Rigid Thermoplastic Polyurethanes


 Number/Link: WO2017/146948  WO2017/146949

Applicant/Assignee: Eastman Chemical

Publication date: 31 august 2017

Gist”: A “rigid”, high Tg polyester diol is extended with 4,4′ MDI

Why it is interesting: Rigid, high modulus TPUs have been known for a long time – see e.g. Upjohn’s classic patent on ‘Isoplast’ from 1981. These materials are high hardblock TPUs made from diisocyanates, chain extenders with only a small amount of high molecular weight diol as an impact modifier. According to the current invention however, rigid TPUs can be made using less than 40% (w/w) of diisocyanate, a high Tg polyester diol and optionally some chain extender.  The polyester is prepared from ‘rigid’ diols like isosorbide or 1,4-cyclohexanedimethanol together with a ‘rigid’ diacid like terephthalic acid, such that the diol has a MW of more than 400 Dalton and a Tg of more than 40°C. The diisocyanate is pref. 4,4-MDI. The rigid TPUs have a Tg of more than 145°C and a tensile modulus of 1 GPa or higher. They are said to be less moisture sensitive than conventional rigid TPUs.


Soft Ionomeric TPU


 Number/Link: US20160347900

Applicant/Assignee: Univ. Akron; Covestro

Publication date: 1-Dec-2016

Gist”: TPU is prepared with ionomeric groups having bulky counter-ions

Why it is interesting: According to this invention a novel type of plasticized thermoplastic polyurethane can be made  by incorporating as chain extender a diol containing an ionic group with a bulky counter ion. It is said that the steric hindrance of the bulky counter ions creates additional free volume that softens the polymer and lowers the melt viscosity. In the examples N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES) is used together with bulky alkylammonium cations. The softest TPU shown has a 37 Shore A hardness at 25% hardblock content and 7.6 mole% BES-tetrakis(decyl)ammonium. This accounts for a 35 point hardness decrease compared to an ionomer-free control sample.

N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid

N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid

Classic PU Patent of the Month: ICI’s Perfect Elastomer (1995)


 Number/Link: WO 97/21750

Applicant/Assignee: ICI

Publication date: 19-06-1997

Gist”: A polar polyether softblock and highly symmertrical hardblock results in a near-perfect polymer morphology.

Why it is interesting: ICI’s “perfect PU elastomer” is accomplished by reacting a polar, low-reactive polyether triol (75% EO random, 42 OHv) and a ‘stacking’ chain extender (MEG) with a symmetrical diisocyanate (4,4′ MDI).  Some water can be added to a density of about 400 kg/m³. This combination results in a remarkable polymer morphology with a ‘nano’ phase-separated hard domain and a very ‘clean’ soft phase, resulting in a very high (>1) and symmetrical damping peak (tan δ) and an incredibly flat storage modulus (E’) up to about 200°C.  Damping at positive temperatures  is virtually zero, resulting in a very high resilience.  The patent actually claims the shape of the DMTA trace rather than the composition of the polymer.
The elastomer is not completely “perfect” in that it has relatively low mechanical properties, such that it is perferably used in a structural- or fiber/particle reinforced composite.

1Hz DMTA trace of ICI's "perfect elastomer".

1Hz DMTA trace of ICI’s “perfect elastomer”.

TPU from HDI and H12MDI


 Number/Link: WO2016/054320

Applicant/Assignee: Lubrizol

Publication date: 7-04-1016

Gist”: TPU from a blend of HDI and H12MDI has improved creep and wet modulus

Why it is interesting: Polymeric materials used for in vivo medical applications like catheters, need to be hydrolytically stable and retain physical properties like stiffness, resilience, flexibility etc. in wet conditions.  It is known that conventional TPUs based on aromatic or cyclo-aliphatic isocyanates tend to show some softening in aqueous environments. For this reason copolyamides (COPAs) and polyether-block-polyamides (PEBAs) are often preferred over TPU for use in medical devices.  According to this invention, TPUs that can replace COPA and PEBA in medical applications can be produced using a blend of 1,6-hexanediisocyanate (HDA) and H12MDI. In the examples polyether TPUs, prepared from 2000MW polytetramethyleneether diol, butanediol and a 19:1 HDI:H12MDI isocyanate blend at harblock contents ranging from 15 to 50%, convincingly show improved creep properties and wet modulus when compared to conventional TPU and a commercial PEBA material.



TPU from POM-Polyether Polyols


 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.