Anhydrous liquid phase-based paper literature deacidification effect evaluation method

Abstract

The invention relates to a paper literature deacidification effect evaluation method based on an anhydrous liquid phase, which comprises the following steps: setting an effectiveness index and a safety index, obtaining each index value of a deacidified paper sample by adopting a corresponding detection method, and comparing the values with a preset threshold value to realize evaluation of the deacidification effect. The effectiveness indexes comprise pH, alkali reserves, deacidification uniformity, polymerization degree and zero-distance tensile strength, and the safety indexes comprise chromatic aberration, appearance deformation and deacidification liquid safety; the deacidification uniformity is evaluated through the distribution uniformity of alkali reserves, and the distribution uniformity of the alkali reserves is that the relative standard deviation of the alkali reserves of a plurality of parts of the paper sample is less than 30%, and the alkali reserves of each part are 0.12-0.60 mol / kg. According to the method, systematic and comprehensive evaluation on the deacidification effect is realized, a clear standard can be provided for industrial admission of deacidification materials and processes, invalid or harmful deacidification treatment is avoided, development of a deacidification repair technology is promoted, and long-term storage and safe utilization of paper documents are realized.

Description

Technical Field

[0001] This invention relates to the field of paper document restoration and preservation technology, specifically to a method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase. Background Technology

[0002] Paper, as a medium for writing and document archives, plays a vital role in recording history and transmitting civilization. The vast amount of ancient books and documents preserved in my country throughout history were mostly written and printed on handmade or machine-made paper. They are precious cultural heritage of the Chinese nation, possessing irreplaceable historical and cultural value. However, with the passage of time, paper documents undergo a series of destructive changes, including acidification, yellowing, brittleness, insect infestation, and a decline in mechanical properties.

[0003] Acidification is the main culprit affecting the long-term preservation of paper documents. Deacidification and restoration of paper documents has received widespread attention worldwide, but research has mainly focused on deacidification materials, processes, and equipment, with very little research on evaluating the effectiveness of deacidification. Only a few institutions both domestically and internationally have conducted evaluation studies on the effectiveness of deacidification, achieving some results.

[0004] In 1991, the Canadian Conservation Institute evaluated three commercial large-scale deacidification processes (Wei T'O, DEZ, and FMC), with evaluation indicators including pH value, alkali reserves, Lab value, zero-distance tensile strength, degree of polymerization, and carbonyl group.

[0005] In 1994, the Library of Congress evaluated the Bookkeeper deacidification process, using indicators such as pH value, alkali reserves, deacidification uniformity, strength indicators before and after aging, and whiteness and color indicators.

[0006] In 2010, the National Diet Library of Japan launched a survey on the safety and effectiveness of batch and overall deacidification technologies. The survey mainly evaluated the safety and effectiveness of DAE deacidification technology and Bookkeeper deacidification technology, which had been used in Japan. The deacidification test subjects were mainly Japanese domestic publications from the 1950s and 1980s (162 double-sided printed materials), covering Diet minutes, books, magazines, newspapers, maps (diazo salt photosensitive paper), coated paper, neutral paper, tracing paper, Japanese books, leather books, bound volumes, documents in storage boxes, labels, sticky notes, and markings written with ballpoint pens or highlighters.

[0007] The main evaluation indicators are: pH value, alkali content, degree of polymerization, while also taking into account strength performance indicators and subjective evaluation of appearance performance.

[0008] In 2011, the German National Library and the Berlin State Library used Papersave. TM LibertecTM and CSCBook Saver TM The process involved large-scale deacidification of a portion of its collections from 1994 (DNB) and 1998 (SBB) to 2011. The sustainability of this large-scale deacidification was scientifically assessed through analysis of 443 deacidified books from the two libraries. The article points out that the quality and sustainability of large-scale deacidification can currently only be evaluated using two parameters: the pH value of the treated paper and the concentration of the so-called alkaline reserve deposited in the paper structure.

[0009] The International Organization for Standardization (ISO) published ISO / TS18344:2016, "Effectiveness of paper deacidification processes," in 2016. In 2023, my country revised and adopted the national standard GB / Z42964-2023, "Effectiveness of Deacidification Processes for Library Paper Documents," which uses pH value, alkali reserves, deacidification uniformity, and degree of polymerization as evaluation indicators, while folding endurance is an optional indicator.

[0010] These evaluation studies and findings have provided valuable guidance for standardizing deacidification operations and evaluating deacidification effects. However, existing evaluation methods have limitations. The latest ISO / TS18344:2016 and GB / Z 42964-2023 standards specify a pH level above 6.5 without mentioning an upper limit. However, a higher pH after deacidification is not necessarily better. Excessively high pH levels can lead to alkaline hydrolysis and significant color changes in paper documents. Similarly, higher alkali reserves are not always better; excessive alkali reserves can cause significant color changes and blurred ink. Therefore, deacidification effect evaluation should have upper limits to avoid over-deacidification affecting paper documents.

