FIELD: chemistry.
SUBSTANCE: present invention relates to a method for thermal stabilisation of a polymer obtained by ring-opening polymerisation, as well as a method of producing polyhydroxy acids, a method of analysing metal residues in a polymer and polylactide. Said polymer contains residues of a Sn(II), Sb(III), Pb(II), Bi(III), Fe(II), Ti(II), Ti(III), Mn(II), Mn(III) or Ge(II)-containing catalyst. Thermal stabilisation is carried by treating the polymer at temperature higher than melting point thereof with a peroxide in amount of at least 0.2 wt % based on the weight of the polymer. The peroxide is selected from a group consisting of ketone peroxides, organic hydroperoxides, peracids, hydrogen peroxide and mixtures thereof. Molar ratio of peroxy functional groups from said peroxide to metal ranges from 1 to 100. Said metal is selected from a group consisting of Sn(II), Sb(III), Pb(II), Bi(III), Fe(II), Ti(II), Ti(III), Mn(II), Mn(III) and Ge(II). The method of producing polyhydroxy acids involves converting one or more monomers, dimers and/or oligomers of a hydroxy acid to a polyhydroxy acid using a Sn(II), Sb(III), Pb(II), Bi(III), Fe(II), Ti(Il), Ti(III), Mn(II), Mn(III) or Ge(II)-containing catalyst and treating the obtained polyhydroxy acid with a peroxide. The method of analysing metal residues in a polymer involves dissolving the polymer in an organic solvent, adding Fe(III), oxidising the metal and reducing Fe(III) to Fe(II), adding water, complexing the Fe(II) to form a coloured complex, determining content of Fe(II) and establishing content of metal in the polymer.
EFFECT: optimising a method for thermal stabilisation of polymers obtained by ring-opening polymerisation, particularly polylactic acid.
16 cl, 5 tbl, 3 dwg, 4 ex
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