Composition and Application of Waterborne Polyurethane

Waterborne polyurethane resin is a uniform lotion formed by dispersing polyurethane in water. It has the advantages of non combustion, low odor, non pollution, energy saving, convenient operation and processing, etc.
Chinese name Waterborne polyurethane resin Application Examples of synthesis in leather finishing agents, coatings, adhesives and other fields Classification of synthesis of anionic waterborne polyurethane Waterborne polyurethane consists of polyurethane aqueous solution, polyurethane aqueous dispersion and polyurethane lotion Waterborne polyurethane is mainly composed of macromolecular polyols, polyisocyanates, hydrophilic chain extenders, chain extenders, salifying agents, catalysts, crosslinking agents and other additives.
The flexible chain segment of polyurethane (PU) composed of macromolecular polyols is a soft segment, which is irregularly curled at room temperature, giving PU a certain degree of flexibility. Its structure and molecular weight affect the water resistance, solvent resistance, hardness and adhesion, and coating feel of PU. Commonly used polyols include adipic acid based polyester polyols, polypropylene glycol, polyethylene glycol, polytetrahydrofuran polyols, polycarbonate polyols, polycaprolactone polyols, hydroxyl terminated polydimethylsiloxane, etc.
Polyisocyanates form the rigid chain segment of PU - the hard segment, with high cohesion energy. The micro area of the hard segment at room temperature is glassy or microcrystalline, and its structure affects the weather resistance, hardness, solvent resistance, low temperature resistance, and wear resistance of PU.
Commonly used aliphatic polyisocyanates include isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, etc,
Aromatic polyisocyanates include toluene diisocyanate, diphenylmethane diisocyanate, etc.
The main function of chain extender is to increase the molecular weight of polyurethane and provide hard segment content.
Commonly used are small molecule alcohol chain extenders and amine chain extenders, such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, propylene glycol, isophorone diamine, ethylenediamine, etc. An important raw material for hydrophilic chain extender waterborne polyurethane, providing hydrophilic functional groups,
Commonly used hydrophilic chain extenders include dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, sodium ethylenediamine ethanesulfonate, N-methyldiethanolamine, triethanolamine, etc. The salifying agent reacts with the hydrophilic functional group to provide a stable lotion.
Commonly used salt forming agents include triethylamine, ammonia, sodium hydroxide, acetic acid, hydrochloric acid, etc.
Catalysts selectively regulate the reaction rate of - NCO with - OH and H2O. Commonly used catalysts include tertiary amine and organic metal catalysts, such as triethylamine, N, N-dimethylcyclohexylamine, triethylenediamine, stannous octanoate, butyltin dilaurate, bismuth isooctanoate, potassium acetate, etc.
The crosslinking agent crosslinks linear PU into a body shape, improving its water resistance, hardness, and solvent resistance. Commonly used crosslinking agents include trimethylolpropane, triethanolamine, glycerol, diethylenetriamine, etc. Other additives often require the addition of defoamers, leveling agents, thixotropic agents, light stabilizers, antioxidants, etc. according to industry usage needs and legal and regulatory requirements. The application of waterborne polyurethane has the advantages of low VOC, low odor, non combustible, easy modification, and excellent mechanical properties, and is widely used in adhesives, inks, leather finishing agents, and automobiles