Patent ID: 11939436
Assignee: EVONIK OPERATIONS GMBH
Field: Other special machines (Mechanical engineering)
Classification: CPC C  B | IPC B  C

Claim 0:
1. A method for producing a population of particles of a polymer, wherein the polymer is polybutylene terephthalate (=PBT) or polyethylene terephthalate (=PET) or a copolymer comprising polybutylene terephthalate and/or polyethylene terephthalate, wherein the polymer is dissolved in an organic solvent which solvent is selected such that it completely solubilizes the polymer only at a temperature of the solvent above 100° C., comprising:
a) heating the solvent and the solid polymer immersed in the solvent at least to a first temperature, at which first temperature the polymer completely dissolves as indicated by a resulting solution showing no turbidity, wherein the weight of the polymer in relation to the total weight of the solvent and the polymer is in the range of 0.25 wt. % to 50 wt. %,
b) cooling the solution, wherein the cooling is practiced until a second temperature is reached at which second temperature clouding of the solution starts,
c) further cooling the solution at a rate in a range of 0.05° C./min to 5° C./min or keeping the solution at the second temperature or at a temperature up to 3° C. below the second temperature for at least 5 min and then cooling the solution at a rate in a range of 0.05° C./min to 5° C./min, wherein cooling occurs at least until a third temperature is reached at which third temperature turbidity does not further increase, and
d) separating the particles formed during step b) or c) from the solution,, wherein independently for each of steps a), b) and c) either turbidity of the solution is measured during the respective step or the first, second and third temperature, respectively, is determined in a separate procedure, wherein the solvent in which the PBT or the PBT comprising copolymer is dissolved in step a) is at least one solvent selected from the group consisting of a cyclic ketone, a lactone, an aromatic alcohol, an aromatic aldehyde, an aromatic ester comprising only one ester group or a glycol ether comprising at most 10 carbon atoms in total and the solvent, in which the PET or the PET comprising copolymer is dissolved in step a) is at least one solvent selected from the group consisting of a cyclic ketone, a lactone, an aromatic alcohol or a non-aromatic cyclic or an aliphatic alcohol, an aromatic aldehyde or an aromatic ester comprising only one ester group,
wherein turbidity is determined by a light-scattering technique.