Polyether polyols are oligomers with ether bond (- R-O-R -) in the main chain and more than 2 hydroxyl groups (- OH) in the end group or side group. With low molecular weight polyols, polyamines or compounds containing active hydrogen as initiators, - and oxidized olefins are ring opened and polymerized under the action of catalyst. The oxidized olefins are mainly propylene oxide (propylene oxide) and ethylene oxide (ethylene oxide), of which propylene oxide is the most important. Polyol initiators include binary alcohols such as propylene glycol and ethylene glycol, ternary alcohols such as glycerol trimethylolpropane, and polyols such as pentaerythritol, tetraol, xylitol, sorbitol, and sucrose; The amine initiator is diethylamine, diethylenetriamine, etc.
Polyether: propylene glycol polyether with molecular weight of 800-2000, trimethylolpropane polyether with molecular weight of 400-4000 and hydroxyl terminated polytetrahydrofuran are commonly used. Polyether resin used as adhesive should remove the alkaline catalyst left during polymerization, because they can catalyze the dimerization of isocyanate and affect the quality of adhesive. It is usually neutralized with acid to make polyether slightly acidic (which does not affect the reaction of polyurethane). Polyether used to prepare polyurethane adhesive has strict requirements. In addition to hydroxyl value and acid value, it is required that the content of potassium and sodium ions should be less than 10, and the water content should be less than 0.05%, otherwise gel may be generated. The polyurethane adhesive prepared with polyether resin has good water resistance, impact resistance and low temperature performance.
Polypropylene oxide glycol
Polypropylene oxide glycol, also known as polypropylene glycol (PPG), is prepared in a glass lined or stainless steel reactor. Add the mixture of initiator (1,2-propanediol or dipropylene glycol) and catalyst (potassium hydroxide) into the kettle for catalyst preparation, heat it to 80~100 ℃, remove the solvent in the catalyst under vacuum, so as to promote the generation of alcohols. Then transfer the catalyst into the reactor, heat it to 90~120 ℃, add propylene oxide into the reactor at this temperature, and keep the pressure in the reactor at 0.07~0.35MPa. At this temperature and pressure, propylene oxide is continuously polymerized until it reaches a certain molecular weight. Under negative pressure, after the residual epoxy propane monomer is evaporated, the polyether mixture is transferred to a neutralization kettle, neutralized with acid substances, and then filtered, refined, and added with stabilizer to obtain the product.
Precautions for use of recycled polyether polyol
(1) Due to hygroscopicity, do not contact with air directly.
(2) Avoid open fire, and avoid heating in the air for a long time. In particular, the insulation materials and clothing penetrated by polyether polyols often catch fire naturally, so pay attention.
(3) When adhering to the skin, wash the eyes with plenty of water. When entering the eyes, wash the eyes with water for more than 15 minutes.
(4) In case of overflow, use saw dust, yellow sand, cloth and other permeable substances to remove them, and then use a large amount of water to flush them away.
Containers for polyether polyols can be made of steel, aluminum, polyethylene or polypropylene. The storage temperature should not exceed 70 ℃. In order to prevent moisture absorption and oxidation, it is recommended to fill the container with nitrogen. Polyether polyol products are generally packed in clean, dry, sealed and leak free galvanized iron drums. Keep away from sun, rain and fire during storage. It is not restricted by the storage rules of flammable liquids, but it should be avoided from entering groundwater or surface water, because it is not easily biodegradable.
Polyether polyols can be generally divided into four categories. One is polyoxypropylene polyol (PPG), which is copolymerized with propylene oxide or propylene oxide and ethylene oxide with polyol or organic amine as initiator. It is the main product series of polyether polyols and polyurethane production in China; Second, polymer grafted polyether polyol (POP), such as acrylonitrile or styrene grafted with polyol, can significantly improve the hardness of soft polyurethane foam and improve its bearing capacity, which is mainly used to manufacture high bearing polyurethane foam; The third is the polymerization of tetrahydrofuran glycol or polyurethane elastomer, and the second is polyoxyethylene glycol (PEG). Polyether glycol is polymerized with ethylene oxide using ethylene glycol or diethylene glycol as the initiator, and is widely used in cosmetics, medicine, chemical fiber, rubber, paper making, electroplating, food processing and other industries.
