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 ripnening 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

 

Novel Cellopener for Flexible- and Viscoelastic PU Foams

Patent Title: POLYURETHANE FOAM WITH AQUEOUS POLYMER DISPERSION  & VISCOELASTIC POLYURETHANE FOAM WITH AQUEOUS POLYMER DISPERSION

 Number/Link: WO2016/100306 & WO2016/100263

Applicant/Assignee: Dow

Publication date: 23-06-2016

Gist”: Dispersions of acid modified olefins in water act as cellopeners

Why it is interesting: According to this invention aqueous dispersions of acid-modified olefins can be used as cellopeners for conventional, high resilience and viscoelastic foams. The examples show that a 40% ‘solids’ dispersion of an acrylic acid – ethylene copolymer in water, used in about 1 to 2% on the total isocyanate-reactive composition has a clearly positive effect on foam air-flow properties. The polymer dispersions can be made according to Dow’s proprietary BLUEWAVE™ extrusion technology.

The BLUEWAVE dispersion process

The BLUEWAVE dispersion process

 

Reactive Cellopener for Polyurethane Rigid Foams

Title: REACTIVE CELL OPENER COMPOSITION, POLYOL COMPOSITION, AND OPEN-CELLED POLYURETHANE FOAM

 Number/Link: US2014/0231708

Applicant/Assignee: LG Electronics

Publication date: 21-08-2014

Gist”:  A silicon oil together with the lithium-salt of 12-hydroxystearic acid is used as cellopener for rigid VIP foams.

Why it is interesting: While coventional rigid insulation foams are closed-celled, rigid foams for use in vacuum insulation panels (VIPs) need to have a very high open cell content together with a cell size which is as small as possible. The current invention relates to reactive cellopeners comprising a silicone ‘base’ oil and the metal salt of a fatty acid having a (isocyanate-reactive) hydroxy group.  In an example the Li-salt of of 12-hydroxystearic acid is produced from LiOH and the fatty acid using a silicone oil as reaction medium. The composition, having a 30% solids content, is then used as a cellopener in a rigid foam formulation resulting in a cell size of about 90μm and 98% open cell content at a density of about 50 kg/m³. A perfluoroalkane nucleating agent was used as well.

12-hydroxystearic acid

12-hydroxystearic acid