Got the Universal Tire Patch Kit?  It uses a special vulcanizing cement that chemically bonds the patches and strings to the rubber of the tire.  

Note that when you first use the tube of glue that came in your tire patch kit, the shelf life of the remaining glue is reduced.  How long it remains viable is hard to guess.  Months, perhaps a year.  We recommend replacing a partially used tube of glue as soon as you get back home.   

If you need more glue, this is the stuff to order.

The tube contains 20 ml, enough for about six tire repairs.