Method for making alkyl-.alpha.-cyanoacrylate from depolymerizat

Details Method for making alkyl-.alpha.-cyanoacrylate from depolymerizat Method for making alkyl-.alpha.-cyanoacrylate from depolymerizat

1994-10-03

1995-07-25

Brust, Joseph Paul

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitriles

558372, C07C25330

Patent

active

054363632

ABSTRACT:
A depolymerization and purification process, by which a poly(alkyl-.alpha.-cyanoacrylate) feed is depolymerized into high-purity cyanoacrylate monomers without the use of a high-boiling heat transfer medium such as tricresyl phosphate. The poly(alkyl-.alpha.-cyanoacrylate) feed, which contains one or more polymerization inhibitors such as hydroquinone and phosphorus pentoxide, is first introduced into a thin-film evaporator for a depolymerization reaction. The temperature of the film evaporator is maintained at about 200.degree..about.260.degree. C., and operated under a vacuum of 1.about.20 mm Hg. The produced gas stream from the depolymerization reactor is subject to a two-stage heat transfer process for condensation and purification. The first stage involves a very-high temperature condenser (about 150.degree. C.). The residue collected in the first stage condenser contains primarily dimers of .alpha.-cyanoacrylate. The second stage involves a conventional condenser at room temperature or lower temperature. The gaseous stream leaving the intermediate very-high temperature condenser contains primarily the desired cyanoacrylate monomer, thus it can be conveniently condensed in a conventional condenser, and the product is a very high purity cyanoacrylate product. This process eliminates the need of using a high-boiling heat transfer medium, thus eliminating the production of liquid waste, while allowing high-yield and high-purity final product of cyanoacrylate monomers to be produced in a continuous manner.

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