Temperature Stable Memory Foams

Patent Title: VISCOELASTIC POLYURETHANE FOAMS WITH REDUCED TEMPERATURE SENSITIVITY

 Number/Link: WO2018/169833

Applicant/Assignee:  Covestro

Publication date: 20 September 2018

Gist”: A polyol blend comprising a relatively low-EO monol,  diol and triol is foamed with TDI

Why it is interesting: Viscoelastic or “memory” foams are popular materials for pillows and mattresses. One drawback of these materials is the sensitivity of hardness to room temperature variations. According to this invention the hardness variations can be reduced by preparing the foams form TDI and a polyol blend comprising a monofuntional polyether with an EO content of less than 20%, a polyether diol and a polyether triol both with an EO content of less than 45% together with water, catalysts and other additives. The polyol blend can optionally be made in situ.  The foams show an E'(15°C)/E'(30°C) ratio between 1 and 4, a Tg of less than 20°C (defined as the temperature of max. tanδ),  together with high air flow and tear strength values.

DMTA

DMTA trace of foam according to the invention

Classic PU Patent of the Month: ICI on “High EO – Pure MDI” Flexible Foams (1991)

Patent Title: Polyurethane Foams

 Number/Link: EP0547765

Applicant/Assignee: ICI

Publication date: 23-06-1993

Gist”: Flexible foams can be based on 4,4’MDI if the polyol contains 50 to 85% EO

Why it is interesting: The first flexible PU foams were all based on toluene diisocyanate and so-called “conventional polyols” (i.e. almost all-propylene oxide polyols). Attempts to replace TDI by the only other commercially viable diisocyanate (4,4′ MDI) failed because of premature phase separation of the highly symmetrical polyurea ‘hard block’, resulting in unstable foaming. The problem was eventually solved by using prepolymers and polymeric MDI, as mentioned before.  More than 10 years later it was shown that it is possible to make flexible foams with 4,4′-MDI if the polyol is polar enough to prevent early phase separation.  This was established by using polyols with high ethylene oxide content. The resulting foams have superior comfort and durability properties compared to both TDI and MDI flexible foams.

4,4'-MDI

4,4′-MDI

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