The Securities and Exchange Commission on Wednesday approved a rule forcing mutual funds to name independent board chairmen and requiring three-quarters of the board to be unaffiliated with management. The SEC voted to approve the controversial rule 3-to-2 with SEC Chairman William Donaldson casting the deciding vote against two other fellow Republicans to vote in line with Democratic commissioners Roel Campos and Harvey Goldschmid. The new rule is aimed at eliminating potential conflicts of interest in the $7.5 trillion industry. The rule is expected to take effect in 18 months.