Isolation and Properties of Dispersants from Western Hemlock Bark

This report describes in detail the quantitative chemical analysis of western hemlock bark’s principal constituents, the development of economic means for isolating certain commercial compounds from the bark and an evaluation of the resulting tannin-based dispersant-deflocculant in drilling muds. Both fresh and mill-run bark were analyzed for wax, flavonoids, tannin, water-soluble carbohydrates, phlobaphene, phenolic acids, lignin, and holocellulose. Fresh bark contained large amounts of holocellulose and extractives including 13 percent tannin. Aged bark contained large amounts of phenolic acids and comparatively lower amounts of holocellulose and extractives (tannin drops to 3 percent). Mill-run bark was selected as the raw material for a commercial tannin-based dispersant. The bark is processed by continuous high temperature extraction with sodium sulfite under controlled time, temperature, pH, and chemical addition conditions. Analysis of the commercial product indicated it is composed almost entirely of tannin, phlobaphene, and phenolic acid fractions. Evaluation of the product “Rayflo” was made against competitive tannin and lignin-based dispersants for effects on fluid loss, yield value, viscosity, and gel strength of fresh water and low-line drilling muds. The product was also evaluated as a deflocculant for ceramic clay and dispersant for carbon black in synthetic rubber manufacture.

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