Patent Title: POROUS THERMOPLASTIC MEMBRANES

 Number/Link: WO2017/178482

Applicant/Assignee:  BASF

Publication date: 19-october-2017

“Gist”: Semi-permeable membranes are made by phase inversion of all-hardblock TPU solutions

Why it is interesting: ‘Breathable” membranes show a high resistance to liquid water permeation (LEP) combined with a high water vapour permeability (WDD). According to this invention breathable polyurethane membranes can be prepared by dissolving an all-hardblock thermoplastic polyurethane in a polar, aprotic solvent (like N-methyl pyrrolidone) together with a water soluble compound, casting a film and coagulating the film with water. In the examples diisocyanates (MDI, TDI and HDI) are stoichiometrically reacted with chain extenders (MEG, BDO and HDO).  The resulting materials were schredded and dissolved in NMP together with some glycerol. 150 μm thick films were cast on glass and coagulated in water, resulting in membranes with an average pore size ranging between 4 and 500 nm.  The membranes are said to be useful to make breathable fabrics for outdoor wear e.g. (“Gore Tex” (TM) – type materials)

N-methyl-2-pyrrolidone