Lubricant treatments for free-radical polymerizations

A process to prepare an ethylene-based polymer, said process comprising polymerizing a mixture comprising ethylene, at a pressure greater than, or equal to, 100 MPa, in the presence of at least one free-radical initiator;

• and in a reactor system comprising at least one reactor and at least one Hyper-compressor;
• wherein at least one oil formulation, optionally comprising one or more lubrication agents, is added to the Hyper-compressor if a peroxide level of the at least one oil formulation, the at least one lubrication agent, or both the at least one oil formulation and the at least one lubrication agent ≤10 ppm;
• and wherein at least one of the following steps takes place if the peroxide level >10 ppm before adding the at least one oil formulation to the Hyper-compressor:
• A) thermally treating the one or more lubrication agents, in an oxygen-free atmosphere, at from 50° C. to 200° C. for from 1 hour to 24 hours, to achieve a peroxide level ≤10 ppm, based on the weight of the lubrication agent(s), and then adding said agent(s) to the oil formulation, prior to adding the oil formulation to the Hyper-compressor;
• B) thermally treating the oil formulation, in an oxygen-free atmosphere, at from 50° C. to 200° C. for from 1 hour to 24 hours, to achieve a peroxide level ≤10 ppm, based on the weight of the oil formulation, prior to adding the oil formulation to the Hyper-compressor;
• or
• C) a combination of A and B;
• and
• the Hyper-compressor does not contain, when the one or more oil formulation is present, a compound selected from the following compounds i) through iv):
• wherein, for Compound 1, R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, an alkyl, or an alkoxy;
• wherein, for Compound 2, R1 is selected from OH or O—R, wherein R is alkyl;
• and R2, R3, R4 and R5 are each independently selected from H, an alkyl, or an alkoxy;
• wherein, for Compound 3, R1, R2, R4 and R5 are each independently selected from H, an alkyl, or an alkoxy;
• and R3 is selected from H or an alkyl;
• or
• iv) a combination of two or more of Compounds 1 through 3.