Degradable Polyurethane Elastomers

Patent Title: DEGRADABLE EXTRUSION RESISTANT COMPOSITIONS AND ARTICLES OF MANUFACTURE

 Number/Link: WO2018/013288

Applicant/Assignee:  Baker Hughes Inc.

Publication date: 18 January 2018

Gist”: Polyester-PU elastomers are compression moulded together with fine particles of acid or base

Why it is interesting: The invention is about moulded polyurethane parts for use as temporary components in boreholes and which can be controllably degraded. The degradability is achieved by compression moulding polyester PU elastomers together with an acidic or basic fine powder.  In an example a polyester-TDI ‘full’ prepolymer is reacted with 1,3-propanediol-bis-(4-aminobezoate) and compression moulded with a sulfamic acid powder. The moulded parts could be degraded within 2 weeks in water of 50-90°C.

vibracure

1,3-propanediol bis-(4-aminobenzoate)

 

Polyurethane Tissue Adhesives

Patent Title: URETHANE DECOMPOSING METHOD AND URETHANE DECOMPOSING AGENT

 Number/Link:  US2016/0257800

Applicant/Assignee: Obihiro University

Publication date: 8-09-2016 (priority PCT/JP)

Gist”: Prepolymer from ether-ester polyol and aliphatic isocyanate

Why it is interesting: There is a growing trend in current surgerical practice to replace sutures and staples with adhesives. These tissue adhesives need to have a particular set of properties, like the correct viscosity, hardening speed, biodegradability and toxic and allergenic properties. Current surgical adhesives are often cyanoacrylates, which react very fast, are brittle and show poor biodegradability, or protein-based adhesives which are costly and form weak bonds. According to this invention an improved polyurethane tissue adhesive can be prepared from an isocyanate-ended prepolymer based on an aliphatic isocyanate and a polyol.  The polyol is prepared from a starter polyol or amine which is reacted with a mixture of an alkoxide and about 10-20% of a  lactide (or glycolide or cyclic acid anhydride).  The lactide is randomly copolymerized with the alkoxide using DMC catalysis. The polyol is then reacted with an aliphatic isocyanate, pref. HDI or IPDI in a NCO/OH ratio of about 8:1. After that monomeric isocyanate is removed by thin film distillation down to less than 1% free monomer.
The adhesives are said to be fast, non-toxic, non-allergenic and biodegradable.

L-Lactide

L-Lactide

Thermoreversible Polyurea

Patent Title: DYNAMIC UREA BONDS FOR POLYMERS

 Number/Link: W02016/069582

Applicant/Assignee: University of Illinois

Publication date: 6-05-2016

Gist”: Urea bonds prepared from sterically hindered amines and isocyanates

Why it is interesting: The N-C bond in urea is very stable due to conjugation of the lone electron pair of the nitrogen atom with the cabonyl group.  According to this invention, the nitrogen atom can be subsituted with a strongly hindering group such that the coplanarity, and therefore most of the conjugation, of the C-N and C=O bonds is lost. These hindered urea bonds are much less stable and can reversibly depolymerize at relatively low temperatures. Thermoreversible bonds can be useful in a number of smart materials such as self-healing-, “4D printing”- , and reprogrammable shape memory materials. In an example a shape memory material with a Tg of 53°C and a Young’s Modulus of about 2 GPa was prepared by reacting 2-(t-buylamino)ethanol (TBAE) and trimerized hexamethylene diisocyanate (THDI). The ‘permanent shape’ of the material could be re-programmed by forcing the material in a new shape for 72 hours at 60°C.

Polurethane-urea with thermoreverisble urea bonds

Poly(urethane-urea) with thermoreverisble urea bonds