Method for deacidifying and reinforcing acidified paper cultural relics

Abstract

The invention discloses a method for deacidifying and reinforcing an acidified paper cultural relic, which specifically comprises the following steps: placing the acidified paper cultural relic to be treated in a supercritical kettle, conveying a deacidifying and reinforcing liquid into the supercritical kettle, then introducing supercritical carbon dioxide, adjusting the temperature and pressure of the supercritical kettle, and carrying out deacidifying and reinforcing treatment on the paper cultural relic. The deacidification reinforcement liquid is an ethanol solution of polyethyleneimine. According to the invention, polyethyleneimine is used for deacidification and reinforcement of paper by adopting a supercritical fluid technology, new functional groups appear in the treated paper, and the color difference of the paper before and after treatment is small. The supercritical fluid technology is combined with the deacidification agent, so that not only can deacidification be realized, but also the physical strength of the paper can be obviously improved, and an in-situ protection effect on the paper cultural relics is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of cultural relics protection, and in particular relates to a method for deacidification and reinforcement of acidified paper cultural relics. Background Art

[0002] Paper cultural relics are an important part of cultural heritage, recording a large amount of precious historical data. According to the first national movable cultural relics census data bulletin, as of October 31, 2016, there were 108,154,907 movable cultural relics in China, of which paper cultural relics accounted for more than 30%. However, due to improper preservation or long-term preservation, they are suffering from aging, oxidation, acidification and other hazards at a rate of 1.33% per year. Among them, 95% of paper documents and books are acidic paper, and about 60% have a pH value of less than 5. Paper acidification has become a major problem that plagues the protection of paper cultural relics.

[0003] At present, the reinforcement and deacidification of paper cultural relics are mainly concentrated in aqueous solution method, non-aqueous solution method, gas phase method, etc. The aqueous solution method uses alkaline or bicarbonate of calcium, magnesium, and barium to prepare an aqueous solution, and then uses hydroxyethyl cellulose as a reinforcement agent to achieve aqueous solution deacidification; the disadvantage is that the paper is easy to swell when absorbing water, and the surface is easy to deform or wrinkle. The non-aqueous solution method dissolves or disperses deacidification materials such as magnesium oxide, magnesium carbonate, ethoxy compounds of magnesium and titanium, methoxymethyl magnesium carbonate, and organic reinforcement materials in an organic solvent. As the deacidification proceeds, the solvent evaporates continuously to achieve non-aqueous solution deacidification; the disadvantage is that most of the organic solvents used will have an impact on the environment. For example, the release of Freon will damage the ozone layer, and perfluoroheptane is a permanent organic pollutant. The gas phase method uses deacidification materials such as ammonia, diethyl zinc, morpholine, cyclohexyl carbonate, ethylene oxide, etc. to form gas under vacuum to penetrate into paper cultural relics to achieve the purpose of gas phase deacidification, but the gas phase deacidification method can generally only deacidify cultural relics, not reinforce them.

[0004] Most of the deacidification agents currently used contain alkaline metal ions, which will catalyze the hydrolysis and breakage of cellulose in paper, affecting the integrity of paper. In addition, most of the deacidification agents used can only achieve the deacidification effect, but cannot be reinforced, and the deacidification and reinforcement process is complicated. Therefore, the present invention designs and selects suitable paper cultural relics deacidification and reinforcement composite functional materials, and combines relevant processes to prevent environmental pollution caused by the deacidification and reinforcement process. Summary of the invention

[0005] The purpose of the present invention is to provide a method for deacidification and reinforcement of acidified paper cultural relics, which comprises placing the acidified paper cultural relics to be treated in a supercritical reactor, conveying a deacidification and reinforcement liquid into the supercritical reactor, and then introducing supercritical carbon dioxide, adjusting the temperature and pressure of the supercritical reactor, and performing deacidification and reinforcement treatment on the paper cultural relics;

[0006] The deacidification and consolidation liquid is an ethanol solution of polyethyleneimine.

[0007] Furthermore, the mass concentration of the polyethyleneimine is 0.1% to 5%.

[0008] Furthermore, the molecular weight of the polyethyleneimine is 300-10000, preferably 600-1800.

[0009] Furthermore, the flow rate of the supercritical carbon dioxide is 3-6 L / min.

[0010] Furthermore, in the step of adjusting the temperature and pressure of the supercritical fluid, the temperature is adjusted to 32-60°C, and the pressure is adjusted to 8-16MPa.

[0011] Furthermore, the deacidification and reinforcement treatment time is 20-120 minutes.

[0012] In one embodiment of the present invention, a 15 cm×21 cm acidified paper is taken and placed in a supercritical reactor; 10 mL of a 1% polyethyleneimine (molecular weight 1800) ethanol solution is taken and introduced into the supercritical reactor in which the acidified paper is placed; the temperature in the supercritical reactor is adjusted to 40° C. and the pressure is adjusted to 16 MPa; the flow rate of CO2 is 4 L / min; the pressure is released after 35 minutes; the paper is taken out after the pressure drops to normal pressure, thereby completing the deacidification and reinforcement treatment of the acidified paper.

