Abstract:
An aromatic polyester having recurring monomer units derived from terephthalic acid, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, 4,4&#39;-biphenol, and resorcinol. This polyester is melt processible and may be amorphous or semi-crystalline.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the field of aromatic polyesters, especially melt processible amorphous and semi-crystalline aromatic polyesters. 
     There are a large number of aromatic monomers that can be used to make polyesters. As a result, a virtually infinite number of different aromatic polyester compositions are possible, each having its own unique set of physical and chemical characteristics. 
     U.S. Pat. No. 4,083,829 issued to Calundann et al. describes a wholly aromatic melt processible polyester consisting essentially of recurring units of p-oxybenzoyl, 2,6-dicarboxynaphthalene, symmetrical dioxy aryl, and isothaloyl and/or meta-dioxy phenylene. 
     U.S. Pat. No. 4,188,476 issued to Irwin describes an aromatic polyester consisting essentially of the recurring units p-oxybenzoyl, terephthaloyl, 2,6-dioxynaphthalene or 2,6-dioxyanthroquinone, and m-oxybenzoyl or 1,3-dioxyphenylene. 
     U.S. Pat. No. 4,318,841 describes a polyester of 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, terephthalic acid, and resorcinol. 
     SUMMARY OF THE INVENTION 
     The present invention provides an aromatic polyester consisting essentially of recurring monomer units derived from terephthalic acid (&#34;TA&#34;), 6-hydroxy-2-naphthoic acid (&#34;HNA&#34;), p-hydroxybenzoic acid (&#34;HBA&#34;), 4,4&#39;-biphenol (&#34;BP&#34;), and resorcinol (&#34;R&#34;). This polyester is melt processible and may be amorphous or semi-crystalline, depending on the exact composition and the processing employed. 
     It is an object of the present invention to provide a novel wholly aromatic melt processible polyester. 
     It is another object of the present invention to provide a process for making a polyester consisting essentially of recurring monomer units derived from terephthalic acid, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, 4,4&#39;-biphenol, and resorcinol. 
     Other objects and advantages of the present invention will be apparent to those skilled in the art from the following description and the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In one preferred embodiment of the present invention, a polymer having monomer units derived from HBA (20-40 mole %), HNA (10-40 mole %), TA (15-30 mole %), BP (5-20 mole %), and R (5-20 mole %) is made by combining HBA, HNA, TA, BP, and R in the desired proportions with a polycondensation catalyst, such as potassium acetate, and acetic anhydride, and heating the mixture in an oxygen-free atmosphere. 
     The polymers of the present invention may be amorphous, exhibiting a glass transition temperature (&#34;T g  &#34;) and no melting point (&#34;T m  &#34;), or semi-crystalline, exhibiting both a T m  and a T g . The T g  of the polymers of this invention are typically in the approximate range of 100°-120° C., as measured by DSC (differential scanning calorimetry). 
     Although not limited to a particular viscosity, the polymers of the present invention preferably have an inherent viscosity of at least about 1.5 dl/g, more preferably about 2.0-5.0 dl/g, as determined in a pentafluorophenol solution of 0.1 percent polymer by weight at 60° C., and a melt viscosity of at least about 400 poise, more preferably at least about 500 poise, at a shear rate of 1000 s -1  measured at 230° C. in a capillary rheometer using an orifice 1 mm in diameter and 30 mm long. 
     The polymer of the present invention may be used to form films, fibers, or other articles for any number of specific applications, including structural applications, optical applications, and the like. It is particularly useful where amorphous LCP is needed, e.g. transparent films for optical applications. 
    
    
     The following Examples illustrate several embodiments of the present invention. However, the invention should not be construed as limited to the embodiments illustrated. 
     EXAMPLE I 
     To a 500-ml 3-neck flask equipped with a half-moon shaped PTFE stirrer blade, gas inlet tube, thermocouple, and a Vigreux column connected to a condenser and receiver, were added: 
     
         ______________________________________41.440 g HBA (0.3 mole)              18.600 g BP (0.1 mole)56.456 g HNA (0.3 mole)              11.012 g R (0.1 mole)33.226 g TA (0.2 mole)              0.02 g potassium acetate105.48 g acetic anhydride (2.5% excess).______________________________________ 
    
