Mitsubishi Chemical Corporation said it has dropped plans to build a $1 billion chemical plant in Geismar. The company announced Tuesday it would not build the plant, which would have produced methyl methacrylate (MMA), a raw material for acrylic resins used to make automobile lamp covers, signboards, aquarium tanks, paints and building materials. It would have been the largest manufacturer of MMA, producing up to 350,000 tons annually.