use 1031 money to pay off mortgages ?

[Daniel Blau]

I have two lines of credit used to purchase properties which are adjustable rate ... and now given the increased prime rate they are not such great rates any longer.    if i sell an investment property is there is a way to use the money to pay off the mortgage on that property ?   what about to pay off the mortgage on another investment property ?   is this allowed or is there a "creative" way to do this ?  

thanks Dan