It is a colorless, stable and viscous hydroscopic liquid, and is almost odorless and tasteless. It is miscible with water, ethanol and various organic solvents.
Physical and Chemical Properties
Propylene glycol is scientifically named as “1,2-propanediol”, and has a chemical formula of CH3CHOHCH2OH and a molecular weight of 76.10. There is a chiral carbon atom in the molecule. Its racemate is a hygroscopic viscous liquid and is slightly spicy. It has a specific gravity of 1.036 (25/4 °C), a freezing point of-59 °C, and a boiling point of 188.2 °C, respectively 83.2 °C (1,333 Pa). It is miscible with water, acetone, ethyl acetate and chloroform, and is soluble in ether. It is soluble in many essential oils, but is not miscible with petroleum ether and paraffin oil. It is relatively stable to heat and light, and is more stable at low temperatures. Its L-isomer has a boiling point of 187 to 189 °C and a specific optical rotation [α] of D20-15.0°. It can be oxidized at high temperatures to propionaldehyde, lactic acid, pyruvic acid and acetic acid.
Figure 1 the molecular structure of propylene glycol.
Propylene glycol is a diol having the general nature of the alcohol. It can react with inorganic and organic acids to generate mono-or di-esters. It reacts with propylene oxide to generate ether, with hydrogen halide to generate halohydrin, and with acetaldehyde to generate methyl dioxolane.
Eyes-rabbit 100 mg mild
Dry powder, foam, sand, water.
Flammability hazard characteristics
Flammable; generate irritating smoke upon combustion
1. It is used as a resin, a plasticizer, a surfactant, and materials for emulsifier and demulsifier. It is also used as antifreeze and heat carrier.
2. It is used as gas chromatography stationary phase, solvents, antifreeze, a plasticizer and a dehydrating agent.
3. A carrier solvent; wetting agents; moisturizing agents; anti-caking agents; antioxidants; texturizing agents; surfactant; stabilizer; a thickener; dough modifiers; emulsifiers; flavoring agents; excipient; processing aids.GB2760-96 lists it as food processing aids.
It is mainly used as solvents for a variety of flavors, colors and preservatives, and as extraction solvents for vanilla beans, roasted coffee grains and natural spices. It is used as moisturizing agents and softeners for candy, bread, packaged meats and cheese. It is also used as mildew agents for noodles and sandwiches class. Addition of 0.006% in soymilk enables the flavor not to change upon heating and produces white glossy packaging tofu, which undergoes volume expansion when fried.
4. Propylene glycol is an intermediate for fungicide difenoconazole.
5. It is used a solvent. Preservatives, colorings, antioxidants and other poorly water-soluble food additives can be dissolved therein, which is then added into food; it is strongly hygroscopic and has food moisturizing and anti-freeze effect. China stipulates its use for pastry, and the maximum usage is 3.0g/kg.
6. Propylene glycol is an important raw material for unsaturated polyester, epoxy resin, and polyurethane resin. The use amount in this area accounts for about 45% of the total consumption of propylene glycol. Such unsaturated polyester is used extensively for reinforced plastics and surface coatings. Propylene glycol is excellent in viscosity and hygroscopicity and is non-toxic, and thus is widely used as hygroscopic agent, antifreeze, lubricants and solvents in the food, pharmaceutical and cosmetic industry. In the food industry, propylene glycol reacts with fatty acid to give propylene ester of fatty acids, and is mainly used as food emulsifier; Propylene glycol is a good solvent for flavorings and pigments. Propylene glycol is commonly used as solvents, softeners and excipients, etc. in the pharmaceutical industry for the manufacture of various types of ointments and salves. Propylene glycol is also used as a solvent and a softener for cosmetic since it has good mutual solubility with various spices. Propylene glycol is also used as tobacco moisturizing agents, antifungal agents, food processing equipment lubricants and solvents for food marking ink. Aqueous solution of propylene glycol is an effective anti-freeze agent.
7. It is used as a drug carrier, and agents for drug particles. It can be used as humectants, softeners, solvents and the like in cosmetics. It can be used as tobacco flavor, tobacco moisturizing agents, preservatives and the like in the tobacco industry. It can be used as flavor, food coloring solvents, food packaging softeners, food release agent and the like in food industry. It can also be used for the production of unsaturated polyester resins, and is also raw materials for plasticizers, dehydrating agents, surfactants, curing agents and binders. It can also be used in paints, pesticides, coatings and other industries.
8. It is used in aviation de-icing fluid, refrigerant and antifreeze, food and spices, fragrances, cosmetics and personal care products, heat transfer fluids, hydraulic and brake fluids, paints and coatings, pet food/animal feeding stuffs, medicines, polyurethane, unsaturated polyester resin and the like.
1,2-Propanediol is hygroscopic. 1,2-Propanediol is sensitive to excessive heat (tends to oxidize at high temperatures). 1,2-Propanediol can react with oxidizing materials. 1,2-Propanediol is incompatible with acid chlorides, acid anhydrides, chloroformates, and reducing agents. 1,2-Propanediol dissolves many essential oils. A mixture of 1,2-Propanediol with hydrofluoric acid and silver nitrate was put in a glass bottle which burst 30 minutes later.
FAO/WHO (2000): ADI is 0 to 25mg/kg.
LD50 is 22 to 23.9 mg/kg (mouse, oral).
GRAS (FDA, §184.1666, 2000).
