While this is definitely a question for your attorney, as various states may have adopted different versions or modified versions of UCC 9, I can give you a little bit of information.
Basically, a lender can obtain a PMSI in Inventory over a prior existing blanket or "All inventory" lien if they meet the specific requirements spelled out in the Article.
https://www.law.cornell.edu/ucc/9/article9(b) [Inventory purchase-money priority.]
Subject to subsection (c) and except as otherwise provided in subsection (g), a perfected purchase-money security interest in inventory has priority over a conflicting security interest in the same inventory, has priority over a conflicting security interest in chattel paper or an instrument constituting proceeds of the inventory and in proceeds of the chattel paper, if so provided in Section 9-330, and, except as otherwise provided in Section 9-327, also has priority in identifiable cash proceeds of the inventory to the extent the identifiable cash proceeds are received on or before the delivery of the inventory to a buyer, if:
(1) the purchase-money security interest is perfected when the debtor receives possession of the inventory;
(2) the purchase-money secured party sends an authenticated notification to the holder of the conflicting security interest;
(3) the holder of the conflicting security interest receives the notification within five years before the debtor receives possession of the inventory; and
(4) the notification states that the person sending the notification has or expects to acquire a purchase-money security interest in inventory of the debtor and describes the inventory
You may want to read this article for a little bit of background.
http://www.abfjournal.com/articles/benef...exities-is-key/