Acrylic-based injection materials with improved curing properties

A hydrogel forming composition comprising:

• a) at least one water-soluble (meth)acrylic compound,
• b) at least one free radical initiator,
• c) at least one catalyst for free radical formation, and
• d) water,
• wherein the at least one catalyst for free radical formation is an amine compound of formula (I)
• wherein:
• (i) R1 to R5 represent independently from each other linear or branched alkyl groups having 1 to 6 carbon atoms and optionally having one or more oxygen atoms, and n has a value of 0;
• (ii) R1 to R8 represent independently from each other linear or branched alkyl groups having 1 to 6 carbon atoms and optionally having one or more oxygen atoms, and n has a value of 1;
• or
• (iii) R1, R2, R7, and R8 together form a 5- or 6-membered ring structure with the two nitrogen atoms, R3 to R6 represent independently from each other linear or branched alkyl groups having 1 to 6 carbon atoms and optionally having one or more oxygen atoms, and n has a value of 1.