JP2002194695A - Paper for protection and preservation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protecting and preserving paper usable for a long period in a stable state and useful for securely leaving valuable cultural assets to posterity, usable in contact with an object to be preserved for a long period without exerting adverse effect on the object, causing little discoloration and lowering of strength of the paper and protecting the object from the acidic component and dust in air and the humidity change, etc., of the air and provide a method for the evaluation of the safety of paper. SOLUTION: Papers having different pH values of cold water extracts are provided, a test specimen is sandwiched between laminates of the above papers and subjected to accelerated aging test for definite period under preset temperature and humidity condition, and the influence of the contacting paper on the test specimen is evaluated. The influence of the protecting and preserving paper on the object to be preserved and the degradation of the protecting and preserving paper are evaluated by the above procedure and the protecting and preserving paper having high safety can be obtained by complying with the standard. The above standard is satisfied by using a neutral paper having a cold water extract pH of 6.5-10.0 and the total inorganic anion content of <=300 mg/kg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to paper which can be used in a stable state for a long period of time, and relates to a paper for protection and preservation for preserving valuable cultural heritage for future generations.
More specifically, the present invention relates to a paper that protects the object to be preserved from the effects of acid components in air, dust, changes in humidity, and the like, with little discoloration and reduction in strength even when used indirectly for a long time.

[0002]

2. Description of the Related Art In the 1980's, the problem of deterioration of acid paper became a big topic among people engaged in preservation of materials mainly in libraries. This led to the establishment of the National Diet Library's “Preservation Measures Group” and “Acid Paper Measures Group”, which, as part of their activities, called for the use of neutral paper in publications. Used by up to 80% of publications.

[0003] However, the term "neutral paper" has been coined as a synonym for acidic paper in which a conventional sizing agent is fixed with aluminum sulfate, and is usually called neutral paper including alkaline paper. Also, in Japan, there is still no standard for paper with consideration for preservability, and the definition of neutral paper is ambiguous. However, in 1988, cold water was the only standard described in the National Diet Library Monthly Report 332. At present, acid-free paper and alkaline paper having an extraction pH value of 6.5 or more are regarded as neutral papers and are used as criteria.

On the other hand, in the United States in 1984, "Permanence Standards for Printed Library Materials" or "AN
SI Z39.48-1984 "was enacted. At present, the International Organization for Standardization (ISO) is establishing standards for recording paper for storage purposes. ANS
The following Table (1) shows a comparison between the I and ISO standards, and shows the standards.

Table (1)

[0006] Even if the internal and external definitions and standards described above are complied with, it is extremely difficult to obtain a protection / preservation sheet that is safe for the object to be preserved. That is, neutral paper (hereinafter, referred to as "neutral paper") using a defined wood pulp and having a pH of 6.5 to 10.0 with cold water extraction having an alkaline reserve of 2% CaCO _3. The present inventors have found that there are many types of paper which cause discoloration and reduced strength.

On the other hand, as a method for evaluating the safety of paper,
At a set temperature and humidity for a certain period (for example, 80 ° C., 80%
R. H. A known method (called the hanging method) is to measure the discoloration and the decrease in strength after hanging and exposing the sample in a thermo-hygrostat to perform forced deterioration treatment.
However, comparing the object to be preserved as a valuable paper material, there are very few cases where it is stored as a single paper material, and it is overwhelmingly often stored in contact with paper of various characteristics. It is a fact. For this reason, this method cannot be an evaluation method for accurately judging the safety of the object to be preserved.

That is, the pH value of cold water extraction is 6.5 to 10.0.
In many cases, even neutral paper having the following formula (1) contains migrating substances (mainly inorganic anions) in the paper. However, the effect cannot be confirmed by the hanging method, and it is difficult to determine the safety of the paper. That is,
The effect of migrating substances cannot be seen.

