Usually, the process by adding recycled PET to spin will be quite unstable. Namely, the IV (intrinsic viscosity) value of recycled PET, even treated with SSP (solid state condensation), is unstable and its IV value is different from the virgin PET. Therefore, chemical fibers manufacturers in China are looking for a recycling modifier that can stabilise the IV value of recycled PET and overcome the instability of the spinning process caused by the addition of recycled PET.
The solution will be
(1) 1250PET/ 1400PET is added in advance to produce recycled PET pellets. Then it is mixed with virgin PET material for spinning yarns
(2) Mixing PET virgin material, recycled PET and 1250PET/ 1400PET to spin
The IV recycled PET after treatment with SSP has indeed improved. However, the viscosity during processing is still unstable and the viscosity will undergo frequently sudden drops. So the purpose of adding 1250PET and 1400PET is to make:
(1) The viscosity of the SSP treated PET can be more stable during processing such as spinning, injection, extrusion… etc.
(2) The time point at which the viscosity decrease of the SSP-treated PET occurs during the processing such as spinning, injection,…etc. can be delayed. In other words, viscosity reduction occurs after the viscosity of PET can be stabilised for a longer period of time during processing.
(3) Minimise the IV gap between recycled PET and virgin PET. The IV of the recycle PET after SSP treatment will still be lower than that of the virgin PET. In addition, the viscosity reduction of the recycle PET occurs faster than virgin PET during the processing such as spinning, injection, etc. Adding 1250PET and 1400PET can effectively improve these problems of recycled PET.
