酸碱度对纸张降解趋势的影响及脱酸理论碱用量研究——以20世纪90年代机制纸为例

doi:10.6023/A25030061

摘要/Abstract

纸张和纸质文物在长时间的使用或保存后会逐渐酸化降解直至损毁失去价值, 根据纸张酸化程度及其降解趋势评估纸张的状态有助于实现对纸张的针对性脱酸保护. 考虑到纸张本体酸碱度(pH值)是影响纸张降解的一个重要因素, 本工作以20世纪90年代的机制纸为研究对象, 研究了不同初始pH值的纸张在人工干热加速老化条件下的酸化趋势和降解速率常数, 并表征分析了包括pH值变化、氧化度和色差等纸张综合性能的变化. 90 d周期的加速干热老化结果显示, 所研究的机制纸的降解遵循一级动力学, 并在碱性状态下呈现出较低的降解速率常数; 同时酸性机制纸的pH值下降较快, 氧化度明显升高, 表现出发暗黄化, 而碱性机制纸能保持碱性至近中性的状态, 拥有更低的氧化度和更小的色差. 此外不论是强碱还是强酸处理, 极端的酸碱性环境均会导致纸张纤维素数均聚合度的下降. 该机制纸的合适pH值范围为7~8.5. 在此基础上, 本研究提出脱酸理论碱用量的计算方法, 参考纸张酸化降解趋势下的合理pH值范围, 将碱用量拆解为脱酸处理量和额外碱保留量进行分析并给出计算公式. 本研究方法可推广至其他类型纸张的降解趋势分析, 理论碱用量的计算可为实际脱酸中的碱量控制提供科学指导, 避免脱酸过程中碱过量造成的纸张碱性降解等二次损伤.

关键词: 机制纸, 酸碱度, 酸化降解速率常数, 脱酸适宜pH值, 脱酸理论碱用量

Paper and paper-based cultural artifacts gradually undergo acid hydrolysis degradation during prolonged use or storage, ultimately leading to structural failure and loss of value. Assessing the condition of paper based on its acidification level and degradation trends facilitates targeted deacidification conservation strategies. Given that the inherent pH of paper is a critical factor influencing its degradation, this study focuses on 1990s machine-made paper as the research subject, employing gel permeation chromatography (GPC) to investigate the acidification tendencies and degradation rate constants of papers with varying initial pH values under artificial dry-heat accelerated aging conditions. Non-destructive characterization methods were further employed to analyze changes in comprehensive paper properties, including pH, oxidation degree, and color difference. Results from the 90 d accelerated dry-heat aging experiment revealed that the degradation of the studied machine-made paper follows first-order degradation kinetics. Alkaline paper exhibited smaller degradation rate constants and slower degradation rates. Acidic machine-made paper demonstrated rapid pH decline, significant oxidation and visible darkening/yellowing, while alkaline machine-made paper maintained an alkaline to nearly neutral state, with a lower oxidation degree and a smaller color difference. However, regardless of whether it is subjected to strong alkaline or strong acidic treatment, extreme acidic or alkaline environments will lead to a decline in the degree of polymerization of cellulose in the paper. The optimal pH range for this machine-made paper was identified as 7~8.5. Building on these findings, a theoretical calculation method for alkali dosage in deacidification is proposed. By considering the appropriate pH range under acidifica- tion degradation trends, the alkali dosage is decomposed into acid neutralization amount and alkali retention amount for analysis, with calculation formulas provided for different deacidification targets. This research can be extended to degradation trend analyses of other paper types, while the alkali dosage calculation provides a reference for practical deacidification processes to avoid secondary damage caused by excessive alkalinity.

Key words: machine-made paper, pH, acidizing degradation rate constant, suitable pH value for deacidification, calculation of alkali dosage in deacidification

引用此文

夏文卓, 刘恒, 王思浓, 唐颐. 酸碱度对纸张降解趋势的影响及脱酸理论碱用量研究——以20世纪90年代机制纸为例[J]. 化学学报, 2025, 83(5): 527-534.

Wenzhuo Xia, Heng Liu, Sinong Wang, Yi Tang. The Influence of pH on Paper Degradation Trends and Calculation of Alkali Dosage in Deacidification: Taking the Machine-Made Paper of the 1990s as an Example[J]. Acta Chimica Sinica, 2025, 83(5): 527-534.

