Tupperware, maker of the iconic plastic kitchenware boxes, has filed for bankruptcy in the US after years of financial struggles. Tupperware Brands Corp is seeking to sell the business while continuing to operate. It has officially filed for bankruptcy with Chapter 11 creditor protection under US bankruptcy law. The US firm revolutionized the world of housewares with its bowls, dishes and kitchen containers, becoming a symbol of post-World War II prosperity. But the Orlando-based company, founded in 1946 by Earl Tupper, has been struggling amid a fiercer competition in the market for household…