[0009]

DISCLOSURE OF THE INVENTION The present invention is to provide a paper that can be used in a stable state for a long period of time, and that protects and preserves precious cultural heritage safely for future generations. . That is, even if it is used for a long time indirectly to the preservation material, it does not adversely affect the preservation material, and the protection / preservation paper itself is also less discolored and has a reduced strength.
An object of the present invention is to provide a protection / preservation paper for protecting an object to be preserved from the influence of an acid component in air, dust, a change in humidity, and the like.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the influence of the protection / preservation paper on the object to be preserved cannot be confirmed by the hanging method, but can be confirmed by a specific evaluation method. Further, from the evaluation results, it was found that all the inorganic anions in the paper, particularly sulfur-based anions, greatly affected the preservability of the protective / preserved paper itself and the safety of the paper to be preserved. Furthermore, it has been found that by keeping the total amount of inorganic anions below a certain level, it is possible to achieve good preservability, in particular, safety to the material to be preserved.

That is, the protected / preserved paper according to the present invention is a neutral paper having a pH value of cold water extraction of 6.5 to 10.0 and a total inorganic anion content of 3 kg / kg of dried paper.
It is characterized in that it is not more than 00 mg.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The total inorganic anion content of the present invention is defined as an ion chromatography analysis of inorganic anions.
F ⁻ , Cl ⁻ , NO ₂ ⁻ , Br ⁻ , NO ₃ ⁻ , measured using an onPac AS4A separation column (4 × 250 mm)
The total amount of anions such as PO ₄ ³⁻ and SO ₄ ²⁻ is expressed in mg per kg of paper sample weight after drying at 105 ° C. for 2 hours. Further, the sulfur-based anion is an anion such as a sulfate ion, a sulfite ion, and a thiosulfate ion. Furthermore, the cold water extraction pH value is JIS P-8133.
It is a value measured based on "test method of paper, paperboard and pulp-water extract pH".

The papermaking fibers used in the present invention include softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), and softwood bleached sulphite pulp (NBS).
ECF without bleached chemical pulp such as P) and chlorine bleaching method
-Non-wood fibers such as TCF pulp, cotton rug, linter, hemp, flax and the like are used alone or in combination.

If necessary, non-wood fibers such as bamboo, straw, kenaf, esparto and bagasse, rayon, vinylon,
Synthetic fibers such as nylon and recycled paper may also be used in some cases. However, basically, unless the virgin pulp of high purity with a small content of lignin or hemicellulose is used, it exceeds the total inorganic anion content shown in the present invention,
This is not desirable because it is likely to cause discoloration and strength reduction.

The above-mentioned various wood pulp and non-wood fibers are said to have been sufficiently washed, but the chemicals used during the manufacturing process usually remain. Cl
^{_{-, NO 3 -, PO 4}} 3-, an anion total amount of SO ₄ ^2-or the like, 50～700Mg corresponds to the pulp weight 1kg per after drying is adhered, even cold water extraction pH values from 6.0 to 9 .8. In particular, when recycled paper is used, it cannot be used until it is thoroughly washed and the total amount of residual anions and the presence or absence of other migrating substances are checked.

When the various pulp described above is disintegrated and the handmade paper made of pulp fiber alone is measured, the total amount of the anions adheres to 20 to 100 mg per 1 kg of the dried paper weight, and is extracted with cold water. The pH value was also 6.3 to 6.7. That is, even if a material having a considerably high purity is used, the obtained paper shows a weak acidity. Of course, it must be taken into account that the water used also contains anions.

Based on the above results, in order to obtain neutral paper having a pH value of cold water extraction of 6.5 or more, a filler exhibiting alkalinity is used. The filler is preferably an existing inexpensive powder such as calcium carbonate (no matter whether heavy or light), magnesium carbonate, aluminum hydroxide, magnesium hydroxide, etc., and these can be used alone or as a mixture. However, a solid acid filler such as clay is not preferred. The amount used is 0.02 to 100 parts by weight of papermaking fiber.
１５15.0 parts by weight. If it is less than 0.02 parts by weight, the pH value of cold water extraction may be lower than 6.5, which is not preferable. Even if it is used at 15.0 parts by weight or more, the pH value does not exceed 10.0, so it is unnecessary. . Also, ANSI and I
It is not necessary to be concerned with the 2% CaCO ₃ equivalent of the SO standard value.
This is because some of the objects to be preserved extremely dislike the alkalinity. Rather, it is often desired to use a cold water extraction pH value of about 6.5 to 7.5 with a use amount of 2% CaCO ₃ or less.

