JP2739917B2 - Paper that prevents deterioration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to paper whose deterioration has been prevented.

[0002]

2. Description of the Related Art Sizing agents are usually used to impart water resistance to paper and prevent recording bleeding. In a conventional acidic papermaking, the paper is treated with a rosin-based sizing agent or the like, and treated with aluminum sulfate as a fixing agent to give a desired sizing degree. Further, this aluminum sulfate was also effective in generating pitch and slime. However, when aluminum sulfate is used, the presence of a sulfate group causes a dehydration reaction with the passage of time, which causes a problem of so-called deterioration such as yellowing and reduction in strength of the paper. In acidic papermaking, usually, aluminum sulfate is added to the pulp at 1 to 2%, and the pH of the pulp slurry at this time becomes 4 to 5. When trying to neutralize pulp slurry to prevent paper degradation,
As shown in FIG. 1, the effect of the rosin-based sizing agent sharply decreases at a pH of 6 or more, so that a paper which can be practically used and has excellent prevention of deterioration cannot be obtained.

On the other hand, there is a so-called neutral paper which is excellent in preventing deterioration. In a neutral paper, a neutral sizing agent such as an alkyl ketene dimer or an alkenyl succinic anhydride is used as a sizing agent, a cationic polymer is used as a retention aid, and calcium carbonate is used as a filler. In the neutral papermaking technique, the extraction pH of the paper is about 7.9 to 9.0. In this case, the pH of the pulp slurry for papermaking is as alkaline as the extraction pH, so that the entire paper layer structure is the same. pH. Neutral papermaking has many operational problems, such as generation of pitch and slime and contamination with a neutral sizing agent, as compared with conventional acidic papermaking, and has the disadvantage of increasing costs.

[0004]

SUMMARY OF THE INVENTION The present inventors have studied a paper excellent in operability and deterioration prevention and a method for producing the same. As a result, the present inventors have found that a system using aluminum sulfate and alkenyl succinic anhydride in combination is used for papermaking. It has been found that good results can be obtained by using a water-soluble alkaline salt in the pulp slurry and further applying an alkali metal salt of an acid having a pKa of 5 to 14, thereby achieving the present invention.

Accordingly, an object of the present invention is to provide a paper which prevents deterioration of the paper and which is excellent in operability even though the sizing method uses aluminum sulfate, and a method for producing the paper.

[0006]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
When making a paper with a pulp slurry for papermaking adjusted to pH 6.5 to 7.5 containing at least one filler and aluminum sulfate, alkenyl succinic anhydride and a water-soluble alkaline salt, pKa5 in an aqueous solution at 25 ° C.
A paper coated with an alkali metal salt of an acid of from 1 to 14, wherein the at least one filler is dispersed in water at 10% by weight and the pH of the dispersion (hereinafter referred to as 10% by weight of the filler)
Of the liquid at the time of dispersion. ) Is 4.0 to 8.0,
Achieved by paper characterized in that the cold water extraction pH of the paper is between 7.5 and 9.0.

In the present invention, the generation of pitch and slime is prevented by adding aluminum sulfate to the pulp slurry for papermaking. Furthermore, it was found that the addition of aluminum sulfate was effective in reducing the stain on the paper machine due to the neutral sizing agent, and at the same time, the expression of sizing degree and effective prevention of paper deterioration were realized.

In the present invention, the papermaking slurry is kept near neutral, and after the sheet is formed, only the surface layer of the sheet is made slightly alkaline by size press coating or the like during the papermaking process to prevent the deterioration of the paper. It is. Although the deterioration of the paper is greatly affected by light, a sufficient effect was obtained by taking measures against the surface layer of the paper.

Regarding the deterioration of paper, as shown in FIG. 2, when the extraction pH of paper is lower than 6.0, the deterioration becomes a practical problem.
In addition, as previously mentioned in FIG. 1, the rosin-based sizing agent sharply decreases in sizing degree at pH 6 or more. As a result of studying the sizing agent, the present inventors have found that alkenyl succinic anhydride can be used from the viewpoint that the sizing degree is exhibited at a pH of 6 or more and that it can be used in combination with aluminum sulfate. However, even with alkenyl succinic anhydride, if the pH is 8 or more, the size decreases, and it cannot be put to practical use. Therefore, in the present invention, the pH of the pulp slurry for papermaking is adjusted.
Was adjusted to 6.5-7.5, and the final cold water extraction pH of the paper was 7.5-9.5 by coating with an alkaline salt.
0, preferably 7.6 to 8.6. If the extraction pH of the paper is 9.0 or more, the pen writing size (J, TAPPI Standard Test Method for Paper Pulp No. 12) is reduced as shown in FIG. 3 and cannot be put to practical use. Therefore, it has been found that this papermaking method can realize a sufficient degree of sizing and effective prevention of paper deterioration.

