Skip to main content

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, 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 20000 kg 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 products are 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

 

Applying procedure

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 l0 mm (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.

 


Labels:

Comments

Post a Comment

Popular posts from this blog

Difference Between Sulfate And Sulfonate In Shampoo

  Sulfates and sulfonates have two things in common. First, they're all anionic surfactants. Second, they are often used for personal care applications. But there are many differences. They have different molecular mechanisms. They have different functions and they have different raw materials.   Sulfates Sulfate is a compound. It has carbon bonds and oxygen and sulfur bonds. They include substances such as sodium lauryl sulfate and sodium lauryl ether sulfate.   At low pH, these substances plus the c-o-s bond hydrolyze to produce alcohol and inorganic sulfate. At a high pH, sulfate is stable in the base and, if ethoxylated to a relatively high level, produces a low-foaming alkali-soluble surfactant. Sulphates can be prepared by reaction of fatty alcohol or fatty alcohol ethoxylates with reagents such as SO3 or chlorosulfonic acid (CSA).   The reason shampoo becomes thick foam in the shower is that it contains sulfate. Most shampoos and household cleansers contain su...
Post a Comment
Read more

How Is Ethyl Bromide Prepared From Ethyl Alcohol 2

  1. Preparation of ethyl bromide  from ethyl alcohol and hydrobromic acid Start with a 1-liter double neck round bottom flask with a drop funnel and wide bend. The bend is connected to a long and efficient condenser assembly and receiver for downward distillation. First, place 281ml (or 415 g) 48% hydrobromic acid in a flask, then add 65ml (or 120 g) of concentrated sulfuric acid in batches, while shaking. As it cools, a small quantity of 145ml (or 100 g) 95% ethanol is slowly added to the mixture of sulfuric acid and hydrobromic acid. Then 109ml (or 200g) of concentrated sulfuric acid is slowly added to the drop funnel, and the ethyl bromine obtained by slow distillation is collected in the cold receiver flask. The crude ethyl bromine was washed with equal volume of concentrated hydrochloric acid, then washed with water and a small amount of 5% sodium bicarbonate solution, then washed with water, and finally dried the ethyl bromine with anhydrous calcium chloride. The crude ...
Post a Comment
Read more

What is Polyether Polyol

  Polyether polyol is prepared by ring-opening polymerization of epoxide monomers (such as ethylene oxide, propylene oxide and 1,2-epoxybutane) and a compound containing two or more active hydrogen atoms (called an initiator). In the presence of alkali catalyst, active hydrogen compounds initiate ring opening and oxide addition will continue until the required molecular weight is obtained. The number of hydroxyl groups in polyether polyol is determined by the number of unstable hydrogen atoms in the initiator. If the initiator has two active hydrogen, glycol will be formed. The reactivity of polyether polyol  to isocyanates depends on the initiator and the type of epoxy monomer that ends the ring-opening polymerization. The primary hydroxyl produced by polyol capped with ethylene oxide is more reactive than the secondary hydroxyl produced by propylene oxide, which is ideal for applications requiring rapid curing time. However, the use of initiator based on ethylene oxide and a...
Post a Comment
Read more