CA2017714A1 - Liquid crystalline copolyesters of 4-hydroxybenzoic acid and substituted 4-hydroxybenzoic acids - Google Patents

Abstract

ABSTRACT
Disclosed is a copolymer capable of forming an optically anisotropic melt comprising recurring structural units of Formulas I, II, and optionally III

I, II, III, wherein each R is independently a chemically inert substituent; and each R1 is independently benzoil or phenoxy. The present invention also relates to a 36,711-F

process for preparing the copolymer. The copolymer of the present invention usually have a melting point below 350°C and can be readily melt extruded into fibers, films or the like.

36,711-F

Description

~7~

MELT PROCESSABLE THERMOTROPIC
AROMATIC COPOLYESTERS AND PROCESS
FOR PREPARING SAME

The present invention relates to a class of copolyesters which display optical anisotropy in the molten state and to articles such as fibers and ~ilms obtained from the copolyesters. The present invention also relates to a process for preparing such copolyesters.
Liquid crystalline polymers (LCPs) are macro-molecules possessing significant orientation in either the molten state or in concentrated solution. The state of their solution (lyotropic) or melt (thermotropic) is between the boundaries of solid crystals and isotropic liquids. In the solid state these highly ordered polymers display exceptional strength propertie~ in the direction of orientation. By designing molecule~
containing only relatively inert chemical bonds, preparation of thermally and oxidatively stable high-performance materials is possible.
A review of thermotropic LCPs can be found in Kwolek et al., "Liquid Crystalline Polymers", "Encyclo~edia of Pol~mer Science and Engineerin~" 2nd .

36,711-F -1-" `, - , ~:L7'71~

Ed, Vol. 9, pp 23-55 (1987). Among those listed are polyesters. Many li~uid crystalline polyesters display several of the desirable attributes of these compounds.
Unfortun~tely, most have too high o~ a melt temperature (e.g., 400C or more) for economical melt fabrication.
There is a growing need in the thermoplastic engineering industries to provide for new and improved polyesters and copolyesters which possess a high degree o~ proce~sability while concurrently exhibiting superior mechanical properties such as high tensile strength.
According to the present invention, there i5 now provided a copolymer capable of forming an optically anisotropic melt comprising recurring structural units of Formula I, II~ and optionally III:

~ ~ C ~ II, ~ (R)3 ~ ~ C ~ III, wherein each R is independently a chemically inert substituent; and each R1 is independently benzoil or phenoxy.
Another aspect of the present invention relates to a process for preparing the above-mentioned 36,711-F -2-~77~

copolymers which comprises contacting a compound of Formula I':

(R) L~
~ ~ o_R3 I', with a compound o~ Formula II':
R1 (R)3 O
R3-o ~ c-R2 II', and optionally with a compound o~ Formula III':

~ (R)3 R3-o ~ -C_R2 III', wherein each ~ i~ independently a chemically inert ~ubstituent; R1 is benzoyl or phenoxy; each R2 is independently hydroxyl 9 halogen or phenoxy; and each R3 i~ independently hydrogen or C1~6 acyl, 3 under polymerization conditions to ~orm the copolymer.
Pre~erably, R used in Formulas I through III
and I' through III' is independently selected from the 36,711-F _3_ C~ ~3 ~ r~ r~

group consisting of hydrogen, halo, lower alkyl and methoxy. Most preferably7 R is each occurrence hydrogen.
Desirable molar percent ranges for these copolyesters are from 35 mole percent to 95 mole percent ~ of independently recurring units of Formula I, from 5 mole percent to 65 mole percent of independently recurring units of Formulas II or from 5 mole percent to 65 mole percent of independently recurring units of Formula~ III, or from 5 mole percent to 50 mole percent of independently recurring units oE Formulas II, III and IV wherein the ratio of Formula II and III units to Formula IV units varies from 100:0 to 10:90.

