Patent ID: 7271282

Claim:
A process for preparing an alicyclic dicarboxylic acid diester represented by the formula (1) wherein A 1 represents a cyclohexane ring or cyclohexene ring, X is a hydrogen atom or methyl, R 1 and R 2 are the same or different and each is a branched-chain alkyl group having 3 to 18 carbon atoms, a straight-chain alkyl group having 1 to 18 carbon atoms, a straight-chain alkenyl group having 2 to 18 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms; and having the following properties: 1) a total acid number of 0.05 mgKOH/g or less, 2) a sulfated ash content of 10 ppm or less, 3) a sulfur content of 20 ppm or less, 4) a phosphorus content of 20 ppm or less, 5) a peroxide value of 1.0 meq/kg or less, 6) a carbonyl value of 10 or less, 7) a volume resistivity of 1×10 11 Ω·cm or more, 8) a hydroxyl value of 3 mgKOH/g or less, and 9) a water content of 100 ppm or less, the process comprising the steps of (i) subjecting a) an alicyclic dicarboxylic acid represented by the formula (2) wherein A 1 and X are as defined above, or an anhydride thereof, and b)an aliphatic monohydric alcohol having 1 to 18 carbon atoms or an alicyclic monohydric alcohol having 3 to 10 carbon atoms each having a peroxide value of 1.0 meq/kg or less to esterification reaction in the absence of a catalyst or in the presence of a sulfur-free and phosphorus-free catalyst, or subjecting a′) an alicyclic dicarboxylic acid diester represented by the formula (3) wherein A 1 and X are as defined above, R 3 and R 4 are the same or different and each is a branched-chain alkyl group having 3 or 4 carbon atoms or a straight-chain alkyl group having 1 to 4 carbon atoms, and b′) an aliphatic monohydric alcohol of 5 to 18 carbon atoms or an alicyclic monohydric alcohol of 3 to 10 carbon atoms each having a peroxide value of 1.0 meq/kg or less to ester interchange reaction in the absence of a catalyst or in the presence of a sulfur-free and phosphorus-free catalyst selected from the group consisting of tetra(C 3 -C 8 alkyl)titanate, titanium oxide, titanium hydroxide, sodium alkoxide of 1 to 4 carbon atoms, sodium hydroxide, C 3 -C 12 fatty acid tin salt, tin oxide, tin hydroxide, zinc oxide, zinc hydroxide, lead oxide, lead hydroxide, aluminum oxide and aluminum hydroxide, to thereby obtain a reaction mixture containing the diester represented by the formula (1), (ii) removing excess starting materials from the reaction mixture obtained in step (i) to thereby obtain the diester in a crude form, (iii) neutralizing the crude diester obtained in step (ii) and washing the neutralized crude diester with water, (iv) purifying the crude diester neutralized and washed with water in step (iii) by treatment with 1 to 4 adsorbents, and (v) dehydrating the diester purified in step (iv).