[0013] In another embodiment of the present invention, a 15 cm×21 cm acidified paper is taken and placed in a supercritical reactor; 10 mL of a 1% polyethyleneimine (molecular weight 600) ethanol solution is taken and introduced into the supercritical reactor in which the acidified paper is placed; the temperature in the supercritical reactor is adjusted to 40° C. and the pressure is adjusted to 10 MPa; the flow rate of CO2 is 4 L / min; the pressure is released after 45 minutes; the paper is taken out after the pressure drops to normal pressure, thereby completing the deacidification and reinforcement treatment of the acidified paper.

[0014] The pH value of the paper treated by the method of the invention is between 6.9 and 8.5, the alkali reserve can reach 0.709 to 1.198 mol / kg, and the mechanical strength can be increased by 10 to 20%.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0016] 1. The present invention uses polyethyleneimine as a deacidification reinforcement agent. Polyethyleneimine is safe and non-toxic, and polyethyleneimine is a wet strength agent for paper, which is an inherent component of paper. Deacidification of paper can not only achieve the deacidification of paper cultural relics, but also in-situ reinforcement of paper cultural relics from the fiber level. No metal salt ions are introduced during the deacidification reinforcement process, thereby preventing the subsequent hydrolysis of paper fibers by metal ions in the paper.

[0017] 2. The present invention uses polyethyleneimine as a deacidification reinforcing agent. The amino group in polyethyleneimine is alkaline and can react with acidic substances in paper, thereby improving the deacidification efficiency without introducing additional acidic substances. The amino group in polyethyleneimine can chelate metal ions in paper to prevent further hydrolysis of paper fibers. In addition, the amino group in polyethyleneimine can form hydrogen bonds with hydroxyl groups in paper fibers to reinforce the paper in situ.

[0018] 3. The present invention adopts polyethyleneimine as a deacidification reinforcement agent, which can be used for the deacidification reinforcement treatment of paper cultural relics with different acidification degrees. The pH value, mechanical strength and alkali reserve of the paper after deacidification reinforcement all achieve good results.

[0019] 4. The present invention uses supercritical CO2 fluid technology to deacidify and reinforce acidified paper, and realizes in-situ deacidification and reinforcement of paper in an integrated manner. Supercritical CO2 is used as a solvent and paper penetrant, and can evenly penetrate into the gaps and interior of paper fibers under high pressure, and the deacidification and reinforcement effects are more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The results of the effect of supercritical CO2 pressure on the pH value and alkali reserve of paper after deacidification and reinforcement in Example 1 are shown.

[0021] Figure 2 The results of the effect of supercritical CO2 pressure on the mechanical properties of paper after deacidification and reinforcement in Example 1.

[0022] Figure 3 The results of the effect of the molecular weight of polyethyleneimine on the pH value and alkali reserve of paper after deacidification and reinforcement in Example 2 are shown.

[0023] Figure 4 The results of the effect of the molecular weight of polyethyleneimine on the mechanical properties of paper after deacidification and reinforcement in Example 2 are shown.

[0024] Figure 5 This is the infrared spectra of the paper surface before and after treatment with polyethyleneimine of different molecular weights in Example 2. DETAILED DESCRIPTION

[0025] Deacidification and reinforcement are important research contents in the protection of paper cultural relics, but the limitations of existing deacidification and reinforcement technologies restrict the development of paper cultural relics protection. The present invention adopts supercritical fluid technology to use polyethyleneimine for deacidification and reinforcement of paper, and uses carbon dioxide as a supercritical solvent to study the effects of supercritical pressure and the amount of polyethyleneimine on the deacidification and reinforcement effects of paper. The results show that the pH value, alkali reserve and mechanical properties of the treated paper are significantly improved compared with those of untreated paper. Among them, the pH value of the paper can be increased from 4.12 to 8.17, and the alkali reserve is increased to more than 0.7 mol / kg. Characterization analysis shows that new functional groups appear in the paper after treatment, and the color difference of the paper before and after treatment is small. The use of supercritical fluid technology combined with a deacidifying agent can not only deacidify, but also significantly improve the physical strength of the paper, which plays a role in in-situ protection of paper cultural relics.

[0026] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0028] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0029] Example 1

[0030] Effect of polyethyleneimine on deacidification and strengthening of paper under different supercritical CO2 pressures

[0031] Take a whole page of paper (15cm×21cm) from a book in 1950 and place it in a supercritical reactor; prepare 10mL of ethanol solution of polyethyleneimine (molecular weight 1200) with a mass concentration of 1%, and pass it into the supercritical reactor where the acidified paper is placed; the temperature in the supercritical reactor is 40°C, and the supercritical pressures are set to 8MPa, 10MPa and 14MPa respectively; the CO2 flow rate is 4L / min; release the pressure after 35min; take out the paper after the pressure drops to normal pressure, and complete the deacidification and reinforcement treatment of the acidified paper.

