JP2739918B2 - 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. Furthermore, this aluminum sulfate was also effective in preventing the generation of pitch and slime. However, when aluminum sulfate is used, a dehydration reaction occurs over time due to the presence of sulfate groups.
This causes a problem of deterioration. In acidic papermaking, usually
Aluminum sulfate is added to the pulp by 1-2%,
At this time, the pH of the pulp slurry becomes 4 to 5. When trying to neutralize pulp slurry for the purpose of preventing paper deterioration, the effect of the rosin-based sizing agent is as shown in FIG.
When the ratio is 6 or more, the paper sharply decreases, and thus 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 papermaking pulp slurry using aluminum sulfate and an internal sizing agent in combination is used. PKa
It has been found that good results can be obtained by coating an alkali metal salt of an acid of 10.0 or more, and the present invention has been achieved.

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.
A paper made by coating a paper made with a papermaking pulp slurry containing at least one filler, aluminum sulfate and an internal sizing agent, and an alkali metal salt of an acid having a pKa of 10.0 or more in a 25 ° C. aqueous solution. The pH of the dispersion obtained when 10% by weight of the at least one filler is dispersed in water (hereinafter referred to as the pH of the liquid when 10% by weight of the filler is dispersed) is 4.0 to 8.0. And the cold water extraction pH of the paper is between 7.5 and 9.0.

In the present invention, the pulp slurry for papermaking is set to be slightly acidic, and after the sheet is formed, only the surface layer of the sheet is made weakly alkaline by size press coating or the like during the papermaking process to prevent paper deterioration. Is what you do. 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.

[0008] As shown in Fig. 2, the deterioration of paper causes a practical problem when the paper extraction pH is 6.0 or less.
In addition, as previously mentioned in FIG. 1, the rosin-based sizing agent sharply decreases in sizing degree at pH 6 or more. The present inventors have studied a paper which is excellent in preventing deterioration of the paper and which has an excellent sizing property.As a result, it was found that the paper was made using a filler, a paper pulp slurry containing aluminum sulfate and an internal sizing agent. PK in 25 ° C. aqueous solution
a Coating with an alkali metal salt of an acid of 10.0 or more, and adjusting the pH of the paper for cold water extraction to 7.5 to 9.0, preferably 7.6 to 8.6.
By doing so, it has been found that expression of a sufficient size and effective prevention of paper deterioration can be realized. Paper extraction p
When H is 9.0 or more, the pen writing size (J, TAPPI Standard Test Method for Paper and Pulp No. 12) is reduced as shown in FIG. 3 and cannot be put to practical use.

In a pulp slurry for papermaking, an alkaline salt such as calcium carbonate, which has been conventionally used for neutral papermaking, is not used as a filler.
Is 4.0 to 8.0. 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,
The pH of the pulp slurry for papermaking may be 6.0 or more, and the sizing degree is sharply reduced with a rosin-based sizing agent or the like. 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 decreases, and the pH of the paper extracted with cold water is reduced.
The amount of the alkali metal salt of an acid having a pKa of 10.0 or more to be applied is required to be 7.5 to 9.0,
On the contrary, it tends to deteriorate.

Examples of the filler include kaolinite, illite, titanium dioxide, plastic pigment and the like, or a mixture of two or more thereof. The pH of the liquid at the time of dispersion is 4.0 to 8.0. Other fillers can be used in combination as long as it is within the range where 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 sizing agent used in the present invention includes rosin, alkyl ketene dimer, alkenyl succinic anhydride and the like, as well as those used as ordinary paper-making chemicals. .5% is appropriate.

The amount of aluminum sulfate used is 0.1
5 to 3.0%. A pulp slurry for acidic papermaking using aluminum sulfate has a pH of 4 to 6.

