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

 

Polythiourethanes for 3D Printing

Patent Title:  THIOURETHANE POLYMERS, METHOD OF SYNTHESIS THEREOF AND USE IN ADDITIVE MANUFACTURING TECHNOLOGIES

 Number/Link: WO2017/160810

Applicant/Assignee:  Univ. Texas

Publication date: 21-September-2017

Gist”: Photolatent bases are used to catalyse the polythiol-polyisocyanate reaction

Why it is interesting: According to this invention reactive systems useful for additive manufacturing processes can be prepared from polythiols, diisocyanates and a photolatent base.  When irradiated the photolatent base will split off a non-nucleophilic base which will catalyse the thiol-isocyanate reaction. The systems can be prepared such that the resulting materials show improved mechanical properties over current 3D printed materials.  In an example 2,2′-(ethylenedioxy)diethanethiol and pentaerithritol tetrakis(3-mercaptopropionate) are reacted with HDI using 1,1-dimethyl-1-(2-hydroxypropyl)amine-p-nitrobenzimide (DANBA) as a photolatent base.

Example of pholatent base (DANBA)

PU-Acrylate/Epoxy IPN for 3D Printing

Patent Title: PHOTOCURABLE COMPOSITIONS FOR THREE-DIMENSIONAL PRINTING

 Number/Link:  WO 2016/153711

Applicant/Assignee: Dow

Publication date: 29-09-2016

Gist”: Acrylate-capped PU prepolymer is copolymerized with epoxides using UV radiation

Why it is interesting: This case is about UV-curable compositions to make flexible materials using additive manufacturing, especially stereolithography.  A prepolymer of an isocyanate and a ‘flexible’ polyol is capped with a hydroxy-functional acrylate, then mixed with a multifunctional epoxy, a multifunctional acrylate ‘monomer’ (a crosslinker also acting as reactive diluent) and two photoinitiators:  one radical and one cationic.  In the example a 6 to 8000 Mole weight diol is capped with TDI and then with hydroxyethyl acrylate.  The prepolymer is then mixed with 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 1,6-hexanedioldiacrylate and two photoinitiators.  After UV curing the materials had a shore A hardness between about 60 and 80 and an elongation at break between about 70 and 200.

3,4-Epoxycyclohexylmethyl-3,4- epoxycyclohexane carboxylate

3,4-Epoxycyclohexylmethyl-3,4-
epoxycyclohexane carboxylate

Dual-Cure PU for 3D Printing

Patent Title: POLYURETHANE RESINS HAVING MULTIPLE MECHANISMS OF HARDENING FOR USE IN PRODUCING THREE-DIMENSIONAL OBJECTS

 Number/Link: US2016137839

Applicant/Assignee: Carbon3D

Publication date: 19-05-2016

Gist”: Isocyanates are blocked with ethylenically unsaturated blocking agents

Why it is interesting: This invention relates to additive manufacturing of 3D objects using photocurable liquids. The liquid consists of a diisocyanate, or a difunctional isocyanate-ended prepolymer, which is blocked with an ethylenically unsaturated blocking agent, for example t-butylaminoethylmethacrylate (TBAEMA). The photocurable liquid further comprises a diol (or diamine), a photoinitiator and a ethylenically unsaturated diluent, for example a methacrylate or a styrene.  The liquid can then be selectively cured into an intermediate solid 3D object by irradiation with UV light using conventional “printing” methods. After an optional washing stage the intermediate object can be finally cured using heat.

TBAEMA

TBAEMA

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)