[0011] Meanwhile, ISO / TS18344, published in 2016, only evaluates the effectiveness of deacidification processes and does not set appearance performance indicators. Therefore, researching scientific, systematic, and comprehensive paper-based methods for evaluating the effectiveness of deacidification is necessary and urgent for the healthy development of the deacidification industry, guiding industry access for deacidification materials and methods, and improving the deacidification and remediation effect. Summary of the Invention

[0012] To address the problems existing in the prior art, the purpose of this invention is to provide a method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase, which can scientifically evaluate the deacidification and repair effect of paper documents based on anhydrous liquid phase, taking into account both effectiveness and safety, and improving the reliability of detection.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase includes the following steps: by setting effectiveness indicators and safety indicators, the paper sample after deacidification is tested using corresponding detection methods to obtain the values ​​of each indicator, and the values ​​are compared with preset thresholds to evaluate the deacidification effect;

[0015] The effectiveness indicators include pH, alkali reserves, deacidification uniformity, degree of polymerization, and zero-distance tensile strength; the safety indicators include color difference, appearance deformation, and safety of the deacidification solution.

[0016] The uniformity of deacidification is evaluated by the uniformity of alkali storage distribution, wherein the relative standard deviation of alkali storage in multiple parts of the paper sample is less than 30%, and the alkali storage in each part is between 0.12 and 0.60 mol / kg.

[0017] Furthermore, the pH threshold of the effectiveness index is 7.5–10, and the alkali storage threshold is 0.12–0.60 mol / kg.

[0018] Furthermore, the deacidification uniformity also includes the uniformity of the deacidification element content distribution. The uniformity of the deacidification element content distribution is determined by SEM-EDS detection of the metal element content in the cross-section of the paper sample. The relative standard deviation of the detection values ​​in multiple parts is less than 30%. The uniformity of the deacidification element content distribution is an optional indicator.

[0019] Furthermore, the degree of polymerization index requires that, after accelerated aging, the degree of polymerization value of the deacidified paper sample is higher than that of the undeacidified control group paper sample.

[0020] Furthermore, the zero-pitch tensile strength index requires that, after accelerated aging, the zero-pitch tensile strength value of the deacidified paper sample is higher than that of the undeacidified control group paper sample.

[0021] Furthermore, the color difference index is the color difference value ΔE between the paper samples before and after deacidification. * The color difference value ΔE is not greater than 3.0. * Calculated using the following formula:

[0022]

[0023] Where: ΔE * The color difference value of the paper document before and after deacidification; ΔL * Δa represents the difference in brightness L* of the paper document before and after deacidification. * Δb represents the difference in red-green hue (a*) of the paper document before and after deacidification; * The difference in yellow-blue tint b* between the paper document before and after deacidification.

[0024] Furthermore, the appearance deformation indicators include the shrinkage rate in the length, width, and thickness directions of the paper sample, which is no more than 1.50%, and there is no adhesion, warping, or wrinkling.

[0025] Furthermore, the safety of the deacidification solution is evaluated by the following standards: the air in the deacidification operation and storage environment complies with GB / T 18883, and the deacidification solution is tested by GB / T 21606 and belongs to GHS category 5 / unclassified.

[0026] Furthermore, the effectiveness index also includes folding endurance, which is an optional index. It is required that the folding endurance value of the deacidified paper sample after accelerated aging is higher than that of the control group paper sample without deacidification.

[0027] Furthermore, the safety indicators also include the image and text color density change rate, which is an optional indicator, wherein the change rate of black samples is no greater than 6% and the change rate of colored samples is no greater than 3%.

[0028] In summary, the present invention has the following advantages:

[0029] This application provides a method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase. By controlling the upper and lower limits of pH threshold and alkali storage threshold, it effectively avoids damage to paper documents caused by excessive deacidification and balances the deacidification effect with document safety. For the first time, the evaluation index is divided into effectiveness index and safety index. The effectiveness index ensures the durability of the documents after deacidification, while the safety index ensures the usability of the documents, achieving dual protection of durability and safety. Regarding the uniformity of deacidification, it proposes the relative standard deviation of alkali storage distribution and the quantitative standard of alkali storage in each part, solving the problem of ambiguity in the uniformity evaluation of existing methods. Regarding appearance deformation, it clarifies the quantitative requirements of length, width, and thickness expansion rates, replacing the subjective judgment of existing technologies. Regarding the safety of deacidification liquid, it ensures the environmental safety of deacidification operation and document use by clarifying standards. It introduces zero-pitch tensile strength as a core strength index, which is less affected by paper uniformity and has reliable data. It is especially suitable for fragile documents with severe aging and makes up for the limitations of folding endurance. Through a systematic index system and threshold requirements, this method achieves a systematic and comprehensive evaluation of the deacidification effect, which can provide clear standards for industry access of deacidification materials and processes, avoid ineffective or harmful deacidification treatments, promote the standardization and scientific development of deacidification and remediation technologies, and ultimately achieve the long-term preservation and safe utilization of paper documents. Attached Figure Description

[0030] Figure 1 This embodiment uses a segmentation mode for detecting alkali reserves to evaluate the uniformity of deacidification.

