JP3158628B2 - Coating composition for newsprint paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for newsprint paper suitable for multicolor offset printing, and more particularly to a multicolor offset rotary printing with cold set type ink having high whiteness and opacity. The present invention relates to a coating composition for obtaining newsprint paper having suitable surface strength (particularly, wet surface strength), print gloss, ink adhesion, and ink setability, and excellent in offset printability.

[0002]

2. Description of the Related Art Recently, color printing has been remarkable in daily newspapers, especially sports papers. In addition, although the colorization of the advertising surface of daily newspapers has been increasing rapidly, the printing power is inferior to the fliers of folds, which are often used for coated paper, so the power to appeal to the visual is insufficient, and newspapers suitable for color printing Demand for printing paper is growing.

On the other hand, since the mass printing must be performed in a short time due to the social mission of newspapers, the printing speed has been further increased, and it has been desired to improve the suitability for offset printing such as paper peeling and ink setting. I have.

Conventionally, as a measure for improving the suitability for offset printing, a method of applying starch or polyvinyl alcohol to improve the surface strength of newsprint paper (so-called clear coat) has been used. Particularly in Japan, newsprint is generally coated with a clear coat (or surface size) of starch. However, in this method, although a corresponding effect can be obtained in improving the surface strength at the time of drying in the absence of water, since the starch itself has high water absorption, the water resistance is low and the wet surface strength is hardly improved. In addition, a large amount of starch is applied to the surface to increase the denseness of newsprint paper, thereby reducing ink absorption. In high-speed offset printing using cold-set (penetrating) ink, ink setting is poor. There was a problem. Furthermore,
Offset printing suitability such as print gloss and ink deposition was not sufficient. In addition, newsprint paper that has been starch-clear coated has drawbacks such as poor dimensional stability such as stretching due to water absorption when a large amount of dampening water is used in offset printing, and reduced printing workability. . Furthermore, newspaper printing paper coated with starch has poor whiteness and opacity, so that there is a problem that the pulp composition of the base paper needs to be changed to improve the paper quality as newsprint paper.

[0005]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to obtain newsprint paper free from the above-mentioned drawbacks. As a result, the present inventors have found that a specific ratio of a water-soluble polymer compound and a copolymer latex can be obtained. By using a coating composition containing a binder and, if desired, using a specific amount of an organic pigment in combination, whiteness, opacity, surface strength (particularly wet surface strength), printing gloss, and ink adhesion It has also been found that the suitability for offset printing of ink sets and the like is dramatically improved, and that extremely excellent newsprint can be obtained. Based on this finding, the present invention has been completed.

[0006]

Thus, according to the present invention, 100 parts by weight of a binder composed of 90 to 40% by weight of a water-soluble polymer compound and 10 to 60% by weight (in terms of solid content) of a copolymer latex are provided. 30% by weight as a pigment
The present invention provides a coating composition for newsprint paper, comprising the following organic pigment . Further, according to the present invention, the coating composition for newsprint paper is applied to one side of base paper.
Newspaper printing paper coated with 0.5 to 3.5 g / m ²
Provided.

[0007] The water-soluble polymer compound used as one component of the binder in the present invention is necessary for appropriately adjusting the viscosity of the coating composition and maintaining workability in the coating equipment. The water-soluble polymer compound that can be used is not particularly limited, and specific examples thereof include starch, polyvinyl alcohol, casein, and cellulose derivatives such as methylcellulose and carboxymethylcellulose. Starch such as oxidized starch, phosphorylated esterified starch and enzyme-modified starch is preferred for the coating composition of newsprint for offset printing.

[0008] The copolymer latex used as another component of the binder in the present invention is not limited by its synthesis method, but an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit are essential components. Latex of the copolymer. Although the monomer composition for obtaining the copolymer is not particularly limited, the aliphatic conjugated diene monomer 2
0 to 50% by weight, aromatic vinyl monomer 10 to 74% by weight
Is preferable. The copolymer may contain, in addition to the above two components, a unit derived from a monomer copolymerizable therewith. Specific examples thereof include an ethylenically unsaturated acid monomer and an ethylenically unsaturated amine.

The aliphatic conjugated diene monomer imparts flexibility to the copolymer. When the amount is less than 20% by weight, the copolymer becomes hard, and when the amount is more than 50% by weight. In such a case, the water resistance is undesirably reduced. Specific examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-
Although 1,3-butadiene and the like can be shown, 1,3-butadiene is particularly preferred.

The use of the aromatic vinyl monomer has the effect of imparting appropriate hardness and water resistance to the copolymer. If the amount is less than 10% by weight, the above effect is insufficient. If the amount is more than 74% by weight, the film-forming property is reduced and the adhesive strength is reduced. Specific examples of the aromatic vinyl monomer include styrene, α-methylstyrene, monochlorostyrene, vinyltoluene and the like, and among these, styrene is preferred.

