1 . an ester copolymer resin having a general formula i !. ho . paren open - st . coarcooro . paren close - st .. sub . n h i ! wherein ar represents 2 , 6 - naphthalene group or phenylene group , r represents ethylene group or 1 , 4 - cyclohexylene group , and n is a number of 100 to 1000 and a polymer alloy having a solubility parameter of 10 . 8 to 11 . 9 consisting essentialy of the ester copolymer and a polycarbonate resin are provided . the ester resin and the alloy are transparent and has a heat resistance and a hot water resistance resisting sterilization of food , a good heat sealebility to aluminum closure , and recycling ability with pet resin .