Tall oil facts for kids
Tall oil, also known as liquid rosin or tallol, is a thick, yellowish-black liquid with a strong smell. It's a useful by-product created when making wood pulp for paper. This happens mainly from pine trees using a method called the kraft process.
The name "tall oil" comes from the Swedish word tallolja, which means 'pine oil'. Tall oil is one of the biggest chemical by-products from a kraft paper mill. For every ton of pulp made, about 30 to 50 kilograms of crude tall oil are produced. It can add a small but important amount to the mill's income.
How Tall Oil is Made
Making tall oil starts during the kraft process, which is how wood is turned into pulp for paper. In this process, wood chips are cooked with strong chemicals at high temperatures. This cooking changes natural substances in the wood, like rosin and fatty acids, into a type of soap.
This soap mixes with the used cooking liquid, which is called "weak black liquor". This black liquor is about 15% dry material. It then gets thicker in special machines called evaporators. After the first step, it's about 20–30% dry and is called "intermediate liquor".
The soaps naturally start to float to the top in the storage tanks for these liquids. They are then skimmed off, much like skimming cream from milk. This collected soap is called raw rosin soap. It's then left to settle or spun in a centrifuge to remove as much black liquor as possible.
Finally, the raw rosin soap goes to a special area called an acidulator. Here, it's heated and mixed with sulfuric acid. This process turns the soap into crude tall oil (CTO). Adding special chemicals called flocculants can make this whole process faster and result in cleaner soap.
The amount of soap produced depends on the type of pine tree. Most pine trees give about 5 to 25 kilograms of soap per ton of pulp. However, Scots pine trees can yield much more, from 20 to 50 kilograms per ton. Scots pine grown in northern Scandinavia can even give over 50 kilograms per ton! Around the world, about 2 million tons of crude tall oil are processed each year.
What's Inside Tall Oil
The exact mix of crude tall oil changes a lot. It depends on the types of wood used to make the pulp. A common way to check the quality of tall oil is by its "acid number." If only pure pine trees are used, the acid number can be high, around 160–165. But if a mix of softwoods and hardwoods is used, the acid number might be lower, around 125–135.
Crude tall oil usually contains several important parts:
- Resins: These have resin acids, like abietic acid.
- Fatty acids: These include palmitic acid, oleic acid, and linoleic acid.
- Fatty alcohols.
- Sterols and other similar compounds (about 5–10%).
By using a process called fractional distillation (which separates liquids based on their boiling points), we can get different parts of tall oil. One part is called tall oil rosin. This has less resin, usually 10–35%. If we reduce the resin even more, down to 1–10%, we get tall oil fatty acid (TOFA). TOFA is inexpensive and mostly made of oleic acid. It's a good source of useful fatty acids.
Uses for Tall Oil
The different parts of tall oil are used in many ways:
- Tall oil rosin is used in adhesives (like glues), rubber products, and inks. It also works as an emulsifier, helping liquids mix that normally wouldn't.
- The thick, sticky part called pitch is used as a binder in cement. It's also an adhesive and an emulsifier for asphalt (the material used for roads).
- TOFA (tall oil fatty acid) is a cheaper and vegetarian-friendly option compared to animal fats like tallow. It's used to make soaps and lubricants (which reduce friction).
- When TOFA is combined with another chemical called pentaerythritol, it's used in adhesives and oil-based varnishes (coatings that protect wood).
- When TOFA reacts with certain chemicals called amines, it creates substances called polyamidoamines. These are used as hardening agents for epoxy resins, which are strong glues and coatings.
See also
In Spanish: Tall Oil para niños