In the present invention, an existing sizing agent or paper strength enhancer is required and the minimum amount is provided by internal addition or a size press, but use of an anion or a surfactant-containing agent is avoided as much as possible. There is a need. As a sizing agent, using alkyl ketene dimer or alkenyl succinic anhydride, etc.
Cationized starch or the like is used as a fixing agent. However,
It is important that the amount used is adjusted so that the total inorganic anion content per kg of the dried paper is 300 mg or less. If necessary, a coloring agent such as a wet paper strength enhancer or a dye or pigment can also be used in consideration of the above points.

The paper for protection and preservation of the present invention is obtained by preparing a slurry mainly comprising the above-mentioned papermaking fiber and filler, adding a sizing agent and a fixing agent thereto, and making the paper with an existing paper machine. In addition, coloring and embossing can be performed as necessary. At this time, it is important to avoid the use of extra materials and to use pulp with high purity and to make the composition as simple as possible.

Next, a method for evaluating the safety of the protection / preservation paper proposed by the present invention will be described. It is a well-known fact that paper degradation progresses from the time the paper is manufactured. Generally, it is said that the higher the pH value of paper extracted with cold water, the longer the life of the paper. However, at the actual storage site, the storage object is directly wrapped with paper having a cold water extraction pH value of 6.5 to 7.5, and further a storage box made of paper having a cold water extraction pH value of 8.5 to 10.0. The storage method is adopted. In other words, the object to be preserved is prevented from directly touching a highly alkaline substance or a low acidic substance. The use of highly alkaline paper for the storage box is intended to neutralize acidic components in the air inside and outside the box and protect the storage object.

The present inventors have found that the pH value of cold water extraction is 6.5 to 6.5.
Even if the paper shows 10.0 and is indirectly connected to an acidic paper of 6.4 or less for a long time, an experiment was conducted to find a paper with little discoloration or reduction in strength, and it was confirmed that measurement was possible by a specific method. I found it. The specific method is to use papers having different cold water extraction pH values, and sandwich a sample piece of each type of acidic paper and neutral paper between texts bound with each paper,
At a set temperature and humidity for a certain period (for example, 80 ° C., 80%
R. H. This is a method for measuring discoloration and change in strength after performing a forced deterioration treatment in a thermo-hygrostat. By measuring by the insertion method (hereinafter referred to as “insertion method”), it is possible to grasp the correlation between adjacent papers having different pH values, which was impossible with the conventional hanging method.

The protective / preserved paper measured by the insertion method preferably retains a strength remaining ratio of 50% or more after the forced deterioration treatment. If it is less than 50%, the protection / preservation paper itself is broken, and the purpose cannot be achieved. Further, the color difference after forced deterioration is preferably 9.9 or less. 9.
If the color difference is larger than 9, the appearance will not only be worse,
The effect on the object to be preserved becomes significant. That is, a change in the color difference means that the causative substance is present in the protection / preservation paper. For this reason, there is an extremely high risk that the causative substance affects the object to be preserved.

According to the insertion method, the influence on the storage object and the pH
By measuring the interrelationship of papers with different values, it is possible for the first time to evaluate the safety of protected and stored paper in actual use. When the insertion method is evaluated, the safety of the object to be preserved and the protection / preservation paper itself can be maintained even when the protection / preservation paper is manufactured using the conventional hanging method, pH value and alkali reserve value specified by ANSI and ISO standards. May not be ensured. That is, the conventional method cannot evaluate the true safety. This is because, as described above, the migrating substances (mainly inorganic anions) contained in the paper are not considered.

When the safety of the protection / preservation paper and the discoloration and strength deterioration of the protection / preservation paper itself were evaluated by the insertion method, these phenomena revealed that the total inorganic anion content in the paper could not be considered so far. It has been found to affect.

The total inorganic anion content of paper with little discoloration or strength reduction must be 300 mg or less per kg of paper weight after drying.
Desirably less than mg. 1kg paper weight after drying
If the total inorganic anion content per unit exceeds 300 mg, the discoloration and strength deterioration of the protection / preservation paper become remarkable, and the influence on the preservation object becomes large. This is confirmed by the insertion method. In particular, when the amount of sulfur-based anion exceeds 70 mg, this phenomenon becomes remarkable.