In order to adjust the pH of the pulp slurry for papermaking to 6.5 to 7.5 with a water-soluble alkaline salt, an alkaline salt such as calcium carbonate conventionally used for neutral papermaking is used as a filler. Instead, a filler having a pH of 4.0 to 8.0 at the time of dispersion at 10% by weight is used. However,
Even if a small amount of an alkaline salt such as calcium carbonate is mixed, it can be used as long as the pH of the liquid at the time of the dispersion is in the range of 4.0 to 8.0. When the pH of the liquid at the time of dispersion is 8.0 or more, it is not easy to add a water-soluble alkaline salt to the pH range of the present invention, and the size is reduced even when alkenyl succinic anhydride is used. I do. Further, when the pH of the liquid at the time of dispersion is 4.0 or less, the pH of the pulp slurry for papermaking is lowered, and a large amount of a water-soluble alkaline salt for adjustment is required, which tends to cause deterioration.

The filler may be, for example, kaolinite, illite, titanium dioxide, plastic pigment or a mixture of two or more of these. The dispersion has a pH of 4.0 to 8.0 when dispersed. Other fillers can be used in combination as long as they can be used. Further, even if the filler has a pH of 4.0 or less, or 8.0 or more, the filler can be adjusted to a pH of 4.0 to 8.0 at the time of dispersion by surface treatment or coating on the filler. You can use this if you like. In the present invention, it is particularly preferable to use kaolinite, illite or titanium dioxide from the viewpoint of operability. The filler is usually added to the paper in an amount of 3 to 30% by weight.

The alkenyl succinic anhydride used as a sizing agent in the present invention is used as a general papermaking chemical, and its addition amount is suitably 0.01 to 0.5%.

In the present invention, aluminum sulfate is used from the viewpoint of operability. The amount of aluminum sulfate used is 0.5 to 3.0%. Since the pulp slurry for acidic papermaking using aluminum sulfate has a pH of 4 to 5, the pH of the pulp slurry is adjusted to 6.5 to 7.5 with a water-soluble alkaline salt. Examples of the water-soluble alkaline salt include hydroxides such as sodium hydroxide and potassium hydroxide, silicates such as sodium silicate, carbonates such as sodium carbonate, potassium carbonate and sodium hydrogen carbonate, hydrogen carbonate, and phosphorus. There are phosphates such as sodium acid and disodium hydrogen phosphate and hydrogen phosphate.
The amount of the water-soluble alkaline salt to be added can be appropriately adjusted within the range where the pH of the pulp slurry for papermaking is 6.5 to 7.5, but is preferably 0.01 to 5.0%.

The pulp used in the present invention is mainly made of chemical pulp from the viewpoint of preventing deterioration. However, even if recycled pulp or mechanical pulp is used, paper with relatively little deterioration can be obtained.

In addition, cationized starch, a retention aid, a dye, a paper strength enhancer, an antifoaming agent, and the like can be appropriately added as internal additives.

Further, in the present invention, 2
PKa in a 5 ° C. aqueous solution is 5 to 14, preferably 6 to
Apply the alkali metal salt of acid 13 Usually pKa5
The aqueous solutions of the alkali metal salts of the acids Nos. To 14 exhibit weak to alkaline properties, and by applying this aqueous solution, the deterioration can be prevented without impairing the sizing degree. At a pKa of 5 or less, the aqueous solution of the alkali metal salt of an acid becomes neutral to acidic, and the pH adjusting effect is lost. Further, at a pKa of 14 or more, the alkalinity becomes too strong.
Affects size. 25 acids that can be used
There is no particular limitation on inorganic and organic compounds as long as they have a pKa in the range of 5 to 14 in an aqueous solution of ° C.
Examples of the alkali metal include sodium and potassium. Salts that can be used include, for example, sodium hydrogen carbonate (pKa 6.35), sodium carbonate (p
Ka 10.33), disodium hydrogen phosphate (pKa
7.20), sodium phosphate (pKa 12.35),
Can be mentioned. The coating amount is adjusted so that the cold water extraction pH of the paper is 7.5 to 9.0, and is usually 0.01 to 5.0 g / m ² , preferably 0.02 to 5.0 g / m ^2.
2.0 g / m ² . The coating method can be selected from existing coating methods such as a size press coat, an air knife coat, a blade coat, a roll coat, and a bar coat, but a size press coat is preferable from the viewpoint of operability.

An aqueous polymer, a surface sizing agent, a pigment, a dispersant, an antifoaming agent, a dye, a flow modifier, and the like can be added to the aqueous solution of an alkali metal salt of an acid having a pKa of 5 to 14.

The paper of the present invention may be used for general office paper, printing paper,
Used for various types of base paper for coating and transfer paper for indirect electrostatic copying.

