JPH10251991A - Coated base paper for web offset printing - Google Patents

Abstract

(57) [Summary] A base paper for producing coated paper for offset rotary printing which has good drainage during papermaking, high interlaminar strength and air permeability. SOLUTION: After adding a filler and a cationized starch to a pulp suspension, 750 to 1000 m ² / g is used as a drainage improver.
Base paper for coated webs for offset rotary printing, to which a structural anionic silica sol having a specific surface area in the range described above is added. Preferably, at least one of anionic, cationic or amphoteric polyacrylamide is blended as a paper strength enhancer. Further, base paper for coated paper for offset rotary printing, to which cationic polyacrylamide as a drainage improver and a structural anionic silica sol having a specific surface area in the range of 750 to 1000 m ² / g are added. Preferably, at least one of anionic, cationic or amphoteric polyacrylamide is blended as a paper strength enhancer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated base paper for web offset printing (hereinafter, may be abbreviated as a coated base paper). More specifically, the present invention relates to a coated base paper for producing a coated printing paper having high interlayer strength and air permeability.

[0002]

2. Description of the Related Art In recent years, the importance of printed materials as a medium for publishing and advertising has been re-recognized, and visualization, colorization, and upgrading of printed materials have been promoted. , Called coated paper). In particular, there is a great demand for coated paper for offset printing which is most widely used for multicolor printing.

[0003] In offset printing, after printing water and ink on the paper surface, the paper is rapidly dried at 115 to 125 ° C to finish it. When offset printing is performed on coated paper, it is included in the coated base paper when dried at high temperature. Conventionally, there has been a problem that a state in which the coating layer swells due to evaporation of the water, that is, so-called "blistering" occurs, and the value as coated paper is reduced.

[0004] As a method of improving the blistering of a coated paper, a method of increasing the strength against the force applied in the thickness direction of the coated base paper, that is, a method of increasing the interlayer strength, and a method of increasing the air permeability of the coated base paper have conventionally been used. A method of releasing water vapor in the base paper has been adopted. The interlayer strength of the coated base paper is adjusted by increasing or decreasing the rate of addition of the paper-strengthening agent. Among the paper-strength enhancers, cationized starch is inexpensive and highly effective. Generally, a method of adjusting by changing is used. Also, JP-A-6-94639 discloses that
Coated base paper for offset rotary printing to which cationized starch and another paper strength agent are added in combination is disclosed.

[0005]

When the basis weight of the coated base paper is increased, the water content of the coated paper is also increased, whereby blistering is more likely to occur during offset printing. In order to prevent the occurrence of rings, the rate of addition of the cationized starch added to the coated base paper had to be further increased. However, even if the interlayer strength of the coated base paper reaches a desired level by increasing the addition rate of the cationized starch, the drainage on the wire deteriorates in the manufacturing process of the coated base paper, so that the drier is used. Drying load increased, and a large amount of steam was required.

On the other hand, even if the interlayer strength of the coated paper is increased by a method using another paper strength enhancer without using a cationized starch and a method using a cationized starch and another paper strength enhancer in combination, It is difficult to sufficiently improve the drainage on the wire,
In addition, there is also a problem that the air permeability of the coated base paper is deteriorated.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies in order to solve the above-mentioned various problems in producing a coated base paper, and as a result, a filler and a cationic starch have been added to a pulp suspension. 750-750 as a drainage improver
It has been found that by adding a structural type anionic silica sol having a specific surface area of 1000 m ² / g, a coated base paper having sufficient interlayer strength and drainage can be produced.

Preferably, the addition rate of the structural anionic silica sol (per absolute dry weight of pulp) is 0.005 to 0.005.
0.1% by weight.

More preferably, an anionic, cationic or amphoteric polyacrylamide is used as the paper strength agent.

[0010] It is particularly preferable that the total amount of nitrogen in the base paper when the paper strength enhancer is added is from 300 to 450 parts by weight pp.
m.

