Process for producing aromatic liquid crystalline polyester and film thereof

An aromatic liquid crystalline polyester prepared by a process comprising the steps of:

• charging 80 to 20 mol % of a compound represented by the following formula (I) and 20 to 80 mol % of a compound represented by the following formula (II) into a reaction vessel;
• conducting polycondensation reaction of the charged mixture at a temperature from 270 to 350° C. at normal pressure to produce an aromatic liquid crystalline polyester having a flow temperature of 210° C. or more and lower than the polycondensation reaction temperature by 30° C. or more;
• discharging the aromatic liquid crystalline polyester in a molten state from the reaction vessel and solidifying;
• then, pulverizing the solidified polyester into particles having a particle size of 3 mm or less;
• and heat-treating at a temperature from 200 to 310° C. still in the solid state under inert gas atmosphere,
• in the formula, R1 represents a hydrogen atom, formyl group, acetyl group, propionyl group or benzoyl group, and R2 represents a hydrogen atom, methyl group, ethyl group, propyl group, benzyl group or phenyl group,
• in the formula, R1 and R2 are the same with those defined in formula (I), R1s in formulae (I) and (II) may be the same or different from each other, R2s in formulae (I) and (II) may be the same or different from each other, and the flow temperature means a temperature (° C.) at which the melt viscosity measured by a capillary type rheometer is 48,000 poise when a resin which has been melted by heating at a temperature raising rate of 4° C./min is extruded through a nozzle having an internal diameter of 1 mm and a length of 10 mm under a load of 100 kgf/cm2,
• wherein the aromatic liquid crystalline polyester comprises 80 to 20 mol % of the following repeating unit (A) and 20 to 80 mol % of the following repeating unit (B):