Extruded resorcinol-formaldehyde, phenol-formaldehyde and phenol-resorcinol-formaldehyde gel resins
A continuous process is provided for preparing a solid gel resin selected from resorcinol-formaldehyde gel resins, phenol-formaldehyde gel resins, and phenol-resorcinol-formaldehyde gel resins, using an extruder having at least one feed zone with a first temperature and at least one reaction zone with a second temperature that is higher than the first temperature. The process comprises steps of adding ingredients to the extruder at the feed zone, mixing the ingredients under heat to effectuate reaction between the ingredients to produce a liquid product exiting the extruder, and converting the liquid product exiting the extruder to the solid gel resin. A solid gel resin produced by the continuous process is also provided.
1. A continuous process for preparing a solid gel resin selected from resorcinol-formaldehyde gel resins, phenol-formaldehyde gel resins, and phenol-resorcinol-formaldehyde gel resins, using an extruder having at least one feed zone with a first temperature and at least one reaction zone with a second temperature that is higher than the first temperature, the process comprising steps of:
adding ingredients to the extruder at the at least one feed zone;
mixing the ingredients under heat to effectuate reaction between the ingredients to produce a liquid product exiting the extruder, wherein the liquid product has a polydispersity (Mw/Mn) in a range of from 1.08 to 1.30; and
converting the liquid product exiting the extruder to the solid gel resin with heat remaining in the liquid from the extruder wherein the solid gel resin product is completely cross-linked in all three dimensions and is essentially not soluble at room temperature in a non-degrading solvent selected from N N-dimethylformamide and dimethylsulfoxide.
2. The continuous process of claim 1 , wherein the second temperature is in a range of from about 60° C. to about 190° C.
3. The continuous process of claim 1 , wherein the first temperature is in a range of from about 30° C. to about 115° C.
4. The continuous process of claim 1 , wherein the converting step comprises cooling down the liquid product to yield the solid gel resin.
5. The continuous process of claim 1 , wherein the converting step comprises heating the liquid product to yield the solid gel resin and the heating is achieved by infrared heating or thermal heating.
6. The continuous process of claim 1 , wherein the ingredients include a precondensate selected from a precondensate of phenol and formaldehyde, a precondensate of resorcinol and formaldehyde, and a precondensate of phenol, resorcinol and formaldehyde.
7. The continuous process of claim 6 , wherein the ingredients further comprise formaldehyde.
8. The continuous process of claim 7 , wherein the formaldehyde is in an aqueous solution having a concentration of from about 25 wt. % to about 50 wt. %, based on the weight of the aqueous solution.
9. The continuous process of claim 6 , wherein the precondensate is produced by heating the ingredients.
10. The continuous process of claim 9 , wherein the heating comprises heating the ingredients to a temperature in a range of from about 20° C. to about 120° C.
11. The continuous process of claim 6 , wherein the precondensate has a number average molecular weight in a range of from about 150 to about 1,500 Dalton.
12. The continuous process of claim 6 , wherein the precondensate has a viscosity in a range of from about 5 to about 100 cps.
13. The continuous process of claim 1 , wherein the ingredients include a catalyst selected from an acid and a base.
14. The continuous process of claim 13 , wherein the catalyst is an acid selected from acetic acid, formic acid, lactic acid, citric acid, and oxalic acid.
15. The continuous process of claim 1 , wherein the ingredients have a molar ratio selected from formaldehyde:resorcinol, formaldehyde:phenol and formaldehyde:(phenol+resorcinol) and the molar ratio is in a range of from about 0.75 to about 3.5.
16. The continuous process of claim 1 , wherein the extruder has a cooling zone between the reaction zone and the exit of the extruder, and the cooling zone has a third temperature.
17. The continuous process of claim 16 , wherein the third temperature in the cooling zone is in a range of from about 40° C. to about 120° C.
18. The continuous process of claim 1 , wherein the extruder has at least one vent to let water escape out of the extruder.
19. The continuous process of claim 1 , wherein the ingredients are substantially reacted with each other such that the solid gel resin has free formaldehyde of less than 1.5%.