[0032] The pH value, alkali reserve and mechanical properties (tensile strength and folding times) of the paper surface before and after deacidification and reinforcement treatment were measured. Figure 1 and 2As shown. Using polyethyleneimine as a deacidifying agent and supercritical CO2 fluid to deacidify and reinforce paper, the pH value of the paper increased under different pressures, from 4.12 of the base paper to above 7.5, and reached 8.17 under a pressure of 10MPa; the alkali reserve varied with the change of supercritical pressure, all greater than 0.7mol / kg, which shows that the use of polyethyleneimine changed the surface pH value of the fragile paper, neutralized the acidic substances in the paper, and the paper surface had a high alkali reserve and was weakly alkaline. At the same time, the tensile strength and folding times of the paper were improved after treatment.

[0033] Example 2

[0034] Effects of different molecular weight polyethyleneimine on deacidification and strengthening of paper

[0035] Take a whole page of paper (15cm×21cm) from a book in 1950 and place it in a supercritical reactor; prepare 10mL of ethanol solution of polyethyleneimine (mass concentration is 1%) with molecular weights of 600, 1200 and 1800 respectively, and pass it into the supercritical reactor where the acidified paper is placed; set the temperature in the supercritical reactor to 40°C and the supercritical pressure to 10MPa; the CO2 flow rate is 4L / min; release the pressure after 40 minutes; take out the paper after the pressure drops to normal pressure, and complete the deacidification and reinforcement treatment of the acidified paper.

[0036] The pH value, alkali reserve and mechanical properties (tensile strength and folding times) of the paper surface before and after deacidification and reinforcement treatment were measured. Figure 3 and 4 As shown. Polyethyleneimine with different molecular weights has a good deacidification effect on paper, the pH value is significantly improved, and the paper is weakly alkaline. The alkali reserve of paper increases rapidly from zero to 0.8 mol / kg. In addition, polyethyleneimine with different molecular weights has a significant improvement on the mechanical properties of paper, enhancing the tensile strength of paper and significantly improving the number of folding endurance. The functional groups of paper fibers before and after treatment were analyzed, such as Figure 5 ATR-FTIR characterization shows that compared with the base paper, new peaks appear at low wavenumbers; in addition, at 1000cm -1 The new peak compared with the base paper is attributed to the CN group at 3690 cm -1 New peaks also appeared at 3330cm. The appearance of new peaks indicates that polyethyleneimine interacts with paper fibers to form new functional groups or compounds. Compared with the base paper, the peak at 3330cm -1 There is a slight change in the position of the peak attributed to the hydroxyl group, which may be due to the formation of hydrogen bonds between polyethyleneimine and paper fibers, which improves the strength of the paper.

[0037] Paper whiteness is an indicator of the color of the paper surface, which is of great significance for evaluating the safety of paper before and after deacidification. The whiteness of paper is mainly expressed by L, a, and b values, where L value indicates the lightness of the paper, a indicates the red-green degree of the paper, and b value indicates the yellow-blue degree of the paper. The color difference and whiteness ΔE results of paper treated with polyethyleneimine of different molecular weights under supercritical CO2 fluid are shown in Table 1.

[0038] Table 1 Effect of polyethyleneimine molecular weight on whiteness and color difference of paper after deacidification

[0039]

[0040] The results show that different molecular weight polyethyleneimine has little effect on the L, a, and b values ​​of paper. At the same time, different molecular weight polyethyleneimine has no obvious effect on the color difference of paper, indicating that this method has no obvious effect on the color of paper before and after deacidification.

Claims

1. A method for deacidification and reinforcement of acidified paper cultural relics, characterized in that: The acidified paper cultural relics to be treated are placed in a supercritical reactor, a deacidification and reinforcement liquid is transported into the supercritical reactor, and then supercritical carbon dioxide is introduced, and the temperature and pressure of the supercritical reactor are adjusted to perform deacidification and reinforcement treatment on the paper cultural relics; The deacidification and consolidation liquid is an ethanol solution of polyethyleneimine.

2. The method according to claim 1, characterized in that The mass concentration of the polyethyleneimine is 0.1% to 5%.

3. The method according to claim 2, characterized in that The molecular weight of the polyethyleneimine is 300-10000.

4. The method according to claim 1, characterized in that: The flow rate of the supercritical carbon dioxide is 3-6 L / min.

5. The method according to claim 1, characterized in that In the step of adjusting the temperature and pressure of the supercritical fluid, the temperature is adjusted to 32-60° C., and the pressure is adjusted to 8-16 MPa.

6. The method according to claim 1, characterized in that The deacidification and strengthening treatment takes 20-120 minutes.

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