A process for propylene preliminary polymerization in liquid phase that occurs in a continuous preliminary polymerization reactor may include feeding a propylene monomer and a Ziegler-Natta catalyst system having (a) a pro-catalyst having an internal electron donor comprising a substituted phenylene aromatic diester, (b) a catalyst activator and optionally (c) an external donor, into the continuous preliminary polymerization reactor, wherein the feeding is carried out without pre-contact of the pro-catalyst with the catalyst activator, and also without pre-contact of the catalyst activator with the propylene monomer before entering the continuous preliminary polymerization reactor.

A method of continuously producing an ethylene-vinyl acetate copolymer in a polymerization vessel containing a reaction liquid containing ethylene, vinyl acetate, a polymerization initiator and methanol, the polymerization vessel being connected via piping to a heat exchanger circulating a coolant, the method includes the steps of: supplying ethylene, the polymerization initiator and methanol to the polymerization vessel; introducing pressurized gas containing ethylene present in a gas phase portion of the polymerization vessel into the heat exchanger; supplying vinyl acetate cooled to between −50° C. and 23° C. to an upper portion of the heat exchanger; flowing vinyl acetate down in the heat exchanger while absorbing ethylene; letting vinyl acetate dissolving ethylene out of a bottom portion of the heat exchanger and adding to the reaction liquid in the polymerization vessel; and taking the reaction liquid out of the polymerization vessel. This provides a method of efficiently removing heat during polymerization of an ethylene-vinyl acetate copolymer.

A method of continuously producing an ethylene-vinyl acetate copolymer in a polymerization vessel containing a reaction liquid containing ethylene, vinyl acetate, a polymerization initiator and methanol, the polymerization vessel being connected via piping to a heat exchanger circulating a coolant, the method includes the steps of: supplying ethylene, the polymerization initiator and methanol to the polymerization vessel; introducing pressurized gas containing ethylene present in a gas phase portion of the polymerization vessel into the heat exchanger; supplying vinyl acetate cooled to between −50° C. and 23° C. to an upper portion of the heat exchanger; flowing vinyl acetate down in the heat exchanger while absorbing ethylene; letting vinyl acetate dissolving ethylene out of a bottom portion of the heat exchanger and adding to the reaction liquid in the polymerization vessel; and taking the reaction liquid out of the polymerization vessel. This provides a method of efficiently removing heat during polymerization of an ethylene-vinyl acetate copolymer.

A process (and a related system) for collecting samples of a polymerization catalyst or of a catalyst-containing polymer from an operation unit, having an upper end and a lower end, of a polymerization plant, including the steps of: a) extracting a prefixed amount of product from the lower end of the operation unit through a discharge valve; b) directing the product towards a filtering unit through an inlet valve; c) flushing an inert gas through the filtering unit; d) outgassing the filtering unit, through the outlet valve; and e) displacing the filtering unit, for collecting the sample.

A process (and a related system) for collecting samples of a polymerization catalyst or of a catalyst-containing polymer from an operation unit, having an upper end and a lower end, of a polymerization plant, including the steps of: a) extracting a prefixed amount of product from the lower end of the operation unit through a discharge valve; b) directing the product towards a filtering unit through an inlet valve; c) flushing an inert gas through the filtering unit; d) outgassing the filtering unit, through the outlet valve; and e) displacing the filtering unit, for collecting the sample.

A process (and a related system) for collecting samples of a polymerization catalyst or of a catalyst-containing polymer from an operation unit, having an upper end and a lower end, of a polymerization plant, including the steps of: a) extracting a prefixed amount of product from the lower end of the operation unit through a discharge valve; b) directing the product towards a filtering unit through an inlet valve; c) flushing an inert gas through the filtering unit; d) outgassing the filtering unit, through the outlet valve; and e) displacing the filtering unit, for collecting the sample.

The present invention relates to an olefin-based polymer satisfying requirements: (1) a melt index (MI, 190° C., 2.16 kg load conditions) ranging from 1.0 to 10.0 g/10 min; (2) a density (d) ranging from 0.875 to 0.895 g/cc; (3) 0.5 J/g≤dH(100)≤3.0 J/g and 1.0 J/g≤dH(90)≤6.0 J/g as measured by successive self-nucleation/annealing (SSA) using a differential scanning calorimeter (DSC); (4) 15≤T(90)−T(50)≤30 and 50° C.≤T(50)≤75° C. as measured by SSA using a DSC; and (5) a melting point (Tm) of 55° C.≤Tm≤80° C. as measured using a DSC. The olefin-based polymer according to the present invention is a low-density olefin-based polymer and has a highly crystalline region introduced therein, thereby exhibiting high mechanical stiffness.

The present invention relates to an olefin-based polymer satisfying requirements: (1) a melt index (MI, 190° C., 2.16 kg load conditions) ranging from 1.0 to 10.0 g/10 min; (2) a density (d) ranging from 0.875 to 0.895 g/cc; (3) 0.5 J/g≤dH(100)≤3.0 J/g and 1.0 J/g≤dH(90)≤6.0 J/g as measured by successive self-nucleation/annealing (SSA) using a differential scanning calorimeter (DSC); (4) 15≤T(90)−T(50)≤30 and 50° C.≤T(50)≤75° C. as measured by SSA using a DSC; and (5) a melting point (Tm) of 55° C.≤Tm≤80° C. as measured using a DSC. The olefin-based polymer according to the present invention is a low-density olefin-based polymer and has a highly crystalline region introduced therein, thereby exhibiting high mechanical stiffness.

The present disclosure relates to an ethylene/1-hexene copolymer having excellent flexibility and processability and useful for manufacturing high-pressure heating pipes, PE-RT pipes or large-diameter pipes.

The present disclosure relates to an ethylene/1-hexene copolymer having excellent flexibility and processability and useful for manufacturing high-pressure heating pipes, PE-RT pipes or large-diameter pipes.