PURIFICATION PROCESS FOR POLYETHER-CARBONATE POLYOLS

Abstract

Alkylene carbonates are removed from polyether-carbonate polymers by contacting the polyether-carbonate with an absorbent at a temperature of 30 to 150° C. The process is effective and inexpensive. The purified polyether-carbonate is useful for making polyurethanes as well as in many other applications.

Claims

1. A process for removing an alkylene carbonate from a polyether-carbonate, comprising contacting a starting polyether-carbonate that contains at least 0.25 weight-%, based on the weight of the starting polyether carbonate, of one or more alkylene carbonates, with a solid absorbent that contains pores having an average pore size of at least 1 nm up to 100 nm at a temperature of 30 to 150° C. and at which temperature the starting polyether-carbonate is a liquid.

2. The process of claim 1 wherein the absorbent is selected from one or more of alumina, magnesium silicate, a molecular sieve, silica gel, clay and an organic polymer.

3. (canceled)

4. The process of claim 1 wherein the absorbent has a pore volume of 0.25 to 2 mL/g.

5. The process of claim 1 wherein the absorbent is a crosslinked porous polymer in the form of a particulate solid.

6. The process of claim 5 wherein the absorbent is a styrene-divinylbenzene copolymer, a crosslinked polyolefin, or crosslinked acrylic monomer.

7. The process of claim 5 wherein the crosslinked porous polymer is unfunctionalized and lacks ion exchange capacity.

8. The process of claim 5 wherein the crosslinked porous polymer is an anion exchange resin.

9. The process of claim 5 wherein the crosslinked porous polymer is a cation exchange resin.

10. The process of claim 1 wherein the absorbent is a zeolite.

11. The process of claim 1 wherein the starting polyether-carbonate contains 0.5 to 15% by weight of the alkylene carbonate, based on the combined weight of polyether carbonate and alkylene carbonate.

12. The process of claim 1 wherein the alkylene carbonate includes propylene carbonate, ethylene carbonate or both propylene carbonate and ethylene carbonate.

13. The process of claim 1 wherein 40 to 100 weight % of the alkylene carbonate is removed.

14. The process of claim 1 wherein the temperature is 60 to 85° C.

Description

EXAMPLES 1-2

[0031] The polyether-carbonate used in these and the following examples is a nominally 3500 number average molecular weight triol made by polymerizing a feed composition containing 2.63 wt % glycerin, 11.00 wt % ethylene oxide, 2.90 wt % carbon dioxide and 83.47 wt % propylene oxide. It contains mostly secondary hydroxyl groups, and contains residual propylene carbonate and ethylene carbonate.

[0032] For Example 1, a sample of the polyether-carbonate is introduced into a 20 mL scintillation vial at ambient temperature. 0.1 g of the mixture is removed, dissolved in 0.5 g of methanol and analyzed by gas chromatography to ascertain the starting alkylene carbonate concentration through comparison with a calibration curve generated using standards of known concentrations of propylene carbonate in a polyether polyol. The starting alkylene carbonate concentration is about 3.5% by weight.

[0033] 0.25 g of strong acid-type, macroporous styrene-divinylbenzene copolymer ion exchange resin beads having sulfonic acid groups in the acid form and an average pore size of 22 nm (Amberlyst 70, from DuPont) are added and the resulting slurry is stirred at 50° C. for 48 hours. Samples of the supernatant polyether-carbonate are taken at 4, 24 and 48 hours and analyzed as above for alkylene carbonate concentration.

[0034] Example 2 is performed using the same general method, except the temperature is 70° C. throughout. The amounts of absorbent and starting polyether-carbonate/alkylene carbonate mixture and the results obtained are as indicated in Table 1.

TABLE-US-00001 TABLE 1 Removal of Alkylene Carbonate with Strong Acid Ion Exchange Resin Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 4 hr 24 hr 48 hr 1 9 0.4 50 2.17 1.91 1.69 1.51 2 11 0.5 70 1.95 1.63 0.91 0.50

[0035] The strong acid ion exchange resin is an effective absorbent at all temperatures tested. However, better performance is seen at higher temperature, i.e., at 70° C., as is seen by comparing the results of Example 1 with those of Example 2.

