CANADA STOCKS-TSX firm as copper producers slip but energy shares gain

* TSX up 18.54 points, or 0.12 percent, at 15,527.93 * Five of 10 main index sectors rise * First Quantum, Teck drop with copper price By John Tilak TORONTO, Sept 9 (Reuters) - Canada's main stock index edged higher on Tuesday as a rise in energy stocks boosted by stronger U.S. oil prices was partially offset by weakness in some commodity producers, weighed down by weak copper prices. With the price of copper dropping 2.2 percent, First Quantum Minerals Ltd shed 2.7 percent