Further, in the coated base paper for web offset printing of the present invention, a coated base paper having a high basis weight requires an even higher interlayer strength in addition to ensuring a high level of air permeability. The present inventors have conducted intensive studies to solve this problem, and as a result, after adding a filler and a cationized starch to the pulp suspension, a cationic polyacrylamide as a drainage improver, 750 to 1000 m ² / g By adding a structural type anionic silica sol having a specific surface area of
With sufficient interlayer strength and drainage, and good air permeability,
It has been found that coated base paper can be manufactured.

Preferably, the addition rate of the structural anionic silica sol (per absolute dry weight of the pulp) is 0.005 to 0.005.
0.1% by weight.

More preferably, the weight ratio (A / B) of the addition amount of the cationic polyacrylamide (A) and the structural type anionic silica sol (B) is 0.1 to 1.0.

More preferably, an anionic, cationic or amphoteric polyacrylamide is used as the paper strength agent.

Particularly preferably, the total amount of nitrogen in the base paper when the paper strength enhancer is added is from 350 to 500 parts by weight pp.
m.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the coated base paper for offset rotary printing of the present invention will be described in detail. At the time of adding the filler and the cationized starch to the pulp suspension,
It is considered that the pulp fiber and the filler form flocs loosely bound by the cationized starch. The large size flock loosely coupled in this way
It has high water retention and tends to deteriorate drainage. Further, since the bonding area between the fibers is not large, it is considered that the contribution to the purpose of improving the interlayer strength of the coated base paper is small.

If a structural type anionic silica sol having a specific surface area of 750 to 1000 m ² / g is added to the loosely bound floc, the silica sol particles enter the floc and neutralize the charge. , Flocs are reduced and densification occurs. As a result, the freeness is improved by reducing the floc size, and the interlayer strength of the coated base paper is improved by increasing the inter-fiber bonding area.

On the other hand, when the dispersion type anionic colloidal silica having a specific surface area in the range of 300 to 700 m ² / g is used, sufficient drainage cannot be obtained. This is because, in the case of dispersed anionic colloidal silica, since the individual silica sol particles are in a dispersed state, the physical binding property is inferior to that of the structural anionic colloidal silica in which a plurality of particles are bonded. It is thought that it is.

When the addition rate of the structural anionic silica sol (per absolute dry weight of pulp) is less than 0.005% by weight, the effect of improving drainage is small. Since the effect of improving the water content is almost the same as the case of 0.1% by weight, 0.005 to 0.1% by weight
Is desirable.

Further, by using an anionic, cationic or amphoteric polyacrylamide as a paper strength enhancer, a higher level of interlayer strength can be obtained. The total amount of nitrogen in the base paper when the paper strength enhancer was added was 300
If it is less than ppm by weight, the effect of improving the interlayer strength is small, and if it exceeds 450 ppm by weight, the obtained interlayer strength is 45%.
Since it is almost the same as the case of 0 ppm by weight, 3
The range of 00 to 450 ppm by weight is desirable.

On the other hand, after adding a filler and a cationized starch to the pulp suspension, a cationic polyacrylamide is added to the pulp suspension.
When a structured anionic silica sol having a specific surface area of 750 to 1000 m ² / g is used, the cross-linking action on finer fibers and filler particles is smaller than when using a cationized starch and a structured anionic silica sol. It is considered that this action brings about a very efficient coagulation effect, and expresses high interlayer strength, drainage and good air permeability.

When a dispersion type anionic colloidal silica having a specific surface area in the range of 300 to 700 m ² / g is used, due to the difference in the particle structure of the silica sol, sufficient interlayer strength, drainage, and air permeability are obtained. I can't get it.

When the addition rate of the structural anionic silica sol (per pulp) is less than 0.005% by weight, the effect of improving drainage is small. Since the effect of improving drainage obtained is almost the same as the case of 0.1% by weight, 0.005 to 0.1%
% By weight is desirable.

