Organic peroxide heat stabilizer

1. A process for preparing a thermally stable organic peroxide solution comprising admixing an organic peroxide and an N-heterocyclic heat-stabilizing compound comprising at least one nitroxyl radical with the N atom of the nitroxyl radical forming part of the ring, wherein the temperature of the beginning of decomposition of said solution comprising the stabilizer is greater than the temperature of the beginning of decomposition of the solution not comprising the stabilizer.

2. The process as claimed in claim 1 , characterized in that the heat-stabilizing compound is represented by at least one of the following formulae (I), (II) and (III):

in which R 1 , R 2 , R 3 and R 4 , which can be identical or different, represent a hydrogen atom, a halogen atom, a saturated or unsaturated and linear, branched or cyclic hydrocarbonaceous group a polymer chain or a functional group;

in which R 5 , R 6 , R 7 and R 8 , which can be identical or different, can be chosen from the same family of group as that for R 1 , R 2 , R 3 and R 4 and, furthermore, can represent a hydroxyl group —OH or an acid group, such as —COOH or —PO(OH) 2 or —SO 3 H;

X in the formula (III) representing:

a divalent group chosen from methylene —CH 2 —, —C(OR°)(OR′)—, carbonyl —C(O)—, oxy —O— and —CHZ-, with Z representing a monovalent residue chosen from cyano (—CN), hydroxyl (—OH), amino (—NR°R′), alkoxy (—OR°—), iminoyl (—N═CR°R′), carboxylate (—OC(O)—R°) or amide (—NHR°—C(O)R′) groups and with R° and R′, which are identical or different, representing a hydrogen atom, a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 20, or a benzyl or phenyl group, or

a phosphonate group —OP(O)RR′ with R′ and R′ having the same meaning as Z.

3. The process as claimed in claim 2 wherein said halogen atom is selected from the group consisting of fluorine, chlorine, bromine, iodine, and a mixture thereof.

4. The process as claimed in claim 2 wherein said saturated or unsaturated and linear, branched or cyclic hydrocarbonaceous group comprises an alkyl or phenyl radical.

5. The process as claimed in claim 2 wherein said functional group is selected from the group consisting of a cyano group —CN, an ester group —COOR, an amide group —CON(R) 2 , an alkoxyl group —OR, and a phosphonate group —PO(OR) 2 , with R representing a hydrocarbonaceous chain having from 1 to 9 carbon atoms.

6. The process as claimed in claim 1 , characterized in that the heat stabilizer is represented by the following formula:

with n being able to vary from 1 to 20.

7. The process as claimed in claim 1 , characterized in that the heat stabilizer is chosen from 2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl -1-piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, 2,2,5,5,-tetramethyl-1-pyrrolidinyloxy, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl monophosphonate or 3-carboxy-2,2,5,5-tetramethylpyrrolidinyloxy.

8. A composition comprising at least one organic peroxide which is/are stable on storage and stable toward heat, characterized in that it comprises at least one organic peroxide and at least one N-heterocyclic heat-stabilizing compound including at least one nitroxyl radical with the N atom of the nitroxyl radical forming part of the ring for preparing a thermally stable solution of organic peroxide, the temperature of the beginning of decomposition of said solution comprising the stabilizer being greater than the temperature of the beginning of decomposition of the solution not comprising the stabilizer.

9. The composition as claimed in claim 8 , characterized in that the organic peroxide is selected from the group consisting of dialkyl peroxides, hydroperoxides and their salts, peroxyketals and peroxyesters.

10. The composition as claimed in claim 8 , characterized in that the organic peroxide is dicumyl peroxide, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane or the disodium salt of 1,3- and 1,4-bis(2-hydroxyperoxideprop-2-yl)benzene.

11. A process for the manufacture of a composition as claimed in claim 8 , characterized in that at least one N-heterocyclic heat-stabilizing compound including at least one nitroxyl radical with the N atom of the nitroxyl radical forming part of the ring for preparing a thermally stable solution of organic peroxide, the temperature of the beginning of decomposition of said solution comprising the stabilizer being greater than the temperature of the beginning of decomposition of the solution not comprising the stabilizer, is added to the organic peroxide.