Waterborn Polyurethane perpolymer-water dispersion

[silebi66]

I have some query about aqueous polyurethane production.

It is usually made through three stages, the pre-dispersion, dispersion, and post dispersion, and the phase

inversion process is crucial for producingaqueous polymer dispersion with little or no external surfactants

added. This process is made through dispersing the highly water-insoluble polymer into

water, but the problem is that they don't normally form stable solutions in water due to their hydrophobic

nature. As a result, large amount of external emulsifiers are required to be dispersed in under high shear force.

I wonder is any good mixing machine or process for this, such as the high shear rotor-stator, anchor impeller, or others ?



Thank you very much for your kindly suggestion.

 

[jari001]

Try talking to these people, they make rotor-stator devices for high shear mixing:

http://www.silverson.com/

If you can swing it, get a mixing consultant's input or spend some time on the AIChE website to find some application advice on mixing.

Without further details regarding the process I would imagine you would need a combination of devices; one device that combines the two fluids and then special agitators in the receiving vessel(s) to keep the emulsion stable.

 

[silebi66]

Water Based Polyurethanes Dispersions(PUDs) are becoming important for the surface coating industry. Besides, PU synthetic process includes acetone process, melt dispersion process, pre-polymer mixing process, and ketimine process.
The flowing method by dispersing PU into water with low cost dispersions through anionic polymerization (pre-polymer mixing process) since they are stable at alkaline pH values > 7.and the dispersing agent is normally a bishydroxy carbvoxylic acid in commercial .
PUD Synthesis Process
1. Prepolymer Manufacture
The polymerization will be done by bulk or solution polymerizing the ingredients of the prepolymer. Thus, the ingredients forming the prepolymer, e.g., the polyisocyanates, the active hydrogen-containing compounds and the water-dispersibility enhancing compounds are combined to form the prepolymer.
2. Dispersion in Aqueous Medium
Once the prepolymer blend is formed which is incorporate amount of hydrophilic ioinc group, and dispersed in an aqueous medium to form a dispersion of the blend. Dispersing the prepolymer can be done by any conventional technique,ex. the rotor-stator mixer.
3. Polymer Neutralization
In those instances in which the prepolymer includes water-dispersibility enhancing compounds which produce pendant carboxyl groups, these carboxyl groups can be converted to carboxylate anions for enhancing the water-dispersibility of the prepolymer.
4. Chain Extension
The production involves chain-extension of the pre-polymer which have lower molecular weight into long polymer chain. As chain extender, at-least one of water, inorganic or organic polyamine having an average of about 2 or more primary and/or secondary amine groups, amine functional polyols.

My query is following :
1. What is appropriate particle size for PUD ? (ex. small particle may form high MW polymer or more viscous?
2, Is the rotor-stator mixer is proper for PUD dispersion scale-up process (Ex. 20m3 reactor) ?
3. For this phase inversion mechanism (pre-formed polymer in water / water in oil) , it seems mainly affected by different neutralizing agents, different amount of carboxylic acid group, operating temperature(phase inversion temp), solvent/PU ratio, and material addition rates(water or pre-polymer feed rate). What is the most important factor ?
Any kind of suggestion and hint to be really appreciated your generous help.