SUSPENSION POLYMERIZATION OF ALKOXYAMINES WITH STYRENIC AND (METH)ACRYLIC MONOMERS

1 . A process for suspension polymerization of (meth)acrylic and/or styrenic monomers to obtain beads of a composition comprising at least one block copolymer, the process comprising the following two successive synthesis steps:

Step 1:

in a stirred reactor comprising water, 0.5 to 4% by mass of a suspension agent constituting the aqueous phase,

introducing an organic phase consisting of at least one alkoxyamine and at least one acrylic and/or styrenic monomer with a nitroxide/monomer molar ratio of between 1/50 and 1/1000 and an aqueous phase/organic phase mass ratio of between 3 and 10, the alkoxyamine carrying at least one nitroxide corresponding to the following formula:

where R L is a monovalent group with a molar mass greater than 15.42 g/mol; and R a and R b are identical or different alkyl groups having from 1 to 40 carbon atoms, optionally linked together so as to form a ring and optionally substituted by hydroxyl, alkoxy or amino groups;

polymerizing monomers in a suspension up to a minimum mass conversion rate of 80% at a temperature of between 15° C. and 140° C.;

Step 2:

introducing into the previous polymerized suspension at least one methacrylic and/or styrenic monomer and at least one mercaptan with a mercaptan/nitroxide molar ratio of between 2/1 000 and 8/1000 and with a mass ratio of the monomers (acrylic and/or styrenic from step 1)/(methacrylic and/or styrenic monomers from step 2) of between 25/75 and 70/30;

polymerize with stirring the monomers up to a minimum conversion rate of 95% at a temperature of between 15° C. and 140° C.

introducing an initiator soluble in the aqueous phase to complete the polymerization up to a minimum mass conversion rate of 99% with a rate of between 0.1 and 2% relative to the mass of total organic Phase; and

filtering, washing, and then drying the beads.

2 . The process as claimed in claim 1 , wherein a surfactant is added to the aqueous phase during Step 1 in proportions varying from 1 to 10 000 ppm.

3 . The process as claimed in claim 1 , wherein the mercaptan is designated R-SH with R as an alkyl radical which is linear or non-functionalized or not, having from 3 to 12 carbons.

4 . The process as claimed in claim 1 , wherein the monomers of Step 1 are chosen from butyl acrylate, 2-ethylhexyl acrylate and styrene, alone or in combination, and the monomers of Step 2 are chosen from methyl methacrylate, methacrylic acid and styrene, alone or in combination.

5 . The process as claimed in claim 1 , wherein the nitroxide is N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

6 . The process as claimed in claim 1 , wherein the alkoxyamine is 2-([tert-butyl [1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2 methylpropionic acid.

7 . The process as claimed in claim 1 , wherein the alkoxyamine is the addition product of 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2 methylpropionic acid and butanediol diacrylate.

8 . A composition obtained from the process of claim 1 .

9 . The composition as claimed in claim 8 , having a weight-average molecular mass of between 10,000 and 200,000 g/mol with a dispersity index of between 2 and 4.

10 . A bead obtained from the process of claim 1 .

11 . A process for three-dimensional printing or as such or for manufacturing objects by molding, injection, compression or extrusion, the process comprising adding the beads as claimed in claim 10 .