A method for processing a sample for determining the degree of polymerization of cellulose in paper documents
By removing non-fibrous impurities from paper documents and employing ash content determination and sheet preparation, the problem of inaccurate cellulose polymerization degree determination results in paper documents was solved, achieving more accurate polymerization degree determination and deacidification to enhance protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2023-08-02
- Publication Date
- 2026-07-21
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of paper document preservation technology, specifically a method for sample preparation for determining the degree of polymerization of cellulose in paper documents. Background Technology
[0002] Paper, as a medium for writing and document archives, plays an important role in recording history and passing on civilization.
[0003] However, during long-term use and storage, paper documents gradually become eroded and damaged by various factors. This manifests outwardly as yellowing and brittleness, even crumbling at the slightest touch. Internally, it involves paper acidification, aging, breakage of the cellulose chains that make up the main raw material of paper, and a decrease in the degree of polymerization. When the degree of polymerization drops below 200, the strength is completely lost, and the paper pulverizes. Therefore, the degree of polymerization is a very important indicator for judging the degree of aging of paper documents, and the degree of cellulose polymerization is also used as one of the evaluation indicators for the deacidification and strengthening protection of paper documents.
[0004] Currently, the method for determining the degree of polymerization of cellulose pulp is the copper ethylenediamine viscosity method, which follows the national standard GB / T 1548-2016 "Determination of intrinsic viscosity value in copper ethylenediamine (CED) solution for pulp". Sampling is performed according to GB / T 740-2003 standard. A measured mass of the sample is placed in a dissolving bottle, and 25 mL of water and 25 mL of copper ethylenediamine (CED) solution are added to dissolve it. The time it takes for the solution to pass through a capillary viscometer is then measured. Finally, the intrinsic viscosity value and degree of polymerization of the pulp are calculated.
[0005] Existing technologies directly use existing pulp cellulose polymerization degree determination methods to measure the cellulose polymerization degree of paper documents, and the measured results are significantly lower than the true values. Currently, most studies directly use paper samples for measurement, and the inaccurate measured values greatly affect the research progress of deacidification, enhancement and protection of paper documents.
[0006] Therefore, in order to improve the effectiveness and accuracy of deacidification and enhancement protection of paper documents, it is particularly important to develop an accurate sample preparation method suitable for the determination of the degree of polymerization of cellulose in paper documents. Summary of the Invention
[0007] To address the problems existing in the prior art, the purpose of this invention is to provide a sample preparation method for determining the degree of polymerization of cellulose in paper documents, which can accurately calculate the mass of paper sample required for determining the degree of polymerization of paper documents, thus facilitating the acquisition of accurate degree of polymerization measurement values.
[0008] To achieve the above objectives, the present invention adopts the following technical solution:
[0009] A method for preparing paper document samples for determining the degree of polymerization of cellulose includes the following steps: cleaning the paper document samples to remove non-fibrous impurities.
[0010] The ash content of paper document samples after decontamination treatment was determined.
[0011] Based on the intrinsic viscosity value of the paper document sample, obtain the actual oven-dry pulp volume required to determine the degree of polymerization of the paper document;
[0012] The required paper sample mass for determining the degree of polymerization of the paper document is calculated based on the actual oven-dry pulp volume and the ash content of the paper document sample.
[0013] Furthermore, when the ash content of the paper document sample is >5%, the ash content is first reduced, and then the mass of paper sample required for determining the degree of polymerization of the paper document is calculated.
[0014] Furthermore, the process of reducing the ash content of paper document samples includes the following steps:
[0015] The decontaminated sample is then soaked in water.
[0016] The soaked sample was then subjected to a decomposition process.
[0017] The slurred sample is then filtered.
[0018] The filtered slurry sample is then processed into a film;
[0019] The ash content of the prepared sample is determined. If the ash content is >5%, the above steps are repeated until the ash content is ≤5%.
[0020] Furthermore, the soaking treatment involves tearing the cleaned sample into small pieces and immersing it completely in water for 5 to 10 hours.
[0021] Furthermore, the decomposition process involves using a standard fiber decomposer to decompose the soaked sample into pulp without fiber bundles.
[0022] Furthermore, the filtration process involves diluting the loosened pulp to a concentration of 0.05–0.1% in a standard papermaking machine, vacuum filtering, then adding water to dilute again, and vacuum filtering again, repeating this process 2–3 times.
[0023] Furthermore, the sheet forming process involves diluting the filtered pulp to a concentration of 0.1–0.2% in a standard sheet forming machine, forming a wet sheet under vacuum, and then drying the formed sheet to a constant weight.