More preferable molar percent ranges for these copolyesters are from 50 mole percent to 90 mole percent of independently recurring units of Formula I, from 10 mole percent to 50 mole percent of independently recurring units of Formulas II or III, or from 10 mole percent to 50 mole percent o~ independently recurring unit~ of Formulas II, III and IV wherein the ratio of Formula II and III units to Formula IV units varies from 100:0 to 10:90.
The most preferred molar percent ranges are from 60 mole percent to 90 mole percent of independently recurring units of Formula I, from 10 mole percent to 40 mole percent o~ independently reaurring unit3 of Formulas II or III, or from 10 mole percent to 40 mole 3 percent of independently recurring units of Formulas II, III and IV wherein the ratio of Formula II and III units to Formula IV units varies from 100:0 to 10:90.

36,711-F _4_ ~7 ~14 The copolymer of the present invention preferably have a weight average molecular weight of 2,000 to 200,0~0, more preferably 10.000 to 30,000. The molecular weight may be determined by standard techniques such as end group determination using infra red spectroscopy. The preferred copolyesters of this invention have a melting point o~ less than 350C.
The copolymers may be formed by a variety of ester-forming techniques from difunctional organic compounds possessing functional groups which upon polycondensation form the requisite recurring units.
For example, the functional groups of the organic aromatic compounds may independently contain carboxylic acid groups or acid halide groups and functional groups reactive therewith such as hydroxyl or acyloxy groups.
The hydoxyl group is preferably esterifled.
The difunctional organic compounds (monomers) which can be used in the present invention may be represented by the following Formulas I', II' and III'I:

3o 36,711-F -5--6- 2 ~ ~7 71~
(~)4 ' ~ o-R3 I', R1 (R) ~ 3 ~
R3-o ~ c_p2 II', R3-o ~ c-R2 III , lS wherein R, R1, R2 and R3 are a~ defined above.
Preferably, ~ is hydrogen; R1 is benzoyl or phenoxy; ~2 i9 hydroxyl; and R3 is hydrogen or acetyl. Thu~, preferred monomers are (I') 4-acetoxybenzoic acid; (II') 3-benzoyl- or 3-phenoxy-4-acetoxybenzoic acid; and ~III') 3-phenyl-4-acetoxybenzoic acid.
The monomer can be polymerized by any known techniques. For example, the organic compounds may be allowed to react under anhydrous conditions in an inert atmosphere via a melt acidolysis procedure7 in a suitable solvent via a solution procedure, or in a heat exchange medium via a slurry polymerization as described in U.S. Patent No~ 4,067,852. Additional suitable reaction conditions are described in U.SO Patent No.

4,1187372~ A preferable technique i9 the melt acidoly9is technique.
Preferably, the polymerization can be carried out at a temperature of from 200C to a temperature 36,711-F -6-.
-~ ~ . ' i , .

2 ~ :L rl 7 ~

above the melting point, but below decomposition temperature of the resultant copolymer, more preferably from 260 to 360C. The reaction time may range from 1 to 24 hours, preferably from 2 to 8 hours. The polymerization is preferably carried out at atmospheric pressure. It is preferable to reduce the pressure at the end of polymeri~ation. Superatmospheric or subatmospheric pressures can also be uqed if desired.
A catalyst may or may not be used in the polymerization process. If one is used, representative catalysts for use in the process include dialkyl tin oxides (e.g., dibutyl tin oxide), diaryl tin oxides, titanium dioxide, alkoxy titanium silicates, titanium alkoxides, Lewis acids, hydrogen halides (e.g., HCl), alkali and alkaline earth metal salts of carboxylic acids (e.g., sodium acetate). The quantity of catalyst utilized typically is from 0.001 to 1 weight percent based upon total reactant weight, and most commonly from 0.01 to 0.2 weight percent. In a preferred method of polymerization, a catalyst is not u ed.
Liquid crystalline copolyester melts of this invention may be extruded into articleq quch a~ fibers which have outstanding strength and stiffness and will maintain their useful properties at elevated temperatureq. Such fibers would be useful as tire cord~, reinforcement in hoses, cable~, conveyor belts or composite structure~ with matrixes prepared from other re~inous materials. The films formed from the copolyesters which will have excellent solvent and chemical resistance. In addition, the films will have low flammability and good electrical insulating properties. The films would be useful as cable wrap, electric motor dielectric film and wire insulation. In 36,711-F _7_ 2 ~

general, the copolyesters of the present invention are useful for the manufacture of shaped articles such as those whicn are injection molded possessing high strength, stiffness, chemical resistance and low flammability.
Conventional additives and proce3sing aids can be added to the copolyester melts o~ the invention to improve the properties of articles made therefrom.
Examples of additives are oxidation stabilizers; heat stabilizers; ultraviolet light (UV) stabilizers;
lubricants; mold release agents; dyes and pigments;
fibrous or powdered fillers and reinforcing agents;
nucleating agents; and plasticizers.

