Method for preparing an elastomer from a hydroxylated fatty acid and elastomer obtained by such a method
A method for preparing a polymer of the elastomer type based on a monomer selected from polyhydroxylated fatty acids and esters of a polyhydroxylated fatty acid and a C1-C18 aliphatic chain alcohol is disclosed. This method includes preparing a reaction medium by bringing the monomer with a polyol, this reaction medium being catalyst free, then a step of heating the reaction medium in order to implement the copolymerisation of the monomer and of the polyol and the cross-linking of the polymer thus formed, with at least the initial phase of this heating step being implemented at a reduced pressure.
1 . A method for preparing a polymer based on a polyhydroxylated fatty acid, comprising, successively, steps of:
preparation of a reaction medium by bringing together:
a monomer consisting of a dihydroxylated fatty acid or an ester of a dihydroxylated fatty acid and of an alcohol with a linear or branched, saturated or unsaturated, optionally substituted, aliphatic chain, said aliphatic chain including from 1 to 18 carbon atoms, and
glycerol, in an amount of 15 to 25% by weight with respect to the total weight of said reaction medium,
the reaction medium having a molar ratio of glycerol to the monomer between 0.16 and 1.04 and wherein the glycerol and the monomer represent at least 90% by weight of the reaction medium,
said reaction medium being free of catalyst,
and heating of said reaction medium at 120 to 200° C. to carry out the copolymerisation of said monomer and of said glycerol and the crosslinking of the polymer thus formed, at least an initial phase of the heating step being carried out at a pressure comprised between 400 and 800 mbar, wherein the duration of the initial phase is comprised between 30 minutes and 5 hours.
2 . The method according to claim 1 , wherein said monomer is a methyl or ethyl ester of the dihydroxylated fatty acid.
3 . The method according to claim 1 , wherein said monomer is obtained by depolymerising cutin.
4 . The method according to claim 1 , wherein the preparation of said reaction medium comprises mixing said glycerol with a composition resulting from the depolymerisation of cutin.
5 . The method according to claim 1 , wherein said heating step is carried out for a period of at least 4 hours.
6 . The method according to claim 1 , comprising, during said heating step, before a gel point of said polymer has been reached, a step of eliminating bubbles present in said reaction medium.
7 . The method according to claim 1 , wherein the preparation of the reaction medium is carried out at a temperature higher than or equal to 50° C.
8 . The method according to claim 3 , wherein said monomer is obtained by depolymerising tomato cutin.
9 . The method of claim 1 , wherein the duration of the initial phase is about 90 minutes.
10 . The method of claim 1 , wherein the monomer is 10,16-dihydroxyhexadecanoic acid or its methyl or ethyl ester.