Shellac, also known as shellac, is an economically valuable forest by-product and important industrial raw material. It is the secretion of shellac shellac parasitic on certain plants, mainly composed of shellac resin, shellac wax, shellac pigment, and also contains a small amount of impurities such as sugar, salt, protein, corpse and wood dust Wait.
The use of shellac has a long history. About two thousand years ago, it was used to bond agricultural tools and used as medicine, but mainly used water-soluble shellac pigments as scarlet dyes and cosmetics. At that time, the processing purpose of shellac was almost to obtain this shellac dye.
Shellac resin role: Place of production of shellac concentrated, unstable output, shellac is mostly distributed at 70 ° -120 ° east longitude, 8 ° -32 ° north latitude, especially 19 ° -26 ° north latitude. The countries that produce shellac in the world, except Yunnan, my country, are mainly Southeast Asia and South Asia, Vietnam, Myanmar, Laos, Thailand and India. Among them, India is the most, followed by Thailand.
Shellac resin is the main component of shellac, which accounts for 60% -85% of the weight of the original gum, 85-92% of the granular rubber, 90% -94% of the tablet glue, and 97% -98.5% of the dewaxed glue. Shellac resin is a solid solution composed of lactone and gum ester of hydroxycarboxylic acid. The structure of the resin is very complicated, and it is currently recognized that it is a flexible grid composed of hydroxy fatty acids and sesquiterpene acids, and the gap contains a mixture of low molecular fatty acid esters. Some of these low molecular fatty acid esters play a role in plasticity. The average molecular weight of shellac resin is about 1000, which can be expressed by C60H90O5. It is an acidic resin with an average molecule containing at least 1 free carboxyl group, 5 hydroxyl groups, 3 lipid groups and one aldehyde group.
Hard resin and soft resin shellac resin can be clearly divided into two parts when extracted with ether: the part dissolved with ether (about 30%) and the part not dissolved in ether (about 70%), the former is called "soft" "Resin" is a cohesive balsam-like substance; the latter is called "hard resin" or "pure resin", and its softening point is about 10 ° C higher than that of tablet glue. The resin is 550, hard resin is nearly 2000. Hard resin and soft resin have different physical and chemical properties.