Examples of oxidation stabilizers and heat stabili~ers are halides of metals of group I of the Periodic Table, used alone and used as a mixture with copper (I) halides or sterically hindered phenols in concentrations from 0.001 to 1 weight percent based on Z0 the weight of the copolyester composition.
Examples of UV stabilizers are substituted resoroinols, salicylates, benzotriazoles, benzophenones and mixtures of these. The stabilizers may be added, for example, in amounts from 0.001 to 2 weight percent based on the weight of the copolyester composition.
Dyes and pigments can be used, for example, in amounts from 0.001 to 5 weight percent based on the weight o~ the copolyester composition. Examples are nigrosine, titanium dioxide, cadmium sulfide, phthalo cyanine dyes, ultramarine blue and carbon black.
Examples of fillers and reinforcing agents are carbon fiber3, glass fibers, amorphous silica, calcium 36,711-F -8-.
.

2~77~
_9~

silicate, aluminum silicate, magnesium carbonate, kaolin? chalk! powdered quartæ, mica and feldspar, which may be pressnt in a concentra'ion from 0.5 to 70 weight percent, based on the tctal weight of the filled material.
Examples of nucleating agents are talc, calcium fluoride, sodium phenylphosphonate, alumina and finely divided polytetrafluoroethylene. Suitably, the nucleating agent may be present in an amount from 0.001 to 1 percent by weight.
Plasticizers, such as phthalates, hydrocarbon oils and sulfonamides can be included in an amount of from 0.0001 to 20 weight percent, based on the weight of the composition.
Also included in the composition of the invention, in additlon to or in partial replacement of the reactants of Formulas I, II, III or IV are amounts of other aromatic polymerizable units whose presence do not interfere with the excellent mechanical properties of these copolyesters. Examples o~ such aromatic units comprising these additional repeating units are 2-hydroxy-6-naphthoic acid 9 4-hydroxy-4'-carboxybiphenyl and 3-hydroxybenzoic acid.
According to the present invention, there are provided improved copolymers which posqeqs a low melting point, preferably below 350C while concurrently exhibiting superior mechanical property such a~ high tensile strength.
The present invention will be described with reference to the following Examples.

