| 摘要 |
A polymeric composition is made up predominantly from a polymer containing monomeric units of 4-methyl pentene-1, having a melt flow index of 0.01 to 1000 and containing up to 5% by weight of a polymer of a second component which is an aliphatic 1-olefine, the homopolymer of which melts above 275 DEG C., said polymer of the second component being present in a quantity such that the polymeric composition has a mean spherulite size when compression moulded from 265 DEG to 280 DEG C. and then quenched, of not more than 5 microns. The composition preferably has an ash content below 0.02% and a light transmission of at least 90% in 1/8 -inch section. The polymeric composition may contain up to 30% by weight of monomeric units of a third component which is a polymer of a linear 1-olefine having 4 to 18 carbon atoms e.g. butene-1, pentene-1, hexene-1, or heptene-1. These third monomers may be added randomly to the polymerizable mixture. The two component polymeric compositions may be prepared by (1) sequentially polymerizing 4-methyl pentene-1 with the second component which is an aliphatic 1-olefine using a stereospecific catalyst, or (2) polymerizing the second component before any substantial quantity of any other monomer has been polymerized, e.g. in a preliminary stage, or (3) initially polymerizing 4-methyl pentene-1 or the linear 1-olefine in a small amount, subsequently polymerizing the second component, and thereafter polymerizing the bulk of the 4-methyl pentene-1, or (4) polymerizing 4-methyl pentene-1 and the second component together, until all the pentene is polymerized and subsequently polymerizing the second component. The polymerization is effected in the presence of a conventional " low pressure " catalyst such as TiCl3 activated by an organometallic compound. Hydrogen may be present. De-ashing of the polymer slurry is carried out by known methods but dry reagents are preferably used. Sixty-seven examples are given. The second component may be 3-methyl-penten-1, 4,4-dimethyl pentene-1, 3-methyl butene-1, 3-methyl hexene-1, 3-ethyl pentene-1, or vinyl cyclohexane. |
