEP> 8.4 <SEP> 650 <SEP> 1.4 <tb> <SEP> 7 <SEP> 375 <SEP> 4.7 <SEP> 480 <SEP> 1.1 <tb> <SEP> 8 <SEP> 360 <SEP> 6.5 <SEP> 552 <SEP> 1.2 <tb> <SEP> 9 <SEP> not <SEP> spun <SEP> - <SEP> - <SEP> <SEP> 10 <SEP> 375 <SEP> 4.9 <SEP> 453 <SEP> 1.1 <tb> <SEP> 11 <SEP> 375 <SEP> 1.5 <SEP> 339 <SEP> 0.5 <tb> <SEP> 12 <SEP> 360 <SEP> 8.3 <SEP> 608 <SEP> 1.5 <tb> EMI24.2 Heat <SEP> Treated <SEP> Properties <tb> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> (grams <SEP> Modulus <SEP> (percent) <tb> <SEP> per <SEP> (grams <tb> <SEP> denier <SEP> per <tb> <SEP> denier <tb> <SEP> 22.4 <SEP> 968 <SEP> 2.36 <tb> <SEP> 23.9 <SEP> 1.047 <SEP> 2.33 <tb> <SEP> 6.0 <SEP> 585 <SEP> 1.0 <tb> <SEP> 13.9 <SEP> 907 <SEP> 1.54 <tb> <SEP> - <SEP> - <SEP> <SEP> 8.7 <SEP> 724 <SEP> 1.2 <tb> <SEP> 1.7 <SEP> 429 <SEP> 0.4 <tb> <SEP> 23.9 <SEP> 986 <SEP> 2.46 <tb> The polymer of Example 9 could not be spun at a temperature below 3900C and possessed an excessively high melt viscosity at 3700C. The polymer of Example 11 also possessed an excessively high melt viscosity. The products of Examples 6 and 12 were considered to be superior and yielded heat treated fibre tenacities in excess of 20 grams per denier and heat treated fibre intial modulus values approximating 1,000 grams per denier. EXAMPLES 13 TO 18 Example 4 was substantially repeated with the exceptions indicated. More specifically, the concentration of 6-oxy-2-naphthoyl moiety in the resulting polymer was maintained constant at 5 mole percent, and the concentrations of the other three essential moieties were varied as indicated. Also the pressure employed during final polymerization step was either 1 Torr or 100 Torr as indicated while conducting the final polymerization step at 3700C for 37.5 minutes. The inherent viscosity of the products in each instance and peak temperatures by differential scanning calorimetry are reported below: EMI26.1 <SEP> Percent <SEP> of <SEP> Moieties <SEP> in <SEP> Product <SEP> Pressure <SEP> Inherent <SEP> Differential <tb> Example <SEP> 6-oxy-2- <SEP> 4-oxy- <SEP> 4,4#-dioxy- <SEP> tere- <SEP> at <SEP> Final <SEP> Viscosity <SEP> Scanning <tb> <SEP> No. <SEP> naphthoyl <SEP> benzoyl <SEP> biphenyl <SEP> phthaloyl <SEP> Polymer- <SEP> as <SEP> Calorimetry <tb> <SEP> ization <SEP> Determined <SEP> Peak <tb> <SEP> Temperature <SEP> in <SEP> Ex. <SEP> 2 <SEP> Temperature <tb> <SEP> (Torr) <SEP> ( C) <tb> <SEP> 13 <SEP> 5 <SEP> 45 <SEP> 25 <SEP> 25 <SEP> 1 <SEP> 8.6 <SEP> 370 <tb> <SEP> 14 <SEP> 5 <SEP> 50 <SEP> 22.5 <SEP> 22.5 <SEP> 1 <SEP> 4.6 <SEP> 345 <tb> <SEP> 15 <SEP> 5 <SEP> 55 <SEP> 20 <SEP> 20 <SEP> 100 <SEP> 5.8 <SEP> 346 <tb> <SEP> 16 <SEP> 5 <SEP> 60 <SEP> 17.5 <SEP> 17.5 <SEP> 100 <SEP> 6.21 <SEP> 339 <tb> <SEP> 17 <SEP> 5 <SEP> 65 <SEP> 15 <SEP> 15 <SEP> 100 <SEP> 8.1 <SEP> 337 <tb> <SEP> 18 <SEP> 5 <SEP> 70 <SEP> 12.5 <SEP> 12.5 <SEP> 100 <SEP> 8.1 <SEP> 339 <tb> The melt extrusion temperatures, and the average single filament properties before and after heat treatment are reported below: : EMI28.1 <SEP> As-Spun <SEP> Properties <tb> Example <SEP> Melt <SEP> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> No. <SEP> Extrusion <SEP> (grams <SEP> Modulus <SEP> (percent <tb> <SEP> Temperature <SEP> per <SEP> (grams <tb> <SEP> ( C) <SEP> denier) <SEP> per <tb> <SEP> denier) <tb> <SEP> 13 <SEP> 375 <SEP> 4.9 <SEP> 550 <SEP> 1.0 <tb> <SEP> 14 <SEP> 360 <SEP> 5.3 <SEP> 615 <SEP> 1.0 <tb> <SEP> 15 <SEP> 345 <SEP> 7.2 <SEP> 597 <SEP> 1.33 <tb> <SEP> 16 <SEP> 345 <SEP> 8.1 <SEP> 638 <SEP> 1.41 <tb> <SEP> 17 <SEP> 360 <SEP> 8.4 <SEP> 621 <SEP> 1.54 <tb> <SEP> 18 <SEP> 375 <SEP> 6.8 <SEP> 592 <SEP> 1.30 <tb> EMI28.2 <SEP> Head <SEP> Treated <SEP> Properties <tb> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> (grams <SEP> Modulus <SEP> (percent) <tb> <SEP> per <SEP> (grams <tb> <SEP> denier <SEP> per <tb> <SEP> denier) <tb> <SEP> 8.5 <SEP> 740 <SEP> 1.07 <tb> <SEP> 18.2 <SEP> 855 <SEP> 2.0 <tb> <SEP> 27.2 <SEP> 1.079 <SEP> 2.57 <tb> <SEP> 27.1 <SEP> 1.059 <SEP> 2.67 <tb> <SEP> 24.8 <SEP> 1.077 <SEP> 2.38 <tb> <SEP> 15.0 <SEP> 886 <SEP> 1.63 <tb> EXAMPLE 19 To a 5 gallon 316 stainless steel autoclave equipped with a sealed stirrer, gas inlet tube, and distillation head connected to a condenser were added the following: (a) 898 grams of 6-acetoxy-2-naphthoic acid (3.9 moles); (b) 8,270 grams of 4-acetoxybenzoic acid (45.9 mole); (c) 3,620 grams of 4,4'-biphenol diacetate (13.3 mole); (d) 2,225 grams of terephthalic acid (13.4 mole); and (e) 1.5 gram of potassium acetate catalyst. The autoclave was thoroughly purged of oxygen by evacuation and refilling with nitrogen three times. Thereafter a nitrogen flow of 4 SCFH was passed through the autoclave. The hot oil jacket in the autoclave was raised to 2600 C. When the contents of the autoclave reached 2000C, the temperature of the hot oil jacket was raised to 2900C and held at that temperature for 1 hour, raised to 3200C and held at that temperature for one-half hour, and then raised to 3700C for the remainder of the polymerization. When the polymerization melt reached approximately 3600C, the nitrogen purge was terminated, and a 100 Torr pressure was placed upon the reactor until a reactor torque comparable to 1,750 poise (Instron rheometer, 10 sex 1, 3700C, 4 inch x 0.03 inch die) was obtained. The autoclave next was pressurized to 30 psi with nitrogen, and a polymer strand was extruded into water, and was pelletized. The polymer pellets were dried at 1300C for 16 hours. While using an Arburg Model 221E/150 injection moulding machine with an 18 mm barrel, tensile and flexural test specimens were moulded at 3400C. The tensile bars had a cross-section of 1/16 inch x 1/8 inch, and the flexural bars had a cross-section of 1/8 inch x 1/2 inch. Flexural testing was conducted at room temperature on an Instron Testing Unit according to ASTM D790. Tensile testing was conducted using Type V tensile bars according to ASTM D638. Izod impact was determined using ASTM S256. Heat deflection testing was determined using flexural bars set on edge according to ASTM D648. Tensile Properties Modulus: 1,590,000 psi Strength: 27,200 poise Elongation: 2.6 percent Flexural Properties Modulus: 1,200,000 psi Strength: 17,600 psi Izod Impact 5.3 ft lb/in Heat Deflection Temperature 4330F at 264 psi. EXAMPLE 20 The polymer preparation portion of Example 19 was substantially repeated with the exceptions indicated. After the initial nitrogen purging, 150 grams of acetic anhydride were added through a liquid additions port to the autoclave. Also, the polymerization was terminated when a reactor torque comparable to 1,000 poise (Instron rheometer, 10 sex 1, 3700C, 4 inch x 0.03 inch die) was obtained. The polymer exhibited an inherent viscosity of 8.65 as determined in Example 2. The polymer was melt extruded through a 31 hole spinneret while at a temperature of 3520 C. The holes of the spinneret measured 0.005 inch x 0.007 inch. The polymer throughput was 0.85 gram/hole/minute, and the resulting yarn was taken up at a rate of 1,530 metres per minute. The resulting as-spun fibres exhibited the following average single filament properties: Tenacity (grams per denier) 7.8 Initial modulus (grams per denier) 600 Elongation (percent) 1.4 Following thermal treatment in a dry nitrogen flow at 3000C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 