Foam material on the basis of phenolic resin
View Patent ↗Disclosed is a method of preparing a bio-based thermosetting foam material with improved properties, in particular improved flame retardant properties, which method includes the steps of a) producing a prepolymer by condensation of at least one phenolic compound and formaldehyde in a ratio of 1:1.0 to 3.0 using 0.15 to 5 wt % of an alkaline catalyst in the temperature range of 50 to 100° C. until the refractive index of the reaction mixture is 1.4990 to 1.5020, b) adding 2 to 40 wt % of at least one natural polyphenol at a temperature of 50 to 100° C., c) adding 2 to 10 wt % of one or more emulsifiers and mixtures thereof, d) adding 2 to 10 wt % of one or more foaming agents and mixtures thereof and e) adding 10 to 20 wt % of a curing agent and f) curing. All wt % being related to the amount of the raw materials used.
1. A method for preparing a foam comprising:
a) preparing a prepolymer by condensing at least one phenolic compound and formaldehyde in a ratio ranging from 1:1.0 to 1:3.0 in the presence of 0.15 to 5 wt % based on an amount of employed raw materials of a basic catalyst in a temperature range from 50 to 100° C. to form a reaction mixture until a refractive index of the reaction mixture is in the range from 1.4990 to 1.5020,
b) adding from 5 to 40 wt % based on the amount of employed raw materials of at least one natural polyphenol at a temperature of 50 to 100° C.,
c) adding from 2 to 10 wt % based on the amount of employed raw materials of one or more emulsifiers and mixtures thereof,
d) adding from 2 to 10 wt % based on the amount of employed raw materials of one or more blowing agents and mixtures thereof, and
e) adding from 10 to 20 wt % based on the amount of employed raw materials of a curative, and
f) curing.
2. The method of claim 1 wherein the ratio of the at least one phenolic compound to formaldehyde is in the range from 1:1.5 to 1:2.5.
3. The method of claim 1 wherein a free phenol content of the prepolymer obtained in step a) is <10%.
4. The method of claim 1 wherein the refractive index is 1.4995-1.5015.
5. The method of claim 1 wherein the natural polyphenol is selected from a tannin or a lignin compound or a cashew nut shell liquid.
6. The method of claim 1 wherein the natural polymer is added in a concentration of 5 to 20 wt % based on the amount of employed raw materials.
7. The method of claim 1 wherein the natural polyphenol is added at a temperature of 75 to 85° C.
8. The method of claim 1 wherein the emulsifier is selected from adducts of ethylene oxide or of propylene oxide on saturated and unsaturated fatty acids, hydroxyl fatty acids, fatty alcohols, glycerides or vegetable oils or dimethyl phthalate, diethylene glycol, phthalic anhydride or mixtures thereof.
9. The method of claim 1 wherein the blowing agent is selected from isopropyl chloride, isopentane, cyclopentane, butane, pentane, hexane, heptane or mixtures thereof.
10. Insulation comprising a foam prepared by the method of claim 1 .