Temperature Stable Memory Foams


 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 trace of foam according to the invention

Catalyst System for Frothed Foams


 Number/Link: WO2018/075302

Applicant/Assignee:  Rogers

Publication date: 26-April-2018

Gist”: A mixture of  a metal acetylacetonate and a catalytic inhibitor prevents premature curing

Why it is interesting:  A catalyst system that prevents premature curing of frothed (PORON® – type) foams consists of  ferric acetylacetonate catalyst and a β-diketone inhibitor e.g. acetylacetone or dibenzoyl methane. The catalyst combination allows for handling of the raw materials at 55°C for 5 minutes without reacting.  Frothed foams tend to have improved properties, like compression set as compared to conventional foams.


Tris(acetylacetonato)iron(III)  (Wikipedia)

Flexible PU Foams Containing Latent Aldehydes


 Number/Link: WO2017/001543

Applicant/Assignee: Shell

Publication date: 5 january 2017

Gist”: Flex foams from polyether polyols containing latent aldehydes show improved compression set

Why it is interesting: Aldehydes are a by-product of the alkylene oxide production. These aldehydes need to be removed before the alkylene oxide can be used in the manufacture of polyether polyols because even minor amounts of these impurities are considered undesirable and detrimental for polyol and foam properties. According to this invention, omitting the extra purification step of the alkylene oxide results in polyols with a certain amount of free- and latent aldehydes.  (‘latent aldehyde’ being an aldehyde incorporated in the polyether polyol with a labile bond). After removal of the free aldehyde, the polyols with (pref) >150ppm latent aldehydes (mostly propionaldehyde and acetaldehyde) can be used in the preparation of flexible foam with improved wet and dry compression set properties. While the examples indeed show some (but not a dramatic) improvement of compression set, no mention is made of eventual release of the aldehydes in the atmosphere, which (in my opinion) is a much bigger problem than compression set.



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.



Classic PU patent of the Month: PORON ® Foams (1979)

Title: Polyurethane foam product and process of manufacture thereof from thermosetting frothed mixture

 Number/Link: US4216177

Applicant/Assignee: Rogers

Publication date: 5-08-1980

Gist”: Frothed flexible foam

Why it is interesting: PORON is a popular brand of microcellular elastomeric/flexible polyurethane foams produced by Rogers Corporation. The original process, as documented in this patent, is quite simple:  a flexible foam formulation (in the examples) based on TDI, caprolacton diol, polymer polyol, some chain extender, amine catalyst and surfactant is frothed instead of blown with water or a physical blowing agent. The reacting froth is poured on release paper and heated to cure. Release paper can also be applied on top resulting in an integral skin on both sides of the layer. Frothing instead of blowing results in an improved compression set, different hardness-density relationship and a better control over cell structure. A unique material.

PORON foams

PORON foams