When the weight ratio (A / B) of the cationic polyacrylamide (A) and the structural type anionic silica sol (B) is less than 0.1, the effect of improving drainage and air permeability is small. Even if it exceeds 1.0, the obtained effect of improving drainage and air permeability is almost the same as that of the case of 1.0, so that 0.1 to 1.0% by weight is desirable.

Further, by using an anionic, cationic or amphoteric polyacrylamide as a paper strength enhancer, a higher level of interlayer strength can be obtained. Regarding the total amount of nitrogen in the base paper when the paper strength enhancer was added, 35
If it is less than 0 ppm by weight, the effect of improving the interlayer strength is small, and if it exceeds 500 ppm by weight, the obtained interlayer strength is 4%.
Since it is almost the same as the case of 50 ppm by weight,
A range of 350 to 500 ppm by weight is desirable.

In the base paper for coating in the present invention, additives usually used in papermaking, such as fixing agents, sizing agents, defoamers, slime control agents, dyes, coloring pigments, fluorescent agents, pitch control agents, pH adjustment Agents and the like can be appropriately added as needed.

As the pulp, a mechanical pulp made from wood fibers and plant fibers such as hemp, a mechanical pulp, a recycled pulp obtained from the chemical pulp and the mechanical pulp, a synthetic pulp, an inorganic fiber and the like are appropriately selected and used.

As the filler, known and commonly used materials generally used in the papermaking industry are appropriately used. Further, pigments contained in waste paper, broke, and the like can be reused as fillers.

As a paper making method, for example, a paper making pH of 4
So-called neutral papermaking or the like, which is based on acidic papermaking having a pH of about 5 or less, or a weakly acidic papermaking pH of about pH6 to about pH9, which is mainly made of an alkaline filler such as calcium carbonate, is appropriately selected. As the paper machine, a fourdrinier paper machine, a twin wire machine, a round paper machine, a Yankee paper machine or the like is appropriately used.

The coated paper for printing is produced by coating one or both sides of the base paper for coating of the present invention with a coating liquid containing a pigment and an adhesive as main components. This coating liquid is generally adjusted to have a solid content of 40 to 75% by weight, preferably about 45 to 70% by weight. In forming a coating layer by applying a coating liquid on a coating base paper, a coating layer may be formed by coating the coating liquid once, or a multi-layer structure may be formed by dividing the coating liquid into an undercoat layer and an overcoat layer. It is good. In the case of a multilayer structure, the undercoat layer and the overcoat layer need not have the same coating liquid composition,
The composition of the coating liquid can be appropriately changed according to the required quality level.

As a method of forming a coating layer, a conventionally used coating apparatus such as a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die slot coater, a gravure coater, etc. The coating liquid is applied to the surface of the coating base paper using various coaters such as a brushless coater, a brush coater, and a size press coater.
These coating devices may be used in any form of on-machine or off-machine coater.

The coating amount of the coating liquid on the base paper for coating is usually about ² to 50 g / m ^{2 on} one side in terms of dry weight, but in consideration of blank paper quality, printability and the like of the obtained coated paper. ~ 3g
It is desirable to adjust it in the range of about / m ² .

As a method for drying the wet coating layer, various methods such as steam heating, hot air heating, gas heater heating, electric heater heating, infrared heater heating, high frequency heating, laser heating, and electron beam heating are used. There is no particular limitation.

The coated printing paper thus obtained can be subjected to on-machine or off-machine calendar processing. For example, a conventional apparatus such as a machine calendar, a super calendar, a soft compact calendar, etc. Is appropriately used.

[0035]

The present invention will now be described in detail with reference to examples. The present invention is not limited to the embodiments. All parts and percentages described in the examples are by weight. The measured values in the examples were obtained by the following methods.

