Method for the Production of a Thermoplastic Polyurethane Powder by Means of Precipitation Polymerisation

A process for producing a thermoplastic polyurethane powder by precipitation polymerization, comprising the steps of:

• i. providing
• A) a solvent mixture comprising at least one first aprotic solvent A1) having a relative permittivity εr of 3 to 20 and at least one second aprotic polar solvent A2) having a relative permittivity εr of at least 24, the relative permittivity εr being measured in each case at 20° C. and 100 kHz;
• B) at least one polyol having a molar mass of between 60 g/mol and 250 g/mol;
• C) at least one diisocyanate;
• D) optionally a catalyst;
• E) optionally a chain regulator E1) and/or an additive E2);
• ii. reacting the polyol B) with the diisocyanate C) in the solvent mixture A) at a temperature of not more than 150° C., optionally in the presence of the catalyst D), the chain regulator E1) and/or the additive E2), to give the thermoplastic polyurethane, wherein the thermoplastic polyurethane precipitates as a solid in the solvent mixture A), forming a dispersion;
• iii. removing the solvent mixture and optionally washing the thermoplastic polyurethane with a solvent;
• and
• iv. drying the thermoplastic polyurethane to give the thermoplastic polyurethane powder;
• wherein the thermoplastic polyurethane powder has
• a mass-average molar mass Mw of >35 000 g/mol;
• an allophanate content of <0.25 mol % based on the total thermoplastic polyurethane powder;
• and
• 25.0% by weight of a particle fraction of <0.500 mm, based on the total thermoplastic polyurethane powder, and/or a ratio of centrifuge-average molar mass Mz to mass-average molar mass Mw of <4.0.