Composition and Application of Waterborne Polyurethane
Water-based polyurethane resin is a uniform emulsion formed by dispersing polyurethane in water. It has the advantages of non-combustibility, low odor, no pollution to the environment, energy saving, and convenient operation and processing.
| Chinese name | Water-based polyurethane resin | should be used | Leather finishing agents, coatings, adhesives, etc. |
| Composition Example | Synthesis of anionic waterborne polyurethane | Category | Polyurethane water solution, polyurethane water dispersion and polyurethane emulsion |
Composition of waterborne polyurethane
Waterborne polyurethane is mainly composed of macromolecular polyols, polyisocyanates, hydrophilic chain extenders, chain extenders, salt-forming agents, catalysts, crosslinking agents and other additives. agent composition.
Macromolecular polyol
The soft segment that constitutes polyurethane (PU), the soft segment, is randomly coiled at room temperature, giving PU a certain degree of flexibility, and its structure and molecular weight affect PU. Excellent water resistance, solvent resistance, hardness and adhesion, coating feel and other properties. Commonly used polyols include adipic acid-based polyester polyols, polypropylene glycol, polyethylene glycol, polytetrahydrofuran polyols, polycarbonate polyols, polycaprolactone polyols, and hydroxyl-terminated polydimethylsiloxanes.
Polyisocyanate
The rigid segment that constitutes PU—the hard segment, has a large cohesive energy, and the micro-region of the hard segment at room temperature is glassy secondary crystal or crystallite, and its structure affects the PU Weather resistance, hardness, solvent resistance, low temperature resistance and wear resistance and other properties. Commonly used aliphatic polyisocyanates include isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, etc., and aromatic polyisocyanates include toluene diisocyanate, diphenyl methyl methane diisocyanate, etc.
Chain extender
The main function of the 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.
Hydrophilic chain extender
The important raw material of water-based polyurethane provides hydrophilic functional groups. Commonly used hydrophilic chain extenders include dimethylolpropionic acid, dimethylolbutyric acid, ethyl Sodium diaminoethanesulfonate, N-methyldiethanolamine, triethanolamine, etc.
Salt forming agent
Reacts with hydrophilic functional groups to provide a stable emulsion. Commonly used salt-forming agents are triethylamine, ammonia water, sodium hydroxide, acetic acid, hydrochloric acid, etc.
catalyst
Selectively control the reaction rate of -NCO with -OH and H2O, commonly used catalysts are tertiary amines and organometallic catalysts, such as: triethylamine, N , N-dimethylcyclohexylamine, triethylenediamine, stannous octoate, butyltin dilaurate, bismuth isooctanoate, potassium acetate, etc.
Crosslinker
Crosslink the linear PU into a body shape to improve the water resistance, hardness and solvent resistance of PU. Commonly used crosslinking agents are trimethylolpropane, triethanolamine, glycerin, diethylenetriamine, etc.
Other additives
According to the needs of the industry and the requirements of laws and regulations, it is often necessary to add defoamers, leveling agents, thixotropic agents, light stabilizers, antioxidants, etc.
Application of waterborne polyurethane
Water-based polyurethane has the advantages of low VOC, low odor, non-combustibility, easy modification and excellent mechanical properties, and is widely used in adhesives, inks, leather finishes, Automotive paint and advanced wood paint and other industries.
Water-based polyurethane adhesive
Water-based polyurethane adhesive has good bonding performance, and the physical properties of the film can be adjusted in a wide range. Bonding of various substrates has been widely used in shoe glue, automotive interior glue, vacuum plastic, woodworking glue, etc.
Water-based polyurethane coating
As a finishing agent, water-based polyurethane has good cold resistance, solvent resistance, film-forming properties, bending resistance, wet and dry wiping resistance, adhesion, etc., and has been widely used Used in leather finishing agents, fabric coatings, automotive varnishes, etc.
Water-based polyurethane ink binder
Water-based polyurethane is used as ink binder, which has excellent adhesion, color development, flexibility and wear resistance.
With the improvement of the national environmental protection control policy, the rapid development of water-based polyurethane is bound to gradually replace oil-based polyurethane. At present, water-based polyurethane leather finishing agent, water-based polyurethane shoe glue, Water-based polyurethane vacuum plastic has become the mainstream product in the industry.
