Preparation And Film Properties Of Silicon-containing Hybrid Water-dispersible Polyisocyanate Curing Agent

With the rapid development of the polyurethane industry in the direction of environmental protection and green,two-component waterborne polyurethane coatings have gradually been applied to various fields in the polyurethane industrial coating.Two-component waterborne polyurethane coatings were mainly composed of water-based hydroxyl components and water-dispersible polyisocyanate components.Solvent-based polyisocyanate curing agent had low viscosity and high NCO content,but because was not hydrophilic,it can’t be uniformly mixed with the water-based hydroxyl component to completely react and crosslink,resulting in uneven,non-compact and low gloss coating film.The performance did not meet the requirements,so it can’t be widely used in industrial production and life.In this paper,the HDI trimer（HT-100）was modified by using silicon-containing compounds to prepare a water-dispersible polyisocyanate curing agent with excellent properties such as good hydrophilicity,high NCO content,low viscosity and strong application adaptability.After mixed with water-based automobile paints of various colors to make two-component water-based polyurethane coatings,the performance of the paint film was studied.Theγ-aminopropyltrimethoxysilane（KH-540）was used as the modifier,and the nano SiO₂ particles were subjected to lipophilic modification treatment to produce modified H-200.Water-dispersible polyisocyanate curing agent with silicone（WSi DP）was prepared by using modified H-200,3-cyclohexylaminopropanesulfonic acid（CAPS）,and HT-100 as the main raw materials to react under the catalysis of triethylamine（TEA）.When the dosages of modified H-200 and CAPS were 2.5%and 3.0%,respectively,the prepared WSi DP had better comprehensive performance than other products.The WSi DP appearance was colorless,clear and transparent,and its NCO content was about20.0%.Water-dispersible polyisocyanate curing agent with silicone had excellent thermal storage stability and good water dispersibility,the gloss on the two-component bright paint films prepared for it was about 95°,and the film hardness can reach 2H.The silane coupling agent Y was synthesized by the addition reaction to dimethylaminoethyl methacrylate and KH-540.Then through the reaction to silane coupling agent Y with HT-100,a polyisocyanate curing agent with silicone was synthesized,and was modified by increasing 1,3-propane sulfone to make polyisocyanate curing agent with silicone hydrophilic.Then silicone-containing water-dispersible polyisocyanate curing agent（WYDP）was prepared.3.0%silane coupling agent Y and 3%1,3-propane sulfone can produce WYDP with an NCO content of 20.3%and a solid content of about 99%under reaction conditions at 50℃,which had good thermal storage stability and water dispersibility.A two-component waterborne polyurethane coating was prepared by the synthesized WYDP and water-based hydroxyl resin.The effect of different water-based resins,isocyanate index and film forming aids on the performance of the paint film were discussed.Waterborne hydroxyl resin Neocryl XK-540 and waterborne polyisocyanate curing agent WYDP were formulated into waterborne polyurethane coatings to prepare paint films,which mixed with additives（dipropylene glycol monomethyl ether DPM and dipropylene glycol n-butyl ether DPNB）.When the isocyanate index was 1.5,the performance of the paint film was better than other isocyanate index,and the prepared paint film had excellent storage stability and water resistance.Comparing the comprehensive performance with the commercially available high-quality water-based polyisocyanate curing agent products,the synthesized WYDP meets the performance requirements and was superior to some commercially available products in terms of water resistance and heat resistance.