Polyol processing

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From organic oxygen-containing reactant

Reexamination Certificate

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C528S486000, C528S421000, C210S634000, C210S639000

Reexamination Certificate

active

06762279

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for producing polyols. More specifically, it pertains to an improved process for removing impurities from the polyols, removing alkaline catalysts from the polyols used in the production of polyether polyols, and to polyether polyols produced by said process.
BACKGROUND OF THE INVENTION
Process as for purifying polyether polyols involve either:
1) Neutralisation with an acid followed by dehydration and filtration of the resulting salt crystals.
2) Solvent extraction. Such processes require the use of organic solvents to dissolve the polyol and water to hydrolyse the alcoholate and extract the potassium hydroxide. After separation of the organic and aqueous layers, the organic solvent needs to be removed from the final polyol. This requires time and energy, and therefore is costly. Solvent traces may remain in the final polyol.
3) Ion exchange. Such processes require the use of ion exchange beds or magnesium silicates followed by filtration and also the use of solvent for efficient operation. The resin beds need to be regenerated or disposed of, while the solvent used needs to be thoroughly removed for the same reason as above.
It is generally known that polyether polyols with reduced levels of impurities can, when reacted with a polyisocyanate, produce improved quality flexible polyurethane foams. Therefore, there is a need for a process that reduces the level of impurities in polyether polyols.
The production of a polyether polyol from alkylene oxides is ordinarily carried out by the addition of the alkylene oxides to an initiator compound having active hydrogen atoms in the presence of an alkaline catalyst at temperatures of from about 70° C. to about 160° C. The alkaline catalyst is usually present in quantities of about 0.05 to 2 percent by weight of the reactants. A typical production method for a flexible polyether polyol involves the reaction of propylene oxide with glycerol in the presence of potassium hydroxide. The resulting un-neutralised polyol contains potassium alcoholate. The potassium alcoholate must be neutralised and the potassium salt must be removed so that the polyol will not react adversely with isocyanate in polyurethane production. Therefore, there is also a need for a process that is effective in neutralising the residual alkaline species used in the production of polyether polyols and allows reduction of alkaline catalyst residues after the preparation of these polyether polyols.
It is known that in some cases flexible polyurethane foam odour may create a problem. The causes of odour problems originate from side reactions during polyol manufacture and processing into a polyurethane polymer, as described in e.g. U.S. Pat. No. 5,925,687. Therefore, there is also a need for a means to reduce the odour of the polyurethane foam produced from polyether polyols.
SUMMARY OF THE INVENTION
Surprisingly it has now been found that by using an aqueous organic salt solution or acidic aqueous organic salt solution, improved quality of polyols, especially polyether polyols are obtained. More specifically, impurities and catalyst are reduced from the polyol through the separation of the polyol and salt phase. Furthermore, the purified polyol provides foam with improved stability, which in turn exhibits an improved odor profile.
Therefore, the invention relates to a process for producing polyols. More specifically, it pertains to an improved process of purifying from the polyols, removing alkaline catalysts used in the production of polyether polyols, and to polyether polyols produced by said process.
According to one embodiment, the present invention is directed to producing improved quality of especially polyether polyols which, in turn, are used for the production of improved flexible polyurethane foams. It is generally known that polyether polyols, while still meeting acceptable commercial specifications, can produce improved quality flexible polyurethane foams by reducing the level of impurities. The process of the present invention reduces the levels of these impurities thereby providing polyether polyols which, upon reaction with polyisocyanate, yield a higher quality flexible foam.
According to another embodiment of the present invention, the process of the present invention is effective in neutralising the residual alkaline species used in the production of polyether polyols. The production of a polyether polyol from alkylene oxides is ordinarily carried out by the addition of the alkylene oxides to an initiator compound having active hydrogen atoms in the presence of an alkaline catalyst at temperatures of from about 70° C. to about 160° C. The alkaline catalyst is usually present in quantities of about 0.05 to 2 percent by weight of the reactants. A typical production method for a flexible polyether polyol involves the reaction of propylene oxide with glycerol in the presence of potassium hydroxide. The resulting un-neutralised polyol contains potassium alcoholate. The potassium alcoholate must be neutralised and the potassium salt must be removed so that the polyol will not react adversely with isocyanate in polyurethane production.
The process according to the present invention allows reduction of alkaline catalyst residues after the preparation of these polyether polyols.
According to a further embodiment of the present invention, it has been found that the odour of the polyurethane foam produced from the polyether polyols of the process of the present invention is reduced. It is known that in some cases flexible polyurethane foam odour may create a problem. The causes of odour problems originate from side reactions during polyol manufacture and processing into a polyurethane polymer, as described in e.g. U.S. Pat. No. 5,925,687. The present process reduces the substances from the polyether polyols causing the odour.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a process for purification of a polyol, neutralised or un-neutralised, comprising the step of bringing the polyol into contact with an aqueous organic salt solution, mixing the aqueous organic salt solution and the polyether polyol, allowing the mixture to separate into a polyol phase and a salt water phase, and removing the salt water phase.
According to another embodiment of the present invention, the present invention is directed to a process for purification and neutralisation of a polyether polyol by bringing the un-neutralised polyol into contact with an aqueous organic salt solution and an organic acid, mixing the aqueous organic salt solution, the organic acid and the polyether polyol, allowing the mixture to separate into a polyol phase and a salt water phase, and removing the salt water phase.
The process of the present invention requires an aqueous organic salt solution and a polyether polyol, which may or may not contain an alkaline catalyst.
The process of the present invention is especially useful to polyether polyols, which are prepared using an alkaline catalyst. Methods for the preparation of the polyols are well known and generally involve the reaction of at least one alkylene oxide with an active-hydrogen-containing initiator compound in the presence of an alkaline catalyst. Polyols suitable for use in the present invention include, for example, linear and branched chain polyether polyols having aliphatic or aromatic-aliphatic character. The polyols may be prepared from known active-hydrogen-containing initiators used in the preparation of polyols such as amines and polyhydroxy compounds. The alkylene oxide is typically an alkylene oxide such as ethylene oxide, propylene oxide or butylene oxide. Alkylene oxides may be employed as mixtures.
Polyether polyols and methods for their preparation are, as previously stated, well-known, and illustrative references to said polyols and methods include U.S. Pat. No. 3,865,806, U.S. Pat. No. 4,125,505, U.S. Pat. No. 4,209,609, and the references cited therein. The teachings of these patents and references are incorporated herein by reference.
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