Tall oil
Tall oil ( from swedish: tall = pine), also known as liquid rosin, is an oily mixture, which as the most important by-product in the manufacture of pulp: accumulates (more precisely sulphate pulp, especially with pine wood). It is a black-and- yellow liquid, which is composed mainly of fatty acids ( about 42 to 55%) and resin acids ( about 33 to 47% ) and sterols and other substances. The composition varies greatly due to the origin of resinous wood. In spite of plant origin is not a vegetable oil.
- 2.1 fractionation
- 2.2 Distillation and refining
- 2.3 Products: Fatty acids
- 2.4 Products: tall oil
Production
Tall oil is a by-product of the pulp industry, it includes released during cooking of the pulp extractives of the wood.
Commodity
In addition to the main components cellulose, hemicellulose and lignin, wood contains about 1-3 percent resins. Various types of resins can be distinguished: The resin contained in the so-called parenchymatous cells consisting of triglycerides, fatty acids, resin acids, sterols and sterol esters, and is used to store nutrients. This radial resin ducts in the resin, however, consists primarily of resin acids and terpenes and serves the wound closure in violation of the tree bark.
The traditional method for obtaining the resin of trees by scoring the bark (resins) gains virtually exclusively the resin from the resin gears. In contrast, gained from the production of pulp by the sulfate process all of the resin, ie the proportion of the parenchyma cells also. Accordingly, the product derived from the production of pulp resin contains not only the resin acids, fatty acids and sterols.
Method
The resins fall in pulp production as soaps, called Tallseifen, in the black liquor, and are deposited as such. For these Tallseifen the crude tall oil is deposited as a black, viscous liquid in the first step by the addition of sulfuric acid. Crude tall oil is depending on the origin of 20 to 65 percent resin acids, 15 to 55 percent fatty acids and 5 to 30 percent unsaponifiables. The production of crude tall oil may be carried out continuously or discontinuously, and the yield is between 30 and 40 kg / t pulp.
Further processing and use
Crude tall oil as such has limited applications, for example as emulsifier. Industrially important are those produced by fractionation from the crude tall oil products, especially fatty acids and resin acids.
Fractionation
For the fractionation there is extraction and distillation process, with only the have prevailed distillation process. The requirements for the distillation are high, especially since the products have a high boiling point and at the same time prone to decomposition and polymerization. Furthermore, presents the material through the contained acids and sulfur compounds and the corrosivity associated high demands on the materials for distillation plants.
Distillation and refining
The crude tall oil can be distilled to tall oil rosin with a content of 10 to 35 percent at temperatures between 200 and 285 ° C, a subsequent refining results in fractions of tall oil fatty acids with a rosin content of 1 to 10 percent. Typical tall oil fatty acid fractions contain about 1 to 3 % of saturated fatty acids and a very high proportion of unsaturated fatty acids. The proportion of linoleic acid, and ( slightly) linolenic acid is 45 to 65%, oleic acid is present from 25 to 45%.
Products: Fatty acids
The products from the tall oil find in the processing industry varied use; Tall oil fatty acids ( TOFA ) can be typically used for the same purposes as fatty acids of different origin. They contain, among other unsaturated fatty acids (oleic acid) and are thus a cost-effective source of fatty acids with a low boiling point. How to find an alternative to tallow fatty acids ( from animal products ) applications in soaps. There are also applications where tall oil fatty acids are unrivaled, for example, a large proportion of these fatty acids used in Europe as paint raw materials. Tall oil contains little linolenic acid, which prevents yellowing of white dyes ( as occurs with fatty acids of different origin ). Other products from tall oil fatty acids are polyamide resins for the printing and adhesive industries and epoxy resins.
Products: tall oil
Tall oil rosin ( rosin ) is also used analogously to the balsam resin. A substantial part of the tall oil rosin is in the preparation of paper based on natural resins. Here, the rosin acids, once reacted with fumaric acid or maleic anhydride in accordance with the type of reaction a Diels -Alder addition, converted by dispersing with a sodium hydroxide solution and an emulsifier in an approximately thirty percent dispersion. These dispersions are used in the paper production in order to adjust the water absorption capacity of the paper. Thus, the Description and printability of the paper is improved.
In addition, large amounts of tall oil are used for adhesives and printing inks. A further load, the rubber industry, where tall oil are used as emulsifiers in the production of synthetic rubber. Also relatively small quantities for the production of chewing gum may be used. When impregnation for wooden floors, it also takes place in wood oils use, as well in wood stains. Other applications are in the field of construction chemicals, such as air-entraining agents in concrete. Tall oil pitch is increasingly used as a substitute for bitumen or as an emulsifying additive in asphalt; it does not contain polycyclic aromatics as opposed to bitumen. Tall oil pitch is also used for colored asphalts, caulks, sealants, Betonemulgatoren.