Cross-Linked Melt-Spun Polyurethane Fibers

Title: ISOCYANATE PREPOLYMER COMPOSITION AND CROSSLINKED POLYURETHANE PREPARED THEREFROM

 Number/Link: WO2015/007731

Applicant/Assignee: BASF

Publication date: 22-01-2015

Gist”: Melt spinning a TPU – prepolymer blend.

Why it is interesting: Crosslinked polyurethane fibers are produced by melt-spinning a thermoplastic polyurethane which is melt-blended with a specific isocyanate prepolymer composition.  The prepolymer composition is a mixture of a polymeric MDI and the reaction product of a polyester polyol and an excess of 4.4′-MDI. The polyester polyol is prepared from adipic acid together with 2-methyl-1,3-propanediol (MPdiol) and/or trimethylolpropane. The prepolymer composition is characterized by its low viscosity (probably due to the use of the branched polyester).  The crosslinked fibers show an improved tensile set and temperature resistance.

Polymeric MDI

Polymeric MDI

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 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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