Abstract: Aligning films formed on electrode plates of a liquid crystal cell containing an antiferroelectric liquid crystal are each made of a polyimide film represented by the following chemical formula: ##STR1## wherein x.sub.1 and Y.sub.

Abstract: Linear aromatic copolyamides having good processability, superior thermal stability and excellent mechanical properties are provided. They comprise 55-90 mole % of a repearing unit of ##STR1## and 45-10 mole % of a repeating unit of ##STR2## wherein R.sub.1 and R.sub.2 each is a C.sub.4-12 aliphatic alkylene.

Abstract: Aromatic polyamides of the invention are polyamides comprising a recurring unit ##STR1## and a recurring unit [--NH--Ar.sub.1 --NH--] and copolyamides comprising a recurring unit ##STR2## and a recurring unit [--NH--Ar.sub.2 --NHCO--Ar.sub.3 --CO--] wherein Ar.sub.1 and Ar.sub.2 are, for example, phenylene group, naphthylene group, biphenylene group, and 4,4'-methylenediphenylene group and Ar.sub.3 is, for example, phenylene group, naphthylene group and biphenylene group in which both the bonding chains extend in the coaxial direction or in the parallel direction to axis.The aromatic polyamide of the invention has high glass transition temperature and has heat resistance, high strength, and high elasticity and besides is soluble in various solvents and is excellent in spinnability and film-formability. The aromatic polyamide is molded into fibers or films and can be utilized as electric insulating materials, laminates, varnishes, fabrics, synthetic papers, etc.

Abstract: The invention intends to separating a methyl derivative of naphthalene (2,6-dimethyl naphthalene or 2-methyl naphthalene) from a mixture material in a high purity more than 98 weight %. The starting material is preliminarily treated at a raised temperature up to 220.degree. c. at the highest and with LHSV of 0.1-6 Hr.sup.-1 in the presence of an acid catalyst usually used for olefin polymerization. The treated material is distillated to remove the polymerized impurities and to raise the naphthalene derivative content at least up to 50 weight %. And then the obtained material is subjected to the crystallization under a pressure of 500-2500 kgf/cm.sup.2 at a temperature of 80.degree.-150.degree. C. (for 2,6-DMN) or 10.degree.-35.degree. C. (for 2-MN).