| 摘要 |
1,052,186. Degradation of polyolefines. DOW CHEMICAL CO. Sept. 6, 1963 [Sept. 10, 1962], No. 35332/63. Heading C3P. The molecular weight of a crystalline polymer, rich in isotactic structure, of alphasubstituted olefinic hydrocarbons containing a major proportion by weight of at least one olefine H 2 C = CHR where R is an alkyl or aryl radical, in chemically combined form, is reduced by subjecting the polymer to thermal depolymerization at temperatures between 160‹ and 300‹ C. while in contact with a small but effective amount of bromine or a brominecontaining compound, wherein said compound is essentially decomposed during the process to form the bromide radical. Bromine-containing compounds mentioned are hydrogen bromide and inorganic and organic bromides; lists of such compounds are given. The depolymerization can be carried out by subjecting the isotactic polymer to thermal or thermal and mechanical depolymerization in contact with the bromine-containing compound, the heating usually being from 0À25 to 10 minutes. The depolymerization may be carried out in the presence of a synergistic amount of an organic peroxide, hydroperoxide or azo compound having a half-life of at least two hours as determined in benzene at 100‹ C. In the examples (a) polystyrene is heated in the presence of 1,2-dibromoethyl benzene; 1,2,3,4-tetrabromobutane; 2,3-dibromo succinic acid; 1,1,1- tribromo-2-methyl-2-propanol; 2-bromoethylbenzene; 1,1 - dibromo - 2 - cyclopropylbenzene; 1,1,2,2-tetrabromoethane; carbon tetrabromide; pentabromoethane; di-(1,2-dibromoethyl)benzene; 1,2 - dibromopentane; pentabromomonochlorocyclohexane; bromoform; tris - (2,3 - dibromopropyl)phosphate; 1,1-dibromoethane; a brominated maleic anhydride-propylene glycol polyester (prepared by heating together maleic anhydride and propylene glycol, adding CC2 4 , and brominating with bromine in CC2 4 ); HBr; NH 4 Br; NaBr; KBr and bromine. (b) Polypropylene is heated in the presence of 2,2-dibromo- 1 -cyclopropylbenzene and (c) poly(4-methyl-l-pentene) is heated in the presence of styrene dibromide. |
