'Tall oil' and 'tall oil destillate' are the names given to the most important by-product obtained during the production of sulphite pulp, using the kraft pulping process, in which resin-rich timber varieties undergo decomposition.
'Tall' is the Swedish word for 'pine' (tree). The timber varieties used in production include (Swedish) spruce and pine. Tall oil is a mixture of fatty acids, wood acids (oxo acids), oxidated resin and fatty acids, also their non-saponifiable components. The composition varies, depending on geographical origin.
Tall oil and tall oil distillate are obtained by using acid to break down sulphite pulp produced using the kraft process (pulping). The tall oil soap (black liquor) produced by means of this process is reduced by evaporation to yield crude tall oil, a dark brown, tacky mass that gives off an extremely offensive sulphurous smell. The mass is then purified (tall oil) or sent for fractional distillation (tall oil distillate).
Tall oil products are bright yellow to yellow (tall oil fatty acid, tall oil) or yellow-brown (tall oil distillate), non water-soluble liquids. Both products are used primarily as raw materials for non-yellowing paint, in the production of detergent substances, as mineral flotation collectors and in the production of intermediate chemical products. The products are also used in the paper and chemical industries (emulsifiers for caoutchouc synthesis), also as raw materials for printing dyes and adhesives.