The total inorganic anion content is such that the paper weight after drying is 1
In order to obtain protection and preservation paper of 300 mg or less per kg, the pulp, chemicals and production method to be used must be strictly selected as described above. For example, when a small amount of aluminum sulfate is used, the value naturally becomes 70 mg or more. Also, even if aluminum sulfate is not used as a fixing agent at all, insufficient cleaning of raw material conditioning equipment and transport / papermaking equipment, etc., and contamination of sulfate ions that may be caused by the type and amount of water and chemicals used. In some cases.

The selection of raw materials for papermaking, the selection and use of chemicals, the papermaking method, etc. are thoroughly examined, the total inorganic anion content satisfying the safety standards is determined, and the protection / preservation paper based on the standards is determined. To manufacture.

The inventors of the present invention pay attention to the content of anions caused by acidic substances. The main cause of paper deterioration is hydrogen ions of inorganic acids (eg, HCl and H ₂ SO ₄ ) due to anions. Is considered to be due to acid hydrolysis, which breaks down the intermolecular bond between glucose and cellulose, and to degradation and crystallization of cellulose due to dehydration of sulfuric acid.

Next, the use of the protection / preservation paper of the present invention will be described. Using paper having a basis weight of 150 to 250 g / m ² ,
After manufacturing double-sided and double-sided corrugated cardboards of A, B, C, BA, and E flutes, they are punched to predetermined dimensions and used for assembling type document storage boxes, or pasted with paper having a basis weight of 250 to 1000 g / m ^2. It can be used as a framed mat board having a thickness of 0.8 to 3.0 mm. In addition, basis weight 40-120g
/ M ² paper, and can be used as a simple and safe storage bag for historical materials and photographs. In addition, the use of the protection / preservation paper of the present invention is not limited to the cases described above.

[0030]

EXAMPLE 1 40 parts by weight of softwood bleached kraft pulp (NBKP) and 450 parts by weight of hardwood bleached kraft pulp (LBKP) were mixed with 450 parts by weight.
mlC. S. F. The pulp slurry obtained by beating the mixture was mixed with calcium carbonate (trade name “Charcoal P Light 10”).
0 ", 0.03 parts by weight of Shiraishi Industry Co., Ltd.
Adjusted to a 2% concentration slurry. A sizing agent (trade name “Size Pine K-90”) is used based on the solid content weight of the slurry.
3 ", 0.15% by Arakawa Chemical Industries, Ltd., wet paper strength enhancer (trade name" WS-500 ", Nippon PMC Co., Ltd.)
Was added, and paper was made with a square sheet machine to obtain a protected / preserved paper having a basis weight of 80 g / m ² .

Example 2 40 parts by weight of softwood bleached kraft pulp (NBKP) and 60 parts by weight of hardwood bleached kraft pulp (LBKP) were 400 m
1C. S. F. To the pulp slurry obtained by beating
0.06 parts by weight of the same calcium carbonate as in Example 1 was mixed to prepare a pulp slurry having a concentration of 8%. 0.60% of cationized starch (trade name “Neotack L-1” manufactured by Nippon Shokuhin Kako Co., Ltd.) based on the weight of solid content of the slurry;
After 0.12% of the same sizing agent as in Example 1 was added, protected / preserved paper having a basis weight of 80 g / m ² was obtained using a fourdrinier paper machine in a conventional manner.

Example 3 40 parts by weight of softwood bleached kraft pulp (NBKP) and 60 parts by weight of hardwood bleached kraft pulp (LBKP) were 470 m
1C. S. F. To the pulp slurry obtained by beating
10.0 parts by weight of the same calcium carbonate as in Example 1 was mixed to adjust the pulp slurry to a concentration of 8%. After adding 1.0% of the same cationized starch as in Example 2 and 0.20% of the same sizing agent as in Example 1 with respect to the solid content weight of the slurry, the basis weight was 80 g / g on a fourdrinier paper machine by a conventional method. to give the protection and preservation paper m ^2.

Example 4 40 parts by weight of softwood bleached kraft pulp (NBKP) and 60 parts by weight of hardwood bleached kraft pulp (LBKP) were 450 m in length.
1C. S. F. To the pulp slurry obtained by beating
15.0 parts by weight of the same calcium carbonate as in Example 1 was mixed to adjust to a 2% concentration slurry. After adding 0.20% of the same sizing agent and 0.30% of the wet strength agent as in Example 1, and 1.0% of the same cationic starch as in Example 2, based on the solid content of the slurry, Paper was made using a sheet making machine to obtain a protected / preserved paper having a basis weight of 80 g / m ² .

