Paper deacidification and reinforcement clay nanosheet dispersion liquid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of paper deacidification agents, and particularly relates to a paper deacidification and reinforcement clay nanosheet dispersion liquid as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, preliminary intercalation: adding a clay raw material into a sodium salt-containing aqueous solution, and stirring to form an intercalation structure containing hydrated sodium ions; s2, secondary intercalation: adding the preliminarily intercalated solution into a quaternary ammonium salt solution, and stirring to form a quaternary ammonium salt intercalated clay solution; and S3, cleaning and centrifuging: cleaning and centrifuging the solution subjected to secondary intercalation by using a cleaning solution to remove residual quaternary ammonium salt so as to form a nanosheet dispersion liquid. The raw materials used in the invention are green and environment-friendly, and low in cost; the whole preparation method is simple, efficient, low in requirements for equipment and energy consumption, safe in temperature in the reaction process and especially suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of paper deacidification agents, and in particular relates to a paper deacidification and reinforcement clay nanosheet dispersion liquid, a preparation method and an application thereof. Background Art

[0002] Since ancient times, paper has been the most widely used carrier in human civilization and has played an irreplaceable role in information recording and dissemination. Its preservation and restoration as a cultural heritage has become a cross-disciplinary technical issue involving the general public, cultural relics protection experts and scientific researchers.

[0003] Paper contains a large amount of cellulose, a linear polymer composed of glucose linked by glycosidic bonds. It also contains smaller amounts of hemicellulose and lignin, as well as possible sizing agents. These organic components, by their very nature, are inevitably affected by internal and external factors and subject to acidification, hydrolysis, and oxidation. Furthermore, acid-catalyzed hydrolysis of cellulose in paper is the primary cause of paper damage, leading to a sharp decrease in the cellulose's degree of polymerization and the mechanical properties of paper documents.

[0004] In traditional paper protection materials, organic materials primarily serve as reinforcement, while inorganic materials are limited to deacidification. Inorganic materials, primarily inorganic metals (such as magnesium oxide and magnesium hydroxide), can easily cause excessive alkalinity, leading to brittle and yellowing of the paper.

[0005] Organic materials, primarily organometallic (such as diethyl zinc) and ammonium (such as ammonia) deacidification agents, present significant challenges in terms of operational complexity and cost. For example, Chinese patent CN119571666A describes a paper deacidification and reinforcement microcapsule, its preparation method, and its application. This involves adding a calcium carbonate-ethanol suspension to a chitosan quaternary ammonium salt-carboxymethyl cellulose solution and subjecting it to high-speed shear emulsification. The high cost and operational requirements of the organic materials employed make the process complex and cumbersome, hindering industrial application.

[0006] Existing technologies have yet to achieve a breakthrough in the balance between reinforcement and deacidification, making it difficult to fully meet the practical needs of document preservation. Therefore, there is an urgent need to develop a paper deacidification and reinforcement clay nanosheet that has excellent deacidification and reinforcement capabilities, minimizes color variation, and is more suitable for industrial production in terms of cost and process flow. Summary of the Invention

[0007] The purpose of the present invention is to provide a paper deacidification reinforcement clay nanosheet dispersion and its preparation method and application, so as to solve the problem of how to provide a paper deacidification reinforcement clay nanosheet with excellent deacidification reinforcement ability, small color difference, and more suitable for industrial production in terms of cost and process flow.

[0008] To achieve the above object, the present invention provides the following solutions: A method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper, comprising: S1. Preliminary intercalation: adding clay raw materials into an aqueous solution containing sodium salt and stirring to form an intercalation structure containing hydrated sodium ions; S2, secondary intercalation: adding the initial intercalation solution to the quaternary ammonium salt solution and stirring to form a quaternary ammonium salt intercalated clay solution; S3. Washing and centrifugation: The secondary intercalation solution is washed and centrifuged with a washing solution to remove residual quaternary ammonium salt, thereby forming a nanosheet dispersion.

[0009] Preferably, the clay raw material includes at least one of montmorillonite, mica and kaolin.

[0010] Preferably, the sodium salt includes at least one of sodium nitrate, sodium chloride and sodium sulfate.

[0011] Preferably, the quaternary ammonium salt includes at least one of tetrabutylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0012] Preferably, the mass molar volume ratio of the clay, sodium salt and aqueous solution in step S1 is 1-5 kg:40-60 mol:30-80 L.

[0013] Preferably, the stirring speed in step S2 is 500-1000 rpm, and the stirring time is 6-10 h.

[0014] Preferably, the stirring speed in step S2 is 700-800 rpm, and the stirring time is 6-6.5 h.

[0015] Preferably, the mass volume ratio of the clay to the quaternary ammonium salt solution is 0.1-10 kg:10-100 L.

