Hi Warrior372,
Welcome to the Mattress Forum! :).
The slow recovery latex is essentially a blended SBR latex…but with a chemical package added, I think in a final mixing stage, which works with essentially the same Talalay blended formula but gives it slow response characteristics. I do not know the exact chemicals (slow recovery) used, not sure anyone does on this forum.
Here is a good post from Phoenix regarding natural and sbr latex.
And similar information in this post.
Thanks,
Sensei