Composition comprising a nitroxide, a promoter and optionally a free-radical initiator

1. A scorch retarding composition comprising a nitroxide and at least one crosslinking promoter comprising a group (P) comprising compounds containing at least one double bond.

2. The composition of claim 1 , comprising the nitroxide in weight proportions ranging from 1:0.2 to 1:5 relative to the amount of crosslinking promoter present.

3. The composition of claim 1 , further comprising a free-radical initiator comprising an organic peroxides, an azo compound, or mixtures thereof.

4. The composition of claim 3 , comprising the free-radical initiator in weight proportions of from 1:0.02 to 1:1 relative to the amount of nitroxide present.

5. The composition of claim 3 , comprising the free-radical initiator in weight proportions of from 1:0.02 to 1:1 relative to the amount of promoter used.

6. The composition of claim 3 , further comprising a thermoplastic polymer and/or elastomeric polymer.

7. The composition of claim 6 , wherein said polymer is crosslinked with a peroxide or an azo compound.

8. The composition of claim 7 , wherein the free-radical initiator represents between 0.2 and 5 parts per 100 parts by weight of polymer.

9. The composition of claim 8 , wherein said free radical initiator represents between 0.5 and 3 parts per 100 part by weight of polymer.

10. The composition of claim 1 , wherein the nitroxide is represented by;

in which R 1 , R 2 , R 3 , R 4 , R′ 1 and R′ 2 , which are identical or different, represent a hydrogen atom, a halogen atom, a linear, branched or cyclic, saturated or usaturated hydrocarbon-based group, a polymer chain comprising a polyalkyl (meth)acrylate chain, a polydiene, polyolefin or polystyrene chain, a functionalized group, an ester —COOR group, an amide —CON(R) 2 group, an alkoxy —OR group or a phosphonate —PO(OR) 2 group in which R represents a hydrogen-based chain containing from 1-9 carbon atoms.

11. The composition of claim 10 , wherein said halogen atom is flourine, chlorine, bromine or iodine.

12. The composition of claim 10 , wherein said hydrocarbon-based group is an alkyl or phenyl radical.

13. The composition of claim 10 , wherein said polyalkyl (meth)acrylate chain is polymethyl methacrylate.

14. The composition of claim 10 , wherein said functionalized group is a cyano —CN group.

15. The composition of claim 10 , wherein R′ 1 and R′ 2 are linked together to form a ring comprising:

in which R 5 , R 6 , R 7 and R 8 , which are identical or different, comprise the same family of groups as those for R 1 , R 2 , R 3 , and R 4 or represent a hydroxyl —OH group or an acid group; X in formula (VI) represents a divalent group comprising methylene, —CH 2 —, —C(OR)(OR′)—, carbonyl —C(O)—, oxy —O— or —CHZ— with Z representing a monovalent residue comprising cyano: —CN, amino: —NRR′, alkoxy: —OR, iminoyl —N═CRR′, carboxylate: —OC(O)—R or arminde: —NHR—C(O)R′ groups, in which R and R′, which may be identical or different, represent a hydrogen atom, a liner or branched alkyl group containing a number of carbon atoms ranging from 1 to 10, or benzyl or phenyl group.

16. The composition of claim 15 , wherein said acid group is —COOH or —PO(OH) 2 or —SO 3 H.

17. The composition of claim 15 , wherein X in formula (VI) is phosphonate —OP(O)R″R′″ with R″ and R′″ representing said Z.

18. The composition of claim 1 , wherein the nitroxide is represented by the general formula (VII):

in which R 1 , R 2 , R 3 , R 4 , which are identical or different, represent a hydrogen atom, a halogen atom, a linear, branched or cyclic, saturated or usaturated hydrocarbon-based group, a polymer chain comprising a polyalkyl (meth)acrylate chain, a polydiene, polyolefin or polystyrene chain, a functionalized group, an ester —COOR group, an anide —CON(R) 2 group, an alkoxy —OR group or a phosphonate —PO(OR) 2 group in which R represents a hydrogen-based chain containing from 1-9 carbon atoms, and Y represents a divalent group comprising:

—OC(O)—(CR a R b ) n —C(O))—,

—NH—(CR a R b ) n NH—,

—NHC(O)—(CR a R b ) n —C(O)NH—,

—S—, —O—, R a and R b , which are identical or different, represent a hydrogen atom or a linar or branched alkyl radical containing a number of carbon atoms ranging from 1 to 10 and n represents an integer ranging from 0 to 20.

