Abstract:
PROCESS FOR THE POLYMERIZAITON OF PROPYLENE IN THE GAS PHASE IN WHICH PROPYLENE IN LIQUID FORM IS INTRODUCED INTO A REACTION ZONE, VAPORIZED THEREIN AND POLYMERIZED WITH A CATALYST HAVING HIGH ACTIVITY.
Abstract:
Process for the polymerization of vinyl chloride in the absence of solvents or dispersing agents in two stages. In the first stage the liquid monomers are polymerized to a conversion of from 1 to 15 percent; in the second stage polymerization is continued in the powder phase in the absence of liquid vinyl chloride. The process may be carried out continuously and gives very pure polymers which may be used for all purposes for which polyvinyl chloride is usually employed.
Abstract:
The molecular weight distribution of a polyolefin is narrowed by a process wherein the polyolefin is brought for 0.001 to 100 seconds into a shear gradient whose speed gradient is from 1500 to 200,000 seconds-1. The process may be effected in a screw extruder, a high-speed kneader or a roll mill, and may be in the presence or absence of oxygen. Stabilizers (e.g. see Example 1) also may be present.
Abstract:
In an improvement in the process of the parent Specification for the thermal oxidative degradation and simultaneous purification of linear polyolefins prepared by polymerization of olefins containing 2 to 4 carbon atoms with catalysts containing heavy metals of Group IVa, Va or VIa of the Mendeleeff Periodic Table and which contain small amounts of these catalysts, which comprises dissolving the polyolefin in an inert organic solvent and heating the solution in the presence of oxygen or oxygen supplying compounds for 15 to 200 minutes at 70 DEG to 240 DEG C., the solution of the polyolefin is prepared from a suspension of the polyolefin in the solvent by leading in superheated steam. The superheated steam may be under a pressure of 5 to 100 atmospheres, and basic compounds such as ammonia or alkylamines, air or oxygen may be metered into the steam. In an example a solution of polypropylene is prepared from a suspension thereof in heptane by leading in steam at 14 atmospheres into which ammonia and air have been metered.
Abstract:
Linear polyolefines which have been prepared by the polymerization of olefines containing two to four carbon atoms using as catalysts heavy metals of Group IV(a), V(a), or VI(a) of the Mendelleeff Periodic System are simultaneously purified and thermally degraded by dissolving or swelling the polyolefine in an inert organic solvent and heating the solution in the presence of oxygen or oxygen-supplying compounds for 15 to 200 minutes at a temperature between 70 DEG and 240 DEG C. Optionally the heat-treatment may be effected in the presence of 2 to 20% of water and in the presence of such an amount of an alkaline compound that the pH in the aqueous solution after the heat-treatment step is 6 to 7. Substances which have a large internal surface on to which impurities are absorbed may be added to the polymers before, during, or after the heat-treatment. Suitable substances are carbon, aluminium oxide, bleaching earths, and kieselguhr. The linear polymers may be polyethylene, polypropylene, or copolymers of ethylene and/or propylene and/or butene-1. Specified solvents are tetra- or decahydro-naphthalene, cyclohexane, benzene, toluene, xylene, and ethylbenzene. The oxygen-supplying compounds may be peroxides. Alkaline compounds which may be included in the heat-treatment step are ammonia, sodium, potassium, or calcium hydroxide, hydroxylamine or aniline.