Construction Of Organic Dispersion Systems Based On Nanometer Magnesium Oxide For Deacidification Of Paper Documents

As an essential part of cultural heritage,paper documents represented by ancient books have extremely precious cultural,historical and artistic values.However,the carrier of paper documents,paper,is a porous network structure interwoven with natural cellulose fibers.It is inevitably destroyed by acid hydrolysis and oxidation due to the influence of the external environment as well as other organic components inside the paper,resulting in the rapid degradation of paper documents.Deacidification is an urgent and necessary method for paper documents protection.Although many deacidification methods were reported,a series of problems still exist,such as poor deacidification effect,decreased mechanical strength,powder deposition and ink blurring.The stable dispersions of alkaline nanoparticles in low-polarity organic solvents are the key to achieving safe and efficient deacidification of the acidified paper documents,ensuring the long-term preservation and utilization of paper documents.Based on this,the dispersion stability of alkaline nanoparticles in low-polarity organic solvents was improved by the solvation of short-chain alcohols and steric stabilization of hydrophobic or amphiphilic cellulose-based derivatives.Then these prepared stable dispersions were applied to the deacidification of the acidified paper.The evaluation of aging resistance was carried out by accelerated aging experiments and the mechanism of aging resistance was further analyzed.The detailed works were listed as follows:1.Dispersion properties of alkaline nanoparticles in low-polarity binary organic solvent system.Short-chain alcohols,non-polar organic solvents and alkaline nanoparticles were as raw materials to prepare the stable dispersions by ultrasonic dispersion.The effects of short-chain alcohols,non-polar organic solvents and alkaline nanoparticles and the volume ratio of solvents on the dispersion stability and average particle size of the dispersions were investigated.The results showed that isopropanol（IPA）can effectively improve the dispersion stability and particle size distribution of high electronegativity metal oxide or hydroxide nanoparticles in non-polar hexamethyldisiloxane（HMDO）through solvation.When the volume ratio of HMDO and IPA was 8:2,the mixed dielectric constant（ε_M）of the binary organic solvent system was 5.66,and the nano-magnesium oxide（Mg O）in this dispersion exhibited the best dispersion stability（after standing for 24 h,the transmittance（T）value was 17.73%,and?T was 10.99%）and the smallest and most uniform particle size distribution（the average particle size was 105 nm and the frequency was 70%）.This research may provide new ideas for the development of stable and low-polarity deacidification system containing alkaline nanoparticles.2.Construction of siloxanated modified cellulose stabilized nano Mg O organic dispersions for deacidification of the acidified paper.In response to the problem of insufficient dispersion stability in low polarity multifunctional organic deacidification systems,a synergistic stable dispersion strategy of IPA and siloxanated modified cellulose was proposed based on the spatial stability mechanism of colloidal chemistry.The effect of the chemical structure of trimethylsiloxane cellulose（TMSC）on the dispersion stability and particle size distribution of the nano Mg O in HMDO/IPA were studied.The synergistic dispersion mechanism of TMSC and IPA on nano Mg O in HMDO was clarified through experiments and simulation calculations.Stable nano Mg O organic dispersion was further used for the deacidification of the acidified aging books.The results showed that TMSC-2.05with high degree of substitution（DS=2.05,M_w=53,700）presented the best-promoting effect on the stable dispersion of nano Mg O in HMDO/IPA.Meanwhile,TMSC-2.05 and IPA showed a synergistic dispersion effect.When the addition of TMSC-2.05 was 1.0 wt.%and the volume ratio of HMDO and IPA was 5:5,the nano Mg O organic dispersion(T_2.05MHI（5:5）)exhibited the smallest average particle size（263 nm）and long-term dispersion stability（1 month）.After treatment with T_2.05MHI（5:5）,there was no effect on the appearance and writing clarity of the paper documents.The treated acidic aged-paper possessed sufficient alkali reserves（2.2 wt.%calcium carbonate equivalent（Ca CO₃eq.））and good mildew resistance（grade 1）,which was expected to have excellent stability during natural aging and prolong its life.This research may provide new ideas for simultaneous deacidification and anti-mold treatment of the acidified paper documents.3.Construction of amphiphilic cellulose stabilized nano Mg O organic dispersions for deacidification of the acidified paper.The effect of the chemical structure of alkyl ketene dimer（AKD）grafted cationic cellulose（AKD-g-CMCC）polymers on the dispersion stability and particle size distribution of nano Mg O in HMDO/IPA was studied.A stable nano Mg O organic dispersion was developed and its application effects in deacidifying,enhancing and anti-aging were also evaluated by accelerated aging experiments.The results showed that the synthetic AKD_0.024-g-CMCC_0.223with the highest DS ratio of alkyl chain to quaternary ammonium group（0.11）and the highest molecular weight（2021）could be stably dispersed in HMDO/IPA（volume ratio=5:5）.When the addition of AKD_0.024-g-CMCC_0.223was 0.50 wt.