     The flask was immersed in an oil bath having a temperature control means, and evacuated and flushed three times with nitrogen to eliminate oxygen. The flask and its contents were heated to 200° C. over a period of 60 minutes while being stirred at a rate of 250 rpm. Acetic acid began to distill over immediately, and 10 ml had been collected by the time the temperature reached 200° C. 
     The reaction temperature was then raised at a rate of 1° C./min to 320° C. by which time 96 ml acetic acid had distilled out. The flask and contents were heated for another 60 min at 320° C., by which time a total of 110.5 ml acetic acid had been collected. The flask was then evacuated to a pressure of 1.0 mbar at 320° C. while stirring. The polymer melt in the flask continued to increase in viscosity while the remaining acetic acid was removed. 
     The foregoing process produced a polyester having an I.V. of 2.5 dl/g as determined in a pentafluorophenol solution of 0.1 percent polymer by weight at 60° C., and a melt viscosity of 550 poise at a shear rate of 1000 s -1  measured at 230° C. in a capillary rheometer using an orifice 1 mm in diameter and 30 mm long. 
     DSC (10° C./min heating rate) indicated that the polyester had a T g  of 106° C. Hot-stage cross-polarized optical microscopy indicated a transition temperature from solid to liquid crystalline (T s-lc ) at 170° C. The polymer was optically anisotropic. 
     EXAMPLES II-XIV 
     An additional thirteen compositions were made according to the procedure of Example I, each having a different mole ratio of the five monomer components. 
     Table 1 shows the mole ratio, T g , T m , T s-lc , and I.V. for each composition of Examples I-XIV. 
     
                       TABLE 1______________________________________              T.sub.g                     T.sub.m                            T.sub.s-1c                                   I.V.Ex.  HBA:HNA:TA:BP:R              (°C.)                     (°C.)                            (°C.)                                   (dl/g)______________________________________I    30:30:20:10:10              106    none   170    2.5II   20:30:25:15:10              108    none   280    2.74III  30:20:25:15:10              107    none   275    2.12IV   40:10:25:15:10              106    none   255    1.96V    30:10:30:20:10              111    none   280, 385                                   2.64VI   20:20:30:20:10              108    none   350, 385                                   2.74VII  10:30:30:20:10              113    none   290, 400                                   2.48VIII 20:30:25:10:15              113    none   160    2.10IX   20:30:25:5:20 122    none   163    1.76X    20:40:20:15:5 109    282    125    3.34XI   30:30:20:15:5 109    260    155    2.68XII  30:40:15:10:5 107    205    145    3.30XIII 35:35:15:10:5 107    193           4.14XIV  20:30:25:20:5 112    338           3.93______________________________________ 
    
     EXAMPLE XV 
     A polyester was made and analyzed according to Example I; the analysis showed an I.V. of 2.9, a T g  of 107.5° C., and no T m  (i.e. it was amorphous). This polyester was melt spun into fiber at 248° C. using 1310 psi pressure, using a Micromelt I™ apparatus (custom-made by Hoechst Celanese Corporation of Summit, N.J.) and a throughput of 0.15 g/min, with a take-up speed of 270 m/min, producing a fiber of 8.1 denier. The fiber was drawn to 73 times its as-spun length. Standard measurements indicated that the drawn fiber had a tensile strength of 4.9 g/denier, an elongation of 1.6%, and an initial modulus of 454 g/denier. 
     EXAMPLE XVI 
     A polyester was made and analyzed as in Example IX; the analysis showed an I.V. of 1.63, a T g  of 118.8, and no T m  (i.e. it was amorphous). This polyester was melt spun into fiber at 314° C. using a Micromelt I™ apparatus (custom-made by Hoechst Celanese Corporation of Summit, N.J.) and a throughput of 0.15 g/min and 1310 psi pressure, with a take-up speed of 100 m/min, producing a fiber of 19.7 denier. The fiber was drawn to 30 times its as-spun length. Standard measurements indicated that the drawn fiber had a tensile strength of 3.1 g/denier, an elongation of 3.4%, and an initial modulus of 183 g/denier. 
     Many variations of the present invention not illustrated herein will occur to those skilled in the art. The present invention is not limited to the embodiments illustrated and described herein, but encompasses all the subject matter within the scope of the appended claims.