m-Xylylene Diisocyanate for Polythiourethanes

 

Patent Title: ISOCYANATE COMPOSITION FOR OPTICAL LENSES AND PROCESS FOR PREPARING THE SAME

 Number/Link: US2018/0334531

Applicant/Assignee:  SKC

Publication date: 22 November 2018

Gist”:  m-XDI is prepared from purified m-xylylene diamine and used for improved optical materials

Why it is interesting: Polythiourethanes have a high refractive index, a high transparency and a relatively high impact resistance and their use in optical lenses is well known. In this invention, polythiourethanes are prepared by using ‘pure’ (i.e. 99 to 100%) m-XDI as the isocyanate. The m-XDI is prepared from m-xylylene diamine from which impurities (esp. o-XDA, p-XDA and monoamines) are removed by distillation or crystallization.  Polythiourethanes prepared from 100% m-XDI are said to show improved optical properties such as refractive index, transparency, dispersion (Abbe number), yellowness, cloudiness etc.

XDI

TPU from HDI and H12MDI

Patent Title: NON-SOFTENING RESILIENT THERMOPLASTIC POLYURETHANES

 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.

H12MDI

H12MDI

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