Paper deacidification method of pressurized and atomized borate composite bacterial cellulose

Abstract

The invention discloses a paper deacidification method of pressurized and atomized borate composite bacterial cellulose. The method comprises the following specific steps that the surface of the paper document is pretreated, surface impurities are removed, and paper is placed in an atomization treatment device; preparing a deacidification dispersion liquid, and dispersing borate and bacterial cellulose in a solvent to form a uniform composite dispersion liquid; the deacidification dispersion liquid is atomized into tiny fog drops through an atomization device, and the atomized borate and bacterial cellulose fog drops can be evenly attached to the surface of paper and internal fiber gaps; acidic substances in the paper are neutralized through the synergistic effect of atomized borate and bacterial cellulose, and meanwhile, the mechanical property of the paper is improved by utilizing the physical reinforcing effect of the bacterial cellulose and the chemical crosslinking effect of borate; the atomized paper is dried under certain conditions, and the deacidification and reinforcement process is completed.

Description

Technical Field

[0001] The invention belongs to the field of paper deacidification, and in particular relates to a paper deacidification method using pressurized atomized borate composite bacterial cellulose. Background Art

[0002] Due to the influence of various factors such as age, paper type and environment, paper artifacts will have different degrees of acidification and aging problems. There are two main factors that can cause paper to become acidic: external factors and internal factors. External factors refer to the accelerated generation of acidic substances under the influence of the external environment (such as the gnawing of small animals, the influence of harmful gases and microorganisms). Internal factors mainly include the following four aspects: the hydrolysis and oxidation of residual lignin in the paper to produce acidic substances; acidic fillers added during the pulping and papermaking process, such as acidic rosin and alum; some chlorides will remain in the process of pulping, which will accelerate the effect of alum on paper and cause paper acidification; acidic pigments and inks used in printing, etc.

[0003] Paper is not only prone to acidification, but the degree of acidification will become more serious over time. Relevant studies have pointed out that hemicellulose in paper will produce formic acid and acetic acid under acid catalysis, which will further aggravate the acidification of paper. Therefore, the hydrolysis rate of cellulose under acid catalysis will become faster and faster. In order to prevent acidification from causing irreversible damage to paper, paper must be deacidified and protected in time.

[0004] At present, there are two traditional deacidification methods: gas phase deacidification and liquid phase deacidification. The gas phase deacidification method mainly uses alkaline gas (morpholine, cyclohexylamine, ammonia, etc.) for deacidification. Its advantage is that it can deacidify in batches and has little effect on the morphology of paper samples before and after deacidification. Its disadvantage is that alkaline gas not only harms the human body, but also may cause accidents such as explosions. The liquid phase deacidification method uses alkaline solutions including Mg(OH)2, Ca(OH)2, Ca(HCO3)2 to treat paper samples by spraying or dipping. Its deacidification effect is better, but its disadvantage is that it is easy to discolor and wrinkle the paper sample, and the strong alkaline solution will make the paper sample too alkaline, which will lead to a decrease in its mechanical strength.

[0005] There is also an atomization deacidification method. Like the gas phase deacidification method, the atomization method has the advantage of being able to deacidify in large quantities. The atomization methods are divided into pressurized atomization and ultrasonic atomization. There are some studies on ultrasonic atomization deacidification, which has a good deacidification effect. However, since the power of ultrasonic atomization is smaller than that of pressurized atomization, the deacidification time required is longer, and the particle size of the generated mist particles is larger, which also has a greater impact on the morphology of the paper after deacidification. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a paper deacidification method using pressurized atomized borate composite bacterial cellulose.