[0031] Figure 2 This is a schematic diagram of SEM-EDS sampling used in this embodiment to evaluate the uniformity of the distribution of deacidified element content. Detailed Implementation

[0032] The present invention will now be described in further detail.

[0033] Anhydrous liquid phase deacidification system (suspension type) refers to a deacidification system that uses anhydrous organic solvents to disperse alkaline particles. Currently, more than 90% of paper document deacidification processes worldwide use anhydrous liquid phase deacidification systems.

[0034] This invention addresses the need for evaluating the deacidification and restoration effects of paper documents, overcomes the shortcomings of existing evaluation methods, and provides a more systematic method for evaluating the deacidification and restoration effects of paper documents based on anhydrous liquid phase.

[0035] An evaluation method for deacidification and restoration of paper documents based on anhydrous liquid phase is proposed. By setting reasonable evaluation indicators, reliable detection methods and feasible indicator thresholds, the deacidification and restoration effect of paper documents based on anhydrous liquid phase can be scientifically evaluated.

[0036] The purpose of deacidification and restoration of paper documents is to improve their durability while ensuring usability, so as to better utilize and research them. Evaluation of the effectiveness of deacidification and restoration requires ensuring usability through safety indicators and ensuring durability through effectiveness indicators. The evaluation indicators, detection methods, and threshold values ​​for this evaluation method are as follows:

[0037] Evaluation indicators

[0038] pH

[0039] pH is the most direct indicator of the acidity or alkalinity of paper. The pH value of paper and its changes are the most direct and obvious measure of paper durability. Therefore, the pH value of deacidified paper documents is one of the important indicators for evaluating the deacidification effect.

[0040] Alkali reserves

[0041] The purpose of deacidification is not only to neutralize acids, but also to deposit an alkaline substance to neutralize any future acidity. The adequacy and stability of the alkaline reserve are important criteria for the success of deacidification intervention, and therefore also one of the important indicators for evaluating the quality of deacidification.

[0042] Uniformity

[0043] Paper is composed of multiple layers, each layer being a porous material made up of numerous interwoven fibers. The porous structure of paper is a complex system of interconnected channels (capillaries) of varying sizes. External acidic substances penetrate deep into the paper through these channels, especially in acidic paper, where the acidic substances adhere to the walls of these channels and become part of the paper itself.

[0044] Therefore, the uniformity of deacidification is very important. The uniformity of the distribution of deacidified substances in paper documents is one of the important indicators for evaluating the quality of deacidification. For batch deacidification, the biggest challenge is uniformity. The uniformity of deacidification can be evaluated by the uniformity of the distribution of alkali reserves and the uniformity of the distribution of metal elements in the deacidified substances.

[0045] Alkali content reflects the amount of deacidified substances per unit weight of paper sample. There are corresponding national standards for determining alkali content, and the measurement results are accurate and reliable. Therefore, using the distribution of alkali content in paper samples to indirectly evaluate the uniformity of deacidification is very appropriate.

[0046] The distribution of deacidified particles within a paper sample directly reflects the uniformity of deacidification. Unfortunately, the resolution of existing three-dimensional paper scanning equipment is too low to determine the distribution of nanoparticles. For example, the three-dimensional microscopic imaging system (scanning CT) for paper purchased by South China University of Technology can only identify particles as small as 2 μm, while deacidified particles are typically smaller than 500 nm. Therefore, due to limitations in testing methods, the distribution of deacidified particles within the paper sample can currently only be indirectly represented by measuring the elemental content of the paper sample cross-section using SEM-EDS energy dispersive spectroscopy. However, since the energy dispersive spectroscopy measurement method is limited by the number of samples, it does not measure the distribution of all cross-sections, making the measurement error uncontrollable. Therefore, the uniformity of deacidified metal element distribution is only an optional indicator for reference.

[0047] Degree of aggregation

[0048] Cellulose is both the main component of paper fibers and a key factor in paper strength. Under the same conditions, the longer the cellulose chain, the greater the paper strength. The intrinsic indicators for measuring cellulose chain length are molecular weight and degree of polymerization. Deacidification of paper documents is to improve durability. The degree of polymerization of paper cellulose should not be reduced during the deacidification process. Therefore, after accelerated aging, the comparison of the degree of polymerization of paper samples before and after deacidification is one of the important indicators for evaluating the effectiveness of deacidification.

[0049] flexural strength

[0050] Folding endurance refers to the number of times a sample can be folded at a certain angle under a certain tension until it breaks. The folding endurance test method is very similar to the process of flipping through paper documents, so folding endurance is a very important strength indicator that has a great impact on the use of paper documents.

[0051] Unfortunately, the high sensitivity of folding endurance in detecting the effects of aging is offset by its low repeatability. Many paper documents, due to severe aging and acidification, can have their tensile strength and tear strength measured, but their folding endurance is very low. Therefore, folding endurance is listed as an optional indicator in this evaluation technical specification.

