Open Microcellular Rigid Foams

Patent Title: POLYURETHANE FOAM AND PROCESS FOR PRODUCING SAME

 Number/Link: WO 2018/162372 (German)

Applicant/Assignee:  Covestro

Publication date: 13 September 2018

Gist”: Rigid foam formulation is blown with supercritical carbondioxide

Why it is interesting: Open-celled rigid polyurethane foams are well known and used in vacuum insulation panels. Theoretically the best thermal insulation is obtained with the smallest cell size. According to this invention microcellular rigid foams with a homogeneous cell structure, more than 90% open cells and an average cell diameter of less than 50μm can be prepared by using a rigid foam formulation containing a cellopener and supercritical carbondioxide and allowing it to react and expand in a closed mould. In an example a rigid foam is produced with a density of 67kg/m³, open cell content of 95% and average cell diameter of 17μm.

CO2_phase_diagram

Carbon dioxide (P,T) phase diagram (Wikipedia)

 

TPU Foams

Title: POLYURETHANE FOAMS AND METHOD FOR PRODUCING SAME

Number/Link: US2017/0174818

Applicant/Assignee: Lubrizol

Publication Date: 22-june-2016 (PCT oct. 2015)

“Gist”: TPUs with specific MW and polydispersity are injection moulded together with cellopener and gas in supercritical state

Why it is interesting: The invention relates to injection moulded “flexible foams”, especially useful for footwear applications. Thermoplastic polyurethanes with a Mw of 120,000 to 500,000 and a dispersity index of 1.85 to 2.51 are foamed using a gaseous blowing agent (CO2 or C1 to C6 hydrocarbons etc. ) together with a cellopener (silicone or EO/PO surfactant), such that at least 50% of cells are open.  In the examples the blowing agent is added in supercritical state to the melt before injection moulding. The type of gas used, nor the densities of the foams are mentioned.  Foaming TPU with gas in supercitical has also been file by Nike as discussed before in this blog.

Nike shoe with foamed thermoplastic midsole

 

Supercritically Foamed Thermoplastic Polyurethane

Title: LOW DENSITY FOAM, MIDSOLE, FOOTWEAR, AND METHODS FOR MAKING LOW DENSITY FOAM

 Number/Link: WO2015/017088

Applicant/Assignee: Nike

Publication date: 5-02-2015

Gist”: TPU blown with supercritical CO2 and/or N2

Why it is interesting: This case relates to foamed TPU (or EVA) with densities down to 150 kg/m³. The low density is accomplished by the combination of a conventional physical blowing agent and a supercritical fluid, specifically supercritical CO2 or N2 or a combination of these. The conventional blowing agent is incorporated into the polymer pellets before these are added to the extruder while the supercritical fluid is added to the molten polymer through a port in the extruder barrel.  The material is then extruded or injection moulded. Nike have filed two more patents on this technology: WO2015/017089 and WO2015/017090.

Nike shoe with EVA midsole

Nike shoe with foamed thermoplastic midsole