%,this dispersion（ACMMHI（5:5））exhibited high dispersion stability,small average particle size（200 nm）and low viscosity（2.26 m Pa·s）.The p H value of the treated acidified aged-paper was 8.30 increased from 4.70 and the alkali reserve was 1.00 wt.%Ca CO₃eq..The tensile index and tear index were increased by 40.78%and 27.28%,respectively.It also showed a lower change in paper color（ΔE=0.46）and the appearance and writing clarity.The accelerated aging tests further confirmed that the treated acidified aged-paper with ACMMHI（5:5）has good aging resistance.This research may provide a new idea for simultaneous deacidification and enhancement of the acidified paper documents.4.Multifunctional deacidification of acidified paper based on in-situ quaternization.Focusing on the difficulty that the nano Mg O organic deacidification agent cannot simultaneously realize the deacidification,enhancement and anti-mold,a two-step deacidification synergistic in-situ quaternization treatment（MESC）strategy based on impregnation of nano Mg O organic dispersion and atomization of saturated calcium hydroxide aqueous solution was proposed.The type and concentration of alkaline reagents and the ratio of IPA to H₂O in 2,3-epoxypropyltrimethylammonium chloride（ETA）solutions were investigated on paper fiber structure and the reaction efficiency of in-situ quaternization.The performance of anti-aging and anti-mold on the treated papers were further evaluated through accelerated aging experiments.After two-step deacidification,the treated acidified paper reached the appropriate p H value（9.0）and high alkali reserves（2.2 wt.%Ca CO₃eq.）.When the volume ratio of IPA/H₂O was 8:2,the quaternization reaction efficiency of ETA and paper fiber was the best and the tensile strength and folding endurance of the treated paper were increased by 28.05%and 80%,respectively.It also showed a lower change in paper color（ΔE=1.27）and the appearance and writing clarity.The treated paper also presented excellent anti-mold,anti-bacterial and anti-aging properties.This research may provide new insights into the multifunctional protection of acidified paper documents.5.Action mechanism of nano Mg O organic dispersions on aluminum sulfate acidified paper.To clarify the acidification mechanism of aluminum sulfate（Al₂（SO₄）₃）on paper and the acidification effect of nano Mg O organic dispersions,the presence of aluminum ions(Al³⁺)at different p H was investigated and their mechanism of acidification on paper fibers was clarified.By analyzing the permeability of nano Mg O in deacidified paper,the changes in the degree of polymerization of paper fibers and the content of reducing terminal groups,carboxyl and carbonyl groups during the heat-humid aging process,the action mechanism of nano Mg O organic dispersions on Al₂（SO₄）₃acidified paper were further determined.When the p H<7.0,Al³⁺were hydrolyzed to produce hydrogen ions to promote the acid hydrolysis of the paper fibers.When the p H<4.0,Al³⁺itself may also cause electrophilic action to induce cleavage of celluloseβ-glucosidic bonds.After being treated with four kinds of nano Mg O organic dispersions,the Al₂（SO₄）₃acidified paper was effectively deacidified.Among them,the acidified paper treated by MESC-8/2 exhibited the best anti-aging effect.Because it has achieved uniform deacidification due to strong permeability of saturated calcium hydroxide aqueous solution,which effectively alleviates the acid hydrolysis and oxidation of the acidified paper during the aging process.Cellulose derivatives can also effectively improve the mechanical properties and aging resistance of the treated acidified paper.The low-thermal-stability cellulose derivatives such as AKD_0.024-g-CMCC_0.223,although prone to oxidation during aging process,can alleviate the oxidation and degradation rate of acidified paper fibers.In response to the significant demand for national ancient book protection,this paper constructed a series of low-polarity binary organic dispersion systems based on mild alkaline nano Mg O.The solvation of short chain alcohols and the steric stabilization of hydrophobic or amphiphilic cellulose derivatives jointly improve the stability of the nano Mg O dispersions,achieving uniform and effective deacidification of the acidified paper.The non-covalent interactions of cellulose derivatives or crosslinking of ETA with paper fibers can also simultaneously achieve multifunctional protection such as enhancement or anti-mold and antibacterial.The acidification mechanism of Al₂（SO₄）₃at different p H in paper was clarified.Furthermore,the influence mechanism of cellulose-based derivatives and solvent polarity in the nano Mg O organic dispersions on the deacidification uniformity and aging resistance of acidified paper was elucidated.This work may provide important theoretical and technical support for the protection of the acidic paper documents.