TPU with Moisture-Controlled Flexibility

Title: THERMOPLASTIC POLYURETHANE MATERIALS FOR FORMING MEDICAL DEVICES

Number/Link: WO2017/066381

Applicant/Assignee: Becton Dickinson

Publication Date: 20 april 2017

“Gist”: High hardblock TPU, based on side-chain branched chain extenders, softens in water

Why it is interesting: The invention is related to thermoplastic polyurethanes for medical applications especially for intravenous catheters. These catheters need to have a high stiffness when inserted but need to become flexible once in place to prevent injuries. This is accomplished with TPUs based on MDI, PTMEG and either 2,2-dimethyl-1,3-propanediol (neopentylglycol) or 2-methyl-1,3-propanediol (MPdiol) and having a hardblock content of 50 to 75%. The examples show indeed an increased stiffness at ambient conditions and a larger softening when soaked in saline solution compared to TPU produced with a linear chain extender. It is however not mentioned which linear chain extender was used.

Neopentylglycol

TPU from POM-Polyether Polyols

Title: THERMOPLASTIC POLYURETHANES, PRODUCTION AND USE THEREOF

 Number/Link: WO2015/155084  (German)

Applicant/Assignee: Bayer

Publication date: 15-10-2015

Gist”: Paraformaldehyde-PO polyols are used to make TPU

Why it is interesting: Polyoxymethylene (POM) is a highly crystalline ‘engineering thermoplastic’ often used in blends together with TPU. In this invention POM is not blended but used to make a POM-polyether ‘block’ diol which is then used to make TPU. The diol is prepared by using paraformaldehyde as a starter which is reacted with PO (and optionally CO2) using DMC catalysis. The POM-block acts as a ‘hard block’ and use of the diol allows for an improved control of Tg, melt viscosity, hardness, chemical resistance etc. of the TPU.  In the examples TPU is made from a 2000 MW parafomaldehyde/PO-CO2 block copolymer  together with 4,4’MDI and BDO.

Paraformaldehyde

Paraformaldehyde

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