Patent ID: 8383759

Claim:
A method for producing a liquid crystal polyester, which includes the following steps of: (1) polycondensing a mixture of 65 to 80 mol % of a compound represented by the following formula (I) with 20 to 35 mol % of a compound represented by the following formula (II) (the total of both compounds is 100 mol %) in a polymerization tank at 260 to 350° C. to form a prepolymer while distilled off by-products to be formed, wherein (1-1) the by-products contain a compound in which R 1 and X eliminated from the compound represented by the formula (I) and the compound represented by the formula (II) are bonded, and (1-2) a ratio of by-products to be distilled off to the theoretical amount of by-products formed when the compound represented by the formula (I) is polycondensed with the compound represented by the formula (II) in a stoichiometric relation becomes 95% or more; (2) continuously discharging the prepolymer from the polymerization tank in a molten state, solidifying the prepolymer while successively transferring in one direction, and continuously grinding the solidified prepolymer by a grinder provided at the downstream in a transfer direction to produce prepolymer particles; and (3) heat-treating the prepolymer particles in their solid state under an inert gas atmosphere, thereby subjecting them to solid phase polymerization: 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.