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Knowledge of aqueous PU resin

by:Sinograce Chemical     2020-07-06
Aqueous PU resin, water-borne polyurethane resin, CPU is the abbreviation of PU polyurethane in English. Waterborne PU resin is through water instead of organic solvent, as a new system of polyurethane dispersion medium, is a new type of environmentally friendly polymer materials. Because of their excellent environmental protection, excellent mechanical properties, and good compatibility with other water-based resin, aqueous PU resin is widely used for adhesives, paint, coating products. Aqueous PU resin synthesis: the synthesis of waterborne PU resin is generally diisocyanate, first oligomer polyols, chain extender on the performed reaction, step by step this step reaction mechanism belongs to the polymerization reaction. Reaction to generate a certain molecular weight polymers or high molecular weight of PU resin, and the phase transfer method is adopted to emulsion in water, aqueous PU resin. Waterborne PU resin composite materials: isocyanate, commonly used varieties have aromatic diisocyanate, including TDI, MDI; Aliphatic diisocyanate HDI and alicyclic diisocyanate IPDI, HMDI, etc. Aromatic PU has good mechanical performance, but due to the presence of benzene ring, no yellowing resistance, the thermal activation temperature is higher, limiting its application scope. Aliphatic or alicyclic PU hydrolysis resistance, storage temperature is better than that of aromatic polyurethane, more excellent yellowing resistance. High quality water-based PU resin generally adopt aliphatic or alicyclic isocyanate synthesis. Large molecules polyols: water-based PU resin molecules polyols is mainly used in the synthesis of polyether polyols, polyester polyol, polyethylene glycol, polyethylene tetrahydrofuran ether, polyester amide, acrylic polyol and so on. The polyether type of polyurethane ether base rotation, has good flexibility, good low temperature performance, and ether is not easy to hydrolysis, water resistant performance is better than that of polyester polyurethane. But due to the hydrolysis resistance of polyester itself is bad, so the general materials of polyester type waterborne polyurethane, its relatively short storage period. Chain extender: small molecule chain extender with 1, 4 - Butyl glycol, ethylene glycol, has two acid alcohol and ethylene diamine, hydrophilic chain extender is to the end of isocyanate and polyurethane pre polymers of extender chain at the same time the introduction of hydrophilic groups of substances, divided into anionic, cationic and nonionic three, commonly used have dihydroxy methyl propionic acid ( DMPA) , sodium oxalic taurine, divinyl three amine, methyl diethanolamine, etc. Usually these structure with carboxyl, sulfonic group, or secondary amine, when its side chain on polyurethane molecular chain, can make the PU chain segment can be ionized on functional group. Neutralizing agent: also called into salt, carboxyl, sulfonic group and other groups can be reaction to form polymer reagent of the salt or generate ion group. Anionic waterborne PU neutralizing agent used mainly include triethylamine, ammonia, sodium hydroxide, such as cationic waterborne PU neutralizing agent used mainly include acetic acid, CH3I, epoxy chloropropane, etc. The dissolvent with commonly used solvents: acetone, because waterborne PU viscosity will increase in the reaction process, lead to stir difficulties, inadequate response, adding acetone to reduce viscosity, sufficient to stir to make reaction. Acetone low boiling point, after the synthesis acetone removal from the aqueous PU.
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