24.7 Initial modulus (grams per denier) 965 Elongation (percent) 2.4 EXAMPLES 21 AND 22 Example 4 was substantially repeated with the exception that the relative quantities of the reactants were varied with the 6-oxy-2-naphthoyl moiety being provided a molar concentration of 3 percent and the concentration of potassium acetate used was 100 ppm. The relative molar concentrations of the moieties, and the inherent viscosities, and differential scanning calorimetry peak temperatures of the product are reported below: EMI32.1 <SEP> Molar <SEP> percent <SEP> of <SEP> Moieties <SEP> in <SEP> Product <SEP> Inherent <SEP> Differential <tb> Example <SEP> 6-oxy-2- <SEP> 4-oxy- <SEP> 4.4'-dioxy- <SEP> tere- <SEP> Viscosity <SEP> Scanning <tb> <SEP> No. <SEP> naphthoyl <SEP> benzoyl <SEP> biphenyl <SEP> phthaloyl <SEP> as <SEP> Calorimetry <tb> <SEP> Determined <SEP> Peak <tb> <SEP> in <SEP> Ex. <SEP> 2 <SEP> Temperature <tb> <SEP> ( C) <tb> <SEP> 24 <SEP> 3 <SEP> 62 <SEP> 17.5 <SEP> 17.5 <SEP> 7.62 <SEP> 354 <tb> <SEP> 25 <SEP> 3 <SEP> 57 <SEP> 20 <SEP> 20 <SEP> 8.25 <SEP> 371 <tb> The melt extrusion temperatures and the average single filament properties before and after heat treatment are reported hereafter. The as-spun denier of the fibre in each instance was 5. The heat treatment values which are reported in the table which follows were obtained by heating the as-spun fibres in a nitrogen atmosphere at 3000C for 8 hours. EMI34.1 <SEP> As-Spun <SEP> Properties <tb> Example <SEP> Melt <SEP> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> No. <SEP> Extrusion <SEP> (grams <SEP> Modulus <SEP> (percent) <tb> <SEP> Temperature <SEP> per <SEP> (grams <tb> <SEP> ( C) <SEP> denier) <SEP> per <tb> <SEP> denier) <tb> <SEP> 24 <SEP> 360 <SEP> 7.3 <SEP> 584 <SEP> 1.35 <tb> <SEP> 25 <SEP> 375 <SEP> 8.1 <SEP> 625 <SEP> 1.43 <tb> EMI34.2 <SEP> Heat <SEP> Treated <SEP> Properties <tb> Tenacity <SEP> Initial <SEP> Elongation <tb> <SEP> (grams <SEP> Modulus <SEP> (percent) <tb> <SEP> per <SEP> (grams <tb> <SEP> denier) <SEP> per <tb> <SEP> denier) <tb> <SEP> 24.7 <SEP> 1.006 <SEP> 2.35 <tb> <SEP> 24.3 <SEP> 1.028 <SEP> 2.30 <tb> EXAMPLE 23 To a 300 ml three-neck round bottom flask equipped with a sealed paddle stirrer, gas inlet tube, and a distillation heat connected to a condenser were added the following: (a) 6.9 grams of 6-acetoxy-2-naphtholic acid (0.03 mole); (b) 54.1 grams of 4-acetoxybenzoic acid (0.30 mole); (c) 16.5 grams of hydroquinone diacetate (0.085 mole); (d) 7.1 grams of isophthalic acid (0.0425 mole); (e) 7.1 grams of terephthalic acid (0.0425 mole); and (f) 0.005 gram of potassium acetate catalyst. The reaction flask was thoroughly purged three times with nitrogen. The contents of the flask were initially heated to 2400C from 240C to 3000C over a period of two hours, and from 3000 to 3600C over a period of one hour while being purged with nitrogen at a flow rate of 25 ml per minute. When a temperature of 3600C was reached, the flask was evacuated to 0.55 Torr for 15 minutes. The vacuum was released with nitrogen, and the contents of the flask were allowed to cool. The inherent viscosity (IV) of the polymer was approximately 2.61 as determined in a 1:1 pentafluorophenol:hexafluoroisopropanol solution of 0.1 percent (W/V) concentration at 250C when utilizing a Schott automatic viscometer. When the polymer was subjected to differential scanning calorimetry (200C/min heating rate), it exhibited endotherm peaks at 3350C and 3720 C. The polymer melt was optically anisotropic. The remaining polymer was dried at 1300C for two days and while molten and at a temperature of 3900C was extruded through a single