[0024] Furthermore, the prepared sheet is dried at room temperature or under gradually increasing temperature conditions, with the drying temperature not exceeding 60 degrees Celsius.
[0025] Furthermore, the basis weight of the resulting paper should be controlled to be no more than 50 g / m³. 2 .
[0026] Furthermore, the formula for calculating the required paper sample mass for determining the degree of polymerization in paper documents is as follows:
[0027]
[0028] Where X% represents the ash content measured from the paper document sample.
[0029] In summary, the present invention has the following advantages:
[0030] By removing non-fibrous impurities from paper document samples, and then obtaining the actual oven-dry pulp volume required for determining the degree of polymerization based on the intrinsic viscosity value of the paper document samples, the required paper sample mass for determining the degree of polymerization is calculated using the actual oven-dry pulp volume and the ash content of the paper document samples. Since the influence of non-fibrous impurities such as dust and minerals in the paper documents on the determination of the degree of polymerization of cellulose in the paper documents is eliminated, it is beneficial to obtain a more accurate degree of polymerization value, which can better reflect the length of cellulose chains in the paper sample, thereby better evaluating the current status of the paper documents and the effect of deacidification and enhancement repair. Detailed Implementation
[0031] Currently, the method for determining the degree of polymerization of cellulose in pulp is the copper ethylenediamine (CED) viscosity method. Because it's a viscosity method, the mass of the sample and the concentration of the solution have a significant impact on the results. Pulp is primarily composed of plant fibers with few other impurities, and pulp cellulose dissolves in CED solution. Therefore, determining the degree of polymerization of pulp cellulose according to GB / T 1548-2016 is accurate. However, when this method is used to determine the degree of polymerization of cellulose in paper literature, the samples are not pulp but paper that has been used and stored for a certain period. The composition of paper literature is much more complex than pulp. Besides pulp fibers, paper contains fillers, sizing agents, dust, and other non-fibrous substances. In particular, some papers have high filler content, and inorganic mineral pigments are insoluble in CED solution and do not contribute to the solution viscosity. If the sample is not pre-treated, directly using the existing method to determine the degree of polymerization will yield results significantly lower than the true value. Currently, most studies directly use paper samples for measurement, and inaccurate measurements greatly hinder the research progress on deacidification, strengthening, and protection of paper literature.
[0032] The present invention will now be described in further detail.
[0033] The determination of the degree of polymerization of pulp requires a pure pulp sample that is completely dissolved in a copper ethylenediamine solution to ensure the accuracy of the measurement. If there are non-fibrous impurities, the amount of pulp in the sample will be reduced accordingly, and the viscosity of the solution will be lowered, thus affecting the accuracy of the determination of the degree of polymerization of pulp cellulose.
[0034] Paper documents often contain mineral fillers, which are inorganic and denser than fibers. When the filler content in paper documents is high (e.g., when the filler content is greater than 5%), it will not only affect the sampling amount but also the outflow time during the degree of polymerization test, thus further affecting the test results.
[0035] This invention addresses the need for determining the degree of polymerization of paper documents using the viscosity method. It overcomes the shortcomings of existing methods for sample preparation in determining the degree of polymerization of paper documents and provides a more suitable sample preparation method for determining the degree of polymerization of cellulose in paper documents. The principle is to minimize the influence of non-fibrous impurities contained in the paper documents on the degree of polymerization determination results, thereby improving the accuracy of the determination.
[0036] First, physical cleaning methods are used to remove non-fibrous impurities such as dust that have been absorbed by paper documents during use and storage.
[0037] Then, the ash content of the paper documents was determined according to the national standard (GB / T 742-2018) for the determination of ash content of papermaking raw materials, pulp, paper and paperboard burning residues (ash content) (575℃ and 900℃). The content of inorganic mineral fillers in the paper documents was also determined. When the ash content of the paper documents was greater than 5%, samples for degree of polymerization determination were prepared according to method A; when the ash content of the paper documents was less than or equal to 5%, samples for degree of polymerization determination were prepared according to method B.
[0038] Method A
[0039] After soaking paper samples with an ash (mineral filler) content greater than 5% in clean water for a certain period of time, the paper samples are dissociated into pulp without fiber bundles using a standard fiber dissociator.
[0040] The dissolved pulp is further diluted, and then the pulp is filtered and formed using a standard sheeter. The formed sheets are dried at room temperature to a constant weight, or they can be dried under gradually increasing temperature conditions, with the drying temperature not exceeding 60 degrees Celsius.
