Processes for purifying polyether polyols using ion exchange resins
Processes for purifying polyether polyols via treatment with ion exchange resins. A mixture that includes the polyether polyol and alkali metal ions is passed through a first bed that includes a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to remove alkali metal ions from the mixture. Thereafter, the product is passed through a second bed comprising an anion exchange resin comprising quaternary ammonium groups and a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to thereby produce a purified polyether polyol.
1 . A process for removing alkali metal ions from a polyether polyol, comprising: (a) passing a mixture comprising the polyether polyol and the alkali metal ions through a first bed comprising a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to remove alkali metal ions from the mixture; and (b) passing the product of step (a) through a second bed comprising an anion exchange resin comprising quaternary ammonium groups and a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to thereby produce a purified polyether polyol, wherein the first bed and the second bed are each free of a cation exchange resin that comprises sulfonic acid groups.
2 . The process of claim 1 , wherein the polyether polyol has a hydroxyl number of no more than 56 mg KOH/gram, measured according to ASTM D4274-16.
3 . The process of claim 2 , wherein the polyether polyol has a hydroxyl number of 25 to 35 mg KOH/gram, measured according to ASTM D4274-16.
4 . The process of claim 1 , wherein the mixture comprising the polyether polyol and the alkali metal ions is combined with a mixture comprising water and a polar organic solvent prior to passing the mixture comprising the polyether polyol and the alkali metal ions through the first bed, wherein a relative weight ratio of polar organic solvent and water in the mixture comprising water and polar organic solvent is within a range of 1:1 to 10:1.
5 . The process of claim 4 , wherein the mixture comprising water and polar organic solvent is present in an amount of 10 to 40% by weight, based on the total combined weight of (i) the mixture comprising water and polar organic solvent and (ii) the mixture comprising the polyether polyol and the alkali metal ions.
6 . The process of claim 1 , wherein at least one of a container that includes the first bed and a container that includes the second bed is operated liquid-full throughout the process.
7 . The process of claim 6 , wherein the liquid level in the container operated liquid-full throughout the process is maintained at a level that is at least 95% of the total container height throughout the process.
8 . The process of claim 1 , wherein cation exchange resin that comprises sulfonic acid groups is present in an amount of no more than 1% by weight, based on the total weight of ion exchange resin used in each bed.
9 . The process of claim 1 , further comprising removing organic solvent and water from the purified polyether polyol.
10 . The process of claim 9 , wherein the removing organic solvent and water from the purified polyether polyol comprises at least atmospheric distillation and vacuum distillation.
11 . The process of claim 9 , wherein, after removal of organic solvent and water, the purified polyether polyol has a 2M2P (2-Methyl-2-Pentenal) content of no more than 5 ppm, based on total weight of the polyether polyol, as measured by Headspace Gas Chromatography and Mass Spectrometry (HS GC-MS).
12 . The process of claim 9 , wherein, after removal of organic solvent and water, the purified polyether polyol has a 2M2P (2-Methyl-2-Pentenal) content of no more than 1 ppm, based on total weight of the polyether polyol, as measured by Headspace Gas Chromatography and Mass Spectrometry (HS GC-MS).
13 . The process of claim 12 , wherein the purified polyether polyol has an acid number of no more than 0.1 mg KOH/g measured according to ASTM D7253-16.
14 . The process of claim 12 , wherein the purified polyether polyol has an alkalinity, determined by visual titration, of no more than 0.2 meq/kg.
15 . A process for producing a polyether polyol, comprising: (a) adding an alkylene oxide onto an H-functional starter in the presence of an alkali metal catalyst to produce an alkali metal-containing crude polyol comprising a mixture comprising the polyether polyol and alkali metal ions; (b) passing the mixture through a first bed comprising a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to remove alkali metal ions from the mixture; and (c) passing the product of step (b) through a second bed comprising an anion exchange resin comprising quaternary ammonium groups and a cation exchange resin comprising carboxylic acid and/or phosphonic acid groups to thereby produce a purified polyether polyol, wherein the first bed and the second bed are each free of a cation exchange resin that comprises sulfonic acid groups.
16 . The process of claim 13 , wherein the polyether polyol has a hydroxyl number of no more than 56 mg KOH/gram, measured according to ASTM D4274-16.
17 . The process of claim 15 , wherein cation exchange resin that comprises sulfonic acid groups is present in an amount of no more than 1% by weight, based on the total weight of ion exchange resin used in each bed.
18 . The process of claim 15 , further comprising removing organic solvent and water from the purified polyether polyol.
19 . The process of claim 18 , wherein, after removal of organic solvent and water, the purified polyether polyol has a 2M2P (2-Methyl-2-Pentenal) content of no more than 5 ppm, based on total weight of the polyether polyol, as measured by Headspace Gas Chromatography and Mass Spectrometry (HS GC-MS).
20 . The process of claim 18 , wherein, after removal of organic solvent and water, the purified polyether polyol has a 2M2P (2-Methyl-2-Pentenal) content of no more than 1 ppm, based on total weight of the polyether polyol, as measured by Headspace Gas Chromatography and Mass Spectrometry (HS GC-MS).