Polymerization inhibition of acrylate esters

A method for inhibiting the polymerization of crude dimethylaminoethyl methacrylate during its purification by distillation which comprises conducting said distillation in the presence of an inhibitor combination consisting essentially of a phenolictype polymerization inhibitor selected from the group consisting of:

• o-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis (6-tert-butyl-p-cresol), 4,4'thiobis (6-tert-butyl-m-cresol, 4,4'-thiobis (6-tert-butyl-o-cresol), thiobis (di-sec-amylphenol), 4,4'-butylidene (6-tert-butyl-m-cresol), p,p'-biphenol, 4,4'-methylenebis (2,6-di-tert-butylphenol) and 1,5-naphthalenediol, and an amine-type polymerization inhibitor selected from the group consisting of:
• N-phenyl-1-naphthylamine, N,N'-di-2-naphthyl-p-phenylenediamine, and 7-amino-1-hydroxynaphthalene combined in a weight ratio of 4:1 to 1:4 with the amount of the inhibitor combination being 0.01 to 20% by weight, based on the weight of the pure acrylate ester present in the crude acrylate ester mixture.