hole spinneret (0.005 inch diameter x 0.007 inch) at a throughput rate of 0.42 gram/ minute. The as-spun filament was quenched in ambient air (i.e. at 720F and 65 percent relative humidity) prior to windup at a speed of 1500 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 2.9 and exhibited the following average single filament properties: Tenacity (grams per denier) 6.0 Initial modulus (grams per denier) 590 Elongation (percent) 1.2 Following heat treatment in a nitrogen atmosphere having a flow rate of 2 litres/minute at 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 16.4 Initial modulus (grams per denier) 680 Elongation (percent) 2.54 EXAMPLE 24 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 13.8 grams of 6-acetoxy-2-naphthoic acid (0.06 mole); (b) 99.1 grams of 4-acetoxybenzoic acid (0.55 mole); (c) 37.9 grams of hydroquinone diacetate (0.195 mole); (d) 24.3 grams of isophthalic acid (0.14625 mole); (e) 8.1 grams of terephthalic acid (0.04875 mole); and (f) 0.023 gram of 4-dimethylaminopyridine catalyst. The resulting polymer exhibited an inherent viscosity of 2.15, and a glass transition temperature at 1000C. Monofilaments were spun while the molten polymer was at a temperature of 3450C while employing a windup speed of 1159 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 3.3 and exhibited the following average single filament properties: Tenacity (grams per denier) 6.8 Initial modulus (grams per denier) 470 Elongation (percent) 1.8 Following heat-treatment in the nitrogen atmosphere at 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 17.9 Initial modulus (grams per denier) 484 Elongation (percent) 3.84 EXAMPLE 25 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 13.9 grams of 6-acetoxy-2-naphthoic acid (0.06 mole); (b) 81.1 grams of 4-acetoxybenzoic acid (0.45 mole); (c) 47.6 grams of hydroquinone diacetate (0.245 mole); (d) 20.4 grams of isophthalic acid (0.1225 mole); (e) 20.4 grams of terephthalic acid (0.1225 mole); and (f) 0.009 gram of potassium acetate catalyst, and (g) 0.009 gram of titanium potassium oxalate catalyst. The resulting polymer exhibited an inherent viscosity of 2.49, and a differential scanning calorimetry melt endotherm peak at 3280C. Monofilaments were spun while the molten polymer was at a temperature of 3600C while employing a windup speed of 1799 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 2.3 and exhibited the following average single filament properties: Tenacity (grams per denier) 6.1 Initial modulus (grams per denier) 480 Elongation (percent) 1.4 Following heat-treatment in the nitrogen atmosphere 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 18.8 Initial modulus (grams per denier) 575 Elongation (percent) 3.58 EXAMPLE 26 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 11.5 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 108.1 grams of 4-acetoxybenzoic acid (0.60 mole); (c) 34.0 grams of hydroquinone diacetate (0.175 mole); (d) 14.5 grams of isophthalic acid (0.0875 mole); (e) 14.5 grams of terephthalic acid (0.0875 mole); and (f) 0.009 gram of potassium acetate catalyst. The resulting polymer exhibited an inherent viscosity of 2.35, and differential scanning calorimetry melt endotherm peaks at 3350C and 3850 C. Monofilaments were spun while the molten polymer was at a temperature of 3900C while employing a windup speed of 1074 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 3.5 and exhibited the following average single filament properties: Tenacity (grams per denier) 3.5 Initial modulus (grams per denier) 513 Elongation (percent) 0.75 Following heat-treatment in the nitrogen atmosphere at 