PURPOSE: To obtain a liq. crystalline polyester excellent in flowability and heat resistance and having high elastic modulus and strengths in both the machine and transverse directions by acetylating four specific compds. with acetic anhydride and polycondensing the acetylated compds below a specified temp. under a reduced pressure.

CONSTITUTION: A liq. crystalline polyester comprises structural units of formulas I, II, N, and IV in molar amts. satisfying the relations V, VI, VII, and VIII respectively, has a melt viscosity (at 320°C under a shear stress of 103sec-1) of 50-5,000P, is produced by acetylating compds. of formulae IX, X, XI, and XII with acetic anhydride and polycondensing the acetylated compds. under a reduced pressure at 325°C or lower, and exhibits, even when it contains no filler, a high elastic modulus, high strengths, and a low linear thermal expansion coefficient in both the machine and transverse directions and low anisotropies of these properties.