Synthesis And Application Of Water-dispersible Non-ionic Blocked Isocyanate

Specialty paper is mostly used in packaging,printing,medical treatment,anti-counterfeiting,etc.Surface sizing agent can give special paper properties,such as high strength,high toughness and printability.At present,the isocyanate crosslinking agent is widely used as a surface sizing agent.However,due to the high activity of isocyanate,it will inevitably cause side reactions with water when it is dispersed in water.This will cause a series of problems such as poor stability of the isocyanate aqueous dispersion,short active period,inability to adapt to continuous production,and poor application effect,etc.In this paper,the existing problems of isocyanate modification are solved.The results are as follows:(1)In order to make up for the poor dispersion stability and short pot life of isocyanate in water,this article uses methoxy polyethylene glycol acrylate(MPEG350A)was the hydrophilic monomer,butyl acrylate(BA)was the hydrophobic monomer,and hydroxypropyl acrylate.(HPA)was a functional monomer to synthesize an amphiphilic polyacrylate long chain,which was condensed with isophorone diisocyanate(IPDI)to prepare a polymer surfactant(PAI).Then,a non-ionic water-dispersible polyisocyanate(PIHD)is synthesized by mixing the hexamethylene diisocyanate(HDI)trimer and PAI.The structure of PAI was characterized by means of FT-IR,GPC and 1NMR,and the optimal reaction conditions and hydrophilic monomers for the synthesis of PAI were investigated.The effect of MPEG350A content on the particle size and stability of the emulsion.Combined PIHD with polyvinyl alcohol(PVA1799)to form a surface sizing agent PDP for paper surface sizing,and explore the effect of different concentrations of PIHD emulsion on paper sizing performance.The results showed that:with an initiator dosage of 0.5%,and a reaction time of 3 hours at 90?,the best-performing polymer PAI can be successfully prepared.When n(MPEG350A):n(BA)=2:1 in PAI,the effect of emulsifying HDI trimer according to the same mass ratio was the best.And the PIHD-2 water dispersion is milky white and bluish,its particle size was 136.5 nm,relatively smaller,PDI was 0.135,kinetic stability index TSI was 0.61,the dispersion is relatively stable.its pot life was about 6 h.When the concentration of PIHD-2 reached 20%,it had the best effect on improving the physical properties of paper.The folding endurance,tensile index,tearing index and paper stiffness of paper were respectively 171 times,58.03 N·m/g,14 mN·m2/g,84.5 N·m/g,and the contact angle between paper and water was 90.68°.(2)In order to make the isocyanate aqueous dispersion exist stably for a long time,a blocking agent is used to block the exposed isocyanate groups.Based on the above-mentioned best process for PAI synthesis,use methyl ethyl ketoxime(MEKO)as a blocking agent to obtain water-dispersible blocked isocyanate(PAIM).The isocyanate blocking structure was characterized by FT-IR,and the optimal reaction conditions for the blocking reaction were investigated.The effects of the ratio of hydrophilic and hydrophobic monomers and the amount of HPA on the particle size and stability of PAIM dispersion were analyzed by means of Zeta potential particle size analyzer and stability analyzer.The effect of isocyanate content on the physical properties of paper was studied,and its comprehensive properties were compared with those of commercially available sizing agents.The results showed that when the amount of blocking agent was n(MEKO):n(—NCO)=1.2 and reacted at 60? for 3 hours,the isocyanate can be blocked better.When n(MPEG350A):n(BA)=2:1,w(HPA)=10.4%,w(—NCO)=7.9%,and the sizing agent mass fraction is 10%,the paper folding endurance reached 569 times,the tensile index was 66.83 N·m/g,the tear index was 11.54 mN·m2/g,the stiffness was 92.16 mN,and the contact angle of paper and water is 80.3°.Compared with commercially available sizing agents,PMP-3 had a longer storage period and can adapt to the surface sizing process of special paper.The sizing solution can be stable for more than 6 month at room temperature.The sizing paper reached the isocyanate deblocking temperature during the oven drying process at about 105?.The active isocyanate groups released after deblocking can be combined with paper fibers.At the same time,it has a strong binding ability to ink particles,which can significantly improve ink adhesion.After sizing with PMP-3,the folding endurance of the paper respectively increased by 29.3%,the tensile strength increased by 32.3%,the tearing degree increased by 22.1%and the stiffness increased by 19.5%,which can meet the high performance requirements of special paper.