Abstract: A resin composition comprising a nylon-4,6 resin, an epoxy compound having two epoxy groups and at least one polymer selected from halogenated polystyrenes and halogenated poly-alpha-methylstyrenes, represented by the following general formula (I) ##STR1## (wherein R is a hydrogen atom or a methyl group; X is a bromine or chlorine atom; p is an integer of 1 to 5; and n is an integer of 2 or more).

Abstract: A process for producing a thin-walled cylindrical body of an aromatic polyester, which comprises(A) heating a continuous thick-walled tubular body of an aromatic polyester by introducing it continuously into a heating zone while feeding a pressure fluid into the thick-walled tubular body,(B) expanding the heated thick-walled tubular body into a cylindrical form, and(C) continuously stretching and taking up the resulting cylindrical expanded body, while at least forming a fold-free portion in the expanded body in its longitudinal direction; and a thin-walled cylindrical body of an aromatic polyester characterized by a specific intrinsic viscosity, density, wall thickness, surface roughness (CLA), and difference of its refractive indices in the circumferential direction and in a direction perpendicular to the circumferential direction, and substantial freedom from folded marks which cannot be removed at a temperature of 80.degree. C.

Abstract: Heat-resistant aromatic polyester filaments having heretofore unknown physical properties and a combination of excellent heat resistance and mechanical strength, which (1) is composed of an aromatic polyester in which at least 90 mole % of the structural units are ethylene-2,6-naphthalate units, (2) has a melting point at a constant length (Tm;.degree.C.) of at least 287.degree. C., (3) has a density (d)(g/cm.sup.3) of at least 1.370, (4) is insoluble in a phenol/orthodichlorobenzene mixed solvent (mixing ratio = 6/4 on the weight basis) at 160.degree. C. and (5) meets the requirements expressed by the following formulaeL(Tm - 280) = 400 (I).DELTA. n(d - 1.350) = 70 .times. 10.sup.-.sup.3 (II)L = .lambda.K/(B-b)cos .theta. (III)and the process for the preparation thereof.