All posts by Gerhard Bleys

Prepregs from Glass Fiber and Reactive Polyurethane Powder

Title: PREPREGS AND MOLDINGS PRODUCED THEREFROM

Number/Link: US2014065911

Applicant/Assignee: Evonik

Publication date: 6-03-2014

“Gist”: A reactive polyurethane powder is prepared from a mixture of a solid polyester polyol and a solid dimerised IPDI and subsequently used to make glass fiber prepregs.

Why it is interesting: A polyurethane powder is made from (pref.) a mixture of a solid (at room temperature) polyster polyol and a solid, blocked isocyanate. The isocyanate is preferably an “internally” blocked IPDI. Internally blocked meaning that the isocyanate contains uretidinedione groups. The powder is scattered over a fibrous support and heated to over melting temperature but below curing temperature to make the prepreg. Prepregs made with PU powder instead of the conventional resins have the advantage of being non-sticky, non-toxic and of having a very high storage stability (45 days in the examples).

Prepreg production with reactive PU powder

Sound Absorbing PU-PA Foams

Title: THERMOFORMABLE RIGID POLYURETHANE-POLYAMIDE FOAM

Number/Link: US2014/058005

Applicant/Assignee: BASF

Publication date: 27-2-2014

“Gist”: Rigid, open-celled and thermoformable polyurethane-polyamide foams are produced using short chain di-acids as both chain extender and blowing agent.

Why it is interesting: The reaction of a carboxylic acid group with an isocyanate group results in a mixed anhydride, which after releasing carbon dioxide forms an amide. Because the reaction is relatively sluggish a Lewis base catalyst is used, e.g. N-methylimidazole. In this case a rigid foam-forming formulation based on MDI and (pref.) polyether polyols is further reacted with short chain diacids like azelaic- or glutaric acid. The examples show foam densities of less than 30 kg/m³ without the use of water. The foams are open celled with high air flow and with a Tg of around 90°C, making them thermoformable. This type of foams is used as acoustic bonnet- en roofliners in the automotive industry.

Azelaic Acid

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

Innovation in Polyurethanes

All posts by Gerhard Bleys

Prepregs from Glass Fiber and Reactive Polyurethane Powder

Sound Absorbing PU-PA Foams

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

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