2900C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 13.4 Initial modulus (grams per denier) 661 Elongation (percent) 2.02 EXAMPLE 27 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 11.5 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 81.1 grams of 4-acetoxybenzoic acid (0.45 mole); (c) 48.6 grams of hydroquinone diacetate (0.25 mole); (d) 20.8 grams of isophthalic acid (0.125 mole); (e) 20.8 grams of terephthalic acid (0.125 mole); and (f) 0.009 gram of potassium acetate catalyst. The resulting polymer exhibited an inherent viscosity of 3.47, and differential scanning calorimetry melt endotherm peaks at 3350C and 3750 C. Monofilaments were spun while the molten polymer was at a temperature of 3750C while employing a windup speed of 919 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 4.6 and exhibited the following average single filament properties: Tenacity (grams per denier) 5.8 Initial modulus (grams per denier) 500 Elongation (percent) 1.35 Following heat-treatment in the nitrogen atmosphere at 2800C for 15 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 14.7 Initial modulus (grams per denier) 694 Elongation (percent) 2.25 EXAMPLE 28 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 11.5 grams of 6-acetoxy-2-naphthoic acid (0.05 mole); (b) 72.1 grams of 4-acetoxybenzoic acid (0.40 mole); (c) 53.4 grams of hydroquinone diacetate (0.275 mole); (d) 34.2 grams of isophthalic acid (0.20625 mole); (e) 11.4 grams of terephthalic acid (0.06875 mole); and (f) 0.023 gram of 4-dimethylaminopyridine catalyst. The resulting polymer exhibited an inherent viscosity 1.6, and a differential scanning calorimetry melt endotherm peak at 2650C. Monofilaments were spun while the molten polymer was at a temperature of 3150C while employing a windup speed of 2658 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 1.6 and exhibited the following average single filament properties: Tenacity (grams per denier) 5.1 Initial modulus (grams per denier) 350 Elongation (percent) 2.1 Following heat-treatment in the nitrogen atmosphere at 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 14.9 Initial modulus (grams per denier) 357 Elongation (percent) 4.29 EXAMPLE 29 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 4.6 grams of 6-acetoxy-2-naphthoic acid (0.02 mole); (b) 36.1 grams of 4-acetoxybenzoic acid (0.20 mole); (c) 11.7 grams of hydroquinone diacetate (0.14 mole); (d) 11.6 grams of isophthalic acid (0.07 mole); (e) 11.6 grams of terephthalic acid (0.07 mole); and (f) 0.005 gram of potassium acetate catalyst. The resulting polymer exhibited an inherent viscosity of 1.98, and differential scanning calorimetry endotherm peaks at 3320C and 3500C. Monofilaments were spun while the molten polymer was at a temperature of 3900C while employing a windup speed of 810 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 4.0 and exhibited the following average single filament properties: Tenacity (grams per denier) 4.6 Initial modulus (grams per denier) 500 Elongation (percent) 1.1 EXAMPLE 30 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 4.6 grams of 6-acetoxy-2-naphthoic acid (0.02 mole); (b) 27.1 grams of 4-acetoxybenzoic acid (0.15 mole); (c) 32.1 grams of hydroquinone diacetate (0.165 mole); (d) 13.8 grams of isophthalic acid (0.082 mole); (e) 13.8 grams of terephthalic acid (0.082 mole); and (f) 0.005 gram of potassium acetate catalyst. The resulting polymer exhibited an inherent viscosity of 1.63, and a differential scanning calorimetry glass transition temperature at 1000C and a melt endotherm peak at 3720C. Monofilaments were spun while the molten polymer was at a temperature of 3600C while employing