you are actually using standard cookie authentication with SSO. the lifetime of the cookie is tied to the token lifetime. the login token is only used to create the cookie. when the cookie expires, the browser does not include it in the request.
while you could request and store a refresh token on the server, when the the unauthenticated request comes, you do not know the identity of user. you would need to add a different cookie to store this or you would need to update the cookie before it expires. thus you would implement a sliding window. as you are using owin cookie, you need to code this yourself.