Liquid crystalline polyesters and methods for their production

A liquid crystalline polyester consisting essentially of dicarboxylic acid units of the following formula (1):

• ##STR164## wherein R.sup.1 is bivalent aromatic hydrocarbon group having from 6 to 18 carbon atoms, diol units of the following formula (2):
• --OCH.sub.2 CH.sub.2 O-- (2)
• and p-oxybenzoic acid units of the following formula (3):
• ##STR165## wherein (i) where moles of said units (1), (2) and (3) are represented by [1], [2] and [3], respectively, they satisfy the following formula (I):
• ##EQU84## (ii) the sequence of the units satisfies the following formula
• .ltoreq. r.sub.1 .ltoreq.0.88 or 0.ltoreq.r.sub.2 .ltoreq.0.88
• wherein r.sub.1 is a sequence forming ratio which is defined by formula (II):
• ##EQU85## and r.sub.2 is a sequence forming ratio which is defined by formula (III):
• ##EQU86## where [3-1] represents the mole of p-oxybenzoic acid units having on their --O-- side a further p-oxybenzoic acid, represented by the underlined portion of formula (3-1):
• ##STR166## and [3-4] represents the mole of p-oxybenzoic acid units having on their ##STR167## side a diol unit of formula (2), represented by the underlined portion of the formula (3-4):
• ##STR168## each among the p-oxybenzoic acid units of the formula (3), and (iii) the viscosity of a solution of the polyester as measured in p-chlorophenol/o-dichlorobenzene (30.degree. C., concentration:
• 0.5 g/dl) is at least 0.4 dl/g.