The ethylenically unsaturated acid monomer is preferably used in an amount of 0.5 to 20% by weight in order to increase the adhesive force of the copolymer and to improve the stability of the copolymer latex as a colloid. Used in range. If the amount is less than 0.5% by weight, the above effects cannot be obtained. If the amount exceeds 20% by weight, problems such as polymerization stability occur. Specific examples of the ethylenically unsaturated acid monomer include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid.

The ethylenically unsaturated amine is suitable as a monomer for introducing a gelling site when the copolymer latex is made amphoteric. The amount used is 0.5 to
It is 10% by weight, preferably 1 to 5% by weight. When the amount is less than 0.5% by weight, it is difficult to make the copolymer latex amphoteric. On the other hand, when the amount is more than 10% by weight, the gelation point pH of the copolymer latex is lowered, so that the mixing stability with starch is lowered. And the problem that a large amount of coagulated material is generated during the production of the copolymer latex. Specific examples of the ethylenically unsaturated amine include amino-unsaturated carboxylic acids such as methylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and N, N-dimethylaminoethyl (meth) acrylate. Alkyl esters; aminoalkylamides of ethylenically unsaturated carboxylic acids such as methylaminoethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide; aminoethyl vinyl ether And vinyl pyridines such as 2-vinyl pyridine.

In the present invention, a monomer copolymerizable with each of the above-mentioned monomers can be used in an amount of 40% by weight or less based on all monomers. Specific examples of such a monomer include:
Alkyl esters of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate and butyl acrylate; ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; acrylic acid β
Hydroxyalkyl esters of unsaturated carboxylic acids such as -hydroxyethyl; amides of unsaturated carboxylic acids such as acrylamide, methacrylamide, N-methylolacrylamide, diacetoneacrylamide and derivatives thereof; unsaturated acids such as glycidyl acrylate and glycidyl methacrylate Glycidyl esters of carboxylic acids; other vinyl compounds such as acrolein and allyl alcohol;
Can be mentioned.

The unsaturated carboxylic acid ester is effective for imparting appropriate hardness to the copolymer and increasing air permeability, and its amount is preferably 5 to 30% by weight.
If it exceeds 40% by weight, the water resistance is remarkably reduced, making it unsuitable as the coating composition of the present invention. The ethylenically unsaturated nitrile is effective for improving the printing gloss of coated newsprint (newsprint obtained by printing using newsprint paper obtained by coating a coating composition). The amount is preferably 5-30
% By weight. If it exceeds 40% by weight, the ink setting of the coated newsprint and the decrease in the ink deposition are undesirably caused. Hydroxyalkyl esters of unsaturated carboxylic acids are effective in improving the mechanical stability of the copolymer latex. The use of unsaturated carboxylic acid amides and derivatives thereof can improve the chemical stability and water resistance of the copolymer latex.

In the coating composition of the present invention, the ratio of the water-soluble polymer compound to the copolymer latex (in terms of solid content) is 90 to 40% by weight, preferably 90 to 40% by weight, based on the total weight of both. 80 to 50% by weight, more preferably 80
-60% by weight and the latter is 10-60% by weight, preferably 20-50% by weight, more preferably 20-40% by weight. If the latter is less than 10% by weight, whiteness, opacity,
The effect of improving the surface strength, print gloss and ink adhesion is hardly observed. If it exceeds 60% by weight, the anti-blocking property is deteriorated due to stickiness of the latex copolymer and the workability is deteriorated, and the opacity and ink setting are deteriorated. Disappears.

In the present invention, by using an organic pigment in combination, it is possible to improve not only the whiteness and opacity, but also the characteristics of newsprint paper, such as ink deposition and ink set. Here, it is essential that the pigment used is an organic pigment, and when an inorganic pigment is used, the object of the present invention cannot be achieved.

Specific examples of the organic pigment include a plastic pigment, a binder pigment and a hollow polymer. Of these organic pigments, the plastic pigment and the hollow polymer are generally copolymers containing a styrene monomer as a main component and have a high Tg.
Has almost no effect as a binder, but is extremely effective in improving whiteness and opacity in a well-balanced manner. Examples of the hollow polymer include hollow polymer particles described in JP-A 1-162031. These organic pigments are generally used in the form of powder or latex. The binder pigment has both a function as a binder and a function as a pigment. Binder pigments are also highly effective in improving whiteness and opacity, like hollow polymers. The binder pigment is generally used in a latex state, and examples thereof include those described in JP-B-62-31115.

The amount of the organic pigment used is 30 parts by weight or less based on 100 parts by weight of the binder component (solid content).
If it is used in an amount exceeding 30 parts by weight, there is a concern that the coating workability of the coating composition, particularly the mechanical stability, may decrease, and there is also a risk of sedimentation of particles during long-term storage in a storage tank. When using a binder pigment, in calculating the ratio of the constituent components of the coating composition of the present invention,
It goes without saying that the total amount of the used amount is calculated as a pigment, but at the same time, one half of the used amount is regarded as a copolymer. Therefore, for example, the water-soluble polymer 75
In a composition comprising 25 parts by weight of a copolymer latex (in terms of solid content) which is not a binder pigment and 30 parts by weight of a binder pigment, the total of the binder components is 115 (= 75 + 25 + 30/2) parts by weight, and The total amount of latex (in terms of solid content) is 40 parts by weight (= 25 + 30/2), and the total amount of pigment is 30
Parts by weight. At this time, the water-soluble polymer and the copolymer latex in the binder component (solid content conversion)
Is 65% by weight / 35% by weight (= 75 /%).
40).

