| abstract |
Copolymers consisting of bisphenol-A ("BPA"), terephthalate ("TP"), and carbonate moieties in mol ratio from 2:0.8:1.2 to 2:1.3:0.7, which are melt processable in the sense of (a) showing no more than 10% change in viscosity number upon compression molding for 10 minutes at 320 DEG C. to form a plaque, (b) developing, in 2% (gm./ml.) DCM solution, a "yellowness index" of no more than 10 as observed by ASTM Test No. D-1925, using a 2 cm. path length; which copolymers approximate in properties the alternating copolymer consisting of the above moieties, as indicated by their having viscosity numbers ("I.V.") in the range between 0.6 and 1.5 dl./gm. and TG of 170 DEG to 194 DEG C., with TG vs. I.V. relationship conforming to the formula, TG=192-(11.5/I.V.)+9 and with difference of (TG-HDT) of not over 15 DEG C.; having Izod impact resistance (ft.-lb. per inch of notch) at 25 DEG C. of at least 5; and being essentially free of pyridine and of anhydride linkages. The copolymers preferably have a mol ratio of BPA:TP:carbonate in the range from 2:0.9:1.1 to 2:1.2:0.8, viscosity number of 0.6-1 dl./gm., TG of at least 178 DEG C. by differential scanning calorimetry, heat distortion (or deflection) temperature of at least 170 DEG C., and Izod impact resistance at 25 DEG C. of at least 6 ft.-lb. per inch of notch. Process is disclosed of making such copolymer involving adding, to a solution of bisphenol-A, a solution of terephthaloyl chloride; reacting at 2:1 molar proportions of BPA:TPC in dichloromethane/pyridine; then phosgenating. The product is especially useful in glazing and transparent sheet applications requiring high impact resistance, high abrasion resistance and/or high solvent resistance. |