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图/表 7

图1. (a) MMP、MMP-5.0、MMP-7.3、MMP-8.6和MMP-10.5的XRD图谱; (b) MMP、MMP-5.0、MMP-7.3、MMP-8.6和MMP-10.5的IR图谱; (c) MMP、MMP-5.0、MMP-7.3、MMP-8.6和MMP-10.5的UV-Vis图谱; (d) MMP、(e) MMP-5.0、(f) MMP-7.3、(g) MMP-8.6和(h) MMP-10.5的数码图片

Figure 1. (a) XRD patterns of MMP, MMP-5.0, MMP-7.3, MMP-8.6 and MMP-10.5; (b) IR spectra of MMP, MMP-5.0, MMP-7.3, MMP-8.6 and MMP-10.5; (c) UV-Vis spectra of MMP, MMP-5.0, MMP-7.3, MMP-8.6 and MMP-10.5; Digital images of (d) MMP, (e) MMP-5.0, (f) MMP-7.3, (g) MMP-8.6 and (h) MMP-10.5

图2. (a)加速干热老化前后MMP-5.0、MMP-7.3、MMP-8.6和MMP-10.5的ln(1–1/DPn)随老化时间变化图; (b)加速干热老化前后MMP-5.0、MMP-7.3、MMP-8.6和MMP-10.5表面pH值随老化时间变化图

Figure 2. (a) ln(1–1/DPn) as a function of aging time for MMP-5.0, MMP-7.3, MMP-8.6 and MMP-10.5 before and after accelerated dry-heat aging; (b) the variation of surface pH with aging time for MMP-5.0, MMP-7.3, MMP-8.6, and MMP-10.5 before and after accelerated dry-heat aging

图3. 老化前后(a) MMP-5.0, (b) MMP-7.3, (c) MMP-8.6和(d) MMP-10.5的UV-Vis图谱; 老化前后(e) MMP-5.0, (f) MMP-7.3, (g) MMP-8.6和(h) MMP-10.5的IR图谱

Figure 3. UV-Vis spectra of (a) MMP-5.0, (b) MMP-7.3, (c) MMP-8.6 and (d) MMP-10.5 before and after aging; IR spectra of (e) MMP-5.0, (f) MMP-7.3, (g) MMP-8.6 and (h) MMP-10.5 before and after aging

Aging time/d	OI_UV-Vis
Aging time/d	MMP-5.0	MMP-7.3	MMP-8.6	MMP-10.5
0	1	1	1	1
3	1.04	0.99	1.01	1.02
7	1.39	1.10	1.07	1.26
15	1.40	1.06	1.11	1.27
30	1.50	1.15	1.25	1.29
60	1.59	1.25	1.27	1.29
90	1.63	1.33	1.29	1.50

表1. 不同酸碱性样品在不同加速老化时间下的OIUV-Vis

Table 1. OIUV-Vis of samples with different pH values at various accelerated aging time

Aging time/d	OI_IR
Aging time/d	MMP-5.0	MMP-7.3	MMP-8.6	MMP-10.5
0	1	1	1	1
3	1.09	1.22	1.10	1.08
7	1.06	1.84	1.54	1.03
15	1.16	1.32	1.20	0.71
30	1.53	1.94	1.31	0.92
60	2.58	2.26	1.74	0.82
90	2.71	1.42	1.08	0.80

表2. 不同酸碱性样品在不同加速老化时间下的OIIR

Table 2. OIIR of samples with different pH values at various accelerated aging time

Sample	Aging time/d	ΔL*	Δa*	Δb*	ΔE*
MMP	0	–6.88	4.06	11.20	13.76
MMP-5.0	0	–5.69	2.93	8.26	10.45
	3	–9.26	2.67	8.15	12.62
	7	–8.83	3.20	9.76	13.54
	15	–9.37	4.15	12.41	16.09
	30	–10.03	4.62	13.12	17.15
	60	–10.67	6.38	16.06	20.31
	90	–10.98	7.02	16.85	21.30
MMP-7.3	0	–8.72	2.30	6.93	11.37
	3	–8.48	3.60	9.77	13.43
	7	–8.73	3.88	10.91	14.50
	15	–10.02	3.12	9.85	14.40
	30	–9.71	4.08	11.76	15.79
	60	–9.10	4.94	13.36	16.90
	90	–9.30	5.60	15.81	19.18
MMP-8.6	0	–9.84	2.60	6.88	12.28
	3	–8.91	3.28	9.70	13.57
	7	–7.49	4.38	12.20	14.97
	15	–8.93	3.57	10.99	14.60
	30	–7.43	4.68	12.85	15.56
	60	–8.75	5.20	14.23	17.50
	90	–9.15	5.92	15.44	18.90
MMP-10.5	0	–7.79	2.92	8.05	11.58
	3	–8.91	4.40	11.19	14.97
	7	–11.84	4.17	10.15	16.14
	15	–13.14	4.81	11.69	18.23
	30	–9.17	5.00	13.10	16.76
	60	–10.95	5.25	14.06	18.58
	90	–10.77	6.40	16.40	20.64

表3. 不同酸碱度样品在不同加速老化时间下的色差数据

Table 3. Color difference of samples with different pH values at various accelerated aging time

图4. 不同加速老化时间下(a) MMP-5.0, (b) MMP-7.3, (c) MMP-8.6和(d) MMP-10.5的数码图片. 从左至右分别对应0、3、7、15、30、60、90 d

Figure 4. Digital images of (a) MMP-5.0, (b) MMP-7.3, (c) MMP-8.6 and (d) MMP-10.5 at different accelerated aging time. From left to right, they correspond to 0, 3, 7, 15, 30, 60, and 90 d, respectively

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