A 76-year-old textile mill that was revived by a new owner eight years ago has failed to survive a weak economy and overseas competition and is closing. Amerbelle Textiles in Vernon will shut down by August, leaving 70 employees jobless. Jon Moyer, chief financial officer, said that the company — which dyes, finishes, and coats textiles used for space travel, canopies, flags, shoes, and a range of other items — could not compete with low wages overseas and the slow economy. Owner Doug Rimsky said the company has lost money in each of the eight years he has owned it. As textile mills closed across New England in previous decades, Amerbelle survived by finding a niche market. But in the end, it could not compete with cheap labor in Asia and elsewhere, antipollution rules, and other factors, company officials said.