[0052] Zero-pitch tensile strength

[0053] Unlike the degree of polymerization, which represents the length of cellulose fibers, zero-pitch tensile strength measures the strength of the paper fibers themselves, thus reflecting the paper's overall strength. Compared to folding endurance, using zero-pitch tensile strength offers several advantages:

[0054] (1) Zero-pitch tensile strength is less dependent on small environmental changes, so the observed data are less scattered;

[0055] (2) Zero-pitch tensile strength can be tested with paper of very poor strength, but folding endurance test cannot;

[0056] (3) Zero-pitch tensile strength is a measure of the inherent strength of a fiber and is therefore better related to the degree of chemical degradation; while strictly speaking, folding endurance is a measure of other physical properties, such as brittleness.

[0057] (4) Zero-pitch tensile strength requires less sample material than most other physical testing methods.

[0058] The tensile strength index is also close to the actual application scenario, but the test results are easily affected by the paper uniformity. This non-uniformity includes the non-uniformity of the paper itself and the non-uniformity of aging. Compared with tensile strength, zero-pitch tensile strength is less affected by paper uniformity.

[0059] Therefore, this is a very important strength indicator, especially when folding endurance is unmeasurable, it can be used to represent the strength performance of paper.

[0060] Color difference

[0061] The principle of paper document restoration is to restore it to its original state. The deacidification process should not affect the paper's whiteness, color, or the clarity of the text. Color difference is the most direct indicator of changes in whiteness and color before and after deacidification restoration, and it can also indirectly indicate the extent of text bleeding and diffusion. The fact that deacidification treatment does not lead to significant color difference is one of the indicators of its safety.

[0062] The rate of change of color density in the image / text

[0063] The impact of the deacidification process on the ink on paper documents is one of the most important concerns for cultural relic protection units. If the deacidification process causes the ink on paper documents to fade, it will seriously affect the usability of the documents. The rate of change in the color density of the text and images is one of the most important safety indicators for the deacidification operation.

[0064] Unfortunately, there are two problems with using the color density change rate to evaluate the degree of fading of handwriting during the deacidification process of paper documents. First, the measuring aperture diameter of the color density meter is usually larger than the stroke width of the handwriting. For example, the standard measuring diameter of the X-rite Series 500 spectrophotometer is 3.4 mm, and other options include a 2.0 mm measuring aperture (excluding polarizer), a 6.0 mm aperture, and a 1.6 mm × 3.2 mm micro aperture. Regardless of the measuring aperture, it is larger than the stroke width of the handwriting, so in actual measurement, most of the data obtained are values ​​from blank paper, which significantly affects the test and evaluation results. Second, the test results are greatly affected by the accuracy of the testing instrument and the initial value of the handwriting color density. When the initial value is relatively small, even a small change can cause a large change rate, which also affects the evaluation results. For example, the test accuracy of the X-Rite Series 500 spectrophotometer is specified as the larger of ±0.01 and ±1%. The actual test accuracy may be even higher. When the initial density value is 0.40, a change of 0.01 has a change rate of 2.5%, and a change of 0.02 has a change rate of 5%. Therefore, this indicator is currently only used as an optional indicator for deacidification evaluation.

[0065] Appearance deformation

[0066] After deacidification, the paper should not exhibit macroscopic deformation phenomena such as sticking, warping, and wrinkling. There should be no visible changes in dimensions in any direction, meaning that the shrinkage rate of the paper or book in any direction should not exceed the value visible to the naked eye.

[0067] Safety of deacidification solution

[0068] After deacidification, paper documents come into direct contact with human skin. During the deacidification process, the deacidification solution is also exposed to the working environment. Therefore, the deacidification solution must be safe and environmentally friendly, which is a prerequisite for the deacidification treatment of paper documents.

[0069] Currently, the two most pressing concerns for cultural heritage preservation institutions regarding the deacidification treatment of paper documents are the effectiveness and safety of deacidification, which extends to the evaluation indicators, namely effectiveness indicators and safety indicators. Taking into account macroscopic and microscopic performance indicators, intrinsic and anatomical performance indicators, as well as subjective and objective performance indicators, the following were selected as effectiveness indicators for deacidification: pH, alkali reserves, deacidification uniformity (including the uniformity of alkali reserve distribution and the uniformity of deacidified metal element content distribution, with the latter being optional), degree of polymerization, folding endurance, and zero-distance tensile strength. Folding endurance is an optional indicator. Color difference, the rate of change in image and text color density, appearance deformation, and the safety of the deacidification solution were selected as safety indicators, with the rate of change in image and text color density being an optional indicator.

[0070] Require

[0071] Paper pattern

[0072] Specific A5 test paper was used along with paper documents for deacidification treatment, while some test paper was left untreated as a control group. pH, alkali reserve, deacidification uniformity, degree of polymerization, folding endurance, and zero-distance tensile strength were tested using the test paper instead of the paper documents. Color difference, color density change rate of the image / text, and shrinkage rate were directly tested using the documents.

[0073] sampling

[0074] Sample location

[0075] During the batch deacidification process, paper documents are distributed in different locations of the deacidification device. Samples need to be taken from each location that may affect the deacidification effect for testing. Two samples are taken evenly from the locations with the same or similar effects for testing and recorded as deacidification group 1, deacidification group 2, deacidification group 3, etc.