36,711-F -9-f~ 7 ~. ~

, o--Preparation of 4-Acetoxybenzoic Acid An amount of 4-hydroxybenzoic acid (92.i grams tg), 0.67 mole) was dis~olved in a solution of sodium hydroxide (NaOH) (53.4 g, 1.33 moles) and 1.33 liters (L) of water in a 4 L beaker. The solution was stirred and cooled to a temperature of 0C by adding crushed ice, then acetic anhydride (102.1 g, 1~00 mole) was added. The temperature was maintained at -2C for 1 hour by adding one kilogram (kg) of crushed ice. A
solution of concentrated hydrochloric acid (HCl) (144.7 g, 1.42 moles) in 267 milliliters (ml) of water was added. The slurry was stirred briefly and filteredO
The product was washed twice by stirring it with 2 L
portions of fresh water then filtered and dried in a vacuum oven at 80C for 16 hoursO After recrystal-lization from methyl isobutyl ketone, the product consisted of 111 g of white crystals with a melting point (m.p.) of 192C to 192.5C.
Preparation of 3-Benzoyl-4-Ac_tox~benzoic Acid A solution of benzoyl chloride (24.2 g, 0.30 mole) in 25 ml of cyclohexane was added over 5 minutes to a refluxing mixture of p-methylanisole (44.0 g, 0.36 mole~, anhydrous zinc chloride (0.41 g~
3 mmol) and 75 ml of cyclohexane. The mixture was refluxed under nitrogen for 23 hours. After 2.5 hours, an additional 0.41 g of anhydrous ~inc chloride was added. The resulting black solution was washed two 3 times with 100 ml of 0.5 N sodium hydroxide (NaOH), then with 1 N hydrochloric acid (HC1), then with a 5 weight percent solution of aqueous sodium bicarbonate (NaHC03) and water. The clear yellow solution was dried with magnesium sulfate (MgS04~, then the solvent was removed 36,711-F _10_ ~ 1771 4 and the viscous yellow oil which remained was vacuum distilled through a six lnch Vigreaux column. The product, 2-methoxy-5-methylbenzophenone was collected as a clear colorless oil which slowly crystallized.
An amount of 2~methoxy-5-methylbenzophenone (14.2 g, 62.7 mmol) and a solution of potassium permanganate (KMnO4) (24.8 g, 157 mmol) in 300 ml of water ware stirred under reflux (102C) for one hour.
The reaction mixture was cooled to 45C and sodium hydrogen sulfite (NaHS03) (45 g, 0~44 mols) was dissolved in the reaction mixture. Slowly 50 g of concentrated HCl was added. The white solid which was produced was taken up twice in 250 ml of ether. The combined organic phase was extracted twice with 150 m:L
cf 0.67 N NaOHO The ether phase was dried with MgS04 and the ether was removed. There remained 7049 g of unreacted starting material. The combined basic extracts were acidified with concentrated HC1 and extracted twice with 250 ml of ether. The ether extract~ were dried with MgS04 and concentrated to produce 3-benzoyl-4-methoxybenzoic acid. The product was recrystallized from a mixture of 100 ml of ethanol and 200 ml of water.
A solution of 3-benzoyl-4-methoxybenzoic acid (10.23 g, 40 mole), 100 ml of 48 weight percent aqueous hydrobromic acid (HBr) (149 g, 0.88 mole) and 200 ml of acetic acid was refluxed under nitrogen. After five hour~, a white solid began to separate. After 22 hours, the slurry wa~ cooled in ice and filtered. The white solid which was collected was washed with water and dried in a vacuum oven. There remained white granular 3-benzoyl-4-hydroxybenzoic acid.

36,711-F

Acetic anhydride (10.5 g, 0.103 mmol) was added to a solution of 3-benzoyl-4-hydroxybenzoic acid (l2.5 g, 51.6 mole) anA ~aOH (4.33 g, 0.108 mmol) in 250 ml of water under nitrogen. The clear colorless solution ~as stirred at 8C for one hour. The product separated initially as a colorless oil which soon crystalli~ed to a white solid. The slurry was made strongly acidic by adding concentrated HCl, and was extracted with ether. The ether extract was washed with water, and dried ~ith MgS04 and evaporated to dryness providing crude acetoxy acid. The crude product was recrystallized from a mixture of 200 ml of toluene and 150 ml of cyclohexane to give 3-benzoyl-4-acetoxybenzoic acid with a m.p. of 162.5C to 163C.
Preparation of 3-Phen~l-4-Acetox~benzoic_Acid A solution of 2-hydroxybiphenyl (51.2 g, 0.300 mole), 50 weight percent aqueous NaOH solution (28.6 g, 0.360 mole) and 120 ml of deionized water were added to a one;liter, three-necked, round-bottom flask equipped with a cold water condenser, nitrogen inlet, thermometer, and an air-powered paddle stirrer. The solution was stirred under nitrogen until homogeneous, then 175 ml of a methylene chloride solution o~ bromo ethane (65.3 g, 0.600 mole) and tetrabutylammonium bromide (9.70 g, 0.030 mole) was added with vigorous stirring. The reaction mixture was stirred at room temperature for 22 hours. The mixture was transferred to a one-liter separatory funnel and the organic layer was decanted and saved. Be~ore discarding the aqueous layer, it was extracted with 25 ml of methylene chloride. The methylene chloride extract was added to the organic reaction solution which was added to a bottle containing lOO ml of 10 weight percent aqueous 36,711-F ~12-2~77~ ~

