Aminoalkyl (meth)acrylate stabilisation
The present invention relates to the use of a stabilizing composition comprising at least one N-oxyl compound and at least one polymerization inhibitor other than an N-oxyl compound, for inhibiting transesterification catalyst degradation in a process for the synthesis of aminoalkyl (meth)acrylates. Preferably, the transesterification catalyst is a titanium organometallic compound and the stabilising composition comprises at least one N-oxyl derivative and at least one polymerization inhibitor chosen from phenolic compounds and phenothiazine compounds in a weight ratio of between 1 and 10, preferably between 4 and 10, limits inclusive.
1. A process for synthesizing aminoalkyl (meth)acrylates, comprising the step of transesterifying an alkyl (meth)acrylate of formula (II):
in which R is a hydrogen atom or a methyl group and R 2 is a linear or branched alkyl group having from 1 to 4 carbon atoms,
with an alcohol R1-OH of formula (III):
HO-A-N(R′1)(R′2) (III)
in which
A is a linear or branched C 1 -C 5 alkylene radical,
R′1 and R′2, which are identical or different from one another, represent a hydrogen atom or a C 1 -C 4 alkyl radical,
in the presence of a transesterification catalyst selected from the group consisting of organometallic compounds of one of the following formulas:
M(OR3) 4 in which R3 is a linear or branched C 1 -C 5 alkyl radical and M is a group IV metal or,
M{OC(CH3)═CH—C(CH3)═O} 4 in which M is a group IV metal, whereby the transesterification is carried out in the presence of a stabilizing composition comprising at least one N-oxyl compound and at least one polymerization inhibitor selected from the group consisting of phenol compounds and phenothiazine compounds in a mass ratio of between 1 and 10, endpoints included.
2. The process as claimed in claim 1 , wherein the aminoalkyl (meth)acrylate is dimethylaminoethyl acrylate.
3. The process as claimed in claim 1 , in which the N-oxyl compound is selected from the group consisting of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), 4 -hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-OH-TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidine 1-oxyl (4-Oxo-TEMPO), and mixtures thereof.
4. The process as claimed in claim 1 in which the stabilizing composition comprises at least one polymerization inhibitor selected from the group consisting of phenothiazine, 4-methyl-2,6-tert -butylphenol, hydroquinone, and hydroquinone methyl ether.
5. The process as claimed in claim 1 in which the mass ratio of the N-oxyl compound to the one or more polymerization inhibitors is between 2 and 10, endpoints included.
6. The process as claimed in claim 1 in which the mass ratio of the N-oxyl compound to the one or more polymerization inhibitors is between 4 and 10, endpoints included.
7. The process as claimed in claim 1 in which the mass ratio of the N-oxyl compound to the one or more polymerization inhibitors is between 5 and 10, endpoints included.
8. The process as claimed in claim 1 in which the alcohol R1-OH is dimethylaminoethanol.
9. The process as claimed in claim 1 in which said group IV metal M is titanium.
10. The process as claimed in claim 1 in which said transesterification catalyst is selected from the group consisting of titanium alkoxides, tetraalkyl titanates, and Ti, Zr or Hf acetylacetonates.