Grafting reaction system and grafting process

In a grafting process comprising reacting a solid activated polymer with a monomer contained in a liquid grafting medium, in the presence of free radicals, the improvement comprising inhibiting homopolymerization of said monomer by reacting said activated polymer and monomer in the presence of from 0.1% to 2% by weight of the grafting medium of a homopolymerization inhibitor compound, said inhibitor compound comprising a compatibilizing function toward the grafting medium, said compatibilizing function selected from the group consisting of sulfonic and carboxylic groups and an inhibiting function which acts as a transfer agent for said free radicals, said inhibiting function being an allyl or methallyl unsaturated group, said inhibitor compound having a diffusing capacity through said grafting medium which is greater than its diffusing capacity through said polymer.

Process for inhibiting monomer homopolymerization in a grafting reaction of an activated polymer and monomer, comprising:

• forming a liquid grafting medium containing a monomer and a homopolymerization inhibitor compound comprising a compatibilizing function toward the grafting medium, said compatibilizing function selected from the group consisting of sulfonic and carboxylic groups, and an inhibiting function which acts as a transfer agent for free radicals, said inhibiting function being an allyl or methallyl unsaturated group, said inhibitor compound having a diffusing capacity through said grafting medium which is greater than its diffusing capacity through said polymer;
• adding to said medium an activated solid polymer;
• and reacting said activated solid polymer and said monomer in the presence of said homopolymerization inhibitor compound, wherein said homopolymerization inhibitor compound is present at a level of 0.1-2% by weight of the grafting medium and monomer.