1 4 carbon atoms and d vinyl esters of saturated aliphatic acids having 2 4 carbon atoms representative of these comonomers are alpha beta unsaturated carboxylic acids having 3 8 carbon atoms such as methacrylic acid acrylic acid maleic acid fumaric acid and itaconic acid esters and glycidyl esters of the above acids with c 1 c 8 alcohols and with phenols and naphthols having up to 2 alkyl substituents of 1 4 carbon atoms such as methyl acrylate ethyl acrylate methyl methacrylate ethyl methacrylate butyl acrylate isobutyl acrylate pentyl acrylate hexyl acrylate 2 ethylhexyl acrylate 2 ethylhexyl methacrylate glycidyl methacrylate phenyl acrylate 4 methylphenyl acrylate naphthyl acrylate methyl hydrogen maleate ethyl hydrogen maleate and ethyl hydrogen itaconate and anhydrides of the above acids such as maleic anhydride acrylonitrile and methacrylonitrile other comonomers which can be used are vinyl esters of saturated acids having 2 4 carbon atoms of which vinyl acetate is particularly preferred two particularly preferred ethylene copolymers that can be prepared by this process are those prepared from ethylene carbon monoxide and vinyl acetate and ethylene carbon monoxide and n butyl acrylate the monomers to be copolymerized are typically introduced into the copolymerization reactor with at least one free radical copolymerization initiator according to known copolymerization techniques typical copolymerization initiators which can be used include peroxygen compounds such as lauryl peroxide tert butyl peracetate tert butyl peroxypivalate di tert butyl peroxide di sec butyl peroxydicarbonate as well as tert butyl peroctoate other free radical initiators which can be used include azobis compounds such as e g azobisisobutyronitrile the choice of initiator will depend on the copolymerization temperature since each initiator has its.