Translucent Rigid Foams

Patent Title: TRANSLUCENT POLYURETHANE FOAMS

 Number/Link: WO2018/178139  WO2018/177987  (German)

Applicant/Assignee:  Covestro

Publication date: 4 October 2018

Gist”: Rigid foam formulation is mixed without air to delay nucleation

Why it is interesting: The invention is about translucent rigid foams which are said to be useful as wall and roof elements such as light strips, light domes and the like.  The foams are based on (pref.) trimerized aliphatic diisocyanates and are blown with water.  The composition is degassed and then mixed without inclusion of air to delay nucleation. The resulting foams have a course cell structure and thick cell struts which apparently allows light to pass through.

 

Desmodur N3900

Asymmetric trimer of HDI (iminooxadiazinedione)

Carbamate Blown Rigid Foams

Patent Title: A METHOD FOR PRODUCING AN OPEN CELL RIGID POLYURETHANE FOAM

 Number/Link: WO2018096101  WO2018096102

Applicant/Assignee:  Covestro

Publication date: 31 may 2018

Gist”: An open cell rigid foam is prepared using an amine-CO2 adduct and water as blowing agents

Why it is interesting: According to this invention an open cell rigid spray foam can be prepared from a conventional rigid foam formulation and a blowing agent consisting of 4-12 parts (pref.) on 100 parts of polyol of an adduct of a primary or secondary amine and carbon dioxide, together with 15 to 50 parts of water.  The properties of the resulting open cell, low density foam are said to be largely independent of ambient conditions and spray thickness. The foams are useful for thermal insulation applications in construction.

carbamate

Carbamate of N,N-dimethylaminopropylamine

 

Solid-Solid PU PCM

Patent Title: PHASE-CHANGE MATERIAL FOR STORING THERMAL ENERGY, MANUFACTURING METHOD AND USES OF SUCH A MATERIAL

 Number/Link:  WO2017/198933 (French)

Applicant/Assignee:  UNIV CERGY-PONTOIS

Publication date: 23 november 2017

Gist”: A crosslinked PEG-HMDI elastomer can be used as phase change material.

Why it is interesting: Phase change materials, used to dampen temperature cycles in buildings, are well known. Most organic phase change materials (e.g. paraffines) show solid-liquid phase transitions and therefore need to be macro- or micro-encapsulated. This invention is about polyurethane PCMs with a solid to solid phase transition, and therefore need not be encapsulated. The PU PCM is prepared by reacting a polyethylene glycol with a diisocyanate like HMDI together with a crosslinker like glycerol. The solid elastomer is then ground into powder which can be used in construction materials like plaster or cement. The transition temperature and the latent heat of the PCM is controlled through the mole weight of the PEG (e.g. 1000 to 2000 Da) and the degree of crosslinking.
Solid-solid PU PCMs are not new, see WO2011/089061 (Huntsman), which (in my opinion) presents a more elegant and flexible solution to the problem.

Phase_Change_Materials

Temperature damping by PCM (Wikimedia Commons)

 

Preventing Ostwald Ripening in Rigid PU Foams

Title: PRODUCTION OF FINE CELL FOAMS USING A CELL AGING INHIBITOR

Number/Link: WO2017093058  (German)

Applicant/Assignee: Evonik

Publication Date: 8 June 2017

“Gist”: Perfluorinated hydrocabons reduce Ostwald ripening in PU foam formulations

Why it is interesting: Polymeric foams form by nucleation and growth of gass bubbles in the reacting mixture followed by (or simultaneous with) ageing of the bubbles through coalesence and Ostwald ripening, i.e. the growth of larger bubbles at the expense of smaller bubbles. Ostwald ripening ultimately results in fewer and larger cells, which has a negative effect on the thermal insulation properties of rigid foams. According to this invention the ripening effect can be prevented or reduced by incorporating in the foam formulation an “Ostwald hydrophobe”, i.e. a highly hydrophobic liquid which is largely immiscible with the reacting mixture. Examples of such liquids are perfluorinated hydrocabons with a boiling point of less than 150°C, e.g. perfluoropentane, perfluorocyclohexane and perfluoroisohexene (used in the examples).

Perfluorocyclohexane