Classic PU Patent of the Month: ICI on MDI Prepolymers and “Cold Cure” Flexible Foams (1978)

Title: Liquid polyisocyanate compositions

 Number/Link:  EP10850

Applicant/Assignee: Imperial Chemical Industries

Publication date: 14-05-1980

Gist”: Liquid compositions from 2,4’/4,4′-MDI  prepolymers and polymeric MDI.

Why it is interesting: The first polyurethane flexible foams were all based on toluene diisocyanate (TDI).  Other commericially available isocyanates like “pure MDI”  (4,4’/ 2,4′- diphenylmethane diisocyanates mixtures) and “crude MDI” (mixtures of MDI and its higher homologues) were not suited for flexible foam production: the former because of it’s high crystallinity and therefore too high melting point and the latter because of its too high functionality.  This classic invention solved the problem by prepolymerizing  a 2,4’/4,4′-MDI mixture with a “flexible” polyol to an NCO content of 8 to 26% and then adding 10-50% of crude MDI to obtain a liquid composition. These liquid MDI compositions allowed the production of cold cure moulded flexible foams and the first MDI-based car seat cushions.

Cold cure moulded car seat cushions

Cold cure moulded car seat cushions

Poly (Urethane-Urea) Elastomers from High 2,6-TDI

Title: Polyurethane Elastomers Based on TDI Prepolymers Enriched in the 2,6-TDI Isomer Cured with Trimethylene Glycol Di-(para Amino Benzoate)

 Number/Link: US2014/0309397

Applicant/Assignee: Anderson Development

Publication date: 16-10-2014

Gist”: Elastomers are prepared from TDI containing a high amount of the 2,6 isomer.

Why it is interesting: Commercially available toluene diisocyanate (TDI) usually comes in the 80/20 or the 65/35  2,4/2,6 isomer blend. It is known that higher 2,6 levels result in stiffer hardblocks and a different reaction profile because of the (initially) equal reactivity of the isocyanate groups. According to this invention elastomers prepared from TDI with a 2,6 content of (most preferred) at least 60% results in superior green strength and dimensional stability. High 2,6 TDI-PTMEG prepolymers cured with trimethylene glycol di(p-aminobenzoate) (TGDBA) should even have a superior tear strength and upper hardness limit compared to MDI based elastomers.

TGDBA

TGDBA

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

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