Composite material with EMI shielding properties and process to produce it
摘要
說明書
Diluents, which are suitable for being used under the present disclosure, may comprise but are not limited to hydrocarbon diluents such as aliphatic, cycloaliphatic and aromatic hydrocarbon solvents, or halogenated versions of such solvents. Non-limiting illustrative examples of solvents are butane, isobutane, pentane, hexane, heptane, cyclopentane, cyclohexane, cycloheptane, methyl cyclopentane, methyl cyclohexane, isooctane, benzene, toluene, xylene, chloroform, chlorobenzenes, tetrachloroethylene, dichloroethane and trichloroethane.
For the present disclosure, the propylene polymers are preferably produced by polymerization in liquid propylene at temperatures within the range of 20° C. to 100° C. Preferably, temperatures are within the range of 60° C. to 80° C. The pressure can be atmospheric or higher. Preferably, the pressure is ranging between 2.5 and 5.0 MPa.
Hydrogen is used to control the chain lengths of the propylene polymers. For the production of a propylene polymer with higher MI2, i.e. with lower average molecular weight and shorter polymer chains, the concentration of hydrogen in the polymerization medium needs to be increased. Inversely, the hydrogen concentration in the polymerization medium has to be reduced to produce a propylene polymer with lower MI2, i.e. with higher average molecular weight and longer polymer chains.
In such a sequential arrangement of polymerization reactors, the propylene homopolymer withdrawn from one reactor is transferred to the one following in the series, where the polymerization is continued. To produce propylene homopolymer fractions of different melt indexes, the polymerization conditions in the respective polymerization reactors need to be different; for example, in that the hydrogen concentration in the polymerization reactors differs.
