Crosslinking TPU with Isocyanates.

Title: POLYURETHANE ON THE BASIS OF SOFT THERMOPLASTIC POLYURETHANE

 Number/Link: US2014/0094571

Applicant/Assignee: BASF

Publication date: 3-04-2014 (priority PCT/DE)

Gist”: A soft TPU is crosslinked using isocyanate dissolved in another TPU.

Why it is interesting: Crosslinking thermoplastic polyurethane parts to improve certain mechanical- and creep properties is known. In this case the crosslinking agent is an isocyanate with a functionality larger than 2, preferably an MDI prepolymer.  The isocyanate is dissolved in another TPU by melt blending in a twin-screw extruder at a temperature below 160°C and pelletizing. Pellets of a soft, polyester-based, TPU with a hardblock content less than 5% are mixed with the isocyanate-containing pellets, injection moulded and post-cured to crosslink the moulded part.

A TPU phone case.

TPU phone case.

Classic PU Patent of the Month: The First Polyether Foams (1951)

Title: Verfahren zur Herstellung von Kunststoffen

 Number/Link: DE974371 (German)

Applicant/Assignee: Bayer AG

Publication date: 12-08-1960

Gist”: A prepolymer from a polyether polyol and an excess of isocyanate is reacted with water to produce an elastomeric  foam.

Why it is interesting: This patent specifies the first polyether prepolymers and polyether  foams as invented by Otto Bayer and co-workers.  In the examples an all-EO, 4000 MW triol, prepared from trimethylolpropane and  ethylene oxide is reacted with a surplus of TDI resulting in a 3.2% NCO prepolymer.  This prepolymer is reacted with water to form either elastomeric films or elastomeric (flexible) foams. There are only two claims, the first covering  polyether prepolymers, the second covering both “one-shot” and “full prepolymer” water-blown polyether foams:

PATENTANSPRÜCHE:

1. Verfahren zur Herstellung von Kunststoffen,
dadurch gekennzeichnet, daβ Polyglykolather mit
einem Molekulargewicht von mindestens 500 und
mindestens zwei endstandigen Hydroxylgruppen
mit einem Übersehuβ über die berechnete Menge
an polyfunktionellen aliphatischen oder aromatischen
Isocyanaten und die erhaltenen Polyglykolätherisocyanate
mit Verbindungen mit reaktionsfahigem Wasserstoff
umgesetzt werden.

2. Ausführungsform des Verfahrens nach Anspruch
1, insbesondere zur Herstellung von Schaumstoffen,
dadurch gekennzeichnet, daβ als Verbindung
mit reaktionsfahigem Wasserstoff Wasser verwendet
wird und die Umsetzung mit Wasser gleichzeitig
mit der oder anschlieβend an die Umsetzung
der Polyglykolather und polyfunktionellen
Isocyanate erfolgt.

Dr. Otto Bayer

Dr. Otto Bayer

Polyurethane “Combination Foam”: a TPU/PU Composite

Title: KOMBINATIONSSCHAUM

 Number/Link:  WO2014/023794   (German)

Applicant/Assignee: BASF

Publication date: 13-02-2014

Gist”: Foamed TPU particles are embedded in a foamed elastomer of the same chemical composition to improve mechanical properties.

Why it is interesting: Foamed, closed-cell TPU particles are incorporated in a foamed, open-cell PU matrix which has a higher density and is produced from essentially the same chemicals, resulting in perfect compatibility and adhesion between the two components.  In the examples 30-40 % (w/w) of expanded TPU particles with a bulk density (“Shüttdichte”) of 89 kg/m³ are incorporated in an elastomer with a density of 200-300 kg/m³. Size of the TPU particles is not given but the preferred size range is 1mm to 2 cm.

Expanded TPU particles by BASF

Expanded TPU particles by BASF

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