NaOH solution. The mixture was shaken vigorously for 0.5 hours on a mechanical shaker. The separated aqueous layer was discarded. The organic layer wa5 washed twice with 50 ml of 1 N HCl followed by a 50 ml deionized water wash. The organic solution was stored over anhydrous MgS04 for several hours then the solvent was removed by rotary evaporation to provide a salmon-colored liquid. The sides of the flask were scraped with a glass stirring rod inducing crystallization of the product, 2-ethoxybiphenyl.
A solution of 2-ethoxybiphenyl (19.8 g, 0.100 mole) and 100 ml of carbon disulfide were added to a 250-ml~ three-necked, round-bottom reaction flask equipped with a cold water condenser, nitrogen inlet, thermometer and polytetrafluoroethylene-coated magnetic stir bar. The solution was maintained under nitrogen and brought to a mild reflux at approximately 46C.
Anhydrous aluminum chloride ~AlC13) (13.8 g, 0.104 mole) was added slowly to the refluxing solution via a dropping funnel. A green, heterogeneous mixture was formed. Approximately 60 ml of a carbon disulfide solution containing acetyl chloride (8.07 g, 0.103 mole) wa~ added dropwise to the refluxing reaction solution over 100 minutes. The reaction solution was refluxed for an additional hour after the last acetyl chloride addition, then cooled to room temperature~. The reaction solution was poured slowly into a cold HCl solution and stirred. The contents were then transferred to a 500 ml separatory funnel, shaken, and the separated organic layer was stored over anhydrous MgS04. Before discarding, the aqueous layer was washed with 25 ml of methylene chloride which was added to the saved organic layer. The dried organic layer was filtered and the 36,711-F _13_ r~ 7 ~L ~

volatiles were rotary evaporated off leaving a tan solid which was dried under vacuum at 60C for two hours yielding a crude product. The solid was recrystallized from hexane to give 3-phenyl-4-ethoxyacetophenone.
A mixture of 3-phenyl-4-ethoxyacetophenone (32.2 g, 0.13~1 mole) and 250 ml of p-dio~ane was added to a one-liter, three-necked, round-bottom flask equipped with a pressure equalizing dropping funnel, thermometer and a polytetrafluoroethylene-coated magnetic stir bar. The mixture was stirred to dissolve the solid, then 480 ml of sodium hypobromite solution (0.53 mole), prepared by dissolving NaOH (126 g, 3.15 moles) in 600 ml of deionized water, followed by dropwise addition of 45 ml of bromine (0.87 mole) over a 60 minute time period, was added. The solution temperature rose from 22C to 48C during the addition.
The reaction solution was stirred an additional 15 minutes after the last of the NaOBr addition, then a solution of 40 weight percent aqueous NaHS03 (41.9 g, 1.61 moles) was added to remove any remaining NaOBr.
The solution was then immersed in an ice bath and acidified to a pH of 2 with concentrated HCl. A light yellow solid precipitated upon acidification The solid wa~ filtered, recrystallized from a dioxane and water mixture, filtered and dried under vacuum at 60C
overnight to yield a light yellow solid of 3-phenyl-4--ethoxybenzoic acid.
A solution o~ 3-phenyl-4 ethoxybenzoic acid (26.6 g, 0.110 mole) and 550 ml of acetic acid was added to a one-liter, three-necked, round-bottom flask equipped with a 250 ml pressure equalizing dropping funnel, thermometer, cold water condenser, nitrogen inlet adapter and a polytetrafluoroethylene-coated 36,711-F -14-~77~ ~