[0007] The present invention uses atomization technology to apply a dispersion formed by a composite of borate and bacterial cellulose to paper, and achieves deacidification and reinforcement of paper through the synergistic effect of atomized borate and bacterial cellulose. The specific steps are as follows:

[0008] Pre-treat the surface of paper documents to remove surface impurities, and place the paper in an atomization treatment device;

[0009] Prepare a deacidified dispersion, dissolve borate and bacterial cellulose in a solvent to form a uniform composite dispersion, wherein the mass ratio of borate to bacterial cellulose is 1:1 to 100:1;

[0010] The deacidified dispersion is atomized into tiny droplets by an atomizing device, so that the atomized borate and bacterial cellulose droplets can be evenly attached to the surface of the paper and the internal fiber gaps; the acidic substances inside the paper are neutralized by the synergistic effect of the atomized borate and bacterial cellulose, and the mechanical properties of the paper are improved by utilizing the physical reinforcement effect of the bacterial cellulose and the chemical cross-linking effect of the borate;

[0011] The paper after atomization treatment is dried under certain conditions to complete the deacidification and strengthening process.

[0012] Beneficial effects of the present invention:

[0013] The present invention uses a pressurized atomized borate composite bacterial cellulose dispersion to deacidify the paper sample. Compared with the traditional liquid phase deacidification, it has less impact on the morphology of the paper document and will not cause yellowing, discoloration and wrinkles after the paper sample is deacidified. It also avoids excessive wetting of the paper sample, which leads to the reduction of mechanical strength of the paper sample due to hydrogen bond breakage caused by swelling.

[0014] The present invention utilizes a pressurized atomization method to atomize the borate solution and the bacterial cellulose dispersion into extremely small mist particles (1 nm to 5 μm), so that the borate ions can better penetrate into the interior of the paper sample, and the bacterial cellulose mist particles can better adhere to the paper than the untreated bacterial cellulose dispersion, thereby neutralizing the acidic substances in the paper sample with borax, so that the pH of the paper sample is increased to a certain extent.

[0015] The present invention utilizes the weak alkalinity of the borate solution, which will not make the paper sample too alkaline to damage the internal structure of the paper sample, and the borate ions can better combine with the bacterial cellulose molecules and the hydroxyl groups of the paper cellulose molecules to form intermolecular forces. Therefore, the strength indexes (including tensile strength, tear index, etc.) of the treated paper are significantly improved compared with those before the treatment.

[0016] The present invention greatly saves the time cost required for deacidification and reinforcement, and has a good deacidification effect within 60 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 These are scanning electron microscope images before and after deacidification, the left one is the scanning electron microscope image before deacidification, and the right one is the scanning electron microscope image after deacidification. DETAILED DESCRIPTION

[0018] In order to further understand the present invention, the embodiments of the present invention will be described in further detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0019] The present application is devoted to studying a novel deacidification method, which broadens the application of atomization deacidification, provides ideas for paper document protection, and has certain theoretical significance and application value. The present invention is described in detail below in conjunction with specific embodiments:

[0020] Borate solution is a good deacidification agent. Since the pH of saturated borate aqueous solution is about 9.24, it can effectively avoid the solution from being too alkaline, making the deacidification process gentle and effective. In addition, the SP² electron-deficient structure in the borate radical makes tetraborate have a strong electron-withdrawing ability, which is easy to combine with polyhydroxy compounds to enhance the intermolecular force, thereby improving the mechanical properties of paper.

[0021] Nanocellulose can generally be divided into cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and bacterial cellulose (BC). Although BC has the same molecular formula as CNC and CNF and is also a macromolecule connected by β-D-pyranose glucoside bonds, it is superior to CNC and CNF in purity, degree of polymerization and film-forming properties. In addition to good mechanical properties and biocompatibility, BC also has the characteristics of high crystallinity, large specific surface area, low thermal expansion coefficient, three-dimensional porous structure and anisotropy. Moreover, bacterial cellulose has the same chemical composition as paper cellulose, has high compatibility with the cellulose molecules of paper, has excellent mechanical properties, and is an ideal paper reinforcement material.