a windup speed of 2000 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 1.75 and exhibited the following average single filament properties: Tenacity (grams per denier) 4.4 Initial modulus (grams per denier) 460 Elongation (percent) 1.1 EXAMPLE 31 Example 23 was substantially repeated with the exceptions indicated. The following chemicals were added to the flask: (a) 4.6 grams of 6-acetoxy-2-naphthoic acid (0.02 mole); (b) 27.1 grams of 4-acetoxybenzoic acid (0.15 mole); (c) 32.1 grams of hydroquinone diacetate (0.165 mole); (d) 20.7 grams of isophthalic acid (0.1245 mole); (e) 6.9 grams of terephthalic acid (0.0415 mole); and (f) 0.005 gram of potassium acetate catalyst. The resulting polymer exhibited an inherent viscosity of 1.74, and a differential scanning calorimetry endotherm peak at 3070C. Monofilaments were spun while the molten polymer was at a temperature of 3750C while employing a windup speed of 1234 metres/minute. A section of the resulting as-spun polyester fibre had a denier of 3.4 and exhibited the following average single filament properties: Tenacity (grams per denier) 5.4 Initial modulus (grams per denier) 306 Elongation (percent) 2.2 Following heat-treatment in the nitrogen atmosphere at 2700C for 8 hours the fibre exhibited the following average single filament properties: Tenacity (grams per denier) 12.7 Initial modulus (grams per denier) 370 Elongation (percent) 3.17 EXAMPLE 32 To a 2 litre flask equipped with a 316 stainless steel stirrer, gas inlet tube, and an 11 inch Vigreaux column with distillation head and receiver were added the following: : (a) 124.3 grams of 6-acetoxy-2-naphthoic acid (0.54 mole); (b) 583.8 grams of 4-acetoxybenzoic acid (3.24 mole); (c) 173 grams of hydroquinone diacetate (0.89 mole), or 10 percent excess; (d) 67.3 grams of isophthalic acid (0.40 mole); (e) 67.3 grams of terephthalic acid (0.40 mole); and (f) 0.02 gram of potassium acetate catalyst. The flask was thoroughly purged of oxygen with nitrogen, and a slow purge of nitrogen of approximately 25 ml/minute was applied to the flask. The contents of the flask were initially heated to 2400C from 2400 to 3000C over a period of two hours, and from 3000 to 3600C over a period of one hour. The temperature was first maintained at 3600C for one-half hour, and then for another one-quarter hour at 3600C while under 1 Torr. The vacuum was released, the product was allowed to cool, and was ground in a Wiley mill. The resulting polymer exhibited an inherent viscosity of 5.61 as determined in Example 2, and a differential scanning calorimetry endotherm peak at 3230C. The polymer next was dried for 16 hours at 1300C and tensile and flexural test specimens were moulded at 3400C in an Arburg Model 221E/150 injection moulding machine having an 18 mm barrel. Standard tensile bars having a cross-section of 1/16 inch x 1/8 inch were produced, and standard flexural bars having a cross-section of 1/8 inch x 1/2 inch were produced. Tensile testing was conducted at room temperature using Type V tensile bars and an Instron testing unit according to ASTM D638. Flexural testing was conducted at room temperature according to ASTM D790. Izod impact testing was conducted according to ASTM D256. The following values were obtained: Tensile Properties Modulus: 2,600,000 psi Strength: 25,000 psi Elongation: 1.3 percent Flexural Modulus Modulus: 1,500,000 psi Strength: 22,300 psi Izod Impact 3.3 ft lb/in. Although the invention has been described with preferred embodiments it is to be understood that variations and modifications may be employed without departing from the concept of the invention as defined in the following claims.