Comparative Example 1 40 parts by weight of softwood bleached kraft pulp (NBKP) and 60 parts by weight of hardwood bleached kraft pulp (LBKP) were 460 m
1C. S. F. To the pulp slurry obtained by beating
5.0 parts by weight of Shirato (trade name “Shirato Ichi Grade” manufactured by Kanaya Kogyo Co., Ltd.) was mixed in to adjust the pulp slurry to 8% concentration.
2.0% of a sizing agent (trade name “Size Pine E” manufactured by Arakawa Chemical Industry Co., Ltd.) based on the solid weight of the slurry
And aluminum sulfate (produced by Daimei Chemical Industry Co., Ltd.) at 5.0
%, And the basis weight is 80 g / m.
I got ² papers.

Comparative Example 2 Softwood bleached kraft pulp (NBKP) 40 parts by weight, hardwood bleached kraft pulp (LBKP) 60 parts by weight was 450 m
1C. S. F. To the pulp slurry obtained by beating
0.03 parts by weight of the same calcium carbonate as in Example 1 was mixed to adjust to a 2% concentration slurry. After adding 2.0% of the same sizing agent as in Comparative Example 1, 1.0% of aluminum sulfate, and 0.50% of the same wet strength agent as in Example 1, based on the solids weight of the slurry, Paper was made with a sheet machine to obtain paper having a basis weight of 80 g / m ² .

Comparative Example 3 40 parts by weight of softwood bleached kraft pulp (NBKP) and 60 parts by weight of hardwood bleached kraft pulp (LBKP) were 450 m
1C. S. F. To the pulp slurry obtained by beating
15.0 parts by weight of the same calcium carbonate as in Example 1 was mixed to adjust to a 2% concentration slurry. After adding 2.0% of the same sizing agent as in Comparative Example 1, 1.5% of aluminum sulfate and 0.8% of the same wet strength agent as in Example 1, based on the solids weight of this slurry, Paper was made with a sheet machine to obtain paper having a basis weight of 80 g / m ² .

The chemicals and amounts used in the examples and comparative examples described above are as shown in the following Table (2). The numbers in the table represent% by weight based on the solid content of the slurry. Table (2)

However, E in the table is size pine E, AKD
Indicates size pine K-902, starch indicates cationic starch, band indicates aluminum sulfate, and wet indicates wet paper strength agent.

Next, using the paper samples obtained in Examples and Comparative Examples, a forced deterioration test was carried out based on the evaluation method proposed by the present inventors. Comparative Example 1 First Obtained with Fourdrinier
Using each of the papers of Example 2 and Example 3,
It was bound in 5 sizes. Next, after sandwiching the paper pieces of Comparative Examples 1 to 3 and Examples 1 to 4 between the three types of books, 80%
R. H. In a constant temperature and humidity chamber (Model: PLATINAUS)
PR-3SP, manufactured by Tabai Espec Corp.) for 24 days. The cold water extraction pH value before and after the degradation treatment is J
Measured based on ISP-8133 (Model: TOA pH
Meter HM-78, manufactured by Toa Dempa Kogyo Co., Ltd.)
The color change is measured by a color difference meter (model: CM-370 od, manufactured by Minolta Co., Ltd.), and the change in strength is measured by bending strength (model: MIT-S, manufactured by Toyo Seiki Co., Ltd.). did. The total inorganic ion content and sulfur-based anion content before the deterioration treatment were determined by ion chromatography (model: DI
ONEX 2000i / SP, Dionex Corporation
IonPacAS4A separation column (4 x 250m)
The results measured using m) are expressed in mg per kg of paper sample weight after drying at 105 ° C. for 2 hours. Further, the residual ratio was shown as a percentage value obtained by multiplying 100 by a value obtained by dividing the number of times of the bending strength after the deterioration treatment by the number of times of the bending strength before the deterioration treatment. The results are shown in the following Table (3). As shown in the table, Example 2 (pH = 6.9: neutral paper) was compared with Comparative Example 1 (pH = 6.0: acidic paper) and Example 3 (pH =
9.3: neutral paper) even when in contact with neutral paper. It is shown that the discoloration of the acidic paper increases as it comes into contact with the neutral paper having high alkalinity. Even with neutral paper, the total inorganic anion content is 300 m
g and the sulfur-based anion exceeds 70 mg,
It turns out that discoloration and intensity | strength fall are large. Furthermore, when the same papers are stacked, the discoloration and strength decrease of acid paper are the largest, and neutral paper with high alkalinity has almost the same degree of discoloration but large decrease in strength as neutral paper with low alkalinity. It is shown that. Conventionally, the higher the pH value of the cold water extraction, the longer the life of the paper is. However, in the present invention, even if the pH value is too high, the strength of the paper itself may be reduced (however, the strength is lower than that of acidic paper). Less). Table (3)