19. The composition of claim 1 , wherein the nitroxide is represented by the general formula (VIII):

in which R 1 , R 2 , R 3 , R 4 , which are identical or different, represent a hydrogen atom, a halogen atom, a linear, branched or cyclic, saturated or usaturated hydrocarbon-based group, a polymer chain comprising a polyalkyl (meth)acrylate chain, a polydiene, polyolefin or polystyrene chain, a functionalized group, an ester —COOR group, an amide —CON(R) 2 group, an alkoxy —OR group or a phosphonate —PO(OR) 2 group in which R represents a hydrogen-based chain containing from 1-9 carbon atoms, λ is an integer between 1 and 20, R 9 represents a alkylene group containing a number of carbon atoms ranging from 2 to 12 which are optionally interrupted with an —O— or —NR 10 — with R 10 denoting hydrogen atom, an alkyl group containing a number of carbons between 1 and 12, or a cycloalkyl group, and Q represents a radical —OR 11 , —NHR 12 or —NR 12 R 13 in which R 11 represents a linear or branched alkyl radical containing a number of carbon atoms ranging from 1 to 12, a C 3 -C 12 alkoxyalkyl radical, a cyclohexyl radical, a benzyl radical, a phenyl radical, a tolyl radical or a 2,2,6,6-tetrapiperidyl residue, R 12 and R 13 , have the same meaning as R 11 or forms together with the nitrogen atom which bears them, a 5-, 6- or 7-member heterocyclic radical which optionally also contain an oxygen.

20. The composition of claim 1 , wherein the nitroxide comprises:

wherein n ranges from 1 to 20.

21. The composition of claim 1 , wherein the nitroxide is 2,2,6,6-tetramethyl-1-piperidyloxy, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, bis(1-oxy-2,2,6,6-tetramethyl-4-piperidyl sebacate, 2,2,6-tetramethyl-4-hydroxy-1-piperidyloxy monophosphonate or 3-carboxy-2,2,5,5-tetramethylpyrrolidinyloxy.

22. The composition of claim 1 , wherein the crosslinking promoter is trans-stilbene, divinylbenzene, trans, trans-2,6-dimethyl-2,4,6-octatriene, dicyclopentadiene, 3,7-dimethyl-1,3,6-octatriene (OCIMENE), a compound represented by the general formula (I):

in which R x represents a hydrogen atom or an alkyl group of 1 to 9 carbon atoms and n is an integer between 1 and 3,

or the compounds represented by the general formula (II):

in which R y and R z , which are identical or different, represent an alkyl group of 1 to 4 carbon atoms.

23. The composition of claim 22 wherein the crosslinking promoter is α-methylstyrene, ortho-, meta-, or para-diisopropenylbenzene, 1,2,4-triisopropenylbenzene, 1,3,5-triisopropenylbenzene, 3-isopropyl-ortho-diisopropenylbenzene, 4-isopropyl-ortho-diisopropenylbenzene, 4-isopropyl-m-diisopropenylbenzene, 5-isopropyl-m-diisopropenybenzene, 2-isopropyl-p-diisopropenylbenzene, 2,4-bis(3-isopropylphenyyl)-4-methyl-1-pentene, 2,4-bis(4-isopropylphenyyl)-4-methyl-1-pentene, 2-(3-isopropylphenyl)-4-(4isopropylphenyl)-4-methyl-1-pentene, 2-(4-isopropylpheny)-4-methyl-1-pentene, 2,4-bis(3-methylphenyl)-4-methyl-1-pentene or bis(4-methylphenyl)-4-methyl-1-pentene.

24. The composition of claim 3 , wherein the free-radical initiator is dicumyl peroxide or α, α′—di[(t-butylperoxy)isopropyl]benzene.

25. The composition of claim 6 , wherein the polymer is a linear low density polyethylene, low density polyethylene, high density polyethylene, chlorinated polyethylene, ethylene/propylene/butadiene terpolymers, ethylene/vinyl acetate copolymers, ethylene/propylene copolymers, silicone rubber, chlorosulphonated polyethylene, fluoroelastomers, ethylene/methyl(meth)acrylate copolymers or ethylene/glycidyl methacrylate copolymers.

26. A process for crosslinking a thermoplastic and/or clastomeric polymer, comprising mixing said polymer in the presence of a free-radical initiator, a nitroxide and a crosslinking promoter (P) comprising compounds containing at least one double bond, which may be difunctional or polyfunctional.

27. The process of claim 26 , comprising converting the polymer into molded or extruded articles out during or after crosslinking.

28. Molded or extruded articles obtained according to the process of claim 27 .

29. The composition of claim 19 , wherein the 5-, 6-, or 7-membered heterocyclic radical contains an oxygen.

30. The composition of claim 1 , wherein said at least one promoter comprises methyl methacrylate, lauryl methacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), triallyl phosphate, tetraallyloxyethane, diallyldiglycol carbonate, triallyl trimellitate, trially citrate, diallyl adipate, diallyl terephthalate, dially oxalate, diallyl furmarate, ethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, or a combination thereof.

31. The process of claim 26 , wherein said promoter (P) comprises methyl methacrylate, lauryl methacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), triallyl phosphate, tetraallyloxyethane, diallyldiglycol carbonate, triallyl trimellitate, trially citrate, diallyl adipate, diallyl terephthalate, dially oxalate, diallyl furmarate, ethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, or a combination thereof.