Experimental Study On Vacuum Freeze Drying In Dehydration Protection Of Aqueous Solution

Paper literature are the witness of the history for a country or a region. A large collection of precious paper Literature are kept in libraries, museums, research institutes, and so on. They are the precious cultural heritages of the Chinese nation, and they have important historical and cultural values. Due to the prevailing economic and technical conditions, a large number of paper Literature were used poor quality papers for printing, and as time goes, many paper Literature which suffered acidified, oxidized and biological corrupted were badly deteriorated. A large number of deacidification treatment technologies are applied and widely used in paper Literature because of paper Literature acidification increasingly serious situation. At present, Deacidification of aqueous solution is a mature technology and it is mainly applied to paper Literature, while it is difficult to dry the paper Literature. General drying method will not only take a long time, but also the paper Literature after drying will appear the phenomenon of shrinkage, deformation, etc, thus they will Cause great adverse effects on paper literature. Vacuum freeze drying method remove moisture mainly by sublimation, and is applied widely into many fields. Shrinkage and deformation caused by surface tension of paper literature can overcome by vacuum freeze drying method.Acid paper literature are selected as the research subject. Developed a device which can be used for removing acid in the paper Literature under vacuum, pre-freezing at low temperature and drying under vacuum. And use the device to make experiment on vacuum freeze-drying for acid-processed paper Literature. The process and related data about moving acid in the paper Literature under vacuum, pre-freezing at low temperature and drying under vacuum are considered. The dates about the paper Literature before and after the test were analyzed. The results indicate that the speed and validity had been improved removing acid in the paper Literature under vacuum than applying traditional methods. Paper Literature does not appear shrinkage, adhesion and deformation after vacuum freeze-drying, and the ink handwriting are intact. The influence of procedure parameters (heating temperature, paper document thickness, pressure in drying room) on freeze-drying time and quality were explored, and obtained the sequence of importance and dehydration rate by orthogonal method. The pH, chromatic aberration, tensile strength, tear strength and folding of the paper literature before and after test are considered. And the physical and chemical properties of vacuum freeze-drying for acid-processed paper literature before and after the experiment under two kinds of test were analyzed.The results indicate that the speed and validity had been improved removing acid in the paper literature under vacuum than applying traditional methods. Resistance method is used to measure the eutectic point after paper literature acid and the temperature is1.5～3℃. Pre-cool test does not appear obvious uneven, which accord with the requirement of further vacuum freeze drying. The different treatment levels of procedure parameters had remarkable influence on both vacuum freeze-drying time and the quality, and the importance sequence of the three factors both as follows:paper documents thickness, heating temperature, and pressure in drying chamber. The optimal parameters were a thickness of7mm, heating temperature of25℃and pressure of10-20Pa by optimization analysis. The results indicate that the pH of the paper literature were greater than7, the tensile strength and folding degrees are greatly improved, but the color change and tear strength increase is small. Research results show that the acid-processed under the condition of vacuum can remove paper literature acid. Vacuum freeze drying can maintain the original state of the paper literature, and improve the mechanical strength of the paper literature.From what has been discussed above. The speed and validity had been improved removing acid in the paper literature under vacuum. Vacuum freeze drying can maintain the original state of the paper literature, and improve the mechanical strength of the paper literature. Vacuum freeze drying is a feasible dry processing methods. Vacuum freeze drying line with the current scale acid and its dry paper document requirements.