Private equity firms Apollo Global Management and Bain Capital had until 5pm today to make an offer for the packaging firm under the previous deadline set by the Panel on Takeovers and Mergers.
But RPC said the Panel has extended the deadline to 5pm on 5 December.
It is the second extension with the original deadline set for October 8.
The plastics maker revealed it was in takeover talks with Apollo and Bain Capital in September after facing pressure from investors to raise more cash and cut capital spending.
In July, the company said it would look at proposed disposals to generate capital for expansion or to return cash to shareholders following investor disagreements over its acquisition strategy.
Meanwhile, accountancy regulator the Financial Reporting Council contacted RPC in connection with its compliance with reporting requirements in June.