Though it’s called “small talk” there’s nothing small about it when it comes to a negotiation or mediation (or any other situation where you’re trying to build rapport). If you’re going to have a meaningful conversation with someone you don’t know, or don’t know very well, small talk is a way to start building that bridge to the other party. Only after that bridge is built can the parties reach out to each other and resolve a dispute between them.
The Muse has a number of suggestions on how to start and maintain a conversation.