Preparation Of Water-dispersible Polyisocyanate Crosslinking Agent And Its Effect On Surface Sizing Of Specialty Paper

In recent years,with the increasing demand for specialty papers,research on surface sizing agents for specialty papers has a lso received much attention.For example,nautical map paper is used at sea for a long time,and the paper is often in the original state and strength after being rained;The document paper can still have a certain strength after being wetted by water and perspiration,the degree of ink shedding is low,and the aging period is long;Banknote paper should have good folding and friction resistance during long-term repeated use,and reduce the loss of banknote paper during circulation.Although polyvinyl alcohol-based surface sizing agents can improve some physical properties of paper,they are not effective in improving the wet tensile strength and ink adhesion of paper.In this paper,methoxypolyethylene glycol monomethyl ether(MPEG₃₅₀),HDI trimer?HDIT?and methoxy polyethylene glycol methacrylate(MPEGMA₃₅₀),butyl methacrylate?BMA?as raw materials.Surfactant MPEG-HDIT and copolymer P?MPEGMA-BMA?were synthesized,and the structure was analyzed by infrared spectrometer,nuclear magnetic resonance spectrometer,gel permeation chromatograph,thermogravimetric analyzer,surface tension meter and fluorescence spectrometer.Molecular weight distribution,self-assembly behavior and thermal properties were characterized.Surfactant MPEG-HDIT and copolymer P?MPEGMA-BMA?can be used to emulsify and disperse HDI trimer,obtain MPEG-HDIT/HDIT dispersion and P?MPEGMA-BMA?/HDIT dispersion,and perform emulsion granulation testing of diameter,stability,microtopography and pot life.The paper was surface treated with different proportions of the dispersion as a paper surface sizing agent.The paper measured the performance parameters of the paper after sizing to select the best ratio and concentration of the dispersion.Finally,the above dispersion was combined with polyvinyl alcohol emulsion?PVA?for surface sizing of special paper.The main work and results are as follows:1.Prepare MPEG-HDIT/HDIT dispersion by self-emulsification and apply it to paper surface sizing:The surfactant MPEG-HDIT was synthesized and characterized for its structure,thermal properties and self-assembly behavior.When m_?MPEG-HDIT?:m_?HDIT?is 1:1,the MPEG-HDIT/HDIT dispersion has an emulsion particle size of 106.4 nm,PDI index of 0.193,TSI index of 0.47,and pot life of 7.0 h.When the MPEG-HDIT/HDIT quality score is 15%,it is applied to the surface of the paper for sizing,the sizing degree is large,and the physical properties of the paper are optimally achieved.Due to the high viscosity of PVA,too much PVA cannot penetrate between paper fibers.When the mass ratio of MPEG-HDIT/HDIT to PVA is 1:1,the special paper is sized,the sizing degree is maximized,and the folding resistance is maximized.The degree can reach 3575times,the wet strength retention rate can reach 32.98%,and the contact angle is 102.2°.2.Preparation of P?MPEGMA-BMA?/HDIT dispersion by external emulsification and application to paper surface sizing:The optimum conditions for the synthesis of polymer P?MPEGMA-BMA?were investigated:0.4%benzoyl peroxide?BPO?as initiator and 70%propylene glycol methyl ether acetate?PMA?as solvent.The polymerization temperature was at 90?,the monomer addition time is about 1.5h,and the synthetic polymer has the best comprehensive performance.The molecular weight distribution,structure and self-assembly behavior were characterized by a variety of analytical instruments.When the mass ratio of P?MPEGMA-BMA?to HDIT is 1:1,the emulsion particle size of P?MPEGMA-BMA?-3/HDIT(m_{?MPEGM A?}:m_{?BM A?}=3:1)dispersion is 147.7nm,the PDI index is 0.143,the TSI index is 0.58,and the dispersion is applicable for 6.0 h.At this time,the ability of the polymer to emulsify and disperse the HDI trimer is optimal.10%of the P?MPEGMA-BMA?-3/HDIT dispersion is applied to the surface of the paper for sizing,and the paper exhibits better sizing performance and stronger Physical properties.When the mass ratio of P?MPEGMA-BMA?-3/HDIT to PVA is 1:1,the paper has the best mechanical properties.The folding resistance can reach 3712 times,the wet strength retention rate can be 34.02%,and the contact angle is110.3°;the wet tensile strength of the paper is obviously improved,and the ink detachment condition is improved.