| 摘要 |
Poly-(alkyl methacrylates) are made by polymerizing the alkyl methacrylate present in the mixture obtained by the partial dehydrogenation of the corresponding alkyl isobutyrate. The resulting polymer may be depolymerized thermally to produce pure monomeric alkyl methacrylate. The process is preferably applied to the polymerization of the mixture obtained by dehydrogenating methyl isobutyrate by the process of Specification 952,833. Prior to polymerization the dehydrogenation mixture is preferably freed from the isobutyric acid, formaldehyde and methyl acrylate present therein. The mixture is polymerized by means of catalysts such as hydrogen peroxide, benzoyl, acetyl and benzoyl acetyl peroxides, urea peroxide, tert.-butyl hydroperoxide alkali metal and ammonium persulphates and azodiisobutyronitrite. The mixture may be polymerized as such, or as an emulsion in water containing a sodium alkane sulphonate emulsifier.ALSO:Alkyl methacrylates are made by polymerizing the alkyl methacrylate present in the mixture obtained by the partial dehydrogenation of the corresponding alkyl isobutyrate, separating the resulting poly(alkyl methacrylate) and then pyrolyzing it to form the alkyl methacrylate. The process is preferably applied to the polymerization of the mixture obtained by dehydrogenating methyl isobutyrate by the process of Specification 952,833, which is purified by the removal of the formaldehyde, isobutyric acid and methyl acrylate present therein. An Example (11) describes the pyrolysis of polymethyl methacrylate. |