magnetic stir bar~ The flask was purged with nitrogen and the solution was brought to reflux. Approximately 125 ml of a 48 weigi!t percent solution of HBr was added dropwise over fifteen minutes to the refluxing solution.
The solution was refluxed for 30 hours. Without cooling, the solvent was rotar~ evaporated off leaving a slurry of a pinkish solid. The slurry was poured into one liter of deionized water and the mixture was stirred for one hour and filtered. The filter cake was dried in an 80C vacuum oven for three hours yielding 3-phenyl-4--hydroxybenzoic acid.
A solution of 3-phenyl-4-hydroxybenzoic acid ( 131.1 g, o.o61 mole) and a 50 weight percent aqueous solution of NaOH (10.5 g, 0.131 mole) in 350 ml of deionized water was added to a 500 ml, three-necked, round-bottom flask equipped with a thermometer and a polytetrafluoroethylene-coated magnetic stir bar. The solution was stirred to homogeneity and then immersed in an ice water bath. With the solution temperature at 10C, acetic anhydride (12.7 g, 0.124 mole) was added rapidly with stirring. Immediately, a white precipitate began to form. The reaction mixture was stirred for one hour at 10C, then neutralized with concentrated HCl.
The precipitate was filtered, washed in 500 ml of deionized water for one hour, filtered, and dried in an 80C vacuum oven for three hours yielding an off-white ~olid. The solid was recry~tallized from a toluene and hexane mixture to give a fluffy white solid, 3-phenyl-4--acetoxybenzoic acid with a m.p. of 185C to 187C.
Preparation of 3-Phenoxy-4-Acetoxybenzoic Acid A solution of bromine (79.9 g, Q.500 mole) in 100 ml of carbon tetrachloride (CCl4) was slowly added 36,711-F -15-7 ~ ~

over a 15 minute period to a stirred solution of 4~methylanisole (61.1 g, 0.500 moLe) in 400 ml of CCl4 at 25C in the dark. Gaseous HBr evol~ed. Slight cooling was used to keep the temperature at 25C to 30C.
After 1.5 hours, the evolution of HBr stopped and the deep red solution was allowed to stand in the dark overnight. The reaction mass was washed with aqueous solutions of NaHS03 and NaHC03, then with water. The solution was dried, concentrated and vacuum distilled throu~h a 30 cm column packed with ceramic saddles. The fraction boiling between 102C and 105C at 8 mm Hg was collected. The product, 2-bromo-4-methylanisole was a clear colorless liquid.
A stirred mix'ure of phenol (20.7 g, 0.220 mole) and powdered KOH (12.3 g, 0.220 mole) was slowly heated to 167C under nitrogen. At 120C, the reaction mass became a clear colorless liquid. The pressure was slowly reduced. At 150 mm Hg, water began to distill. When most of the water had been removed, the reaction mass solidified. The white solid was held at 167C and 1 mm Hg for 30 minutes to remove the last traces of water, then cooled to room temperature.
Electrolytic copper dust ~70 milligrams ~mg), 0.0011 gram-atoms), 2-bromo-4-methylanisole ~40.4 g, 0.200 mole) and phenol (10.4 g, 0.110 mole) were added9 then the flask was lowered into an oil bath that had been preheated to 200C. All the solid di~solved. The dark red liquid was stirred under nitrogen at 200C for 3.5 hours. The reaction mass was cooled, diluted with 500 ml of ether, and washed three times with 100 ml portions of 1 N NaOH, then with l N HCl, then with 5 weight percent aqueous NaHC03 solution and with water.
The solution was filtered to remove a few droplets of 36,711-F -16-~ ~ 1. ri~ 7 ~ 4 undissolved black tar, then cooled in dry ice. The product 7 2-phenoxy-4--methylanisole separated as an oil which slowly crystallized.
A solution of 2-phenoxy-4-methylanisole (26.9 g, 0.126 mole), KMnO4 (48.8 g, 0.315 mole), 240 ml of deionized water and 480 ml of pyridine was added to a two-liter, one-necked, round-bottom flask equipped with a reflux condenser and a polytetrafluoroethylene-coated magnetic stir bar. The solution was brought to reflux while stirring for 1.5 hours at which point the solution was brown and the heating mantle was removed. The mixture was brought to near dryness on a rotary evaporator. Approximately 250 ml of deionized water was added to the flask with NaHS03 ~41.6 g, 0.400 mole).
Concentrated HCl was added slowly to the aqueous solution resulting in the precipitation of an off-white solid. The solid was filtered and washed in 600 ml of deioni~ed water for one hour, refiltered and dissol~ed in 250 ml of deionized water with NaOH (0.15 mole). Ihe aqueous solution wa extracted with 125 ml of ether to remove unreacted starting material. The aqueous layer was added dropwise into a rapidly stirred dilute acid solution of HCl (0.2 mole) in 600 ml of water, resulting in the precipitation of a white, finely divided solid.
The white solid wa~ collected and dried at 100C under vacuum for four hours yielding an off-white solid that was 3-phenoxy-4-methoxybenzoic acid.
A solution of 3-phenoxy-4-methoxybenzoic acid (17.0 g, 0.07 mole), a 48 weight percent aqueous solution of HBr (165 ml, 1.39 mole) and 350 ml of glacial acetic acid was added to a l-liter, one-necked, round-bottom flask equipped with a reflux condenser, nitrogen inlet adapter and a polytetrafluoroethylene-36,711-F ~17-~77~