Claims: CLAIMS 1. A melt processable polyester capable of forming an anisotropic melt phase at a temperature below approximately 4000C consisting essentially of the recurring moieties I, II, III and IV wherein: I is EMI45.1 II is EMI45.2 III is a symmetrical dioxyaryl moiety of the formula -0-Ar-0where Ar is a divalent radical comprising at least one aromatic ring which optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foregoing, and IV is a dicarboxyaryl moiety of the formula EMI45.3 where Ar' is a divalent radical comprising at least one aromatic ring which optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, substituted phenyl, and mixtures of the foregoing, wherein said polyester comprises approximately 3 to 15 mole percent of moiety I, approximately 20 to 70 mole percent of moiety II, approximately 7.5 to 38.5 mole percent of moiety III, and approximately 7.5 to 38.5 mole percent of moiety IV. 2. A melt processable polyester according to Claim 1 wherein the symmetrical dioxyaryl moiety III is selected from the group consisting of: EMI46.1 and and mixtures of the foregoing. 3. A melt processable polyester according to Claim 1 or Claim 2 wherein the dicarboxyaryl moiety IV is selected from the group consisting of EMI47.1 and and mixtures of the foregoing. 4. A melt processable polyester according to claim 1 wherein Ar' of the dicarboxyaryl moiety IV is EMI47.2 wherein the bonds are meta and/or para disposed. 5. A melt processable polyester according to claim 1 wherein I is and IV is EMI48.1 6. A melt processable polyester according to claim 1 wherein moiety III is EMI48.2 where the aromatic ring optionally may include substitution of at least some of the hydrogen atoms present thereon selected from the group consisting of an alkyl group of 1 to-4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, and mixtures of the foregoing, and IV is EMI48.3 where the aromatic ring optionally may include substitution of at least some of the hydrogen atoms present thereon selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, and mixtures of the foregoing, and wherein approximately 40 to 90 mole percent of moiety IV is isophthaloyl moiety and approximately 10 to 60 mole percent of moiety IV is terephthaloyl moiety. 7. A melt processable polyester according to claim 1 wherein III is IV is EMI49.1 and where aromatic rings of moieties III and IV optionally may include substitution of at least some of the hydrogen atoms present upon an aromatic ring selected from the group consisting of an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, halogen, phenyl, and mixtures of the foregoing. 8. A melt processable polyester according to any one of the preceding claims wherein said polyester comprises 5 to 10 mole percent of moiety I, 50 to 65 mole percent of moiety II, 12.5 to 22.5 mole percent of moiety III, and 12.5 to 27.5 mole percent of moiety IV. 9. A moulding composition comprising the melt processable polyester of claim 1 and 1 to 60% by weight of a solid filler and/or reinforcing agent. 10. A shaped article formed from a polyester according to any one of claims 1 to 8 or from the moulding composition of claim 9.

Inventors: BENICEWICZ, BRIAN C., CALUNDANN, GORDON W., CHARBONNEAU, LARRY F.
Applicants: CELANESE CORPORATION
Application year: 1983
Main classification: C08G63
IPC codes: C08G63