Gujarat-based DCW today said it will invest Rs 525 crore for increasing its existing production capacities and using the by-products to augment its bottomline.The company said it planned to increase its synthetic rutile production from 30,000 tonnes to 60,000 tonnes and was also setting up a new captive thermal plant of 50 MW capacity for reducing the cost of power.The company would change its mercury cells into membrane cells for increasing the production of caustic soda, S C Jain, CMD of DCW, said.A new iron oxide plant to produce yellow, red and black grades is being set up as well, for about Rs 125 crore and is proposed to go on stream by November-December 2007. The company's capital expenditure plan also includes a proposal to raise Rs 150 crore through the issue of foreign currency convertible bonds (FCCBs) over the next 18 months and a long term loan from a consortium of banks led by SBI, Jain said.DCW informed the Bombay Stock Exchange that it would invest Rs 200 crore for doubling its soda ash capacity to 2 lakh tonnes from 1 lakh tonnes.The company, which manufactures basic chemicals like caustic soda, Chlorine based products Synthetic Rutile, Yellow Iron Oxide and PVC Resin, said its capacity expansion plans were expected to be implemented by March 2008 in stages, beginning September 2007.