Process for extending the shelf life of gaseous olefinic propellants in polyurethane foams
View Patent ↗The invention described herein generally pertains to a composition and a method for improving the shelf life of a gaseous hydrofluoroolefin propellant, the improvement comprising at least the increased aromatic polyester polyol(s) in combination with a tertiary amine catalyst comprising at least two cyclohexyl rings and an aliphatic metal salt catalyst, the amine catalyst having less than 10% nitrogen on a weight basis.
1. A process to improve the shelf life of gaseous hydrofluoroolefin-blown two-component polyurethane foams using reactants contained in “A” and “B” cylinders, comprising the steps of:
adding no less than 50% aromatic polyester polyols of all of the polyols used in the “B” cylinder formulation of reactants, said “B”-side formulation having no more than about 1.5% water by weight; and wherein
at least one aromatic polyester polyol is selected from the group consisting of:
Hydroxyl Number, mg KOH/g
230-250
Water, % by wt., max
0.15
Acid Number, mg KOH/g,
0.6-1.0
Viscosity at 77° F. (25° C.), cP
2,000-4,500
Equivalent Weight (average)
234
Molecular Weight (average)
468
and
Hydroxyl Number, mg KOH/g
335-365
Water, % by wt., max
0.15
Acid Number, mg KOH/g,
0.5-2.0
Viscosity at 77° F. (25° C.), cP
2,500-3,500; and
adding a catalyst combination of a tertiary amine catalyst comprising at least two cyclohexyl rings, said tertiary amine catalyst having less than 11 weight percent nitrogen and an aliphatic metal salt catalyst; and
calculating a catalytic decay ratio as a predictive tool for the polyurethane foam, the catalytic decay ratio defined as the aged gel time in seconds of the polyurethane foam wherein the reactants were exposed to accelerated aging involving storing the reactant combination and propellant at an elevated temperature of 50° C. for approximately 48 days prior to reacting the reactants compared to the non-aged gel time in seconds of the same reactants; and
spraying the polyurethane foam before and after aging to obtain the aged and non-aged gel times;
taking the ratio of the aged gel time compared to the non-aged gel time and determining if the catalytic decay ratio increases approximately to no more than 2 for a polyurethane spray foam and approximately no more than 2.5 for a pour-in-place polyurethane foam.
2. The process of claim 1 wherein
the tertiary amine catalyst has less than or equal to about 10% nitrogen on a weight basis;
said “B”-side formulation having between 0.1-1.3% water by weight.
3. The process of claim 2 wherein
the tertiary amine catalyst has less than or equal to about 8% nitrogen on a weight basis;
said “B”-side formulation having between 0.5-1.0% water by weight.
4. The process of claim 1 wherein the polyurethane foam comprises:
no more than approximately 10% aliphatic polyether polyol.
5. The process of claim 4 wherein the polyurethane foam comprises:
no added aliphatic polyether polyol.
6. The process of claim 1 further comprises the step of adding
at least two aromatic polyester polyols.
7. The process of claim 1 wherein
the aliphatic metal salt is a metal alkanoate.
8. The process of claim 7 wherein
the metal alkanoate is a potassium alkanoate.
9. The process of claim 8 wherein
the potassium alkanoate is potassium octoate.