Method of mixing and device useful thereof

A method of mixing ingredients comprising solid thermoplastic particulates and a viscous material in a first container without first melting the solid thermoplastic particulates, the method comprising:

• feeding a predispersion comprising a substantially homogeneous mixture of the solid thermoplastic particulates and a major portion of the viscous material into a first container, wherein the solid thermoplastic particulates comprise poly(ethylene terephthalate) particles and the viscous material comprises terephthalic acid and monoethylene glycol;
• feeding a remaining minor portion of the viscous material into the first container;
• and
• mixing the ingredients in the first container,
• wherein the major portion of the viscous material comprises a quantity of monoethylene glycol in excess of the quantity required to transesterify substantially all of the poly(ethylene terephthalate);
• and
• wherein the viscous material has a dynamic viscosity of from 200 centipoise (cP) to 200,000 cP at 20° C.