GB928166A - Etching process and improved etching bath - Google Patents

Abstract

928,166. Etching. DOW CHEMICAL CO. June 2, 1960 [June 12, 1959 (3)], No. 19496/60. Class 100 (2). An etching bath comprises a dilute strong acid, a water-immiscible organic fluid, and a filming agent, the last being an organic sulphonic acid or sulphonate, the hydrophobic portion of which consists of two or more organic radicals connected by an amide, ester or ether bridge, at least one of the radicals containing twelve or more carbon atoms in an uninterrupted series of carbon-to-carbon bonds. The proportions are acid 30-200 grams/litre, organic fluid 3-150 grams/litre, filming agent 0.2-20 grams/litre. The acid is nitric acid, to which may be added small amounts of sulphuric, hydrochloric or acetic acid. The organic fluid may be a hydrocarbon aromatic, aliphatic or naphthenic, B.P. 90-390‹ C., e.g. ligroin, kerosene, gas oils, diethylbenzenes, tetramethylbenzenes, diisopropylbenzenes, dodecylbenzene, turpentine, monochlorethylbenzene, ethylbutyl ketone, isophorone, methylhexyl ketone d-limonene,diisodecylphthalate,diamylnaphtha lene, dicapryladipate; in general, esters, ketones, terpenes, ethers. The filming agent may be a salt of an alkali metal, alkaline earth, ammonium or magnesium. The organic radicals may be aryl, cyclo aliphatic or aliphatic, such as hexylbenzene, dipropylbenzene, amyltoluene, ethylnaphthalene. Examples of filming agents are sodium n-methyl-n-(tall oil acid) taurate, sodium dioctyldiphenyloxide monosulphonate, sodium isopropyloleate sulphonate. Specifications 703,814, 709,315, 725,110 and 818,744 are referred to.