[0022] In combination with the above analysis, the present application uses a compound of borate and BC to form a deacidification dispersion and uses pressurized atomization to deacidify paper. The dispersion can be converted into fine particles suspended in the experimental box, allowing borate and BC to better enter the interior of the paper, achieving uniform and gentle deacidification in a short time without changing the morphology of the paper. At the same time, because BC fibers can be embedded in the gaps between paper fibers, a "bridging" effect is formed between paper fibers to strengthen the fiber bonding force, and the BC fibers themselves can be cross-linked with borax, so the borate ions loaded on BC can further improve the mechanical properties of the deacidified paper sample and increase its repair effect on the paper sample.

[0023] Furthermore, the present application also uses pressurized atomization to deacidify paper documents. The principle of pressurized atomization is to use the high-speed airflow generated by the high-speed injection of compressed air from the nozzle to form a negative pressure above the water suction pipe. The salt solution rises rapidly to the nozzle along the water suction pipe under the action of atmospheric pressure, is atomized by the high-speed airflow and sprayed to the conical mist distributor at the top of the spray pipe, and then floats out from the spray port and diffuses into the laboratory. The mist particles produced by pressurized atomization are smaller, and while it is easier to enter the interior of the paper, it is not easy to deform the paper. The advantage of gas phase deacidification having little effect on the morphology of the paper sample before and after deacidification is retained, and the mist particles produced by pressurized atomization will not cause harm to the human body or cause safety accidents such as explosions, and deacidification using this method greatly saves the time cost of deacidification.

[0024] The present application provides a method for deacidifying paper by atomizing borate and bacterial cellulose by pressurized atomization, which is specifically as follows:

[0025] Step (1): Clean the impurities on the surface of the paper document, hang it at room temperature for a period of time, and then place it in the atomization test box.

[0026] Step (2): dissolving borate and bacterial cellulose in deionized water to prepare a uniform deacidification solution.

[0027] Step (3): Pour the deacidification liquid into the pressurized atomization equipment, adjust the air pressure, test chamber temperature and other related parameters to make the deacidification liquid atomized and adhere to the paper document. After a certain deacidification time, take it out and measure the performance of the paper sample.

[0028] Furthermore, the conditions in step (1) are: brushing off impurities on the surface of the paper sample with a soft brush, and then hanging the paper sample in a room at 25° C. for 24 to 72 hours, preferably 48 hours.

[0029] Furthermore, the sample in step (1) is placed flat or suspended.

[0030] Furthermore, the borate solution in step (2) is one or more of lithium tetraborate, sodium tetraborate and potassium tetraborate, with a mass fraction of 5 g / L to 20 g / L, preferably 10 g / L.

[0031] Preferably, the mass ratio of borate to bacterial cellulose in step (2) is 20:1-20:5. The present invention takes into account the viscosity of bacterial cellulose itself. As the concentration of bacterial cellulose increases, the viscosity of the deacidification solution will also increase, and the atomization effect will deteriorate. Therefore, the proportion of bacterial cellulose should not be too high.

[0032] Furthermore, the amount of the deacidification solution in step (2) is 900 ml-3000 ml.

[0033] Furthermore, the air pressure in step (3) is 0.15 kg / cm 2 -0.9 kg / cm 2 . The temperature is 25℃-45℃.

[0034] Furthermore, the deacidification time in step (3) is 12 min-60 min.

[0035] The following are examples. Although only one paper sample is selected in the examples, the method of the examples has a deacidification effect on all ancient books including ancient acidic books, archives, documents, books, newspapers and periodicals, paper, calligraphy and painting, cotton and linen, etc.

[0036] The paper document selected for the experiment is the "Collection of Materials on Sino-US Relations" published in 1960. Its various properties are listed in Table 1: Table 1 Performance of paper documents

[0037]

[0038] Example 1

[0039] Step (1): Use a soft brush to brush away impurities on the surface of the paper sample, then hang the paper sample in a room at 25°C for 48 hours, and then lay it flat on the sample placement table in the test chamber.

