Patent ID: 8759474

Claim:
A method for producing a liquid crystal polyester, which comprises the following steps of: (1) polycondensing a mixture of 70.5 to 71.5 mol % of a compound represented by the formula (I) with 28.5 to 29.5 mol % of a compound represented by the formula (II) (the total of both compounds is 100 mol %) at 260 to 350° C. to form a prepolymer, wherein the prepolymer has a flow initiation temperature of 200° C. or higher, and the mixture is polycondensed until reaching the temperature which is at least 30° C. lower than the polycondensation temperature; (2) removing the prepolymer in a molten state, followed by solidification and further grinding to produce prepolymer particles having a particle size of 3 mm or less; and (3) subjecting the prepolymer particles to a heat treatment at 200 to 310° C. under circulation of an inert gas while remaining in a solid phase state; wherein R 1 represents a hydrogen atom, a formyl group, an acetyl group, a propionyl group or a benzoyl group; R 2 represents a chlorine atom, a bromine atom, or a group selected from the group consisting of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group and a tertiary butyl group; X represents a hydroxy group, an organyloxy group, a halogen atom or an acyloxy group; and X is an integer of 0 to 4 and, when X is 2, 3 or 4, a plurality of R 2 (s) are the same or different from each other; and wherein R 1 and X respectively have the same meanings as those of R 1 and X in the formula (I), and are respectively the same as or different from each other from R 1 and X in the formula (I); R 3 and R 4 each independently represents a chlorine atom or a group selected from the group consisting of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group and a tertiary butyl group; y is an integer of 0 to 3 and, when y is 2 or 3, a plurality of R 3 (s) are the same or different from each other; and z is an integer of 0 to 3 and, when z is 2 or 3, a plurality of R 4 (s) are the same or different from each other.