ARISTECH <ARS> SAYS 1ST QTR SHR ESTIMATE RIGHT Aristech Chemical Corp chairman and chief executive officer Thomas Marshall said analysts' estimates of its 1987 fiscal year earnings of 2.25 dlrs to 2.50 dlrs per share are about right. Addressing a gathering of analysts and institutional investors, Marshall also said that analysts' estimates of its first qtr earnings - 50 cts to 55 cts per share - were "in the ballpark." Marshall said the full year estimates represent more than a 32 pct increase over 1986's fiscal year net of 1.70 dlrs per share. He also said the first quarter estimates were 70 pct higher than 1986's first quarter net of 29 cts per share. Marshall attributibuted the first quarter earnings growth to several factors, including sustained demand in Aristech's major domestic markets and continued growth in exports. Aristech plans to spend approximately 200 mln dlrs over in capital investments over the next three years, Marshall added.