Resin Acid - Production in Tall Oil (chemical Pulping Byproduct)

Production in Tall Oil (chemical Pulping Byproduct)

The commercial manufacture of wood pulp grade chemical cellulose using the kraft chemical pulping processes releases resin acids. The Kraft process is conducted under strongly basic conditions of sodium hydroxide, sodium sulfide and sodium hydrosulfide, which neutralizes these resin acids, converting them to their respective sodium salts, sodium abietate, ((CH₃)₄C₁₅H₁₇COONa) sodium pimarate ((CH₃)₃(CH₂)C₁₅H₂₃COONa) and so on. In this form, the sodium salts are insoluble and, being of lower density than the spent pulping process liquor, float to the surface of storage vessels during the process of concentration, as a somewhat gelatinous pasty fluid called kraft soap, or resin soap.

Kraft soap can be reneutralized with sulfuric acid to restore the acidic forms abietic acid, palmiric acid, and related resin acid components. This refined mixture is called tall oil. Other major components include fatty acids and unsaponifiable sterols.

Resin acids, because of the same protectant nature they provide in the trees where they originate, also impose toxic implications on the effluent treatment facilities in pulp manufacturing plants. Furthermore, any residual resin acids that pass the treatment facilities add toxicity to the stream discharged to the receiving waters.