GB659925A - Method of inhibiting foaming in steam generation and compositions therefor - Google Patents

Abstract

Diethers of polyoxyalkylene glycols having a molecular weight of at least 500, in which the terminal ether groups are attached to different carbon atoms, are prepared by (1) reacting two moles. of an alkyl halide with one mole. of the disodium salt of the polyoxyalkylene glycol; (2) by reacting one mole. of the dihalide of the polyalkylene glycol with two moles. of the sodium alcoholate; (3) via the monoether by reacting an alkylene oxide such as ethylene or propylene oxides or a mixture thereof with a monohydric alcohol, then reacting the sodium alcoholate derived from the resulting monoether with (a) an alkyl halide or (b) an alkylene dihalide, to give the diether. The alkylene radical is preferably ethylene or propylene or polyoxyalkylene chains containing both, preferably in the ratio 1 : 1, may be used. The ether group may be derived from monohydric alcohols such as from the simple alkanols up to higher members such as lauryl, cetyl and octadecyl; alicyclic alcohols such as cyclohexanol, or aralkyl alcohols such as hexyl alcohol. Examples are given of the preparation of the dicetyl and dilauryl ethers of polyethylene glycol, the dicetyl, dilauryl, dioctyl and mixed butyl lauryl diether of polypropylene glycol and the butyl cetyl diether of a polyoxyalkylene chain where the ratio of ethylene to propylene is approximately 1 : 1. The products are employed as foam inhibiting agents.ALSO:An antifoaming agent for steam generator comprises a diether of a polyoxyalkylene glycol having a molecular weight of at least 500 wherein the terminal ether groups are connected to different carbon atoms. The alkylene radical is preferably ethylene or propylene or polyoxyalkylene chains containing both preferably in the ratio of 1 : 1 may be used. The ether groups are derived from monohydric alcohols such as the simple alkanols up to the higher members such as lauryl, cetyl and octadecyl; alicyclic alcohols such as cyclohexanol or aralkyl alcohols such as benzyl alcohol. The foam inhibitors of which numerous examples are given may be employed in admixture with dispersants such as powdered tannin, sodium lignin sulphate, desulphonated lignin, sulphated oils, soaps of oleic acid or tall oils, soda ash, ortho and polyphosphates and may be used in powder or briquette form within the preferred range of 0.001 to 0.1 grains per gallon. The effect of magnesium salts is nullified by the addition of hydroxylated organic compounds such as tannins, tannic acid, gallic acid, pyrogallol, catechol and phloroglucinol.