Classic PU Patent of the Month: Otto Bayer’s Invention of Polyurethane and Polyurea (1937)

Title: Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen

Number/Link: DE728981  (German)

Applicant/Assignee: I.G.Farbenindustrie

Publication date: 12-11-1942

Gist”: Production of polyurethanes by reacting diisocyanates and compounds containing at least two hydroxyl and/or amine groups.

Why it is interesting: This is the patent that marked the start of the polyurethane industry.   It covers both aromatic and aliphatic diisocyanates, notably NDI, MDI, TDI, HDI etc. The examples cover polyurethane and polyurea fibers and films. It is said that Bayer was trying to copy Nylon 6,6, the structure of which is very similar to a PU based on 1,6 hexanediol and 1,6 hexanediisocyanate.  The patent has only one claim:

“PATENTANSPRUCH:
Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen, dadurch gekennzeichnet, daβ man organische Diisocyanate mit solchen organischen Verbindungen
zur Reaktion bringt, die mindestens 2 Hydroxyl- oder Aminogruppen mit austauschbaren Wasserstoffatomen oder mindestens eine Hydroxylgruppe und mindestens eine Aminogruppe ,der genannten Art enthalten.”

Dr. Otto Bayer (1902-1982)

Dr. Otto Bayer (1902-1982)

Thermoplastic Polyurethane with a Percisely Controlled Biodegradation Rate

Title: PROCESS FOR MAKING BIODEGRADABLE AND/OR BIOABSORBABLE POLYMERS

 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)

Thermoplastic Polyurea Elastomers

Title: MELT PROCESSIBLE POLYUREAS AND POLYUREA-URETHANES, METHOD FOR THE PRODUCTION THEREOF AND PRODUCTS MADE THEREFROM

 Number/Link: US2013/0331538

Applicant/Assignee: University of Akron

Publication date: 12-12-2013 (priority PCT)

Gist”: Polyurea is made melt-processable by incorporating hydrogen-bond accepting chain extenders (HACE)

Why it is interesting: It is well known that polyurea elastomers with a decent hardblock content (of e.g. 30-35%) are not melt-processable. Because of very strong (bi-dentate) H-bond formation in the hard domains the material will degrade sooner than flow when heated. In this invention it is proposed to incorporate a relatively small amount of HACE to disrupt the hard domain structure and reduce flow temperature.  In an example a few parts of OH-ended pentamethylenepolycarbonate with a MW of 500 to 800 was used next to the conventional 1,6-hexamethylene chain extender to drop the flow temperature by 50°C while not affecting the tensile strength. (I suppose a NH2-ended polycarbonate could have been used as well to make an all-polyurea material).

Bi-dentate H-bonds between polurea molecules (left) disrupted by a polycarbonate group (right)

Bi-dentate H-bonds between polurea molecules (left) dusrupted by a carbonate group (right)

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