[0076] Insert the test paper into the document to be deacidified, placing it as close to the spine as possible and vertically centered. The test paper should not extend beyond the book block. The position of the test paper within the deacidification device should be meticulously recorded.

[0077] Place the test paper in a thick (preferably thicker than 3 cm) and larger than A5 bound document, starting from page 10, and evenly place the paper samples.

[0078] Sample quantity

[0079] The number of parallel samples is determined according to national standards. The required number of deacidification groups depends on the structure of the deacidification device. Each deacidification group requires one set of 20 paper samples (see Table 1) (add 4 more sheets per group if the test indicators include folding endurance, and add 4 more sheets per group if the test indicators include uniformity of deacidified element distribution), with a size of A5 or larger. The non-deacidified control group requires 12 sheets (add 4 more sheets per group if the test indicators include folding endurance).

[0080] Table 1 Test Items and Paper Sample Quantities

[0081]

[0082] Note: N in the table represents the number of deacidification groups to be tested.

[0083] Sampling time

[0084] All paper samples were tested within 4 weeks after deacidification (including post-treatment measures).

[0085] Before testing, use a brush to remove all loose residues produced during the deacidification process on the paper surface, including alkaline particles accumulated on the surface.

[0086] Test methods and limit requirements

[0087] Accelerated aging

[0088] The accelerated aging test was conducted on the test paper of the deacidification group and the control group using the 100℃ accelerated aging method for paper and paperboard, in accordance with the provisions of Chapter 4 to 9.2 of GB / T 40167-2021.

[0089] The test tubes should be completely sealed and large enough to store the test strips. All test strips should be aged simultaneously in the same laboratory oven, and all test strips should use the same type of glass tube.

[0090] pH

[0091] The pH of the test paper is determined according to the cold extract pH test method in GB / T 1545, which uses water extract pH meter.

[0092] The test results provide the average value and relative standard deviation of the non-aging test paper after deacidification, and the results are retained to two significant figures.

[0093] After deacidification, the pH of the test paper should be between 7.5 and 10 (before accelerated aging).

[0094] Alkali reserves

[0095] The alkali content of the test paper in each deacidification sample group was tested according to GB / T24998.

[0096] The test results provide the average value and relative standard deviation of the alkali reserves of the samples after deacidification treatment without aging, and the results are retained to two significant figures.

[0097] After deacidification, the alkali content of the paper was tested to be between 0.12 and 0.60 mol / kg.

[0098] Deacidification uniformity

[0099] Alkali content uniformity test: The uniformity of deacidification of the paper sample is evaluated by detecting the alkali content (expressed in mol / kg) in six different parts of the sample after deacidification. An example of segmentation is shown below. Figure 1 As shown.

[0100] Due to the limited size of the test paper, one A5 sheet is insufficient for uniformity assessment (1g of test paper is required for each data point in alkali storage testing). Therefore, four test papers were evenly selected from the entire paper literature, and each A5 sheet was cut into six numbered portions. Four portions with the same number were placed together, and according to GB / T24998, they were divided into smaller pieces, mixed thoroughly, and approximately 1g of test paper was weighed out as the test sample.

[0101] The alkali content measured in each part ranged from 0.12 to 0.60 mol / kg. Furthermore, the relative standard deviation of the individual measurements for each of the six parts was less than 30%. The smaller the deviation calculated using this method, the better the uniformity of deacidification.

[0102] Deacidification element distribution uniformity test (optional):

[0103] Four test sheets were evenly selected from the entire paper document. Ten samples were taken from each of the six sections of each sheet, continuously from the center outwards (all in the same direction, sample size 5mm × 5mm). An example of sampling is shown below. Figure 2 As shown in the figure, the thick lines indicate the locations of the cross-sectional samples. SEM-EDS was then used to determine the distribution of deacidified metal element content in the cross-sections of the paper samples. The average of the test values ​​of 20 samples on each cross-section is the test value for that cross-section. The test values ​​of the same location on four paper samples were averaged separately for analysis.

[0104] The relative standard deviation of the individual measurements for the six components is less than 30%. The smaller the deviation calculated using this method, the better the uniformity of deacidification.

[0105] Degree of aggregation

[0106] Pre-treat the paper sample according to the following steps to remove excess alkali residue.

[0107] At room temperature, disperse 1g to 3g of paper sample in a mixer containing 1.5L of 0.1mol / L hydrochloric acid (for a 3g paper sample with a base content of 0.48mol / kg, 1.5L is equivalent to an acid excess of >200 times) for at least 30 seconds. Thoroughly wash the paper sample with water until the wash water is neutral, and dry the test paper sample at room temperature according to Chapter 8 of GB / T1548-2016.

[0108] Before and after accelerated aging, the intrinsic viscosity of the paper sample cellulose was measured with copper ethylenediamine according to the method in GB / T 1548, and the degree of polymerization (DP) was calculated from the intrinsic viscosity value [η] using formula (1).

[0109] DP 0.905 =0.75[η] (1)

[0110] Where: DP—degree of polymerization of cellulose;

[0111] [η]——The intrinsic viscosity of cellulose in a copper ethylenediamine solution.

[0112] When measuring the dry matter content, weigh 1g according to the method in GB / T 1548, accurate to 0.001g.

