What is a "tri-salt polymer" as described by this product that eliminates and prevents mold?
Beside the three-step deprotonation  of (ortho) phosphoric acid, $\ce{H3PO4}$, along

$\ce{H3PO4 &lt;=&gt; H2PO4^- + H+ &lt;=&gt; HPO4^{2-} + 2H+  &lt;=&gt; PO4^{3-} + 3H+}$

where each of the oxygen-bound hydrogen atoms may be substituted by a cation, phosphoric acid may dehydrate partially to yield polyphosphates.  Which seems, reading a related Canadian patent CA2504014 (A1) (deposit in English), the working principle here:



(loc. cit., p. 6; cations generalized)

The know-how includes tuning the proccessing as such that the composition of these blend polyphosphates is obtained reliably, since the complete dehydration simply would yield the waxy polyphosphoric acid used as acidic catalyst in the lab.