Fiber-forming polyesters of aromatic ketohydroxy acids

Fiber-forming melt-spinnable polyester that is optically anisotropic in the melt and consists essentially of the following amounts of recurring units of the structural formulas:

• (a) 25-100 mol % ##STR5## and (b) 0-75 mol % ##STR6## wherein both of R.sup.1 and R.sup.2 are H, CH.sub.3 or Cl or R.sup.1 is H and R.sup.2 is CH.sub.3 or Cl;
• both of R.sup.3 and R.sup.4 are H, CH.sub.3 or Cl or R.sup.3 is H and R.sup.4 is CH.sub.3 or Cl;
• and
• Ar is m- or p-phenylene,
• provided, however, when the amount of (a) is 90-100 mol %, Ar is m-phenylene in at least 30% of the (a) units, and provided further, however, when the amount of (a) is 100 mol % and only one species of (a) is present, R.sup.1 and R.sup.2 are both Cl, and provided still further, however, in copolyesters consisting essentially of two or more different species of (a), only one of said species is substituted and R.sup.1 and R.sup.2 therein are Cl.