Preparation And Characterization Of Blocked Isocyanate

Blocked isocyanate is one of the important crosslinking agents used in the field of baking coatings.As people pay more and more attention to environmental and energy issues,the development of a crosslinking agents with lower deblocking temperature and a blocked isocyanate that can be stably dispersed in water is a new direction of current research.In this paper,glycerol carbonate is used as a blocking agent to prepare low-temperature-deblocking isocyanate,and its application in baking coatings is also studied.On this basis,hydrophilic groups are introduced in order to prepare water-borne blocked isocyanate emulsions.And achieved the following results:1.Glycerol carbonate can block isocyanate quickly and efficiently,and the blocking rate is high.The product after the reaction does not contain free isocyanate groups,the blocking time is about 30 min,and DSC testing result indicated that the deblocking temperature was 101℃.2.The blocked isocyanate curing agent prepared with glycerol carbonate and HDI trimer was compared with the commercial curing agent,named BL3575.It was dound that the lab sample have the similar rheology and performance in the paint which was mixed by using the same paint formula.And the baking temperature of the paint made of lab curing agent in this experiment is 130℃,which is lower than the 140℃ of the paint made of BL3575 curing agent.3.A water-bornebased blocked isocyanate emulsion is prepared via using HDI trimer and glyceryl carbonate and methoxypolyethylene glycol monomethyl ether.The prepared emulsion is white,and the particle size distribution is polydisperse.The emulsion particle size gradually decreased from 282.8 nm to 258.0 nm with the increase of content of methoxypolyethylene glycol monomethyl ether.The DSC testing cure shows that the deblocking temperature of the crosslinking agent emulsion is 108℃.4.In order to improve the application weatherability of the blocked isocyanate emulsion,we introduced a more excellent polyurethane polymer as a hydrophilic polymer when prepared a polyurethane-based blocked isocyanate emulsion with glycerol carbonate.With the increase of polyurethane polymer content,the emulsion particle size decreased from 289.7nm to 133.1nm.As the degree of neutralization increases,the particle size decreases from 133.1nm to 71.68 nm,the potential increases from-10.6mV to-15.9mV,and the deblocking temperature is 110℃,which shows it has potential application in water borne baking paint.