[0016] Preferably, in step S3, the number of times the intercalated modified clay nanosheets are washed with ethanol is 3 to 4 times.

[0017] A paper deacidification reinforcement clay nanosheet dispersion prepared by the preparation method.

[0018] The invention discloses an application of the paper deacidification and reinforcement clay nanosheet dispersion in paper deacidification and reinforcement.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: In the paper deacidification reinforcement clay nanosheet dispersion provided by the present invention, nanosheets are interwoven on the surface of paper fibers to form a reinforcement network, thereby improving mechanical properties; at the same time, the quaternary ammonium salt used for modification can realize the deacidification function, which can well meet the protection requirements of paper cultural relics.

[0020] The alkaline clay nanosheets in the deacidification dispersion provided by the present invention can react with the acidic substances in the paper to neutralize the acidic substances, thereby increasing the pH value of the paper and achieving the purpose of deacidification of the paper. With water or ethanol as a solvent, the method has good paper permeability and is suitable for deacidification treatment of different types of paper. By intercalating and exfoliating the clay, the dispersion is stable in the solvent, and no additional surfactant is required. The deacidification treatment is simple, convenient and uniform.

[0021] The deacidification dispersion prepared by the present invention is uniform, does not contain surfactants as dispersants, and fully disperses the clay nanosheets without agglomeration or precipitation, resulting in excellent deacidification. After treatment of paper, the paper is thoroughly deacidified and, if desired, a certain amount of alkaline clay nanosheets remain on the surface of the paper, slowing further erosion of the paper surface by acidic media that may be present in the storage environment. This reduces the risk of acid regurgitation and reduces the number of paper treatments required.

[0022] After treating paper with the deacidification dispersion provided by the present invention, the paper exhibits no warping, deformation, or wrinkling. This overcomes the problems of existing deacidification methods, such as aqueous solvents causing ink penetration and paper swelling, and organic solvents requiring the addition of fluorinated surfactants, which cause solvent contamination, reduced paper strength after deacidification, and warping.

[0023] After the paper is treated with the deacidification dispersion provided by the present invention, the color difference produced is very small, which overcomes the high color difference caused by the color of the material itself in the existing deacidification method, and is therefore suitable for deacidification treatment of paper of different colors.

[0024] After the paper is treated with the deacidification dispersion provided by the present invention, the tensile strength of the paper is greatly improved, and due to the high temperature resistance and stability of montmorillonite, the paper also has good thermal stability.

[0025] The raw materials used in the present invention are green, environmentally friendly and low in cost; the overall preparation method is simple and efficient, has low requirements on equipment and energy consumption, and the reaction process is safe and temperature-controlled, making it particularly suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work. Figure 1 This is a scanning electron microscope image of the tetrabutylammonium hydroxide intercalated modified montmorillonite nanosheets prepared in Example 1; Figure 2The transmission electron micrograph and selected area electron diffraction pattern of the tetrabutylammonium hydroxide intercalated montmorillonite nanosheets prepared in Example 1; Figure 3 X-ray diffraction patterns of the paper deacidification reinforcement clay nanosheet dispersion prepared in Example 1 before and after reinforcement of bamboo paper; Figure 4 This is a pH diagram of the paper deacidification reinforcement clay nanosheet dispersion prepared in Example 1 of the present invention before and after being reinforced with bamboo paper; Figure 5 This is a scanning electron microscope image of the paper deacidification reinforcement clay nanosheet dispersion prepared in Example 1 after being reinforced with bamboo paper; Figure 6 This is a color difference analysis chart of the paper deacidification reinforcement clay nanosheet dispersion prepared in Example 1 after being reinforced with bamboo paper. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] This embodiment is a method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper, and the specific steps include: S1. Preliminary intercalation: 2 g of montmorillonite raw material was dispersed in 100 mL of aqueous solution, 30 g of sodium sulfate was added for preliminary intercalation, and the mixture was stirred at 450 rpm for 6 h.

[0031] S2, secondary intercalation: The preliminary intercalation solution was added into 20 mL of a 25% tetrabutylammonium hydroxide aqueous solution, and the mixture was stirred at 750 rpm for 9 hours to obtain tetrabutylammonium hydroxide intercalated modified montmorillonite nanosheets.

[0032] S3, cleaning and centrifugation The mixture was washed and centrifuged three times with 99.8% pure ethanol at a speed of 25,000 rpm to avoid aggregation of the nanosheets. Finally, the montmorillonite nanosheets were dispersed in the ethanol to prepare a clay nanosheet dispersion.

[0033] A clay nanosheet dispersion was prepared by the method of Example 1. The clay nanosheet dispersion was alkaline.

[0034] The tetrabutylammonium hydroxide modified montmorillonite nanosheets in Example 1 were observed by scanning electron microscopy, and the images observed were as follows: Figure 1 As shown in .

