Hydrotropic and surfactant properties of novel diisopropyl naphthalene sulfonates

Abstract

A novel surfactant and hydrotrope, sodium diisopropylnaphthalene sulfonate (SDIPNS) has been developed. It contains about 92% diisopropylnaphthalene sulfonate, compared to other materials which are less than 50% diisopropylnaphthalene sulfonate. Aqueous solutions of 34-36% active SDIPNS have dual functionality. They have excellent surface properties and are compatible with conventional anionic, nonionic, and amphoteric surfactants. They demonstrate good laundering detergency in combination with sodium lauryl ethoxy sulfate, with or without builder. They maintain surface activity in 150 ppm hard water (Ca 2+ /Mg 2+ = 2:1), 5% NaCl, pH 2, and pH 12. They are effective hydrotropes. They enhance surfactant solubility, raise the cloud point of nonionic surfactants, and modify the viscosity of surfactant formulations. They are light in color and are low-foaming.A unique sodium diisopropylnaphthalene sulfonate (SDIPNS) that contains about 92% diisopropylnaphthalene sulfonate has both hydrotropic and surfactant properties. There are several definitions of hydrotropy and hydrotropes in the literature. "Hydrotropy is the solubilizing effect in water caused by materials that need not be surface active and that do not need to form micelles to effect their action" (1). Hydrotropes are "shortchain organic compounds with a polar group that could serve as agents to dissolve poorly water soluble substances into water, if added in high concentrations" (2). Surfactants display surface activity.Alkylbenzenesulfonates and alkylnaphthalenesulfonates act as hydrotropes to modify solubilities, viscosities, and other properties of surfactants and surfactant formulations. Sodium toluenesulfonate and sodium xylenesulfonate are the best-known hydrotropes, but alkylnaphthalenesulfonates also possess hydrotropic properties. A paper was presented at the 1997 AOCS Annual Meeting, and subsequently published, describing the hydrotropic properties of some short-chain alkylbenzene-and alkylnaphthalene sulfonates (3). Another paper was presented at the 1998 AOCS Annual Meeting describing some of the hydrotropic properties of a novel alkylnaphthalene sulfonate, SDIPNS. It was published as well (4). This paper describes both hydrotropic and surfactant properties of that material.A 35% active aqueous solution of SDIPNS is a multifunctional ingredient, acting both as an effective hydrotrope and as a surfactant. EXPERIMENTAL PROCEDURESMaterials. SDIPNS is available as high-salt (SDIPNS-HS) and low-salt (SDIPNS-LS) versions. The only difference between them is the sodium sulfate content. The LS version contains less than 1% sodium sulfate, while the HS version can contain up to 7% sodium sulfate. A total of five brands of diisopropylnaphthalene sulfonate is on the market in the United States. About 92% of the naphthalene sulfonate in the materials discussed in this paper is diisopropylnaphthalene sulfonate, as described in a previous paper (4), with the remainder being mono-and triisopropylnaphthalene sulfonates. The material is a mixture of isomers where...

Synthesis and study of the surface properties of long‐chain alkylnaphthalene sulfonates

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