[0113] After accelerated aging, the degree of polymerization of the deacidified test paper must be higher than that of the control group test paper.

[0114] Flexural endurance (optional)

[0115] According to GB / T 457, the longitudinal folding endurance of test paper before and after accelerated aging is tested. The testing instrument is set with appropriate tension to ensure the measurement results are meaningful.

[0116] The average flexural endurance and flexural endurance are determined in accordance with the provisions of GB / T 457.

[0117] After accelerated aging, the folding endurance of the deacidified group test paper should be higher than that of the control group test paper.

[0118] Zero-pitch tensile strength

[0119] According to GB / T 2678.4, the longitudinal zero-pitch tensile strength of the test paper before and after accelerated aging is tested.

[0120] The average zero-distance tensile strength is determined in accordance with the provisions of GB / T 2678.4.

[0121] After accelerated aging, the zero-pitch tensile strength of the deacidified group test paper should be higher than that of the control group test paper.

[0122] Color difference

[0123] According to GB / T 7975, the L of the test paper before and after deacidification is tested. * a * b * Value. Then, according to GB / T 7921, the color difference value ΔE of the samples before and after deacidification is calculated using formula (2). * Two books were taken evenly from each sample group, and two points were taken from each book for testing.

[0124]

[0125] Where: ΔE * —Color difference values ​​of paper documents before and after deacidification;

[0126] ΔL * —The difference in brightness L* of paper documents before and after deacidification;

[0127] Δa * —The difference in red-green hue (a*) between paper documents before and after deacidification;

[0128] Δb * —The difference in yellow-blue tint b* between paper documents before and after deacidification.

[0129] Before accelerated aging, the color difference value of the test paper before and after deacidification should not exceed 3.0. The smaller the value, the smaller the impact of deacidification on the color difference of paper documents.

[0130] Image and text color density change rate (optional)

[0131] According to GB / T 11501, the color density values ​​of the same parts of the paper documents before and after deacidification are tested. Then, the change rate of color density of the samples before and after deacidification is calculated according to formula (3). Two books are taken evenly from each group of samples, and two points are taken from each book for testing.

[0132]

[0133] Where: D0: Color density of the paper document before deacidification;

[0134] D1: Color density of paper documents after deacidification.

[0135] Before accelerated aging, the change rate of paper color density before and after deacidification should not exceed 6% for black samples and not exceed 3% for colored samples. The smaller the value, the less the deacidification affects the color density of the paper document images.

[0136] Appearance deformation

[0137] According to GB / T 451.3-2002, the thickness of the literature before and after deacidification shall be measured using a thickness gauge, in mm, and three significant figures shall be retained.

[0138] The length and width of the literature before and after deacidification were measured with vernier calipers in mm and two significant figures were retained. The three-direction shrinkage rate ε was calculated according to formula (4). Two books were evenly taken from each group of samples for testing. The calculation results were expressed as a percentage and two significant figures were retained.

[0139]

[0140] In the formula: L0: the length, width, and thickness of the literature before deacidification, in mm;

[0141] L1: Length, width, and thickness of the document after deacidification, in mm.

[0142] After deacidification, the paper should not exhibit significant deformation, including obvious adhesion, warping, or wrinkling. Furthermore, the shrinkage rate in length, width, and thickness directions should not exceed 1.50% before and after deacidification. A smaller shrinkage rate indicates less impact of deacidification on the paper's appearance.

[0143] Safety of deacidification solution

[0144] The safety of the deacidification solution is tested according to national standards, and a corresponding test report is provided.

[0145] According to GB / T 18883, the air quality in the deacidification operation environment and the storage environment for deacidified paper documents must meet the indoor air quality standards.

[0146] According to GB / T 21606, the effects of deacidifying solution on human skin were tested. Based on the evaluation provisions of Appendix C of GB / T 21606-2022 "Acute Dermal Toxicity Testing of Chemicals", the deacidifying solution should be classified as Category 5 / Unclassified in the Globally Harmonized Classification and Labelling System (GHS).

[0147] Example 1

[0148] Batch deacidification of paper documents was performed using Class A deacidification solution and deacidification process. The basic parameters of the paper documents are as follows:

[0149] Book A, published by Commercial Press in 1909, quantification 56±3g / m 2 The pH value was 4.46. After deacidification, the paper samples were left in a natural environment for two weeks. All loose residues generated during the deacidification process were removed from the paper surface with a brush, and then various indicators were tested. The deacidification effect is shown in Table 2.

[0150] Table 2 Evaluation Table of Deacidification Effect in Paper Documents (Class A Deacidification Solution and Deacidification Process)

[0151]

[0152]

[0153] The test results above show that the deacidification effect of Class A deacidification solution and process on paper documents is as follows: pH, alkali reserve, deacidification uniformity (minimum alkali reserve and uniformity of alkali reserve distribution in six parts of the deacidified sample), degree of polymerization, zero-distance tensile strength, and safety indicators of the deacidification solution all meet the requirements. However, deacidification uniformity (uniformity of deacidified element content distribution), folding endurance, color difference, color density change rate of images and text, and appearance deformation do not meet the requirements. Since the uniformity of deacidified element content distribution and folding endurance are optional indicators, and the other mandatory effectiveness indicators are qualified, it can be considered that Class A deacidification solution and process are effective for deacidifying paper documents. However, the deacidification process affects the appearance performance of paper documents, including causing obvious color difference, color density change rate, and appearance deformation, which affects the use of paper documents. Therefore, the safety indicators are unqualified. The overall evaluation result is that Class A deacidification solution and process are unqualified and are not recommended for deacidification treatment of paper documents.

