How to use DMC catalyst to produce polyether polyols？
The DMC catalyst is double metal cyanide catalyst. Compared with similar polyols made using basic(e.g.,KOH)catalysts, polyether polyols made from the catalyst have low unsaturations, narrow molecular weight distributions, can have high molecular weight ,and are useful in making a variety of polyurethane products. DMC catalyst is highly active in epoxide polymerization reactions used to prepare polyether polyols. We can yield the DMC more than 20000kg within one year, and thus afford to produce 50～70 ten thousand tons of polyols. This catalyst is white or light yellow powder, is suitable for preparation of polyols with 1~6 functions. Compared with basic catalysts, this catalyst can be used with less amount (30ppm),and reaction time of polymerization is reduced largely, and the polyols products are not necessary to be refined. The DMC is suitable for using in common epoxide polymerization reactors,but it can be better if reactors have both of stirring and cycling systems.
When using the DMC production period is short, thus the costs for production are reduced while the property of productsare advanced.
Conditions wanted for initiators
1. polyethers with 1～3 0r more hydroxyl groups
2.molecular weight:for at least 2 hydroxyl groups---350~1000;for monols---with boiling point more than l00℃
3.∑Mn+ (mainly for K、Naions)≤5ppm
4. water content≤0.1%
5. acid value≤0.15mgKOH/g
1. Weigh certain amount of initiator and the catalyst. The catalyst's amount is generally 30ppm relative to the product (it mainly refers to N220 with 2 hydroxyl groups and N330 with 3 hydroxyl groups).The amount of the catalyst can reduce if the molecular weight of products are relatively high,e.g. for N240, the amount can be 20～25ppm).
2. The mixture is stirred and is stripped under a vacuum with pressure less than l0mm (Hg) ,and is heated to 130~145℃ to remove traces of water from the starter. Generally it needs more than 40min after the temperature rises to 130~145℃.
3. Propylene oxide (PO) or mixture of ethylene oxide (EO) and PO is fed to the reactor, under a pressure of 0.1—0.25Mpa.Additional PO or PO and EO is not added until an accelerated pressure drop occurs in the reactor( temperature can reach above 180℃,but this can not harm the activity of DMC or the properties of products).PO or PO and EO is added while maintaining a reactor pressure generally less than 0.1Mpa,temperature 140±10℃ .
4. After PO or PO and EO addition is complete, the mixture is held at 140±5℃until a constant pressure is observed.Residual unreacted monomer (generally only traces) is then stripped.
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