[0040] Step (2): prepare 1000 mL of 10 g / L sodium tetraborate solution in a beaker, then add the bacterial cellulose dispersion into the solution so that the mass ratio of sodium tetraborate to bacterial cellulose is 20:1, then stir to fully dissolve it, and finally obtain a deacidified dispersion.

[0041] Step (3): Take the deacidified solution prepared in step (2) and add it into the atomizing device. Set the test chamber temperature to 30°C and the inlet air pressure to 0.3 kg / cm 2 .

[0042] Step (4): Start the equipment, take out the paper sample after 36 minutes of deacidification, and measure the properties of the paper sample after natural drying. The pH of the paper sample increased to 7.36, the tear length increased to 1.415 km, and the tear index increased to 2.693 mN·m 2 ·g -1 The color difference of the paper sample before and after deacidification is 1.91.

[0043] Another example Figure 1 As shown, the original paper ( Figure 1 The fiber surface of the paper (center left) is rough, with broken fibers and obvious pores. Figure 1(middle right) A BC cellulose membrane is formed on the surface, interweaving the fibers together. The fiber membrane is complete and flat, and the broken fibers on the surface of the paper are covered by the bacterial cellulose membrane, which has a certain reinforcement effect on the paper.

[0044] Example 2

[0045] Step (1): Use a soft brush to brush away impurities on the surface of the paper sample, then hang the paper sample in a room at 25°C for 48 hours, and then lay it flat on the sample placement table in the test chamber.

[0046] Step (2): prepare 2000 mL of 10 g / L sodium tetraborate solution in a beaker, then add the bacterial cellulose dispersion into the solution so that the mass ratio of sodium tetraborate to bacterial cellulose is 20:3, then stir to fully dissolve it, and finally obtain a deacidified dispersion.

[0047] Step (3): Take the deacidified solution prepared in step (2) and add it into the atomizing device. Set the test chamber temperature to 25°C and the air pressure to 0.6 kg / cm 2 .

[0048] Step (4): Start the equipment, take out the paper sample after 48 minutes of deacidification, and measure the properties of the paper sample after natural drying. The pH of the paper sample increased to 7.27, the tear length increased to 1.428 km, and the tear index increased to 2.652 mN·m 2 ·g -1 The color difference of the paper sample before and after deacidification is 1.52.

[0049] Example 3

[0050] Step (1): Use a soft brush to brush away impurities on the surface of the paper sample, then hang the paper sample in a room at 25°C for 48 hours, and then lay it flat on the sample placement table in the test chamber.

[0051] Step (2): prepare 1500 mL of 10 g / L sodium tetraborate solution in a beaker, then add the bacterial cellulose dispersion into the solution so that the mass ratio of sodium tetraborate to bacterial cellulose is 20:5, then stir to fully dissolve it, and finally obtain a deacidified dispersion.

[0052] Step (3): Take the deacidified solution prepared in step (2) and add it into the atomizing device. Set the test chamber temperature to 25°C and the inlet air pressure to 0.9 kg / cm 2 .

[0053] Step (4): Start the equipment, take out the paper sample after 60 minutes of deacidification, and measure the properties of the paper sample after natural drying. The pH of the paper sample increased to 7.18, the tear length increased to 1.502 km, and the tear index increased to 2.941 mN·m 2 ·g -1 The color difference of the paper sample before and after deacidification is 1.69.

[0054] Comparative Example 1

[0055] Step (1): Use a soft brush to brush away impurities on the surface of the paper sample, then hang the paper sample in a room at 25°C for 48 hours, and then lay it flat on the sample placement table in the test chamber.

[0056] Step (2): Prepare 1000 mL of 10 g / L sodium tetraborate solution in a beaker and fully dissolve it to obtain a deacidified dispersion.

[0057] Step (3): Take the deacidified solution prepared in step (2) and add it into the atomizing device. Set the test chamber temperature to 25°C and the inlet air pressure to 0.60 kg / cm 2 .

