Polyethylene glycol is produced by the stepwise addition of ethylene oxide and water or ethylene glycol. When preparing polyethylene glycol with a larger molecular weight, polyethylene glycol with a lower molecular weight is often used as the initiator. The polymerization reaction can be carried out in gas phase or liquid phase polymerization. In industry, liquid phase polymerization is mostly used, using sodium hydroxide or potassium hydroxide as catalyst. The reaction is carried out in a steel reactor with circulating pump and external heat exchanger or in a batch reactor with mechanical stirring. Modern ethylene oxide production is mostly connected with a by-product ethylene glycol device, so that part of ethylene oxide can be completely converted into ethylene glycol. The raw material entering the ethylene glycol reactor is provided by the ethylene oxide unit. The raw materials enter the adiabatic reactor after being preheated. The hydration of ethylene oxide can also be carried out in a steel reactor equipped with a circulation pump and an external heat exchanger or a batch reactor with stirring. It is prepared by the addition of ethylene oxide and water or ethylene glycol. After multi-effect evaporation of ethylene glycol-aqueous solution at the outlet of the hydration reactor, the steamed water and ethylene glycol are returned to the recovery system. Acid catalyst can be used for the reaction. Because there is almost no induction period, there will be no explosion, and the molecular weight distribution is ideal.
Product List
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| CAS NO. | Product Name | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 6800(8,000cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 200(4.5cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 1500(29cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 600(11cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 300(6cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 3400(93cs(99°c)) | Inquiry |
| 25322-68-3 | Polyethylene glycol,mw 400(7.4cs(99°c)) | Inquiry |
The reaction gradually condenses into polyethylene glycol. When the reaction pressure drops below 98 kPa, the reaction ends. The residual ethylene oxide is replaced with nitrogen and the catalyst is neutralized. As the molecular weight increases during the reaction, polyethylene glycol turns into a viscous solution and finally forms a waxy substance, while still maintaining solubility in water.
The raw material ethylene oxide used in the ethoxylation method must be pure and should be carried out under nitrogen protection. The reaction is to add a quantitative amount of fatty acids and alkaline catalyst into a reaction kettle with stirring and a thermometer, replace the air in the kettle with nitrogen at elevated temperature, and then add ethylene oxide dropwise at a suitable temperature and stable pressure. After the titration is completed, continue to maintain the temperature for a period of time to terminate the ethoxylation reaction.
The ethylene oxide gas used in this method is flammable and explosive, and the reaction temperature and pressure are high, the reaction conditions are very harsh, and the explosion limit is 3% ~ 100%. A large amount of heat generated in the reaction process must also be eliminated in time. The fast reaction speed of this method is one of the major characteristics. Therefore, the requirement for the safety of the reaction is quite high. Under the condition of ensuring safety, the purity of the product obtained by this method is high.
Preparation of Polyethylene Glycol
The catalyst was put into a 2 L autoclave and replaced with nitrogen three times. Evacuate, and then suck in the specified amount of ethylene oxide. After the addition is completed, fill the kettle with nitrogen to a gauge pressure of 0.05 MPa. Slowly raise the temperature under stirring and maintain a certain temperature. After the reaction is completed, replace it with nitrogen once and vent. After suction filtration, PEG (relative molecular mass 2000) was obtained.
Using the dropping method, first add the initiator, catalyst, and color-preventing agent to the autoclave, raise the temperature to a certain temperature, and then add ethylene oxide dropwise to carry out the reaction. Since the feed rate of ethylene oxide can be controlled artificially, the heat released during the reaction can be easily taken away, and the reaction pressure can be controlled below 0.6 MPa, so that the reaction proceeds smoothly and the product is colorless and transparent.
The appropriate reaction temperature is determined to be 120 °C, and PEG400 is used as the starting agent to synthesize PEG2000. The optimal catalyst dosage is catalyst : EO = 0.05 : 100, PECAOO : EO = 1 : 4.
When the polyethylene glycol ether bond breaks above 300 °C, the larger the molecular weight, the greater the tendency to be oxidized. Stabilizers such as hydroquinone can be added to stabilize it.
