Preparation And Properties Of Anion And Nonion Modified Waterborne Polyurethane Curing Agent

With the increasing emphasis on environmental protection,the development of water-based coatings is imperative.Two-component waterborne polyurethane coatings have received extensive attention and research due to their excellent performance,among which waterborne polyurethane curing agents have become the focus of research.The existing waterborne polyurethane curing agents still have the disadvantages of high viscosity,short activation period of two-component coatings,and low hardness of the coating film.In view of this,an anionic and nonionic modified polyisocyanate curing agent was prepared in this paper,which was used for long-term matte waterborne two-component polyurethane coatings.The influence of coating film hardness and gloss,the main contents are:(1)Using cyclohexylaminopropanesulfonic acid(CAPS)as an anionic hydrophilic modifier and polyethylene glycol monomethyl ether(MPEG)as a non-ionic hydrophilic modifier to jointly modify the HDI trimer to prepare water-based HDI Hardener.The influence of the reaction sequence of anionic and nonionic modifiers on the reaction time was studied,and it was found that the first modification of HDI trimer with MPEG had a shielding effect on the reaction of unreacted NCO groups,which would hinder the further modification of polyisocyanates by anionic modifiers;When the addition amount of MPEG increases,the activation period of the coating prepared with the modified curing agent will increase first and then decrease,and the gloss of the coating film will first decrease and then increase.When the addition amount is 2.0 wt%,the gloss of the coating film is the lowest.As the molecular weight of MPEG increases,the activation period of the prepared coating is prolonged.When the modification amount is 2.0 wt%,the activation period of the coating prepared by the curing agent with MPEG molecular weight of 200,400,550 and 750 is 2.5 h,3.0 h,3.0 h and3.5 h,respectively.h.By comprehensively considering the viscosity of the mixed paint,the difficulty of hand stirring and other factors,the most cost-effective water-based curing agent can be obtained by modifying MPEG-400 with 2.5 wt%.The viscosity after mixing is as low as below 2000 m Pa·s,and the paint activation period can be extended to 3.5 h.(2)Using CAPS and MPEG to modify IPDI trimer to prepare water-based curing agent,it is found that the modified IPDI-based water-based curing agent has good hydrophilicity and high NCO content,and the pot life of the prepared coating is as long as 8 h,which is related to the hydrophobicity of the IPDI trimer molecular structure and the low reactivity of the NCO group with water;as the molecular weight of MPEG increases,the viscosity of the modified curing agent and the prepared coating also increases.The optimal conditions after optimization are: when the addition amount of MPEG-400 is 1.0 wt%,the activation period of the coating prepared by IPDI curing agent is more than 8h,the viscosity of the prepared coating changes smoothly with time,and the gloss of the coating film is as low as 11%.It is a super-matt coating film,and the hardness of the coating film reaches 4H;the water-based curing agent is prepared by compounding HDI/IPDI trimer.When the proportion of IPDI trimer is 15 wt%,the comprehensive performance of the water-based composite curing agent is the best.The viscosity is 2000 m Pa s,the hand stirring is good,the curing agent activation period is 8h,the viscosity of the mixed system is the lowest,the gloss of the coating film is8.5%,and the hardness can reach 3H.Compared with the commercially available Bayhrdur2547 product,it has obvious advantages in terms of coating pot life and coating film hardness.