Helly has it right, PET it is - it's the same material as polyester apparently. Also source of one of the the current environmental bugbears, micofibres
AIUI changing drinks bottles into fleeces is an end of life thing. There's no more recycling to be done once it's a fleece.
Perhaps, not entirely so.
Thanks to the indestructability (yes, there is such a word - I just used it) of the material, my fleece was handed down to someone younger and slimmer than me.
Once he has done with it (or become a f@t b@st@rd) I'm sure there'll be sufficient mileage left in the garment for someone else to keep warm.
The stuff just doesn't deteriorate.
ETA - Less re-cycling, more re-use.