Amine-phenolate group 4 type catalysts

Phosgene addition is continued until all the phenolic groups are converted to carbonate functionalities. Some hydrolysis of phosgene to sodium carbonate occurs incidentally. When the reaction is complete, the methylene chloride solution of polymer is washed first with acid to remove residual base and amine, then with water. To complete the process, the aqueous sodium chloride stream can be reclaimed in a chlor-alkali plant, ultimately regenerating phosgene. Many variations of this polycarbonate process have been patented, including use of many different types of catalysts, continuous or semicontinuous processes, methods which rely on formation of bischloroformate oligomers followed by polycondensation, etc. 

Of the Lewis bases, the compounds dimethylaminomethyl phenol, (DMP 10) and tris (dimethylaminomethyl) phenol (DMP 30) are widely used as curing catalysts. They are employed in concentrations of 4-10 parts per hundred of resin with liquid diglycidyl ethers and curing takes place rapidly even at room temperature. Secondary amines also act as Lewis base type catalysts once their active hydrogen atoms have reacted with an epoxide group. A typical example of this type of compound is 2-ethyl 4-methyl imidazole, which finds use both as a curing agent by itself and as a catalyst for anhydride systems. 

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