LEICESTER, Mass. - Morton H. Sigel, founder of Millbrook Distribution Services here, died this month after a long illness. Sigel launched Millbrook in 1960 in Worcester, Mass., and through the years diversified the business from a health and beauty care specialist to a more wide-ranging distributor, offering specialty foods and other products. McKesson Corp. acquired Millbrook in 1986, and Sigel remained there until 1990. He was the first president of the National Association of Service Merchandisers. He is survived by his wife, Vivian, three children and 10 grandchildren.