Polymerization inhibitors

A mixture comprising at least one compound of formula (I),

• wherein
• R is C1- to C4-alkyl
• R1 is C1- or C2-alkyl and
• R2 to R4 are independently of one another H, C1- or C2-alkyl,
• and at least one polymerizable compound, wherein the at least one polymerizable compound is acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, glycerol triacrylate, ethoxylated glycerol triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, butanediol monoacrylate, dicyclopentadienyl acrylate, 2-dimethylaminoethyl acrylate, 2-hydroxyethyl acrylate, or 2-hydroxypropyl acrylate.