coated magnetic stir bar. The solution was heated under nitrogen and refluxed for 16 hours. While still hot, the flask was ~ransferred to a rotary evaporator and the volatiles were removed leaving a salmon-colored solid which was added to 200 ml of 1.25 N NaOH solution (0.25 mole). Most of the solid dissolved~ The insoluble portion was filtered off. The remaining aqueous base solution wa~ added dropwise to a stirred aqueous HCl solution (0.25 mole in 400 ml deionized water) resulting in the precipitation of a salmon-colored solid. The solid was washed in 300 ml ofdeionized water for 1 hour, filtered, dried at room temperature overnight7 and dried under vacuum at 100C
for 1 hour yielding 3-phenoxy-4-hydroxybenzoic acid.
A solution of 3~phenoxy-4-hydroxybenzoic acid (13.9 g, 0.0560 mole), 200 ml of deionized water, and NaOH (11.2 g of 50 weight percent aqueous solution, 0.140 mole) was added to a 500-ml conical flask equipped with a thermometer and a polytetrafluoroethylene-coated magnetic stir bar. The reaction flask was immersed in an ice bath and stirred. Acetic anhydride (12.2 g, 0.120 mole) was added rapidly to the stirred solutior, causing a temperature increase from 7C to 12C.
Approximately one minute after the acetic anhydride addition, a precipitate began to appear. The solution was stirred for one hour at 5C to 7C and was neutralized with concentrated HCl (15 g, 0.15 mole) cau~ing further precipitation. The off-white precipitate was filtered and washed with 200 ml of deionized water for one hour, refiltered and dried at 80C under vacuum for two hours yielding an off-white solid. This product was recrystallized from toluene, filtered and dried one hour under vacuum to yield an 36,711-F -18-. 19.

off-white solid which was 3-phenoxy-4-acetoxybenzoic acid with a m.p. of 181C to 18~Co General Melt Polymerization,Procedure Small-~cale melt polymerizations were carried out in 15 mm internal diameter (I.D.) polymerization tubes for 1 to 3 g quantitieq and in 24 mm I.D.
polymerization tubes for 6 g quantities. The tubes were fitted with a head equipped with an adjustable capillary tube, a combined distillate delivery tube and air condenser, a receiver and a combined nitrogen inlet and vacuum portO The lower portion of the polymerization tube was heated in a small, vertical hot air oven.
After the reactants were added to the polymerization tube7 it was evacuated and refilled with nitrogen three times, then heated to 260~. After the reackants had melted to ~orm a liquid reaction mass, a capillary tube was lowered below the liquid surface and the nitrogen flow was adjusted to show a slow stream of bubbles passing through the liquid. The polymerization was held at 260C until one half of the theoretical amount of acetic acid had been collected. At this point, the temperature was increased and the pressure was reduced at a rate sufficient to keep the rate of acetic acid evolution steady. A typical heating schedule was 1 hour at 260C, 1 hour at 300C and 1 hour at 320C. The liquid was then put under vacuum of 1 mm Hg at 340C for 30 minutes. The viscosity of the reaction mass was periodically measured by moving the capillary through the liquid. The capillary was raised to a position 1 cm above the reaction mass before the mass became solid or extremely viscous. The polymerization was stopped when approximately all the theoretically calculated amount of acetic acid had been collected. The reaction mass was 36,711-F -19-2 0 ~