<Freeness> Measured in accordance with JIS P8121. (Unit: ml)

<Interlayer strength> The interlayer strength was measured using an internal bond tester (manufactured by Kumagai Riki Kogyo).
(Unit: g · cm / in ² ). Interlaminar strength required for a base paper for web offset printing coated paper had a basis weight of 54 g / m ² (absolute dry) base paper with 400g · cm / in ² or more, more preferably 430g · cm / in ² or higher is required. And 74 g / m ²
The amount of basis (bone dry) base paper with 530g · cm / in ² or more, more preferably it requires 580g · cm / in ² or more.

<Air permeability> Measured in accordance with JIS P 8117. (Unit: sec) The base paper for coated web for offset rotary printing having a basis weight of 74 g / m ² requires an air permeability of 20 sec or more, and more preferably 24 sec or more.

<Total Nitrogen Content in Base Paper> The total nitrogen content in the base paper is determined by digital total nitrogen analysis based on the nitrogen content in the base paper conditioned for at least 24 hours in a constant temperature and humidity room at 20 ° C. and 65% RH. The measurement was performed using an apparatus (Model TN-02 manufactured by Mitsubishi Kasei). (Unit: ppm by weight)

Example 1 (base paper blending) LBKP (freeness 440 mlcsf) 70% NBKP (freeness 490 mlcsf) 30% (internally added chemicals) Commercial light calcium carbonate (* expressed by ash content in base paper) * 6% commercial sulfuric acid Band 0.5% Commercially available cationic starch 1% Structural anionic silica sol drainage enhancer (Nissan Eka Nobel BMA780) 0.04%

The pulp and internal chemicals were prepared according to the above-mentioned composition, and a base paper having a basis weight (absolutely dry) of 54 g / m ² was produced. To this base paper, 0.25 g / m ² of starch was adhered by a size press to obtain a coated base paper. The obtained coated base paper was conditioned for at least 24 hours in a constant temperature and humidity room at 20 ° C. and 65% RH, and then the paper quality was measured.

Comparative Example 1 A coated base paper was obtained in the same manner as in Example 1, except that a dispersion type anionic colloidal silica having a specific surface area in the range of 300 to 700 m ² / g was used as the anionic silica sol. .

The coated base papers produced in Example 1 and Comparative Example 1 were evaluated by the above-described evaluation method, and the results are shown in Table 1 below.

[0044]

[Table 1]

Evaluation: Specific surface area is 750 to 1000 m ² / g
In the case of using a structural anionic silica sol having a range of the above, as in Example 1, a sufficient base strength was obtained as a coating base paper having an absolute dry basis weight of 54 g / m ² and good drainage was exhibited. From Comparative Example 1, it can be seen that a dispersion type anionic silica sol having a specific surface area outside the range of the present invention cannot obtain a sufficient internal bond strength.

Example 2 A coating base paper was obtained in the same manner as in Example 1 except that the amount of the structural type anionic silica sol was changed to 0.004%.

Example 3 A coating base paper was obtained in the same manner as in Example 1, except that the amount of the structural type anionic silica sol was changed to 0.01%.

Example 4 A coating base paper was obtained in the same manner as in Example 1 except that the amount of the structural type anionic silica sol was changed to 0.12%.

The coated base papers prepared in Examples 2 to 4 were evaluated by the evaluation method described above, and the results are shown in Table 2 below.

[0050]

[Table 2]

Evaluation: When the addition amount of the structural type anionic silica sol is less than 0.005% as in Example 2, the effect of improving drainage is small, and as in Example 4, 0.1% by weight is used. Even if it exceeds, the effect of improving drainage obtained is 0.
It turns out that it is hardly different from the case of 1% by weight.

Example 5 The same procedure as in Example 1 was carried out except that 0.05% of an anionic polyacrylamide having a degree of cationization at pH 5.0 of -1240 μeq / g was used as a paper strength enhancer. I got the base paper.