[0035] The tetrabutylammonium hydroxide modified montmorillonite nanosheets in Example 1 were observed by transmission electron microscopy, and the images observed were as follows: Figure 2 As shown in .

[0036] The tetramethylammonium hydroxide-modified montmorillonite nanosheets prepared by the above method can react with the acidic substances in the paper to neutralize the acidic substances, thereby increasing the pH value of the paper and achieving the purpose of deacidification of the paper.

[0037] Using ethanol as solvent, it has good paper penetration and is suitable for deacidification treatment of different types of paper.

[0038] By intercalation and exfoliation modification of montmorillonite, the dispersion in ethanol is stable without the need for additional surfactants. The deacidification treatment is simple, convenient and uniform.

[0039] Example 2

[0040] This embodiment is a method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper. The difference from Example 1 is that the specific steps include: S1. Preliminary intercalation: 2 g of montmorillonite raw material was dispersed in 100 mL of aqueous solution, 30 g of sodium nitrate was added for preliminary intercalation, and the mixture was stirred at 450 rpm for 6 h.

[0041] S2, secondary intercalation: The preliminary intercalation solution was added into 20 mL of a 25% tetrabutylammonium hydroxide aqueous solution, and the mixture was stirred at 750 rpm for 9 hours to obtain tetrabutylammonium hydroxide intercalated modified montmorillonite nanosheets.

[0042] S3, cleaning and centrifugation The mixture was washed and centrifuged three times with 99.8% pure ethanol at a speed of 25,000 rpm to avoid aggregation of the nanosheets. Finally, the montmorillonite nanosheets were dispersed in the ethanol to prepare a clay nanosheet dispersion.

[0043] The tetramethylammonium hydroxide-modified montmorillonite nanosheets prepared by the above method can react with the acidic substances in the paper to neutralize the acidic substances, thereby increasing the pH value of the paper and achieving the purpose of deacidification of the paper.

[0044] Using ethanol as solvent, it has good paper penetration and is suitable for deacidification treatment of different types of paper.

[0045] By intercalation and exfoliation modification of montmorillonite, the dispersion in ethanol is stable without the need for additional surfactants. The deacidification treatment is simple, convenient and uniform.

[0046] Example 3

[0047] This embodiment is a method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper. The difference from Example 1 is that the specific steps include: S1. Preliminary intercalation: 2 g of montmorillonite raw material was dispersed in 100 mL of aqueous solution, 30 g of sodium chloride was added for preliminary intercalation, and the mixture was stirred at 450 rpm for 6 h.

[0048] S2, secondary intercalation: The preliminary intercalation solution was added into 20 mL of a 25% tetrabutylammonium hydroxide aqueous solution, and the mixture was stirred at 750 rpm for 9 hours to obtain tetramethylammonium hydroxide intercalated modified montmorillonite nanosheets.

[0049] S3, cleaning and centrifugation The mixture was washed and centrifuged three times with 99.8% pure ethanol at a speed of 25,000 rpm to avoid aggregation of the nanosheets. Finally, the montmorillonite nanosheets were dispersed in the ethanol to prepare a clay nanosheet dispersion.

[0050] The tetramethylammonium hydroxide-modified montmorillonite nanosheets prepared by the above method can react with the acidic substances in the paper to neutralize the acidic substances, thereby increasing the pH value of the paper and achieving the purpose of deacidification of the paper.

[0051] Using ethanol as solvent, it has good paper penetration and is suitable for deacidification treatment of different types of paper.

[0052] By intercalation and exfoliation modification of montmorillonite, the dispersion in ethanol is stable without the need for additional surfactants. The deacidification treatment is simple, convenient and uniform.

[0053] Example 4

[0054] This embodiment is a method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper. The difference from Example 1 is that the specific steps include: S1. Preliminary intercalation: 2 g of montmorillonite raw material was dispersed in 100 mL of aqueous solution, 30 g of sodium sulfate was added for preliminary intercalation, and the mixture was stirred at 450 rpm for 6 h.

[0055] S2, secondary intercalation: The preliminary intercalation solution was added to 20 mL of a 25% tetraethylammonium hydroxide aqueous solution, and the mixture was stirred at 750 rpm for 6 h to obtain tetraethylammonium hydroxide intercalated modified montmorillonite nanosheets.

[0056] S3, cleaning and centrifugation The mixture was washed and centrifuged three times with 99.8% pure ethanol at a speed of 25,000 rpm to avoid aggregation of the nanosheets. Finally, the montmorillonite nanosheets were dispersed in the ethanol to prepare a clay nanosheet dispersion.

[0057] Example 5

[0058] This embodiment is an application method of tetrabutylammonium hydroxide modified montmorillonite nanosheets, specifically comprising: The acidified bamboo paper was immersed in the clay nanosheet dispersion made of tetrabutylammonium hydroxide-modified montmorillonite nanosheets in Example 1, and the bamboo paper was always kept completely immersed in the dispersion for 5 minutes. After completion, the paper was taken out and dried in an oven at 25°C.

