Injection-molded product of polyglycolic acid and production process

Abstract

An injection-molded product is obtained by injection molding a thermoplastic resin material. The thermoplastic resin material comprises a polyglycolic acid homopolymer or copolymer having a repeating unit represented by the following formula (1): ##STR1## in a proportion not lower than 70 wt. % and a repeating unit derived from at least one cyclic comonomer selected from the group consisting of ethylene oxalate and lactide in a proportion not higher than 30 wt. %, and having the following physical properties: (a) a melt viscosity, n*, measured at a temperature of the melting point, Tm, of the polyglycolic acid homopolymer or copolymer +20.degree. C. and a shear rate of 1,000/sec, of 30-10,000 Pa.multidot.s; (b) a melting point, Tm, of at least 150.degree. C.; (c) a melt enthalpy, .DELTA.Hm, of at least 20 J/g; and (d) a density of at least 1.50 g/cm.sup.3 as measured in an unoriented, crystallized form. The injection-molded product has Izod impact strength, unnotched, 25.degree. C., of at least 20 kJ/m.sup.2, tensile strength of a least 60 MPa, tensile elongation of at least 5%, flexural strength of at least 100 MPa, and flexural modulus of at least 5 GPa, and is obtained by injection molding at an injection temperature ranging from the melting point, Tm, of the homopolymer or copolymer to 255.degree. C.