[0154] Example 2

[0155] Batch deacidification of paper documents was performed using a type B deacidification solution and process. The basic parameters of the paper documents are as follows:

[0156] Book B, published by People's Publishing House in 1955, paper basis weight 53±2g / m³ 2The initial pH value was 5.46. After deacidification, the paper samples were left in a natural environment for 2 weeks. All loose residues generated during the deacidification process were removed from the paper surface with a brush, and then various indicators were tested. The deacidification effect is shown in Table 3.

[0157] Table 3 Evaluation Table of Deacidification Effect in Paper Documents (Type B Deacidification Solution and Deacidification Process)

[0158]

[0159]

[0160] The test results above show that the deacidification effect of Class B deacidification solution and process on paper documents is as follows: pH, alkali content, deacidification uniformity (minimum alkali content in the six parts of the deacidified sample), degree of polymerization, folding endurance, and zero-distance tensile strength all fail to meet the requirements. However, the deacidification uniformity (uniformity of alkali content distribution and uniformity of deacidified element content distribution), color difference, color density change rate of images and text, appearance deformation, and safety of the deacidification solution all meet the requirements. Therefore, it can be concluded that although Class B deacidification solution and process do not affect the appearance performance of paper documents, including color difference, color density change rate, and appearance deformation, and the deacidification process is safe with qualified safety indicators, the effectiveness indicators are unqualified, and the deacidification effect does not meet the requirements. Therefore, the overall evaluation result is that Class B deacidification solution and process are unqualified and are not recommended for deacidification treatment of paper documents.

[0161] Example 3

[0162] Batch deacidification of paper documents was performed using a type C deacidification solution and process. The basic parameters of the paper documents are as follows:

[0163] Book C, published by People's Publishing House in 1972, paper basis weight 74±2g / m³ 2 The initial pH value was 5.14. After deacidification, the paper samples were left in a natural environment for 2 weeks. All loose residues generated during the deacidification process were removed from the paper surface with a brush, and then various indicators were tested. The deacidification effect is shown in Table 4.

[0164] Table 4 Evaluation Table of Deacidification Effect in Paper Documents (Category C Deacidification Solution and Deacidification Process)

[0165]

[0166] The test results above show that the Class C deacidification solution and deacidification process are effective for deacidifying paper documents. Except for the folding endurance index, all effectiveness indicators meet the threshold requirements. Because paper documents are very sensitive to the folding endurance test, this reduces repeatability and reliability. This index is for reference only. The other strength indicators of the paper sample after deacidification meet the requirements. Therefore, it can be said that the effectiveness of the Class C deacidification process is qualified.

[0167] The safety indicators of the deacidification process affecting the appearance of paper documents all meet the threshold requirements. There is no obvious deformation in appearance, and the color difference and color density change rate are very small, which does not affect the use of paper documents. Therefore, the safety indicators of the Class C deacidification process are qualified. The overall evaluation result is that the Class C deacidification process is qualified and can be used for deacidification treatment of paper documents.

[0168] The method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase provided in this application achieves a systematic and comprehensive evaluation of the deacidification effect by scientifically setting evaluation indicators, detection methods and thresholds. Its technical effects are mainly reflected in the following aspects:

[0169] 1. Overcome the limitations of existing evaluation methods and avoid excessive deacidification that could damage the literature.

[0170] Existing technologies (such as ISO / TS18344:2016 and GB / Z 42964-2023) do not set upper limits for pH and alkali content, which may lead to problems such as excessively high pH causing alkaline hydrolysis and excessive alkali content causing blurred text after deacidification. This application specifies a pH threshold of 7.5–10 and an alkali content threshold of 0.12–0.60 mol / kg. Through dual control of upper and lower limits, it effectively avoids damage to paper documents caused by excessive deacidification and balances the deacidification effect with document security.

[0171] 2. Construct a comprehensive evaluation system that balances effectiveness and safety.

[0172] Existing evaluation methods focus on the effectiveness of deacidification (such as pH and alkali reserves), lacking a systematic evaluation of appearance performance and safety in use. This application, for the first time, divides the evaluation indicators into effectiveness indicators (pH, alkali reserves, uniformity, degree of polymerization, zero-distance tensile strength, etc.) and safety indicators (color difference, appearance deformation, safety of deacidification solution, etc.). It ensures the durability of the literature after deacidification through effectiveness indicators (such as higher degree of polymerization and zero-distance tensile strength after accelerated aging than the control group), and ensures the performance of the literature in use through safety indicators (such as no adhesion, warping, and color difference ΔE*≤3.0), achieving a dual guarantee of durability and safety.

