- SSP is compulsory
when recycled PET will go for food applications..
- This is the only known way to get rid of monomers
and toxic chemicals that, doesn't matter how good washing
line is, must be removed for FDA approval.
- Here some of the methods commonly used and few words
about a more economical emerging one.
- Solid State Polycondensation applies to crystal polymers (mainly PET and
- What Polycondensation does, is not
only upgrading the IV of the polymer,
that's important anyway, but also remove
monomers and other dangerous chemicals,
specially when raw material is made
out of scraps.
- There are two know ways to do the
- First one is the continuous one,
very effective, high capacity etc.
- Second is the batch system.
- Advantages of first method are the
ones of every continuous line meaning,
when the process is started and all
parameters adjusted, everything run
- Of course, it does if raw material
at the inlet point has a fixed characteristic,
meaning if you set the line to upgrade
the IV by 0,2, for example, and you
feed the system with a polymer with
IV 0,6 the result will be 0,8.
- So, with virgin polymers or, in
other words, if you handle a steady
characteristic product, the result will
- Can this apply to recycled
- You answer it.
- So, let's talk about batch system.
- The batch system SSP is nothing
but a "container" where pellets
(or flakes) are heated up under vacuum
for the period of time variable necessary
to get to the required viscosity.
- This means that whatever you feed
into, you get what you want in terms
of IV because the IV increase is directly
proportional to the residence time that's
under your control.
- Does this sound better ?
- We do think so.
- We did talk about pro's but there are some con's:
- Running SSP means losing almost 20% by weight and this happens because acids, momomers etc. are gone.
- Few companies now are now selling some silicon based "extenders" to increase mechanical properties of the polymer directly into extrusion.
- Some of them got also FDA approval for material at the end of the process so you may take this into consideration.