Aromatic polyester polyol compositions
The present disclosure relates to novel aromatic polyester polyol compositions comprising lignin as a major reactant that is suitable for producing polyurethane rigid foams and coatings.
1. A process for making aromatic polyester polyol containing from 0.5 to 30 weight percent lignin comprising:
a. contacting a reaction mixture comprising
i. an aromatic acid source selected from the group consisting of terephthalic acid, isophthalic acid, phthalic anhydride, polyethylene terephthalate (PET) and mixtures thereof,
ii. a glycol component selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol and their mixtures,
iii. at least one selected from the group consisting of aliphatic diacids and hydroxyl-terminated aliphatic acids,
iv. at least one functional reactant selected from glycerin, pentaerythritol, sorbitol, polyglycerin, tall oil fatty acids, vegetable oil triglycerides, monoester fatty acids, aliphatic diacids, hydroxyl aliphatic acids, and their mixtures at temperature from 230° C. to 240° C. in the absence of lignin to form an intermediate reaction product mixture;
b. adding lignin, lignin incorporation catalyst and propylene carbonate to the intermediate reaction product mixture of (a) and controlling the reaction temperature at 160° C. to 205° C.; and
c. recovering lignin-containing aromatic polyester polyol from the reaction mixture.
2. The process of claim 1 wherein the lignin-containing polyester polyol recovered in step (c) has an as-produced acid number of less than 2 mg KOH/g.
3. The process of claim 1 wherein the aromatic acid source is a recycled or off-spec material.
4. The process of claim 1 further comprising adding organic carbonate to step (a).
5. The process of claim 1 wherein step (b) further comprises adjusting temperature of the intermediate reaction product mixture to 160° C. to 205° C. before adding lignin, lignin incorporation catalyst and propylene carbonate.
6. The process of claim 5 wherein the temperature range of step (b) is 170° C. to 180° C.
7. The process of claim 5 wherein step (c) further comprises adding a glycol component selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol and their mixtures to reduce viscosity of the recovered material.
8. The process of claim 4 wherein the organic carbonate is selected from the group consisting of propylene carbonate, ethylene carbonate and glycerol carbonate.
9. The process of claim 8 wherein the organic carbonate is propylene carbonate.
10. The process of claim 1 wherein the lignin incorporation catalyst is selected from inorganic carbonates and metal oxides.
11. The process of claim 10 wherein the inorganic carbonate is an alkyl metal carbonate.
12. The process of claim 11 wherein the alkyl metal carbonate is potassium carbonate or sodium carbonate.
13. The process of claim 10 wherein the metal oxide is zinc oxide.
14. The process of claim 1 wherein the lignin addition step (b) comprises mixing 5 to 30 weight percent lignin (based on the weight of the finished lignin-containing polyester polyol) with the intermediate reaction product mixture of step (a).
15. An aromatic polyester polyol containing from 0.5 to 30 weight percent lignin having an as-produced acid number of less than 2 mg KOH/g.
16. The aromatic polyester polyol of claim 15 that has not been subjected to post-synthesis treatment to reduce its acid number.
17. The aromatic polyester polyol of claim 16 that is produced without mechanically dispersing a discontinuous phase of solid lignin particles into a continuous phase of polyester polyol.
18. Foam comprising the aromatic polyester polyol of claim 1 .
19. A method for improving the flame resistance of a foam comprising incorporating into the foam an aromatic polyester polyol of claim 1 .