Example 6 The same procedure as in Example 1 was carried out except that 0.1% of an anionic polyacrylamide having a degree of cationization of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer.
A coated base paper was obtained.

Example 7 The same procedure as in Example 1 was carried out except that 0.3% of an anionic polyacrylamide having a degree of cationization of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer.
A coated base paper was obtained.

Example 8 The same procedure as in Example 1 was carried out except that 0.5% of an anionic polyacrylamide having a degree of cationization of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer.
A coated base paper was obtained.

Example 9 As a paper strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was used.
A coating base paper was obtained in the same manner as in Example 1, except for using 05%.

Example 10 Amphoteric polyacrylamide having a degree of cationization at pH 5.0 of 320 μeq / g was used as a paper strength enhancer.
A coating base paper was obtained in the same manner as in Example 1 except that 1% was used.

Example 11 As a paper strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was added.
A coating base paper was obtained in the same manner as in Example 1 except that 3% was used.

Example 12 Amphoteric polyacrylamide having a degree of cationization at pH 5.0 of 320 μeq / g was used as a paper strength enhancer.
A coating base paper was obtained in the same manner as in Example 1 except that 5% was used.

Example 13 The same procedures as in Example 1 were carried out except that 0.05% of a cationic polyacrylamide having a degree of cationization at pH 5.0 of 4850 μeq / g was used as a paper strength enhancer.
A coated base paper was obtained.

Example 14 A coating base paper was prepared in the same manner as in Example 1 except that 0.1% of a cationic polyacrylamide having a degree of cationization of 4850 μeq / g at pH 5.0 was used as a paper strength enhancer. Obtained.

Example 15 The same procedure as in Example 1 was repeated except that 0.3% of a cationic polyacrylamide having a degree of cationization at pH 5.0 of 4850 μeq / g was used as a paper strength enhancer. Obtained.

Example 16 The same procedure as in Example 1 was repeated except that 0.5% of a cationic polyacrylamide having a degree of cationization of 4850 μeq / g at pH 5.0 was used as a paper strength enhancer. Obtained.

The coated base papers prepared in Examples 5 to 16 were evaluated by the above-described evaluation method, and the results are shown in Table 3 below.

[0065]

[Table 3]

Evaluation: From Example 1 and Examples 5 to 8, it was found that a higher interlayer strength was obtained by adding an anionic polyacrylamide paper strength enhancer. It can be seen that those in the range of 450 ppm show particularly high interlayer strength. Similarly, Example 1 and Examples 9 to 12, and Example 1 and Example 13
From 16 to 16, amphoteric and cationic polyacrylamide paper-strengthening agents were added to the total nitrogen content in the paper from 300 to 450 pp.
It can be seen that by adding in the range of m, a coated base paper having a high interlayer strength can be obtained.

Example 17 (Blend of base paper) LBKP (freeness: 440 mlcsf) 70% NBKP (freeness: 490 mlcsf) 30% (internal chemical) Commercial light calcium carbonate (* expressed by ash content in base paper) * 6% Commercial sulfuric acid Band 0.5% Commercially available cationic starch 1% Cationic polyacrylamide drainage enhancer 0.01% Structural anionic silica sol drainage enhancer (Nissan Eka Nobel BMA780) 0.04%

The pulp and the internal chemicals were prepared according to the above-mentioned composition, and a base paper having a basis weight (absolutely dry) of 74 g / m ² was produced. 0.25 g / m ² of starch was adhered to the base paper by a size press to obtain a coated base paper. The obtained coated base paper was conditioned for at least 24 hours in a constant temperature and humidity room at 20 ° C. and 65% RH, and then the paper quality was measured.

Comparative Example 2 A coating base paper was obtained in the same manner as in Example 17 except that a dispersion type anionic colloidal silica having a specific surface area of 300 to 700 m ² / g was used as the anionic silica sol.

