Preparation of copolmers of ethylene with acrylic acid esters in a tubular reactor at above 500 bar

A process for preparing a copolymer of ethylene with an acrylic acid ester by copolymerizing 100 parts by weight of ethylene with from 0.1 to 25.0 parts by weight of an acrylic acid ester or of a solution of free acrylic acid in an acrylic acid ester in a continuously operated tubular polymerization reactor at pressures of from 500 to 5,000 bar and at temperatures of from 50.degree. to 450.degree. C. in the presence of a polymerization initiator which decomposes into free radicals which process further comprises:

• feeding a mixture of ethylene, comonomer and initiator into the tubular polymerization reactor in the form of a main stream at the inlet point of the reactor;
• passing said mixture along said reactor where the ethylene and comonomer polymerize to form a copolymer;
• feeding into the reactor an additional amount of said mixtures in one or more secondary streams(I) at a point or points where a maximum temperature is reached in the reactor due to the heat of polymerization, and feeding a further amount of said mixture into the reactor in one or more secondary streams(II) at a point or points which, relative to the direction of flow of the ehtylene, are positioned upstream of the feed points of secondary streams(I) and upstream of the points at which a maximum temperature is reached in the reactor.