China's largest polyester producer, Sinopec Yizheng Chemical Fibre Co Ltd, on Wednesday posted a 53.6 per cent year-on-year plunge in first half net profit to $6.8 million due to lower product prices. The company said it made 707,162 tonnes of polyester goods in the first six months of the year, up 15.6 per cent on the year-ago period, and plans to boost production for the second half to 711,600 tonnes.