[0041] Next, the amount of residual minerals in the handmade paper sample was determined by the paper ash content determination method. Finally, dried handmade paper samples were taken for testing. Considering the ash content of the paper sample, the sample mass required for the degree of polymerization determination was calculated so that the actual oven-dry pulp content in the paper sample was equal to the amount required for the degree of polymerization test, thereby ensuring the accuracy of the degree of polymerization determination of paper documents.
[0042] Method B
[0043] For paper samples with an ash (mineral filler) content of less than 5%, the required sample mass for degree of polymerization determination is calculated by taking into account the ash content of the paper sample. This ensures that the actual oven-dry pulp content in the paper sample is equal to the amount required for degree of polymerization testing, thereby ensuring the accuracy of degree of polymerization determination for paper documents.
[0044] The operating steps are as follows:
[0045] 1. Take a certain amount of paper document sample, generally with an oven-dry weight greater than 40g, and perform a cleaning treatment. First, use a soft brush to brush off the surface dirt, and then use a vacuum cleaner to vacuum it to remove dust and other non-fibrous impurities that have been adsorbed during the use and storage of the paper document.
[0046] 2. Take a paper sample of about 15g and determine the ash (mineral filler) content in the paper sample according to the national standard (GB / T 742-2018), and denote it as X%. When the ash content of the paper document is X% ≤ 5%, the decontaminated paper sample is used directly for testing. Select the concentration and sample mass M (i.e., the actual oven-dry pulp weight) according to the viscosity value of the sample to be tested. Considering the ash content (X%) of the decontaminated paper sample, calculate the required sample amount according to the following formula. Weigh the sample of a certain mass, accurate to 0.5mg, to obtain the paper sample for determining the degree of polymerization of the paper document.
[0047]
[0048] When the ash content of the paper sample X% > 5%, in order to remove as much ash as possible from the test paper sample and reduce the influence of ash on the test results, continue to reduce the ash content by following the steps below until the ash content of the paper sample X% ≤ 5%, and prepare the sample for degree of polymerization determination.
[0049] 3. Tear the cleaned paper sample into small pieces and soak them in a container of clean water, ensuring that the paper sample is completely submerged in the water. The soaking time depends on the weight of the paper sample. A larger weight requires a longer soaking time, while a smaller weight requires a shorter soaking time, generally 5 to 10 hours.
[0050] 4. Use a standard fiber desorber to desorb the soaked paper sample into pulp without fiber bundles.
[0051] 5. The loosened pulp is then filtered and formed into sheets using a standard sheet forming machine.
[0052] First, the pulp is filtered. In a standard papermaking machine, the dissolved pulp is diluted to a concentration of 0.05-0.1% and then vacuum filtered. Water is added for further dilution, and the process is repeated 2-3 times.
[0053] Next, the pulp is processed into sheets. In a standard sheeter, the filtered pulp is diluted to a concentration of 0.1–0.2%, and a vacuum is applied to form a wet sheet. The sheet is then dried at room temperature to a constant weight, or it can be dried under gradually increasing temperature, but the drying temperature should not exceed 60 degrees Celsius. Furthermore, the basis weight of the resulting sheet is controlled to be no greater than 50 g / m².
[0054] 6. The ash content of the prepared paper sample is determined according to the standard GB / T 742-2018 "Papermaking Raw Materials, Pulp, Paper and Paperboard Residues on Ignition (Determination of Ash Content) (575℃ and 900℃)". After treatment to reduce ash content, the ash content X% ≤ 5%.
[0055] 7. Select the concentration and sample mass M (i.e., actual oven-dry pulp weight) for testing based on the intrinsic viscosity value of the sample, and calculate the required sample amount considering the ash content of the handmade paper sample.
[0056]
[0057] Take a prepared thin sheet, wear gloves, tear the paper sample into pieces, and weigh a sample of a predetermined mass, accurate to 0.5 mg. This yields the paper sample required for determining the degree of polymerization in the paper document. By following these steps, the actual oven-dry pulp volume can be avoided due to the presence of ash during sampling, resulting in a more accurate paper sample mass. This facilitates obtaining a more accurate degree of polymerization value, better reflecting the length of cellulose chains in the paper sample, and thus enabling a better evaluation of the current condition of the paper document and the effectiveness of deacidification and remediation.
[0058] Example 1
[0059] The sample was a book from the 1950s: *A Handbook*, published by A Newspaper in 1959. Testing revealed that the moisture content of the base paper was 7.38% and the ash content was 1.6%. Since the ash content was below 5%, after physical dust removal treatment, the amount of oven-dry paper sample required for determining the degree of polymerization was calculated based on the ash content measurement results. The degree of polymerization was determined according to the national standard method, and the test data are shown in Table 1.