[0058] Step (4): Start the equipment, take out the paper sample after 48 minutes of deacidification, and measure the properties of the paper sample after natural drying. The pH of the paper sample increased to 7.19, the tear length increased to 1.392 km, and the tear index increased to 2.528 mN·m 2 ·g -1 The color difference of the paper sample before and after deacidification is 1.79.

[0059] Table 2 Comparison of deacidified paper performance of the embodiment and the comparative example

[0060]

[0061] By comparing Example 1, Example 2, Example 3, Comparative Example 1 and the original paper, the pressurized atomization deacidification process has a milder deacidification effect on the paper sample due to the production of smaller mist particles, and borax is weakly alkaline and will not make the paper sample yellow due to excessive alkalinity. Therefore, the color difference of all cases is less than 2, and the pH of the paper sample after deacidification is greater than 7, reaching the deacidification standard (pH>6.5). Since BC fibers can be embedded in the gaps between paper fibers, a "bridging" effect is formed between paper fibers to strengthen the fiber bonding force, and the borate ions are loaded to further strengthen the paper sample. Compared with Comparative Example 1 without adding BC, the mechanical properties of the paper sample are increased to a certain extent.

Claims

1. A method for deacidifying paper by pressurized atomization of borate composite bacterial cellulose, characterized in that: The dispersion formed by the composite of borate and bacterial cellulose is applied to paper by atomization technology. Through the synergistic effect of atomized borate and bacterial cellulose, the deacidification and reinforcement of paper are achieved. The specific steps are as follows: Pre-treat the surface of paper documents to remove surface impurities, and place the paper in an atomization treatment device; Prepare a deacidified dispersion, dissolve borate and bacterial cellulose in a solvent to form a uniform composite dispersion, wherein the mass ratio of borate to bacterial cellulose is 1:1 to 100:1; The deacidified dispersion is atomized into tiny droplets by an atomizing device, so that the atomized borate and bacterial cellulose droplets can be evenly attached to the surface of the paper and the internal fiber gaps; the acidic substances inside the paper are neutralized by the synergistic effect of the atomized borate and bacterial cellulose, and the mechanical properties of the paper are improved by utilizing the physical reinforcement effect of the bacterial cellulose and the chemical cross-linking effect of the borate; The paper after atomization treatment is dried under certain conditions to complete the deacidification and strengthening process.

2. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 1, characterized in that: The borate is one or more of lithium tetraborate, sodium tetraborate or potassium tetraborate.

3. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 2, characterized in that: The mass fraction of the borate solution is 5 g / L to 20 g / L.

4. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 3, characterized in that: The mass ratio of the bacterial cellulose to the borate is 20:1 to 20:

5.

5. A paper deacidification method of pressurized atomized borate composite bacterial cellulose according to any one of claims 1 to 4, characterized in that: The atomizing device is a pressurized atomizing device, the air pressure is 0.15kg / cm² to 0.9kg / cm², and the test box temperature during atomization treatment is 25°C to 45°C.

6. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 5, characterized in that: The particle size of the atomized droplets ranges from 1 nm to 5 μm, so as to ensure that the droplets can effectively penetrate the fiber gaps inside the paper.

7. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 5, characterized in that: The dosage of the deacidification dispersion is 900 mL to 3000 mL to meet the deacidification requirements of paper of different sizes and thicknesses.

8. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 5, characterized in that: The atomization treatment time is 12 minutes to 60 minutes, and the specific time is adjusted according to the acidification degree and thickness of the paper.

9. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 1, characterized in that: The paper needs to be hung at room temperature for 24 to 72 hours before atomization treatment to remove static electricity and impurities on the surface of the paper.

10. The method for deacidifying paper by pressurized atomized borate composite bacterial cellulose according to claim 1, characterized in that: When the paper is placed in the atomization test box, it is laid flat or hung to ensure that the paper is evenly atomized.

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