[0019]

As described in detail above, the paper of the present invention has a pH of 4.0 to 8.0 when the filler is dispersed at 10% by weight, despite the size method using aluminum sulfate. 0
The pH of the pulp slurry for papermaking is adjusted to 6.5 to 7.5, and the paper is made.
a. The alkali metal salts of acids a to 14 are coated, and the cold water extraction pH of the paper is adjusted to 7.5 to 9.0, so it is excellent in expression of size and prevention of paper deterioration, and excellent in operability. Paper. In the present invention, the papermaking slurry is kept near neutral, and only the surface layer of the sheet is made slightly alkaline by a size press or the like during the papermaking process after the sheet is formed,
This is to prevent paper deterioration. Although the deterioration of the paper is greatly affected by light, a sufficient effect can be obtained by taking measures against the surface layer of the paper.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the examples,% indicates pulp weight%. In addition, cold water extraction pH is measured according to JISP8133. As the pKa value, a value described in the Chemical Handbook Basic Edition, revised 3rd edition (edited by The Chemical Society of Japan, published by Maruzen, 1984) was used.

Example 1 80 parts by weight of LBKP (csf 390 ml), 20 parts by weight of kaolinite (pH of 4.9 when dispersed at 10% by weight), 1.5% of aluminum sulfate, alkenyl succinic anhydride A pulp slurry was prepared with 0.15% product and 0.3% sodium hydroxide. This pH was 6.6. When this pulp slurry is made into paper and 64.0 g / m ² of high quality paper is produced, sodium carbonate (pKa1
0.33) was applied. At this time, the coating amount of sodium carbonate was 0.2 g / m ² , and the pH of cold water extraction was 7.9. Table 1 shows the degree of Stechigt sizing, the degree of yellowing with a fade meter, and the bending strength of this high quality paper. There was no problem in operability such as contamination of the dryer during papermaking.

Example 2 80 parts by weight of LBKP (csf 390 ml), 20 parts by weight of illite (pH at 6.7 when dispersed at 10% by weight), 2.0% of aluminum sulfate, alkenyl succinic anhydride 0.
A pulp slurry was prepared with 15% and 0.4% sodium hydroxide. This pH was 7.3. When this pulp slurry is made into paper and 55.2 g / m ² of high quality paper is manufactured, sodium bicarbonate (pKa
6.35) was applied. At this time, the coating amount of sodium bicarbonate was 0.3 g / m ² ,
The cold water extraction pH was 7.6. Example 1
Table 1 shows the results of the evaluation in the same manner as in the above. There was no problem in operability such as contamination of the dryer during papermaking.

EXAMPLE 3 80 parts by weight of LBKP (csf 390 ml), 20 parts by weight of titanium dioxide (pH at the time of dispersion of 6.8 at 10% by weight), 2.0% of aluminum sulfate, alkenyl succinic anhydride A pulp slurry was prepared with 0.15% product and 0.4% sodium hydroxide. This pH was 7.3. When this pulp slurry is made into paper to produce high quality paper of 150.1 g / m ² , sodium phosphate (pK
a1.35) of a 1.0% aqueous solution. At this time, the coating amount of sodium phosphate was 1.5 g / m ² , and the cold water extraction pH was 8.8. Table 1 shows the results of evaluating this high quality paper in the same manner as in Example 1. There was no problem in operability such as contamination of the dryer during papermaking.

Comparative Example 1 Fine paper was obtained in the same manner as in Example 1 except that sodium hydroxide was not added and sodium carbonate was not applied. At this time, the pH of the pulp slurry was 5.6,
The cold water extraction pH of the paper was 5.5. Table 1 shows the results of evaluating this high quality paper in the same manner as in Example 1.

Comparative Example 2 Pulp containing 80 parts by weight of LBKP (csf 390 ml), 20 parts by weight of calcium carbonate (pH of 9.4 when dispersed at 10% by weight), and 0.15% of alkenyl succinic anhydride A slurry was prepared. This pH was 7.9. This pulp slurry was paper-made to obtain high quality paper. The cold water extraction pH of this high quality paper was 7.8. Table 1 shows the results of evaluating this high quality paper in the same manner as in Example 1. There was a problem in operability such as contamination of the dryer during papermaking.

[0026]

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between pH and sizing degree of a pulp slurry for papermaking.

FIG. 2 is a graph showing the relationship between paper extraction pH and paper deterioration.

FIG. 3 is a graph showing the relationship between paper extraction pH and pen writing size.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshifumi Iimori 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Sanyo Kokusaku Pulp Co., Ltd. Product Development Laboratory (56) References JP-A-57-139598 (JP, A) JP-A-60-235158 (JP, A) JP-A-57-205595 (JP, A) JP-B-40-565 (JP, B1)

Claims (2)

(57) [Claims] Claims: 1. A paper which has been coated in making a paper with a pulp slurry for papermaking comprising at least one filler and aluminum sulfate, alkenylsuccinic anhydride and a water-soluble alkaline salt, wherein the at least one filler The filler has a pH of 4.0 to 8.0 when dispersed in water at 10% by weight, and the pH of the pulp slurry for papermaking is adjusted to 6.5 to 7.5. The coating has a pKa of 5 to 25 ° C. in an aqueous solution.
14 is performed by applying an alkali metal salt of an acid, and the coated paper has a cold water extraction pH of 7.5 to 7.5.
A paper characterized by being 9.0. 2. The paper according to claim 1, which is used as a transfer paper for indirect electrostatic copying.