[0059] The dried bamboo paper was subjected to X-ray diffraction, and the results were as follows: Figure 3-4 As shown in Figure 3 The X-ray diffraction in the figure shows that the tetrabutylammonium hydroxide modified montmorillonite nanosheets of Example 1 are attached to the paper, and the peak at about 5 degrees is the peak of the montmorillonite nanosheets. Figure 4 The X-ray diffraction in FIG shows that the paper deacidification dispersion of this embodiment has a significant deacidification effect on bamboo paper, and the final pH value is adjusted to 7.8.

[0060] The bamboo paper was observed by scanning electron microscope. Figure 5 As shown in Figure 5 As can be seen from the image in, the tetrabutylammonium hydroxide modified montmorillonite nanosheets of Example 1 are attached to the cellulose of the paper.

[0061] The colorimetric analysis of bamboo paper was carried out using a colorimeter to measure the L (brightness), a (red + / green-), and b (yellow + / blue-) values. The test results are as follows: Figure 6 As shown in FIG, the color difference of the bamboo paper sample after being protected by the clay nanosheet dispersion in Example 1 changes It is about 1, which proves that the clay nanosheet dispersion of Example 1 has good color fidelity.

[0062] Comparative Example 1: This comparative example uses a common MgO-ethanol dispersion as a deacidifying agent to deacidify paper. The difference from Example 5 is that the specific steps include: The acidified bamboo paper was immersed in MgO-ethanol dispersion, and the bamboo paper was always kept completely immersed in the dispersion for 5 minutes. After completion, the paper was taken out and dried in an oven at a temperature of 25°C.

[0063] The colorimetric analysis of bamboo paper was performed using a colorimeter to measure the L (brightness), a (red + / green-), and b (yellow + / blue-) values. The color difference changes of bamboo paper samples after being protected by MgO-ethanol dispersion were also observed. is 2.21, which is close to the threshold that can be recognized by the human eye ( <3.0).

[0064] The tensile strength of bamboo paper was analyzed and tested using a DR-507A tensile testing machine produced by Dongguan Dongri Instrument Co., Ltd. The experimental conditions were based on the Chinese standard GB / T 12914-2018 "Paper and paperboard - Determination of tensile strength - Constant rate of tension (20 mm min-1)". The bamboo paper size was 5 cm × 1.5 cm, and the tensile speed was set to 20 mm min-1 for tensile testing.

[0065] The tensile strength of the reinforced bamboo paper of Example 5 was tested, and the final tensile strength was 12.8 MPa. The tensile strength of the reinforced bamboo paper of Comparative Example 1 was tested, and the final tensile strength was 4.1 MPa.

[0066] Comparison with Comparative Example 1 reveals that the deacidified paper-reinforced clay nanosheet dispersions prepared in Examples 1-3 are stable and uniform. The protected paper exhibits minimal color variation, increases in tensile strength from 4.1 MPa to over 10 MPa, and thermogravimetric analysis shows a decrease in mass loss from 26% to approximately 10% at 250°C.

[0067] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper, characterized in that: include: S1. Preliminary intercalation: adding clay raw materials into an aqueous solution containing sodium salt and stirring to form an intercalation structure containing hydrated sodium ions; S2, secondary intercalation: adding the preliminary intercalation solution to a 25% quaternary ammonium salt aqueous solution and stirring to form a quaternary ammonium salt intercalated clay solution; S3. Washing and centrifugation: The secondary intercalation solution is washed and centrifuged with a washing solution to remove residual quaternary ammonium salt, thereby forming a nanosheet dispersion.

2. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The clay raw material includes at least one of montmorillonite, mica and kaolin.

3. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The sodium salt includes at least one of sodium nitrate, sodium chloride and sodium sulfate.

4. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The quaternary ammonium salt includes at least one of tetrabutylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide.

5. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The mass molar volume ratio of the clay, sodium salt and aqueous solution in step S1 is 1-5 kg: 40-60 mol: 30-80 L.

6. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The stirring speed in step S2 is 500-1000 rpm, and the stirring time is 6-10 hours.

7. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The stirring speed in step S2 is 700-800 rpm, and the stirring time is 6-6.5 h.

8. The method for preparing a dispersion of clay nanosheets for deacidification and reinforcement of paper according to claim 1, characterized in that: The mass volume ratio of the clay to the quaternary ammonium salt aqueous solution with a concentration of 25% is 0.1-10 kg: 10-100 L.

9. A dispersion of clay nanosheets for deacidification and reinforcement of paper prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the paper deacidification and reinforcement clay nanosheet dispersion according to claim 9 in paper deacidification and reinforcement.

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