Preparation And Properties Of Anionic-nonionic Aqueous Polyisocyanate Curing Agent

With the increasing attention paid to environmental protection issues,the development of water-based paint has become a hot spot in the paint industry.Waterborne two-component polyurethane coatings are environmentally friendly and non-toxic.They also have excellent properties such as high wear resistance,flexibility,water resistance,and chemical resistance.They are used in floor coatings,wood coatings,anticorrosive coatings,and waterproofing coatings,automotive repair coatings and other fields are widely used.Waterborne twocomponent polyurethane coatings are composed of aqueous polyisocyanate curing agents and waterborne hydroxyl resins.Waterborne polyisocyanate curing agents as an important component of waterborne two-component polyurethane coatings,play a key role in the performance of paint films.However,the waterborne polyisocyanate curing agents independently developed in China currently have the defects of low NCO content,high viscosity,poor water dispersion performance and poor storage stability.In this paper,the HDI trimer is modified to prepare an aqueous polyurethane curing agent with excellent performance,and the influence of the hydrophilic modifier and its amount,and the synthesis process on the performance of the aqueous polyurethane curing agent and its film are studied.The ionic hydrophilic modifier 3-(cyclohexylamino)-1-propanesulfonic acid(CAPS)and nonionic hydrophilic modifier methoxypolyethylene glycols(MPEG)are used to modify the HDI trimer,and triethylamine(TEA)is used as the neutralizing agent and catalyst,an aqueous polyurethane curing agent with high NCO content,low viscosity,and excellent water dispersibility is prepared.It was found that when the amount ratio of CAPS and MPEG is 0.4 and the amount of TEA is 110%(molar ratio with CAPS),the performance of the synthetic waterborne polyisocyanate curing agent is the best.The prepared curing agent is clear and transparent,with a solid content of 100%,a viscosity of 2368 cp,an NCO content of 20.06%,and has excellent storage stability and water dispersion properties.Using the addition reaction of mercapto groups and olefins,2-hydroxy-ethanethiol modified AMPS oligomers were synthesized using 2-hydroxy-ethanethiol and 2-acrylamide-2-methylpropanesulfonic acid(AMPS),and used it as an ionic hydrophilic modifier,together with MPEG modify the HDI trimer to prepare a waterborne polyisocyanate curing agent.The synthesized curing agent was clear and transparent,with a solid content of 100%,a viscosity of 2169 cp,and an NCO content of 19.89%.The two waterborne polyisocyanate curing agents synthesized in this paper are compared with the commercially available high-quality waterborne polyisocyanate curing agents for comprehensive performance.It is found that the performance of the synthesized water-based polyisocyanate curing agents meet the requirements of the national standard,and the viscosity and NCO content index are better than some commercially available products.Two synthetic waterborne polyisocyanate curing agents and waterborne polyurethane varnish A component FL2301 A were formulated into waterborne polyurethane coatings to prepare paint films.The effect of NCO/OH molar ratio on the properties of paint films and the pot life of the paint were studied.When the NCO/OH molar ratio is 1.5-1.7,the performance of the paint film is better,and the The pot life of the water-based polyurethane coating formulated with the prepared water-based polyisocyanate curing agent is 4 hours.And compared with the commercially available high-quality waterborne polyisocyanate curing agents,it is found that the performance of the film prepared by the synthesized water-based polyisocyanate curing agents is excellent,and reaches the national standard requirements.