[0173] 3. Quantify key indicators to improve the scientific rigor and operability of the evaluation.

[0174] To address the issue of uniformity in deacidification, a quantitative standard is proposed: the relative standard deviation (RSD) of alkali storage distribution is <30%, and the alkali storage in each part is between 0.12 and 0.60 mol / kg. This solves the problem of fuzzy uniformity evaluation in existing methods.

[0175] Regarding appearance deformation, a quantitative requirement is clearly defined that the length, width, and thickness expansion rate should be ≤1.50% and there should be no macroscopic deformation, replacing the subjective judgment of existing technologies;

[0176] Regarding the safety of deacidification solutions, the clear standards of GB / T 18883 (air quality) and GB / T 21606 (skin toxicity) are used to ensure the environmental safety of deacidification operations and literature use.

[0177] 4. Optimize strength evaluation indicators to improve detection reliability.

[0178] Existing methods rely on folding endurance to evaluate strength, but folding endurance testing has low repeatability and poor applicability to fragile documents. This application introduces zero-pitch tensile strength as the core strength indicator (requiring it to be better than the control group after aging). It is less affected by paper uniformity, the data is reliable, and it is especially suitable for fragile documents with severe aging, thus making up for the limitations of folding endurance.

[0179] 5. Guide the standardized development of the deacidification industry

[0180] Through a systematic index system and threshold requirements, this method can provide clear standards for industry access to deacidification materials and processes, avoid ineffective or harmful deacidification treatments (such as the rejection of A and B processes in the example due to failure to meet the index standards), promote the standardization and scientific development of deacidification remediation technology, and ultimately achieve the long-term preservation and safe utilization of paper documents.

[0181] In summary, this application, through a comprehensive, quantitative, and scientific evaluation system, not only solves the problems of missing indicators and unreasonable thresholds in existing methods, but also takes into account the effectiveness and safety of deacidification, providing reliable technical support for the evaluation of deacidification effects in paper documents.

[0182] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for evaluating the deacidification effect of paper documents based on anhydrous liquid phase, characterized in that: Includes the following steps: By setting effectiveness and safety indicators, the corresponding detection methods are used to obtain the values ​​of each indicator on the deacidified paper sample. The values ​​are then compared with preset thresholds to evaluate the deacidification effect. The effectiveness indicators include pH, alkali reserves, deacidification uniformity, degree of polymerization, and zero-distance tensile strength; the safety indicators include color difference, appearance deformation, and safety of the deacidification solution. The uniformity of deacidification is evaluated by the uniformity of alkali storage distribution, wherein the relative standard deviation of alkali storage in multiple parts of the paper sample is less than 30%, and the alkali storage in each part is between 0.12 and 0.60 mol / kg.

2. The method according to claim 1, characterized in that, The pH threshold of the effectiveness index is 7.5–10, and the alkali storage threshold is 0.12–0.60 mol / kg.

3. The method according to claim 1, characterized in that, The uniformity of deacidification also includes the uniformity of the distribution of deacidifying elements. The uniformity of the distribution of deacidifying elements is determined by SEM-EDS detection of the metal element content in the cross-section of the paper sample. The relative standard deviation of the detection values ​​in multiple parts is less than 30%. The uniformity of the distribution of deacidifying elements is an optional indicator.

4. The method according to claim 1, characterized in that, The degree of polymerization index requires that, after accelerated aging, the degree of polymerization value of the deacidified paper sample is higher than that of the non-deacidified control group paper sample.

5. The method according to claim 1, characterized in that, The zero-pitch tensile strength index requires that, after accelerated aging, the zero-pitch tensile strength value of the deacidified paper sample is higher than that of the undeacidified control group paper sample.

6. The method according to claim 1, characterized in that, The color difference index is the color difference value ΔE of the paper samples before and after deacidification. * The color difference value ΔE is not greater than 3.

0. * Calculated using the following formula: Where: ΔE * The color difference value of the paper document before and after deacidification; ΔL * Δa represents the difference in brightness L* of the paper document before and after deacidification. * Δb represents the difference in red-green hue (a*) of the paper document before and after deacidification; * The difference in yellow-blue tint b* between the paper document before and after deacidification.

7. The method according to claim 1, characterized in that, The appearance deformation index includes the shrinkage rate in the length, width and thickness directions of the paper sample not exceeding 1.50%, and there is no adhesion, warping or wrinkling.

8. The method according to claim 1, characterized in that, The safety of the deacidification solution is evaluated by the following standards: the air in the deacidification operation and storage environment complies with GB / T 18883, and the deacidification solution is tested by GB / T 21606 and belongs to GHS category 5 / unclassified.

9. The method according to claim 1, characterized in that, The effectiveness index also includes folding endurance, which is an optional index. It is required that the folding endurance value of the deacidified paper sample after accelerated aging is higher than that of the control group paper sample without deacidification.

10. The method according to claim 1, characterized in that, The safety indicators also include the color density change rate of the image and text, which is an optional indicator, wherein the change rate of black samples is no greater than 6% and the change rate of colored samples is no greater than 3%.

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