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Reasons for Deactivation of Polyurethane Catalysts

1. Preparation and synthesis methods of polyurethane catalysts


In a three-necked flask with a reflux condenser and a stirrer, mix up 227.2g polyethylene glycol with an average hydroxyl number of 187mgKOH/g and a molar mass of about 600g/mol, 94.1g of monohydroxy polyethylene glycol with an average hydroxyl number of 50mgKOH/g and a molar mass of about 1100g/mol, 24.0g of dimethylolpropionic acid, 57.2g of 2-hydroxyethyl acrylate, 0.65g of 2,6-di-tert-butyl P-cresol, 0.32 g of methylhydroquinone, 0.65 g of triphenyl phosphite, and 0.33 g of stilbene at 60°C.


As a polyurethane catalyst, 0.30 g of dibutyltin dilaurate is added to the completely mixed initial charge while bubbling with nitrogen. At 60 to 70°C, 208.7 g of isophorone diisocyanate is added dropwise to the mixture within 60 minutes.


The reaction mixture is then stirred at an internal temperature of 75 to 80°C for 7 hours until its NCO value is 0.89%. Then add 332g of anhydrous acetone, and then add 17.5g of 40% pure 6-amino-4-azahexanecarboxylic acid (sodium salt), and after a few minutes add 64.5g of 10 mass fraction sodium hydroxide aqueous solution. The reaction mixture is diluted with 260 g of water. Finally, the acetone is distilled off at 50°C and 100 mbar.


2. Reasons for the deactivation of polyurethane catalysts


(1) Permanent inactivation. The active components of polyurethane catalysts lose their activity due to the effect (poisoning) of some foreign components, usually permanent inactivation. Most of these foreign components react chemically or ion exchange with the active components of the catalyst to cause changes in the active components. For example, acid catalysts are neutralized by alkalis, and precious metal catalysts are poisoned by sulfides or nitrides. The deactivation of catalyst poisoning is usually manifested as a rapid decrease in activity. The active ingredient is worn or lost due to sublimation during use, and it will also lead to permanent inactivation. This type of inactivation is usually difficult to simply recover.


(2) The active components are gradually inactivated after being covered up, and finally are permanently inactivated. For example, carbon deposits during the reaction process cover up the active components or block the pores of the catalyst, making the reaction materials unable to contact the active components. These covering materials can be removed with certain methods, such as those being inactivated by carbon deposits can regenerate through charcoal regeneration.


(3) The wrong operation will cause the polyurethane catalyst to deactivate, such as excessively high reaction temperature. The drastic change in pressure will cause confusion or destruction of the catalyst bed. Such deactivation cannot be recovered.

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