The coated base papers produced in Example 17 and Comparative Example 2 were evaluated by the above-described evaluation method, and the results are shown in Table 4 below.

[0071]

[Table 4]

Evaluation: Specific surface area 750-1000 m ² / g
When the structural type anionic silica sol having the range of is used, as in Example 17, a sufficient interlaminar strength is obtained as a coating base paper having an absolute dry basis weight of 74 g / m ² , and good drainage, and From the fact that air permeability is shown, and from Comparative Example 2,
It can be seen that a dispersion type anionic silica sol having a specific surface area outside the range of the present invention cannot obtain sufficient internal bond strength and air permeability.

Example 18 A coating base paper was obtained in the same manner as in Example 17 except that the amount of the structural type anionic silica sol was changed to 0.004%.

Example 19 A coating base paper was obtained in the same manner as in Example 17 except that the addition amount of the structural type anionic silica sol was changed to 0.01%.

Example 20 A coating base paper was obtained in the same manner as in Example 17 except that the amount of the structural type anionic silica sol was changed to 0.12%.

The coated base papers prepared in Examples 18 to 20 were evaluated by the above-described evaluation method, and the results are shown in Table 5 below.

[0077]

[Table 5]

Evaluation: When the addition amount of the structural type anionic silica sol is less than 0.005% as in Example 18, the effect of improving the drainage and air permeability is small, and as in Example 20, the effect is improved. It can be seen that even if the content exceeds 1% by weight, the obtained effect of improving the drainage and air permeability is almost the same as the case of 0.1% by weight.

Example 21 The amount of the cationic polyacrylamide drainage improver was
Performed in the same manner as in Example 17 except that the content was 0.002%.
A coated base paper was obtained.

Example 22 The amount of the cationic polyacrylamide drainage improver was
Performed in the same manner as in Example 17 except that the content was 0.004%.
A coated base paper was obtained.

A coated base paper was obtained in the same manner as in Example 17 except that the amount of the cationic polyacrylamide drainage improver was changed to 0.04%.

A coating base paper was obtained in the same manner as in Example 17, except that the amount of the cationic polyacrylamide drainage improver was changed to 0.05%.

The coated base papers prepared in Examples 21 to 24 were evaluated by the above-described evaluation method, and the results are shown in Table 6 below.

[0084]

[Table 6]

Evaluation: When the weight ratio (A / B) of the addition amount of the cationic polyacrylamide (A) and the structural type anionic silica sol (B) is less than 0.1 as in Example 21, drainage and air permeability are required. It can be seen that the effect of improvement is small, and the effect of improving drainage and air permeability obtained even when it exceeds 1.0 as in Example 24 is almost the same as the case of 1.0.

Example 25 A coating base paper was prepared in the same manner as in Example 17 except that 0.05% of an anionic polyacrylamide having a degree of cationization of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer. I got

Example 26 Coating base paper was prepared in the same manner as in Example 17, except that 0.1% of an anionic polyacrylamide having a degree of cationization at pH 5.0 of -1240 μeq / g was used as a paper strength enhancer. I got

Example 27 A coating base paper was prepared in the same manner as in Example 17 except that 0.3% of an anionic polyacrylamide having a degree of cationization of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer. I got

Example 28 Coating base paper was prepared in the same manner as in Example 17, except that 0.5% of an anionic polyacrylamide having a cationization degree of -1240 μeq / g at pH 5.0 was used as a paper strength enhancer. I got

Example 29 As a paper strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was added.
A coating base paper was obtained in the same manner as in Example 17, except for using 05%.

Example 30 As a paper strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was added to 0.1.
A coating base paper was obtained in the same manner as in Example 17 except that 1% was used.

Example 31 As a paper strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was added.
A coating base paper was obtained in the same manner as in Example 17 except that 3% was used.

Example 32 As a paper-strength enhancer, amphoteric polyacrylamide having a degree of cationization of 320 μeq / g at pH 5.0 was added.
A coating base paper was obtained in the same manner as in Example 17 except that 5% was used.