EXAMPLES 3-6

[0036] Examples 3 and 4 are performed by repeating Examples 1 and 2, replacing the strong acid ion exchange resin with Molecular Sieve 13×, a synthetic zeolite in the sodium form. This material has an approximate empirical formula of Na.sub.86[(AlO.sub.2).sub.86(SiO.sub.2).sub.106].nH.sub.2O (n being variable), a nominal pore size of approximately 10 Angstroms, and is provided in the form of 1.4 mm diameter pellets. Results are as indicated in Table 2.

TABLE-US-00002 TABLE 2 Removal of Alkylene Carbonate with Molecular Sieve 13X Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 4 hr 24 hr 48 hr 3 11 0.6 50 2.17 1.89 1.53 1.42 4 10.1 0.5 70 1.95 1.60 1.11 0.92

[0037] This synthetic zeolite absorbent is also effective, again with better performance being seen at the higher temperature.

[0038] The effect of concentration of this absorbent is evaluated by repeating Example 4 using two different levels of absorbent, as set forth in Table 3.

TABLE-US-00003 TABLE 3 Removal of Alkylene Carbonate with Varying Amounts of Molecular Sieve 13X Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 4 hr 24 hr 48 hr 5 10.7 0.5 70 2.07 1.66 1.24 1.08 6 9.7 1.2 70 2.07 1.05 0.56 0.41

[0039] These results show that more rapid alkylene carbonate removal is obtained using a higher concentration of absorbent.

EXAMPLES 7 AND 8

[0040] Examples 1 and 2 are again repeated, replacing the strong acid ion exchange resin with a weak base ion exchange resin. The weak base resin is a macroporous styrene-divinylbenzene copolymer functionalized with tertiary amino groups in the free base form, and is commercially available from DuPont as Amberlite™ IRA96 resin. Results are as indicated in Table 4.

TABLE-US-00004 TABLE 4 Removal of Alkylene Carbonate with Weak Base Ion Exchange Resin Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 4 hr 24 hr 48 hr 7 11 0.5 50 2.17 1.91 1.79 1.68 8 9.9 0.5 70 1.95 1.78 1.33 0.95

[0041] Similar results are seen as before, with better performance being seen at the higher temperature.

EXAMPLES 9 AND 10

[0042] Examples 1 and 2 are again repeated, replacing the strong acid ion exchange resin with a weak acid ion exchange resin. The weak base resin is a macroporous, crosslinked methacrylic acid copolymer containing carboxylic acid groups in the acid form, and is commercially available from DuPont as Amberlite™ CG50 resin. Results are as indicated in Table 5.

TABLE-US-00005 TABLE 5 Removal of Alkylene Carbonate with Weak Acid Ion Exchange Resin Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 4 hr 24 hr 48 hr 9 11.2 0.6 50 2.17 2.09 1.87 1.75 10 9.6 0.5 70 1.95 1.85 1.54 1.29

[0043] Similar results are seen as before, with better performance being seen once again at the higher temperature.

EXAMPLES 11 AND 12

[0044] Example 2 is repeated twice more, replacing the strong acid ion exchange resin with unfunctionalized macroporous styrene-divinylbenzene copolymer beads. This product has a nominal particle size of 1 mm, has a 34 Angstrom mean pore size, a pore volume of 0.94 mL/g and a surface area of 1100 m.sup.2/g. It is commercially available from DuPont as Optipore™ V-503 resin. Results are as indicated in Table 6.

TABLE-US-00006 TABLE 6 Removal of Alkylene Carbonate with Macroporous Copolymer Beads Starting Alkylene Carbonate polyether, Absorbent, Temp, Concentration, Wt-% Ex. g g ° C. 0 hr 5 hr 24 hr 48 hr 11 9.8 0.5 70 2.28 1.96 1.71 1.43 12 10.1 1.0 70 2.28 1.81 1.54 1.33

[0045] The macroporous copolymer beads are also effective in removing alkylene carbonate from the polyether.