However, the sulfur-based anions in Examples and Comparative Examples were carried out by focusing on sulfate ions. Further, when the degree of discoloration that causes no problem in use was compared visually, ΔE
If the value exceeds 10.0 is considered inappropriate,
The following Table (4) shows that those with a residual ratio of 50% or less in strength change were regarded as inappropriate for use. Further, in view of the above results, the protected and preserved paper 1k after drying of the present invention is used.
Based on the weight of g, the total inorganic anion content was set to 300 mg or less, and the safety standard for setting the sulfur-based anion content to 70 mg or less was determined. Table (4)

If the ΔE after the forced deterioration treatment was 9.9 or less, it was regarded as appropriate (（), and if ΔE was 10.0 or more, it was inappropriate (x). Similarly, a residual rate of 50% or more was regarded as appropriate (適), and a residual rate of 49% or less was regarded as inappropriate (x). In addition, the sample which became ○ in both the residual ratio and ΔE was judged as having no practical problem.

Next, typical cold water extraction pH values after the aging (forced deterioration treatment) performed in the present invention are shown in Table (5). However, the numerical value in parentheses indicates the residual rate. Table (5)

As shown in the table, in both acidic paper and neutral paper, the initial pH value decreases with aging, and the higher the initial pH value, the higher the pH value after aging. In addition, it was confirmed that the pH value decreased more greatly when the paper was in contact with the acidic paper than the neutral paper, and the residual ratio of strength was lower. However, the pH in the table
The magnitude of the value is not necessarily proportional to the magnitude of the survival rate.

[0044]

As described above, the protection / preservation paper of the present invention has the following remarkable effects.

(1) Even if the paper has been in contact with papers having different cold water extraction pH values for a long period of time, it is highly safe with little discoloration or reduced strength.

(2) If the forced deterioration test method by the insertion method proposed by the present invention is used, migratory substances (mainly inorganic anions) in paper which could not be confirmed by the conventional hanging method.
It was possible to confirm the effect of the above, and it was possible to determine that the total inorganic anion content in the paper was safe if it was below which level.

(3) In the case of directly wrapping the object to be preserved, the total inorganic ion content in the paper is 3 per kg of the dried paper weight.
The safest ones are those having a water content of not more than 00 mg and a sulfur-based anion content of not more than 70 mg, and exhibiting a cold water extraction pH value as close to 7.0 as possible.

(4) If protective / preserving papers of various basis weights are prepared, safe envelopes, beds, storage boxes, etc. for directly storing the objects to be preserved can be realized, and a matte board for frame mounting, watercolor paper, lithographic paper, etc. It can be widely used for paper materials such as fancy paper and colored and embossed fancy paper. Also,
It is most suitable for printing paper such as official documents for keeping records for future generations.

Claims (4)

[Claims] 1. A neutral paper having a cold water extraction pH value of 6.5 to 10.0 and having a total inorganic anion content of 1 weight after drying the paper.
Protection / preservation paper characterized by being 300 mg or less per kg. 2. The protected and preserved paper according to claim 1, wherein the content of sulfur-based anions in the total inorganic anion content is 70 mg or less per kg of the dried paper. 3. A method according to claim 1, wherein the amount of 0.0
3. The protective / preserving paper according to claim 1, comprising 2 to 15.0 parts by weight of calcium carbonate. 4. An evaluation method in which test papers are sandwiched between papers having different pH values for extraction with cold water, a test sample is sandwiched between papers laminated with each other, and forced deterioration treatment is performed for a certain period of time at a set temperature and humidity. The protection / preservation paper according to any one of claims 1 to 3, wherein the residual strength ratio is maintained at 50% or more and the color difference is 9.9 or less.