Process and apparatus for continuous production of polyesters

In a process for continuous production of a polyester which comprises reacting (A) normally solid terephthalic acid with (B) normally liquid ethylene glycol, to produce a low molecular weight bis-.beta.-hydroxyethylene terephthalate, subjecting said bis-.beta.-hydroxyethylene terephthalate to precondensation under reduced pressure to produce an intermediate ethylene terephthalate product of increased molecular weight, and subjecting said intermediate product of polycondensation under further reduced pressure to increase the molecular weight of the intermediate product and thus produce polyethylene terephthalate, the improvement which comprises

• subjecting a mixture containing solid starting material (A) and liquid starting material (B) to the shearing and homogenizing action of a rotor-stator comprising rows of teeth and holes arranged in a ring-shape on the rotor and stator to form a series of shearing gaps, wherein said mixture is axially sucked into said rotor, subjected to shearing and homogenizing action in said rotor-stator to increase the surface area of said starting material (A), and to produce a homogeneous mixture containing (A) and (B), and then said homogeneous mixture is radially ejected from said stator, and
• introducing said homogeneous mixture into a thin-layer evaporator wherein said starting materials (A) and (B) are reacted with each other to produce a reaction mixture containing said low molecular weight bis-.beta.-hydroxyethylene ester.