Process for avoiding phase separation during solution polymerization of ethylene-1-butene copolymers

A process for polymerizing ethylene-1-butene copolymers in a solution polymerization process by firstly modelling polymer systems for solution polymerization of ethylene-1-butene copolymers and then transferring pressure and temperature conditions from said modelled polymer systems to a solution polymerization process, comprising the steps of

• a) determining the cloud points on the LCST curve for two or more model compositions of a specific ethylene-1-butene copolymer grade comprising ethylene monomer, 1-butene monomer, and ethylene-1-butene copolymer of a specific grade and solvent, whereby the model compositions differ in their weight amounts of at least one of ethylene monomer, 1-butene monomer, and ethylene-1-butene copolymer;
• b) developing a correlation for interpolating cloud points for compositions of said specific ethylene-1-butene copolymer grade comprising ethylene monomer, 1-butene monomer, ethylene-1-butene copolymer of said specific grade and solvent with different weight amounts of at least one of the ethylene monomer, 1-butene monomer, ethylene-1-butene copolymer of said specific grade from the cloud points determined for said model compositions;
• c) predicting phase separation for said specific ethylene-1-butene copolymer grade by interpolating the cloud points from said correlation for a composition of said specific ethylene-1-butene copolymer grade comprising ethylene monomer, 1-butene monomer, ethylene-1-butene copolymer of said specific grade with given weight amounts of at least one of ethylene monomer, 1-butene monomer, ethylene-1-butene copolymer;
• d) selecting pressure and temperature conditions, which in the predicted phase separation data show that the ethylene-1-butene copolymer is completely solved in the solvent;
• e) adjusting at least one parameter selected from the process temperature and pressure in at least one solution polymerization reactor, and optionally the first heat exchanger downstream from the at least one solution polymerization reactor, to said selected pressure and temperature conditions during a solution polymerization process of an ethylene-1-butene copolymer of said specific grade, and
• f) polymerizing ethylene monomer and 1-butene monomer in a solvent in said at least one solution polymerization reactor at the adjusted process temperature and/or pressure in the presence of a polymerization catalyst to obtain an ethylene-1-butene copolymer of said specific grade, which is completely solved in said solvent.