Views: 5 Author: Site Editor Publish Time: 2023-05-26 Origin: Site
Propylene glycol, a colorless viscous liquid in normal state, nearly odorless, slightly sweet on fine smell, highly hygroscopic, miscible with water, ethanol and many organic solvents. Propylene glycol is divided into 1,2-propanediol and 1,3-propanediol, and the common one in the market is 1,2-propanediol with the molecular formula of C3H8O2.
Production Process
1. Epichlorohydrin hydration method
Epichlorohydrin reacts with water at 200°C and 1 to 20 MPa reaction conditions to produce 1,2-propanediol. The waste emission is small, the equipment is less corrosive, the product purity is high and the stability is strong, but the reaction is harsher and the investment in equipment is relatively large.
2. Ester exchange method
Under the condition of atmospheric pressure and 65℃, 1,2propanediol is produced by the transesterification reaction of propylene carbonate (PC) and methanol with sodium methanol as the catalyst. This method has low production cost, a complicated single product refining process, slightly poor quality relative to 1, serious environmental pollution, and low yield.
3. 1,2 Dichloropropane hydrolysis method
1,2 dichloropropane method is divided into direct hydrolysis and first esterification and then hydrolysis of two kinds. Direct hydrolysis is generated by the hydrolysis of dichloropropane in a weak alkali solution; first esterification and then hydrolysis is the reaction of dichloropropane and acid salt to generate esters, ester hydrolysis into alcohol process.
This method has high environmental pollution and high cost.
1. Pharmaceutical engineering
Used as a solvent for insoluble or water-soluble stable drugs to increase their stability, with rapid and extended effect. Used as solvent, softening agent and excipient in the manufacture of various ointments and ointments.
2. Food, beverage
Propylene glycol is an aqueous solvent, which can dissolve water-soluble spices, pigments, preservatives, vitamins, resins and so on. It is mainly used as food emulsifier, moreover, it is an excellent solvent for spices and pigments, and it is used as stabilizer, coagulant and anti-dissolving agent in cakes, etc. It can also be used as softening agent and emulsifier for gum-based candy.
3. Flavor and fragrance, food additives
It can be used as solvent and carrier of edible flavor. Used as a solvent for various spices, pigments, preservatives, extraction solvent for vanilla beans, roasted coffee grains, natural spices, etc.
4. Cosmetics, daily chemical
Propylene glycol is used as a solvent and softener in cosmetics and can be found in almost all forms of color cosmetics, hair care products, lotions, after shave care products, deodorants, mouthwashes, and toothpastes. It is generally used as a wetting agent in combination with glycerin or sorbitol in cosmetics, toothpaste and soap. It is used as a wetting and leveling agent in hair dyes.
5. Tobacco
Propylene glycol is used in tobacco as a humidifier and mold inhibitor.
6. Industrial antifreeze
Industrial propylene glycol plays the role of wetting agent and solubilizer in chemistry, and is a major component in advanced antifreeze.
7. Paints and coatings
Propylene glycol has low freezing point and can be mixed with water in any ratio. It can greatly reduce the overall freezing point of the paint when mixed with water, which enhances the anti-freezing property of the paint, so it is often used as antifreeze agent in paint, which can make the paint not freeze at 0 degrees. Propylene glycol, because of its good compatibility with water and other solvents and high boiling point, is easy to reach the balance in water-based coating system, and can also provide the fluidity of the coating and make the coating dry slowly.
