What Is Epichlorohydrin?
Epichlorohydrin is a highly reactive monomer with epoxy and chlorine groups. It is also known as 2-chloromethyloxirane, 1-chloro-2,3-epoxypropane, and gamma-chloropropylene oxide.
Epichlorohydrin is corrosive and irritates the eyes, nose, and throat. If inhaled, it can cause headache, dizziness, and other central nervous system disorders.
Uses of Epichlorohydrin
Epichlorohydrin is used as a synthetic raw material. In particular, it is often used as the main raw material for epoxy resins, which are widely used in the chemical industry, especially in the automotive and electronics industries. Epoxy resins are used in common paints in the field of coatings, electrodeposition coatings for automotive and industrial applications, and coatings for the inside of drums and cans.
In the field of electronics, they are used for printed circuit boards and coil insulating materials. In the field of civil engineering and construction, they are used for anticorrosion coatings, adhesives and sealants for concrete and steel.
Besides epoxy resins, they are also widely used as synthetic raw materials for glycerin and other products such as epichlorohydrin rubber and glycidyl methacrylate, and as solvents for cellulose acetate, cellophane and ester rubber.
Other applications include cosmetics, pharmaceuticals, surfactants, synthetic raw materials for ion exchange resins, fiber treatment agents, and solvents.
Properties of Epichlorohydrin
Epichlorohydrin has the molecular formula C3H5ClO, molecular weight 92.5, and is a colorless liquid at room temperature with a pungent odor similar to chloroform.
It is flammable with a specific gravity of 1.2058, a melting point of -26°C, a boiling point of 116°C, and a flash point of 31°C. It is slightly soluble in water and readily soluble in organic solvents such as alcohols, ether, chloroform, trichloroethylene, and carbon tetrachloride, but not in hydrocarbons.
Epichlorohydrin is unstable in the presence of acidic and basic substances. It reacts with a variety of substances because of its two highly reactive functional groups, an epoxy group and a chlorinated alkyl group. It is highly volatile with explosive limits ranging from 3.8 to 21% and tends to form explosive mixtures with air. Vapor is heavier than air and tends to stay in low places, so ventilation and local exhaust ventilation should be provided during use.
It reacts violently with metal powder, zinc, aluminum, alcohol, phenol, amines (especially aniline), organic acids, water, etc., causing fire or explosion.
Other Information on Epichlorohydrin
How Epichlorohydrin Is Produced
Epichlorohydrin can be produced in two ways: from allyl chloride, obtained by the reaction of propylene and chlorine, or from allyl alcohol, obtained by the reaction of propylene and acetic acid.
1. Allyl chloride method
Allyl chloride is reacted with hypochlorous acid solution to obtain dichloropropanol. This is then reacted with alkali to produce crude epichlorohydrin by dehydrochlorination, and impurities are removed by distillation.
CH2=CHCH3 + Cl2 → CH2=CHCHCH2Cl + HCl (Synthesis of allyl chloride)
CH2=CHCH2Cl + HOCl → CH2ClCH(OH)CH2Cl
CH2ClCH(OH)CH2Cl → CH2CHOCH2Cl + HCl
2. Allyl alcohol method
Allyl alcohol is chlorinated with chlorine in hydrochloric acid solution to obtain dichloropropanol. This is then dehydrochlorinated by adding alkali to produce crude epichlorohydrin, which is distilled to yield the product epichlorohydrin.
2CH2=CHCHCH3 + 2CH3COOH + O2 → CH2=CHCHCH2OCOCH3 +H2O → CH2=CHCHCH2OH + CH3COOH (synthesis of allyl alcohol)
CH2=CHCHCH2OH + Cl2 → CH2ClCH(OH)CH2Cl
CH2ClCH(OH)CH2Cl → CH2CHOCH2Cl + HCl