Preparation And Performance Of Carboxylic Acid-polyether Water-based Polyisocyanate Curing Agent

Two-component waterborne polyurethane coatings(2K-WPU)are non-toxic and environmentally friendly.They have excellent wear resistance,flexibility,chemical resistance,high and low temperature resistance and adhesion.They have been widely used in industry,flooring,wood,Leather,fabrics and other fields.One of the key components of 2K-WPU is the water dispersible polyisocyanate curing agent(WDP),which plays an important role in the comprehensive properties of coatings.However,at present,the WDP developed independently in China has many defects,such as poor water dispersion,high viscosity,low NCO% content,poor storage stability,poor compatibility with resin components and substandard paint performance.In this paper,carboxylic acid-polyether modifier monomer was synthesized and used in hydrophilic modification of polyisocyanate to prepare carboxylic acid-polyether WDP,and the paint performance was investigated.Polyethylene glycol and acid anhydride are used for ring-opening reaction to generate monoester,and a reactive hydroxy-terminated carboxylic acid-polyether monomer modifier is prepared,which has both carboxylic anion and polyoxyethylene nonionic hydrophilic characteristics.Through theoretical and experimental investigations,the experimental technology of raw materials,feeding ratio,feeding method,reaction conditions,etc.are determined: polyethylene glycol 600(PEG-600)and succinic anhydride(SA)are selected as the reaction raw materials,and the molar ratio is 1.05:1,one By batch feeding,the reaction was carried out at 85-90?,and a colorless,transparent,low viscosity(430-520 cp,25?),reactive hydroxy-terminated carboxylic acid-polyether hydrophilic modifier(PEG-SA)was synthesized,the yield of which was 97.3%.The results of infrared spectrum and hydrogen nuclear magnetic spectroscopy showed that the synthesized modifier was basically consistent with the designed structure.The HDI trimer(base material)was hydrophilically modified by using the abovementioned carboxylic acid-polyether monomer modifier,N,N-dimethylcyclohexylamine(DMCA)as neutralizer,and 1,4-butanediol(BDO)as the crosslinking agent.It was found that using 5%(the mass ratio of the base material)of PEG-SA,90% neutralization degree of DMCA,and 0.5%(the mass ratio of the base material)of BDO,a total reaction of about 5h at 90-95 ?,synthesis PEG-SA-BDO-WDP has the best overall performance-clear and transparent appearance,viscosity(25?)3500 cp,NCO% content 19.45%,storage stability up to 6 months,water dispersion particle size distribution is narrow,average particle diameter is 300 nm.The self-made WDP and water-based hydroxy resin A component(WS 665)are compounded to prepare water-based polyurethane varnish.And the application performance of WDP was investigated.Exploring the influence of the molar ratio of NCO and OH on the performance of the paint film,it is found that the best molar ratio of NCO/OH is 1.3-1.7.At this time,the overall performance of the paint film is the best: pencil hardness 3H,adhesion 0grade,gloss about 48,acid and alkali resistance pass.The two-component system has good compatibility and the pot life of the compound varnish is about 4 hours.Comparing with the representative WDP products on the market,it is found that the performance of the self-made PEG-SA-BDO-WDP in the paint has reached the relevant national standards in all aspects.