PRODUCTION OF PRE-DYED POLYESTER

PURPOSE:To produce a pellet or powder pre-dyed polyester readily, by premixing a polyester with a colorant in a kneader, drying the mixture and melt-kneading, cooling and grinding it. CONSTITUTION:A polyester is melt-kneaded with a pre-dyeing agent (e.g., carbon black, titanium dioxide, or dioxazine pigment) at a weight ratio of about 90:10- 45:55 by using a pressure kneader having Banbury blades and a cooling jacket. In performing the above process, the premixing and the drying are performed in the kneader under conditions represented by fornulas I, II, and III [wherein T is a kneading temperature, Tm is the m.p. of the polyester, and S is time (min)], and the dried premix is melt-kneaded, cooled, and ground to form a pre-dyed polyester. The above pre-dyed polyester can show excellent colorability though the proportion of the colorant added is relatively small, and in addition yarn break difficultly occurs during its spinning.