Distillation: processes – separatory – With chemical reaction – Including step of adding catalyst or reacting material
Patent
1997-03-27
1999-09-14
Manoharan, Virginia
Distillation: processes, separatory
With chemical reaction
Including step of adding catalyst or reacting material
203 41, 203 58, 203 91, 210638, 210664, 210666, 210729, 528502, 568617, 568621, 568682, 568693, B01D 334, C07C 4134, C08G 6510, C08G 6520
Patent
active
059518294
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of separating heteropoly compounds from mixtures comprising polyethers, polyesters and/or polyether esters, a protic component and heteropoly compounds, by removing the protic component from the mixture and subsequently separating off the heteropoly compound as a separate phase.
Polyethers, polyesters and polyether esters are employed widely, for example in hydraulic fluids or as a diol component in the preparation of polyurethanes. They are prepared by cationic polymerization or copolymerization of appropriate monomers, such as, for example, cyclic ethers, acetals, polyalcohols or lactones, with the aid of Bronstedt or Lewis acid catalysts. Catalysts which have proven particularly advantageous for a ring-opening polymerization are heteropoly acids and heteropoly acid salts, referred to collectively below as heteropoly compound(s) or HPA. In various processes for preparing certain novel derivatives, but also for improving the technical feasibility and product quality in the case of existing processes, polymerization is carried out in the presence of protic compounds.
EP-A 0 126 471 discloses, for example, the HPA-catalyzed polymerization of THF and the copolymerization of THF with various other cyclic ethers in the presence of water to form polyether glycols. EP-A 0 158 229 describes the preparation of polyether glycols by copolymerization of cyclic ethers with difunctional and higher polyfunctional alcohols.
According to JP-A 61-200120, lactones can be polymerized, alone or together with cyclic ethers, in the presence of hydroxyl-containing compounds and using heteropoly acids as catalysts.
In accordance with EP-A 0 503 393 and EP-A 0 503 394, polyether glycol monoethers and polyether glycol monoesters can be prepared by polymerizing cyclic ethers in the presence of monoalcohols or monocarboxylic acids and with HPA catalysts.
These polymerization processes for preparing polyethers, polyesters and polyether esters are accompanied by the formation of polymer phases which, owing to incomplete reaction, still include residues of monomer(s), of added protic compound such as water, alcohols, carboxylic acids, etc., any solvents employed, and dissolved heteropoly compound(s). The percentage amount of HPA catalyst dissolved in the polymer phase is considerable with these reactions and may be up to 1% by weight or more, based on the polymer phase. If separation is configured merely as a distillation to remove unreacted monomer, protic additive and any solvent employed from this phase, then the dissolved catalyst is not precipitated out but remains in dissolved form in the polymer. On the one hand, this must be prevented on quality grounds; on the other hand, it is desirable for reasons of cost--since heteropoly acids are very expensive--to recover the majority of the catalyst.
To solve this problem, EP-A 0 181 621 proposes the addition to the polymer phase of a hydrocarbon or halogenated hydrocarbon which does not form an azeotrope with the monomer(s) used, whereby the majority of the dissolved heteropoly compound is precipitated as a separate phase. The hydrocarbon/polymer phase is subsequently treated in a manner known per se with a solid adsorbent. To obtain the polymer, it is necessary at the end, after having separated off unreacted monomer, protic additive and any solvent added, to separate off the latterly added (possibly halogenated) hydrocarbons. A workup technique of this kind has the disadvantage that, owing to the volume of the polymer phase, which is greater as a result of the addition of the (possibly halogenated) hydrocarbon, apparatus of larger dimension is required for the distillation, and consequently the capital investment costs are higher; also, the removal of the added (possibly halogenated) hydrocarbon, whose boiling point is usually above that or those of the monomer or monomers, involves considerable additional energy costs.
In SU 1754732 A1, concentration of the polymer phase to 50-90% polymer is likewise followed by the addition of a hydrocarbon of 1-15
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Fischer Rolf
Jeschek Gerhard
Muller Herbert
Weyer Hans-Jurgen
BASF - Aktiengesellschaft
Manoharan Virginia
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