Degradable Polyurethane Elastomers


 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.


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


Thermoreversible Polyurea


 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

Thermoplastic Polyurethane with a Percisely Controlled Biodegradation Rate


 Number/Link: WO2014/004334

Applicant/Assignee: Lubrizol

Publication date: 03-01-2014

Gist”: Two sets of parameters are given (and claimed) which, when iteratively adjusted, allow to independently modify the mechanical properties and biodegradation rate of a TPU.

Why it is interesting: Many biomedical materials for implants such as screws, bone plates, tissue scaffolds, pins etc need high mechanical properties but also a controlled biodegradation rate which can vary from weeks to years.  According to this case the precise control of the degradation rate is not possible with currently available bio-polymers.  The invention claims two sets of parameters one which controls the physical properties of a TPU like the molecular weight, harblock content, crystallinity etc, and another set which controls the biodegradation rate like the amount of ‘hydrolyzable units’ in the backbone, hydrophilicity ect. It is claimed that both mechanical properties and degradation rate can be independently controlled by adjusting one or more parameters of each set. In the examples TPUs are prepared from HMDI, 1,4-butane diol and poly(lactide-co-caprolactone) diols where the lactide is the hydrolyzable unit.

A poly(lactide-co-caprolactone)

A poly(lactide-co-caprolactone)

Enzymatic Recycling of Polyurethanes


 Number/Link: WO2013/134801 (German)

Applicant/Assignee: Eurofoam

Publication date: 19-09-2013

Gist”: Use of specific enzymes to break down polyurethane into polyamines and its original (polyether)polyols

Why it is interesting: Chemical recycling of polyurethane by hydrolysis, glycolysis etc. is known but requires high temperatures and sometimes (when supercritical water is used) high pressures.  This can lead to side reactions and the contamination of the recycled raw materials. Enzymatic recycling of polyurethanes is known as well but is mostly limited to polyester polyurethanes and esterase enzymes which break down the ester bonds.  The current invention claims that the use of certain hydrolases of the EC3 class, especially arylacylamidase  EC3.5.1.13 selectively breaks the urethane bond. (EC=enzyme comission number). The reaction can be carried out between 30 and 50°C and at a pH of 9.5 to 11. The resulting polyols and amines can be extracted using a polar solvent. While interesting the proposed process may not be very practical as the example shows that 5 days were needed to recycle a 5 gram sample of a model foam.

Schematic representation of the enzyme catalysed reaction.

Schematic representation of the enzyme catalysed reaction.