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


Monodisperse Polymer Polyol


 Number/Link: WO2017/172417

Applicant/Assignee:  Dow

Publication date: 5 october 2017

Gist”: Polymer polyol with a “monodisperse” particle size distribution is prepared by using a specific seeding dispersion

Why it is interesting: It is well known that the use of polymer polyols in flexible polyurethane foam formulations can result in improved airflow and load bearing properties. For optimal results the average particle size of the dispersed polymer needs to be similar to the cell wall thickness. According to this invention a SAN polymer polyol with a controlled and narrow particle size distribution can be prepared by using a seed dispersion which consists of an unsaturated macromer which, together with SAN particles of a particle size between 50 and 500 nm, is dispersed in a base polyol. The macromer is a PO/EO polyether with a (pref.) mole weight of 11000 to 14000 Da and having 4-5 OH groups and 1-2 reactive double bonds. The polymer polyol is prepared by dispersing the seed dispersion in the base polyol together with styrene, acrylonitrile and a solvent (e.g. isopropanol). After polymerization of the monomers the solvent is removed, resulting in a polymer polyol with at least 30% solids, average particle size of 1-3 μm and a size span of 1.25. In the examples the macromer is prepared by capping 1-2 OH groups of a 6-functional 90/10 PO/EO polyol with 3,3-isoprenyl-α,α-dimethylbenzylisocyanate.




Classic PU Patent of the Month: Scott Paper Co. on Reticulated Polyurethane Foams (1964)

Title: Reticulated polyurethane foams and process for their production

 Number/Link: US3171820

Applicant/Assignee: Scott Paper Co.

Publication date: 2-03-1965

Gist”: PU foams are reticulated by hydrolysis or explosion.

Why it is interesting:   Reticulated foams are foams from which the membranes have been removed so that only a three dimensional network of strands or ‘struts’ remains. These materials are commercially available in different grades of stiffness and porosity and are useful in applications such as filtering, sound absorbing, padding and the like. The current invention – filed in 1964 but a ‘continuation’ of an application filed in 1956- teaches the two processes to reticulate PU foam still in use today. The first process uses an aqueous NaOH solution to hydrolyse the cell membranes, in the second process a foam block is brought in an autoclave together with an explosive gas mixture (e.g. a mixture of oxigen and acetylene) which is then made to explode using a spark plug. When executed correctly the explosion removes all cell membranes leaving the struts intact. ‘Explosive recticulation’ is one of my all-time favorite PU inventions: simple, yet very effective and very courageous. In the current culture of hyper-safety where employees have to report paper-cuts, inventions like this are no longer possible.

Recticulate polyurethane foam

A recticulated polyurethane foam

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