Sentry Propylene Glycol (Union Carbide); Sirlene (Dow Chemical).
Dry the diol with Na2SO4, decant and distil it under reduced pressure. [Beilstein 1 IV 2468.]
Ventilated warehouse and low-temperature drying.
A 10μl sample is injected into the gas chromatograph, which has a thermal conductivity detector. The column is 1m × 6.35mm stainless steel column. The filler is polyethylene glycol 20M (Carbowax compound 20M) 4%, and the carrier is a 40/60 mesh sieved polytetrafluoroethylene (Chromosorb T) or similar material. Helium carrier gas has a flow rate of 75ml/min. Injector temperature is 240 °C; column temperature is 120 to 200 °C, temperature increment is 5 °C/min; final temperature is 250 °C. Under specified conditions, the residence time of propylene glycol is about 5.7 minutes, the residence time of three kinds of glycol isomers are respectively 8.2, 9.0 and 10.2 minutes. The area of each peak is determined using any proper method, and then the percentage of propylene glycol area is calculated and transformed into mass percentage.
Explosive hazardous characteristics
explosive when mixed with air
1,2-Propanediol is combustible.
Thick odorless colorless liquid. Mixes with water.
Propylene glycol is used as a solvent, a vehicle for
topical medicaments such as corticosteroids or aciclovir,
an emulsifier and humectant in food and cosmetics,
and as antifreeze in breweries, in the manufactures
of resins. It was present as an occupational sensitizer
in the color film developer Flexicolor?. Patch tests in
aqua are sometimes irritant.
FAO/WHO (1984): Cottage cheese, the cream mixture amount of 5g/kg (used alone or in combination with other carriers and stabilizers).
Japan (1998): Raw noodles, raw stuffing and cuttlefish smoked products ≤2%; skins for dumplings, steamed dumplings, spring rolls and wonton ≤1.2%; other food ≤0.6%.
GB 2760-96: pastry 3.0g/kg, chewing gum.
FDA, §184.1666 (2000): Alcoholic beverages 5%; frosting and candy 24%; frozen dairy 2.5%; flavoring agents, flavor enhancers 97%; nuts and nut products 5%; other food 2.0%.
Medicinal property and application
Propylene glycol has good solubility and less toxicity and irritation, and is widely used as solvents, extraction solvents and preservatives for injections (eg. intramuscular injections, intravenous injections) and non-injectable pharmaceutical preparations (such as oral liquid, ophthalmic preparations, otic preparations, dental preparations, rectovaginal preparations, transdermal preparations, etc.). It is better than glycerol solvent and can dissolve many substances such as corticosteroids (sex hormone), chloramphenicol, sulfonamides, barbiturate, reserpine, quinidine, corticosterone acetate, tetrahydropalmatine sulfate, mechlorethamine hydrochloride, vitamin A, vitamin D, many volatile oils, most of the alkaloids and many local anesthetics.
Propylene glycol is similar to ethanol when used as a bacteriostatic agent, and its efficacy to inhibit mold is similar to glycerin and is slightly lower than that of ethanol. Propylene glycol is commonly used as a plasticizer for the aqueous film coating materials. Its mixture with equal amounts of water can delay the hydrolysis of certain drugs, and increase the stability of the preparation product. It is used as an antimicrobial preservative in 15% to 30% propylene glycol solution and semi-solid formulation, as humectants in about 15% propylene glycol topical formulation, and as solvent and co-solvent in 10% to 30% propylene glycol aerosol solvent, 10% to 25 % propylene glycol oral solution, 10% to 60% injectable formulation and 5% to 80% topical formulation.
[Stability and storage condition] It is very stable at room temperature, but is oxidized when left open at high temperatures (above 280 °C); has a chemical stability after mixing with 95% ethanol or water; can be sterilized by autoclaving or sterile filtration. Propylene glycol has hygroscopicity, and should be positioned at cool and dry place and stored in dark airtight container.
[Incompatibility] It has incompatibility with some oxidants (such as potassium permanganate).
The above information is edited by the Chemicalbook of Jin Yinxue.
Oral-rat LD50: 20000 mg/kg; Oral-Mouse LD50: 32000 mg/kg
Liquid may irritate eyes.
It can be obtained by hydrolysis of Propylene oxide:
Propylene oxide and water are fed in a molar ratio of 1: 15, and react at 150-2000 °C, a pressure of 1.2-1.4 MPa for 30 minutes to obtain 16% aqueous solution of propylene glycol, which is subjected to evaporation to obtain the finished product.
The reaction is performed under catalyzation of sulfuric acid or hydrochloric acid. 0.5% to 1.0% dilute sulfuric acid is added into 10% to 15% aqueous solution of propylene oxide, the mixture is hydrolyzed at 50 to 70 °C; the hydrolysate is neutralized and concentrated under reduced pressure, and refined to obtain the finished products.
The preparation method is a method in which propylene oxide is hydrolyzed to propylene glycol, and which can be carried out in the liquid phase. There are catalytic and non-catalytic processes in industry. Catalytic method is a method in which hydrolysis is carried out in the presence of 0.5% to 1% sulfuric acid at 50 to 70 °C. Non-catalytic process is carried out under high temperature and pressure (150 to 300℃, 980 to 2940kPa), and is used for production in domestic.
Used as a solvent.
Air & Water Reactions
clear viscous liquid