Thermoplastic Polythiourethanes for 3D Printing

Patent Title: THIOURETHANE POLYMERS, METHOD OF SYNTHESIS THEREOF AND USE IN FUSED FILAMENT FABRICATION PRINTING

 Number/Link:  WO2018/035102

Applicant/Assignee:  University of Texas

Publication date: 22 February 2018

Gist”: Polythiourethanes from diisocyanates and dithiols are used in FFF printing

Why it is interesting: Fused Filament Fabrication (FFF), which is actually the same thing as  Fused Deposition Modeling (FDM) is a popular and cheap additive manufacturing technology in which a thermoplastic filament is molten and ‘printed’ in layers. Many off-the-shelf thermoplastics can be used in FFF but these often do not have the correct melt characteristics resulting in printed objects of poor quality. According to this invention FFF-optimized thermoplastics can be prepared by reacting dithiols with diisocyanates into polythiourethanes.  The reaction is carried out in an aprotic solvent and catalysed by a non-nucleophilic base. In an example 2,2′-(ethylenedioxy)diethanethiol is reacted with HDI in DMF and catalysed by triethylamine. FFF printed parts of this polymer are said to show high toughness and less water uptake compared to TPU and polyamides.

polythiourethane

Polythiourethane according to the invention

 

TPU Powder for SLS

Patent Title: USE OF THERMOPLASTIC POLYURETHANE POWDERS

 Number/Link: WO2015/197515 (German)

Applicant/Assignee: Covestro

Publication date: 30-12-2015

Gist”: TPU with very specific melt properties can be used for selective laser sintering

Why it is interesting: Additive manufacturing and “3D printing” using TPU is not new and has been mentioned before in this blog, e.g. the use of TPU in for fused deposition modelling. Fused deposition modelling is a technique where molten thermoplastics are extruded. In powder-based techniques on the other hand, thin layers of thermoplastic powder are selectively ‘sintered’ together using lasers or IR beams.  Powder techniques like laser sintering are said to have economic advantages and allow for the production more complex shapes, but suffer from low mechanical properties and brittleness. According to this application, TPU powders with specific hardness and melt characteristics (as outlined in claim 1) allow for laser-sintered objects with improved mechanical properties. In the examples a TPU is prepared from a butanediol-adipic acid polyester diol, butanediol chain extender and 4,4’MDI.  The TPU, together with some ‘fumed’ silica flow-improvement additive, is then cryogenically grinded to an average particle size of less than 150 micron and subsequently used for laser sintering.

Tetrahedron made by SLS

Tetrahedron made by SLS (© Wikimedia)