Example 33 Coating base paper was prepared in the same manner as in Example 17 except that 0.05% of a cationic polyacrylamide having a degree of cationization at pH 5.0 of 4850 μeq / g was used as a paper strength enhancer. Obtained.

Example 34 The same procedure as in Example 17 was carried out except that 0.1% of a cationic polyacrylamide having a degree of cationization at pH 5.0 of 4850 μeq / g was used as a paper strength enhancer.
A coated base paper was obtained.

Example 35 The same procedure as in Example 17 was carried out except that 0.3% of a cationic polyacrylamide having a degree of cationization at pH 5.0 of 4850 μeq / g was used as a paper strength enhancer.
A coated base paper was obtained.

Example 36 The same procedures as in Example 17 were carried out except that 0.5% of a cationic polyacrylamide having a degree of cationization of 4850 μeq / g at pH 5.0 was used as a paper strength enhancer.
A coated base paper was obtained.

The coated base papers prepared in Examples 25 to 36 were evaluated by the evaluation method described above, and the results are shown in Table 7 below.

[0099]

[Table 7]

Evaluation: Examples 25 to 28: By adding an anionic polyacrylamide paper strength agent,
It can be seen that a higher interlayer strength can be obtained, and that the paper having a total nitrogen content in the range of 350 to 500 ppm exhibits a particularly high interlayer strength. Example 2
9 to 32, and amphoteric from Examples 13 to 16, respectively.
It can be seen that a coating base paper having a high interlayer strength can be obtained by adding a cationic polyacrylamide paper strength agent in the total nitrogen content of paper in the range of 350 to 500 ppm.

[0101]

According to the present invention, by adding a filler and a cationized starch to a pulp suspension, and then adding a structural type anionic silica sol to form a paper, offset printing having sufficient interlayer strength and drainage is achieved. Coating base paper can be obtained. In addition, by adding a filler and a cationized starch to the pulp suspension, adding a cationic polyacrylamide and a structural type anionic silica sol to form a paper, sufficient interlayer strength and drainage, and excellent A coated base paper for offset printing having air permeability can be obtained.

Claims (9)

[Claims] 1. A pulp suspension containing a filler and a cationized starch, and then having a 750-1000 m
^A base paper for offset rotary printing, characterized by adding a structural type anionic silica sol having a specific surface area of ² / g and making the suspension into paper. 2. The coated base paper for offset rotary printing according to claim 1, wherein the addition amount of the structural type anionic silica sol is 0.005 to 0.1% by weight based on the absolutely dried pulp. 3. The coated base paper for offset rotary printing according to claim 2, wherein the paper strength enhancer contains at least one of anionic, cationic and amphoteric polyacrylamides. 4. The coated base paper for web offset printing according to claim 1, wherein the total nitrogen content in the base paper is 300 to 450 ppm by weight. 5. After adding a filler and a cationized starch to a pulp suspension, a cationic polyacrylamide as a drainage improver and a structural anionic silica sol having a specific surface area of 750 to 1000 m ² / g are added. Coated base paper for web offset printing, wherein the base paper is added to the suspension and the suspension is made. 6. The coated base paper for offset rotary printing according to claim 5, wherein the amount of the structural type anionic silica sol is 0.005 to 0.1% by weight based on the absolutely dry pulp. 7. The weight ratio (A / B) of the amount of the cationic polyacrylamide (A) and the amount of the structural anionic silica sol (B) to be added is 0.1 to 1.0.
Coated base paper for web offset printing described in 1. 8. The coated base paper for offset rotary printing according to claim 5, wherein the paper strength enhancer contains at least one of anionic, cationic and amphoteric polyacrylamides. 9. The coated base paper for web offset printing according to claim 5, wherein the total amount of nitrogen in the base paper is 350 to 500 ppm by weight.