The Synthesis Of Blocked Isocyanate Firming Agent And Application

Rude auto filter paper is one kind of paper which is made from natural plant fibers and other raw materials. Its tightness index is small, that is the reason why we should make the raw filter paper coated with resin to overcome some of its drawbacks, such as looseness, softness, weak water-resistance and other shortcomings. Therefore, auto filter paper can meet the requirement of production and using. Water-soluble resin is widely used in the automotive industry impregnated resin, although it is a environment-friendly impregnated resin which also does little harm to human beings, its production cost is pretty expensive and with poor stiffness and water resistance.In this experiment, Water—soluble blocked isocyanate firming agent was prepared in acetone using toluene disocyanate (TDI) and polypropylene glycol-400(PPG-400) as monomers, and sodium bisulfite as blocking agent. With external emulsion method to synthesize a water-soluble blocked isocyanate firming agent which was able to meliorate the waterproof of auto filter paper effectively. It also gave the filter paper with good stiffness, strength, permeability. Further more, this synthetic method was simple with low cost. This dissertation covers two aspects:(1) The synthesis of this water-soluble blocked isocyanate firming agent and properties analyzations.(2) The research of applications and process of this kind of water-soluble blocked isocyanate firming agent.In the research part of synthesis and properties of firming agent, which mainly studied and optimized some influence factors in the processes of pre-polymerization, block-reaction, and emulsification reaction.The best synthesis process:n(NCO)/n (OH)was2.4, the pre-polymerization process was performed under (65±1)℃for1.5h, sodium bisulfite as blocking agent (concentration was25%), accelerator sodium sulfite (nNaHSO3/n(NCO)was1.2;sodium sulfite and sodium bisulfite the mole ratio was0.2); block-reaction process was operated in an ice bath whose temperature was0-5℃for40min, the product would be mixed with emulsifier (AEO-9/OEP-982mass ratio was3/2, the amount of emulsifier was4%) and water, stirred into a crude emulsion, and then poured into the high-shear emulsifier to form a stable emulsion for15min.In the research part of application, my aim was to ameliorate water resistance of the filter paper. The finishing process was that the filter paper was dipped into the working fluid which contained3%starch solution and2%water-based polyurethane firming agent. Without extra working fluid, filter paper was dried under115℃for5min, therefore the filter paper could float for5hours without wetting, with excellent stiffness, strength, and permeability. In addition, the spectroscopic analysis (FT-IR) indicated that the synthetic product was exactly the target product water-soluble blocked isocyanate firming agent. Through the DSC tests result, we could see clearly the reactive temperature of this water-based polyurethane firming agent was around118℃, which was in line with the initial experiment requirement. And the Scanning Electron Microscope (SEM) revealed that continuous film was formed on the surface of filter fabric.