cooled and a polymer plug formed which was removed from the tube, then ground up on a centrifugal grinder.
Melt temperature analysis was carried out using differential scanning calorimetry (DSC) on a 15 mg compressed pellet at a heating and cooling rate of 20C
per minute on a Mettler DSC~30 low temperature cell with a Mettler TClOA thermal analysis processor ~Mettler Instrument Corp., Hightstown, New Jersey).
Optical anisotropy of the copolyester melts can be determined by examination of the materials with the use of an optical microscope. The equipment used for determining the optical anisotropy of the copolyesters of the present invention included a TH 600 hot stage, (Linkham Scientific Instruments LTD, Surrey, England) and a Nikon Optiphot Microscope equipped with crossed polarizers and a 35 mm camera (Nikon Instrument Group, Nikon Inc.). A thin film of the polymers shown in Tables I and II were optically anisotropic above their DSC-determined melting temperature when observed through a polarizing microscope.
Exam~les I-V
P aration of Co ol esters from 4-Acetox benzoic Acid reP _ P_ ~___ Y_ _ and 3-Benzoyl-4-acetox~benzoic Acid The copolyesters of these examples were prepared using the general melt polymerization procedure as d0~cribed above. The mole fraction of the 4-acetoxyben~oic acid (4-ABA), the remainder being 3-benzoyl-4-acetoxybenzoic acid, the glass transition temperature, rg, and the melt temperature, Tm, are shown in Table I~

36,711 F -20-7 ~ 4 Table I
Thermal Data for Copolyesters Prepared From 3-Benzoyl-4-acetoxybenzoic Acid and 4-Acetoxybenzoic Acid Mole Fraction T~ (C) Tm ~C) 0.35 110 152 0.50 120 152 0.65 112 184 10.75 114 306 0.85 --- 334 Examples VI-VIII
Preparation of Copol~esters from 4-Acetoxybenzoic Acid and 3-Phenoxy-4-acet,oxybenzoic_Acid The copolyesters of these examples were prepared using the general melt polymerization procedure as described above. The mole ~raction of the 4-ABA, the remainder being 3-phenoxy-4-acetoxybenzoic acid, the glass transition temperature, Tg, and the melt temperature, Tm, are shown in Table II.
Table II
Thermal Data for Copolye~ters Prepared from 3-Phenoxy-4-acetoxybenzoic Acid and 4-Acetoxybenzoic Acid Mole Fraction Tg (C3 Tm (C) 30.50 116 261 0.60 132 327 0.70 121 326 36,711-F -21-

Claims (9)

1. A copolymer capable of forming an optically anisotropic melt comprising recurring structural units of Formulas I and II:

I, II, wherein each R is independently a chemically inert substituent; and each R1 is independently benzoil or phenoxy.

2. The copolymer of Claim 1 which further comprises a recurring structural unit of Formula III:

III, wherein each R is independently a chemically inert substituent.

3. The copolymer of Claim 1 wherein R is hydrogen, halogen, C-3 alkyl, methoxy or phenyl.

36,711-F -22-

4. The copolymer of Claim 1 which comprises 35 to 95 mole percent of the recurring unit of Formula I, and 5 to 65 mole percent of the recurring unit of Formula II.

5. An article made of the copolymer of Claim 1 or 2.

6. The artical of Claim 5 which is a fiber or a film.

7. A process for preparing the copolymer of Claim 1 which comprises contacting a compound of Formula I':

I', with a compound of Formula II':

II', wherein each R is independently a chemically inert substituent; R1 is benzoyl or phenoxy; each R2 is independently hydoxyl, halogen or phenoxy; and each R3 is independently hydrogen or C1-6 acyl, under polymerization conditions to form the copolymer.

36,711-F -23-

8. The process of Claim 7 wherein the polymerization is carried out at a temperature of from 200°C to a temperature below the decomposition temperature of the copolymer.

9. The process of Claim 7 wherein the polymerization is carried out for 1 to 24 hours.

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