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, according to the present invention, the paper
An alkali metal salt of an acid having a pKa of 10.0 or more in a 5 ° C. aqueous solution is applied. Usually, an aqueous solution of an alkali metal salt of an acid having a pKa of 10.0 or more exhibits alkalinity, and by applying this aqueous solution, deterioration can be prevented without impairing the sizing degree. Below pKa 10.0,
The aqueous solution of the alkali metal salt of the acid becomes neutral to weakly alkaline, and the pH adjusting effect is lost. The acid that can be used is not particularly limited, regardless of whether it is an inorganic compound or an organic compound, as long as it has a pKa in a 25 ° C. aqueous solution of 10.0 or more. Examples of the alkali metal include sodium and potassium. Examples of usable salts include sodium carbonate (pKa 10.33) and sodium phosphate (pKa 12.35). 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. preferable.

An aqueous solution of an alkali metal salt of an acid having a pKa of 10.0 or more may further contain a water-soluble polymer, a surface sizing agent, a pigment, a dispersant, an antifoaming agent, a dye, a fluid modifier, and the like. it can.

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.

[0018]

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
When making a paper with a pulp slurry for papermaking using the same, an alkali metal salt of an acid having a pKa of 10.0 or more in a 25 ° C. aqueous solution is applied, and the pH of the paper in cold water extraction is 7.5.
Since it is adjusted to 9.0, the paper is excellent in expression of size and prevention of paper deterioration, and excellent in operability. In the present invention, the pH of the papermaking slurry is set to 4 to 6, and after the sheet is formed, only the surface layer of the sheet is made weakly alkaline by a size press or the like during the papermaking process 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.

[0019]

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 Chemical Handbook Basic Edition, 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 at the time of dispersion of 4.9 at 10% by weight), 1.5% of aluminum sulfate, alkenyl succinic anhydride A pulp slurry for papermaking having a pH of 0.15% and a pH of 5.1 was prepared. The pulp slurry for papermaking is made into a paper, and
In producing g / m ² high quality paper, a 0.3% aqueous solution of sodium carbonate (pKa 10.33) was applied by a size press. At this time, the coating amount of sodium carbonate was 0.1.
It was 2 g / m ² and the cold water extraction pH was 7.6. Table 1 shows the degree of Stigecht sizing, the degree of yellowing after the fade meter treatment test, and the bending strength of the 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 the time of dispersion of 6.7 at 10% by weight), 2.0% of aluminum sulfate, and 0.4% of alkyl ketene dimer. 1
A pulp slurry for papermaking was prepared at 5%. When the pulp slurry for papermaking is made into high-quality paper of 55.2 g / m ² , sodium carbonate (pKa) is produced by a size press.
A 0.5% aqueous solution of 10.33) was applied. At this time, the coating amount of sodium carbonate was 0.3 g / m ² , and the pH of cold water extraction was 8.1. 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.

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, 0.15 of rosin % To prepare a pulp slurry for papermaking. When the pulp slurry for papermaking is made into high quality paper of 150.1 g / m ² , sodium phosphate (pKa1) is produced by a size press.
2.35) of a 1.0% aqueous solution was applied. At this time, the coating amount of sodium phosphate was 1.5 g / m ² , and the cold water extraction pH was 8.9. 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 carbonate was not applied. The cold water extraction pH of this 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 Papermaking was carried out using 80 parts by weight of LBKP (csf 390 ml), 20 parts by weight of calcium carbonate (pH at the time of dispersion of 10% by weight of 9.4), and 0.15% of alkenyl succinic anhydride. Pulp slurry was prepared. The pulp slurry for papermaking was made to obtain high quality paper. The cold water extraction pH of this high quality paper is 7.8.
Met. 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.

[0025]

[Table 1]

[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 Inside the Sanyo Kokusaku Pulp Product Development Laboratory (56) References JP-A-57-139598 (JP, A) JP-A-57-205595 (JP, A) JP-A-60-235158 (JP, A) JP-B-40-565 (JP, B1)

Claims (2)

(57) [Claims] Claims: 1. A paper coated with at least one filler, and a papermaking pulp slurry containing aluminum sulfate and an internal sizing agent, wherein the at least one filler is based on water. The pH of the dispersion when dispersed by 10% by weight is 4.0 to 8.0, and the coating is performed by applying an alkali metal salt of an acid having a pKa of 10.0 or more in an aqueous solution at 25 ° C., The coated paper has a cold water extraction pH of 7.5 to 9.0. 2. The paper according to claim 1, which is used as a transfer paper for indirect electrostatic copying.