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Addition of Surfactants to Water Magnetite Suspensions

IP.com Disclosure Number: IPCOM000087204D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 4 page(s) / 50K

Publishing Venue

IBM

Related People

Ronay, M: AUTHOR

Abstract

There is a family of surfactants, the polyoxyethylene alkylamines, which may be considered to be the ideal additives to produce magnetically and mechanically stable water-magnetite colloid suspensions with low viscosity and relatively large surface tension. Such additives should be particularly suitable for making magnetic inks for ink jet printers. The polyoxyethylene n-alkylamine series of compounds is by far the most important of the ethylene oxide derived cationic surfactants. The most outstanding examples are the ETHOMEENS* and ETHODUOMEENS*. All these compounds, which are commercially available, are fatty acid-derived.

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Addition of Surfactants to Water Magnetite Suspensions

There is a family of surfactants, the polyoxyethylene alkylamines, which may be considered to be the ideal additives to produce magnetically and mechanically stable water-magnetite colloid suspensions with low viscosity and relatively large surface tension. Such additives should be particularly suitable for making magnetic inks for ink jet printers. The polyoxyethylene n-alkylamine series of compounds is by far the most important of the ethylene oxide derived cationic surfactants. The most outstanding examples are the ETHOMEENS* and ETHODUOMEENS*. All these compounds, which are commercially available, are fatty acid-derived.

The starting materials are those available to the fatty acid industry, mainly coco oil, tallow, soya and cottonseed oil. The nomenclature of the ETHOMEEN series is as follows: In general, the trade name ETHOMEEN is followed by a letter then a virgule and a number. The letter refers to the alkyl group C = coco, S = soya, T = tallow, and O = oleyl. All these are mixtures (of various carbon- chain length) such as are available in the raw materials. The number after the virgule refers to the number of moles of ethylene oxide reacted minus ten.

These cationic surfactants are characterized by a hydrophobic cation when the surfactant is dissolved in water. This makes the surfactant properties dependent on pH. The lower ethylene oxide adducts of predominantly cationic character, being insoluble in water at neutral or basic conditions, will become better surfactants at lower pH's, owing to the formation of water-soluble ammonium ions. This improvement in surfactant properties is not true for oxyethylated amines of predominantly nonionic character (longer ethylene oxide chain) that are already soluble at neutral or basic conditions. An example of polyoxyethylene fatty amines is the family of polyoxyethyleted coconut oil amines ETHOMEEN C/12, ETHOMEEN C/15, ETHOMEEN C/20 and ETHOMEEN C/25.

The reasons for selecting polyoxyethylene fatty acid amines are stated below. The surface of magnetite particles is charged negatively. Because of the cationic nature of the amine group in polyoxyethylene fatty amines, they are attracted to the negatively charged magnetite surface. Once adsorbed, the polyoxyethylene fatty amines form a protective and tightly bound film, which protects the surface from oxidation. This adsorptive and protective effect occurs at many organic surfaces, such as paper. The colloidal suspensions prepared with these surfactants readily adsorb and break on the paper depositing magnetite, and the organic phase in the paper allows the water to evaporate rapidly. Consequently, drying times are short.

The fatty acid of these surfactants should be saturated rather than unsaturated to avoid oxidation of the double bond with time. Coconut oil contains only 5% unsaturated fatty acid. The surface tension lowering effect is inversely proportional to the length of the...