[0060] Table 1. Comparison of data on the degree of polymerization of cellulose in paper documents determined by two sample treatment methods (Handbook A)
[0061]
[0062] Example 2
[0063] The sample is a book from the 1970s: "Selected Works of B", published by B Publishing House in 1972, and is in good condition. Testing revealed that the original paper had a moisture content of 6.69% and an ash content of 18.33%, with the ash content exceeding 5%, requiring filtration with inorganic mineral filler.
[0064] Take 30g of oven-dried paper sample, of which 2g is used for the determination of the degree of polymerization of the original paper sample, and 28g is used for physical dust removal, loosening, filtration, and sheet forming. The basis weight of the hand-formed sheet is 45g / m³. 2 15g of oven-dried sample was weighed from the handmade paper sample for ash content determination (i.e., X%). Based on the ash content determination result, the amount of oven-dried paper sample required to determine the degree of polymerization was calculated. The sample was taken from the handmade paper sample, and the degree of polymerization was determined according to the national standard method. The test data are shown in Table 2.
[0065] Table 2 Comparison of data on the degree of polymerization of cellulose in paper documents determined by two sample treatment methods (Selection B)
[0066]
[0067] Example 3
[0068] The sample is a book from the 1980s: "C Literature", published by C Publishing House in 1982, and is in poor condition.
[0069] Tests showed that the moisture content of the base paper was 6.25% and the ash content was 13.28%, with the ash content exceeding 5%, requiring filtration treatment with inorganic mineral fillers.
[0070] Take 30g of oven-dried paper sample, of which 2g is used for the determination of the degree of polymerization of the original paper sample, and 28g is used for physical dust removal, loosening, filtration, and sheet forming. The basis weight of the hand-formed sheet is 40g / m³. 2 15g of oven-dried sample was weighed from the handmade paper sample for ash content determination (i.e., X%). The amount of oven-dried paper sample required to determine the degree of polymerization was calculated based on the ash content determination result. The sample was taken from the handmade paper sample and the degree of polymerization was determined according to the national standard method. The test data are shown in Table 3.
[0071] Table 3. Comparison of data on the degree of polymerization of cellulose in paper documents determined by two sample treatment methods (C Literature).
[0072]
[0073] 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 preparing samples for determining the degree of polymerization of cellulose in paper documents, characterized in that: Includes the following steps, The paper document samples are decontaminated to remove non-fibrous impurities. The ash content of paper document samples after decontamination treatment was determined. Based on the intrinsic viscosity value of the paper document sample, obtain the actual oven-dry pulp volume required to determine the degree of polymerization of the paper document; The required paper sample mass for determining the degree of polymerization of the paper document is calculated based on the actual oven-dry pulp weight and the ash content of the paper document sample. When the ash content of the paper document sample is >5%, the ash content should be reduced first, and then the mass of paper sample required for the determination of the degree of polymerization of the paper document should be calculated. The formula for calculating the required paper sample mass for determining the degree of polymerization in paper documents is as follows: ； Where X% represents the ash content measured from the paper document sample.
2. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 1, characterized in that: The process of reducing the ash content of paper document samples includes the following steps: The cleaned sample is then soaked in water. The soaked sample was then subjected to a decomposition process. The slurred sample is then filtered. The filtered slurry sample is then processed into a film; The ash content of the prepared sample is determined. If the ash content is >5%, the above steps are repeated until the ash content is ≤5%.
3. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 2, characterized in that: The soaking treatment involves tearing the cleaned sample into small pieces and immersing it completely in water for 5 to 10 hours.
4. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 3, characterized in that: The decomposition process involves using a standard fiber decomposer to decompose the soaked sample into pulp without fiber bundles.
5. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 4, characterized in that: The filtration process involves diluting the loosened pulp to a concentration of 0.05-0.1% in a standard papermaking machine, vacuum filtering, adding water to dilute again, and vacuum filtering again. This process is repeated 2-3 times.
6. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 5, characterized in that: The sheet forming process involves diluting the filtered pulp to a concentration of 0.1-0.2% in a standard sheet forming machine, forming a wet sheet under vacuum, and then drying the formed sheet to a constant weight.
7. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 6, characterized in that: The prepared thin film is dried at room temperature or under gradually increasing temperature, with the drying temperature not exceeding 60 degrees Celsius.
8. The sample preparation method for determining the degree of polymerization of cellulose in paper documents according to claim 6, characterized in that: The basis weight of the resulting paper should not exceed 50 g / m³. 2 .