Synthesis Of C Ross-linked Polyvinyl Alcohol Surface Sizing Agent And Its Strengthening Effect On Special Paper

Paper fibers are mainly based on hydrogen bonding to cross-fix.However,the temperature and humidity of the environment will affect the hydrogen bond strength,resulting in changes in the strength and water resistance of the paper.Therefore,stably improving the physical properties of special paper is an urgent problem to be solved.High-strength and foldable specialty paper must take into account high folding times,good water resistance and writing and printability at the same time.Polyvinyl alcohol is a widely used paper surface sizing agent due to its low price and excellent sizing surface strength.However,the traditional polyvinyl alcohol surface sizing agent can not meet the high requirements of physical properties and writing printability of special paper.Therefore,along with new chemical engineering strategies,it is an essential necessity to chemically modify polyvinyl alcohol to obtain a surface sizing agent with more ideal comprehensive performance.This article first uses two different methods,silane coupling agent and isocyanate,to crosslink and modify polyvinyl alcohol,obtaining polyvinyl alcohol that can be slightly crosslinked during the processing.Meanwhile,an external organic titanium crosslinking agent was synthesized as a coordination crosslinking modification of polyvinyl alcohol.Finally,the synergistic silicone crosslinking,isocyanate crosslinking and organic titanium crosslinking are applied to the surface sizing of polyvinyl alcohol to obtain high-performance special paper.The research content is as follows:(1)Synthesis of silane coupling agent crosslinked polyvinyl alcohol(PVA-KH560)and its application.Polyvinyl alcohol was modified by y-glycidyl etheroxypropyltrimethoxysilane(KH-560),and under alkaline conditions,KH-560 epoxy group reacted with the hydroxyl group in polyvinyl alcohol to successfully graft KH-560 into the polyvinyl alcohol macromolecular chain.After grafting,the siloxyl groups in the molecular chain are further hydrolyzed to form highly active silicon hydroxyl groups.The results showed that PVA-KH560 had the best stability when the mass ratio of polyvinyl alcohol to KH-560 was 9:1.5.The tensile strength and ductility of two-component PVA-KH560/PVA film are greatly improved compared with single-component PVA film.PVA-KH560(9:1.5)and PVA1799 compound sizing can significantly improve the physical properties of paper,and the folding resistance,tensile index,stiffness,tear index,bursting index and contact angle of paper after sizing are 263 times,96.20 N·m·g-1,71.05 mN,15.10 mN·m2·g-1,6.03 kPa·m2·g-1,and 77.81°,respectively,which are increased by 436.7%,119.6%,116.4%and unsizing base paper,respectively.89.9%,80.5%,the contact angle increased by 28.5°.(2)Synthesis and application of blocked isocyanate-based crosslinked polyvinyl alcohol(PVA-IPDI).Polyvinyl alcohol was modified with isophorone diisocyanate(IPDI),the activity of-NCO in IPDI was very high,and the activity of IPDI partial capping was reduced by butanone oxime(MEKO),and in the medium of aprotic solvents,partially terminated IPDI underwent nucleophilic addition reaction with polyvinyl alcohol.The results show that when the molar ratio of MEKO to IPDI is 1.6:1,PVA-IPDI has the best stability.PVA-IPDI(1.6:1)and PVA1799 compound sizing solution sizing paper had the best physical properties,and the folding resistance,dry tensile index,wet tensile index,tear index,bursting index and contact angle of sizing paper were 1827 times,104.75 N·m·g-1,33.97 N·m·g-1,15.39 mN·m2·g-1,7.05 kPa·m2·g-1,and 81.31°,respectively.Compared with the base paper,the physical properties were improved by 3629.5%,186.9%,176.1%,93.5%and 111.1%,and the contact angle was increased by 31.9°.(3)Synthesis and application of organotitanium crosslinked polyvinyl alcohol.Synthesis of organotitanium crosslinker with ethylene glycol,lactic acid,glycerol and butyl titanate.As a delayed crosslinking agent between fibers and polyvinyl alcohol,the titanate ions need to be freed from the binding of organic ligands and crosslinked with hydroxyl groups,so that cellulose and polyvinyl alcohol can be efficiently combined.Organotitanium/crosslinked polyvinyl alcohol/PVA multi-component sizing solution was prepared,and the effect of organotitanium addition amount in sizing solution on the viscosity of the system was analyzed.The mechanical properties,thermal stability and water resistance of organotitanium multi-component sizing solution film were explored.A multi-component sizing solution is applied to the surface sizing of the paper to test the physical properties of the sizing paper.The results showed that when the addition amount of organotitanium was 0.5%,the viscosity of the sizing solution system was the lowest.The multi-component organotitanium/PVA-IPDI/PVA adhesive film had the best mechanical properties,with an elongation at break of 469%and a tensile strength of 35.85 MPa,compared with the two-component PVA-IPDI/PVA film without organotitanium crosslinker,the elongation at break was increased by 170%and the tensile strength was enhanced by 9.46 MPa.The multi-component sizing solution(organotitanium/PVA-IPDI/PVA)sizing paper had a folding resistance of 2319 times,a tensile index of 136.8 N·m2·g-1,a tear index of 17.46 mN·m2·g-1,a stiffness of 61.25 mN,a bursting index of 6.68 kPa·m2·g-1,and a contact angle of 79.34°,compared with the base paper,the test performance was improved by 4632.6%,212.3%,119.6%,86.6%and 100.0%,respectively.The contact angle is increased by 30.01°.Organotitanium crosslinker compound multi-component sizing solution sizing paper shows excellent mechanical properties and writing printability.