In the coating composition of the present invention, in addition to a water-soluble polymer compound, a copolymer latex and an organic pigment, if necessary, a pH adjuster, a lubricant, a fluorescent dye, a viscosity adjuster, a defoamer, Agents and preservatives can be added.

The method of applying the coating composition of the present invention to base paper may be any method commonly used for clear coat and surface size of starch, such as a blade coater, gate roll coater and air knife coater. Well, there is no particular limitation.

The newsprint paper of the present invention can be obtained by applying the coating composition for newsprint of the present invention to a base paper for news paper at 0.5 to 3.5 g / m ² per side.
The coating amount is preferably 1.0 to 3.0 g / m ² , more preferably 1.5 to 2.5 g / m ² . The coating amount is 0.
If it is less than 5 g / m ² , newsprint paper with improved whiteness, opacity, surface strength, print gloss, ink adhesion, etc. cannot be obtained, and if it exceeds 3.5 g / m ² , print gloss, surface strength, etc. However, whiteness, opacity, and ink set are reduced, and particularly when the amount is 5 g / m ² or more, oil absorption is extremely poor, ink set is slowed down, blocking resistance is lowered, and cold set It is no longer suitable as a high-speed offset rotary printing paper for newspapers that use mold ink.

It is not clear why the use of the coating composition of the present invention can provide newsprint paper having excellent offset printing suitability. However, a water-soluble polymer compound such as starch and a copolymer latex are used in a specific ratio. It is considered that the following effects can be obtained by mixing. That is, a water-soluble polymer compound such as starch has a large penetration into newsprint paper during coating, and as a result, the denseness is increased,
Air permeability and oil absorption are reduced, and ink set is inferior. Also,
Since the water absorption of the water-soluble polymer compound is remarkably large, a large amount of dampening water is absorbed in offset printing, and the ink deposition is reduced. On the other hand, by using a copolymer latex in combination, a discontinuous film-forming portion increases on the surface of the coated paper, giving appropriate air permeability and excellent water resistance, and at the same time, a high water-soluble property such as starch. By appropriately controlling the water absorption of the molecular compound, the ink setting and the ink deposition can be improved. T of copolymer latex polymer
Since the g (glass transition temperature) is low, smoothness can be easily obtained in the calendering step, which contributes to the improvement in print gloss.

[0023]

The present invention will be described more specifically with reference to the following examples. The parts and percentages in the examples are on a weight basis unless otherwise specified. The weight of the copolymer latex is calculated on a solid basis.

In this example, the methods for evaluating the properties of the coating composition and the coated paper are as follows. (Gel fraction of copolymer) After immersing a polymer film made from latex in tetrahydrone for 48 hours,
The insolubles are filtered through filter paper, and the dry weight is determined and calculated as the ratio to the weight of the polymer film.

(Blocking resistance)
It shows the state of adhering to a metal calender roll when passed twice through a super calender under the condition of 50 kg / cm. ：: not adhered at all △: slightly adhered ×: considerably adhered (whiteness) Hunter whiteness meter (CM-8, manufactured by Murakami Color Research Co., Ltd.)
Using P), it is measured according to JIS P8123. The larger the numerical value displayed in%, the greater the whiteness. (Opacity) Hunter whiteness meter (Murakami Color Co., CM-
8P), and measured according to JIS P8138. The greater the numerical value expressed in%, the greater the opacity. (Dynamic smoothness) It is measured by a microtopograph (manufactured by Toyo Seiki Co., Ltd.). The smaller the value expressed in μm, the higher the smoothness. (Water absorption) A fixed amount of water is dropped on the surface of the coated paper, and the time until it is completely absorbed is measured. The smaller the value expressed in seconds, the greater the water absorption (water absorption rate). (Oil absorbency) A certain amount of light oil is dropped on the surface of the coated paper, and the time until it is completely absorbed is measured. The smaller the value expressed in seconds, the greater the oil absorption (oil absorption speed).

(Blank gloss) Measured with a gloss meter (manufactured by Murakami Color Co., Ltd., GM-26D). Measure the reflectance at 75-75 degrees. The larger the value expressed in%, the higher the glossiness of the blank paper. (Print gloss) Using an RI tester (manufactured by Akira Seisakusho)
One-color (indigo) solid printing of newspaper ink and two-color (indigo / red)
After solid printing, the gloss is measured using a gloss meter in the same manner as for measuring the gloss of a blank sheet. (Two-color printing) After solid printing with yellow ink for newspaper using an RI tester, then red ink for newspaper is overprinted.
The density of the red ink is measured with an ink densitometer, and the degree of arrival of the red ink is determined. Larger numbers are better. (Sucking Swimsuit Meat) Using a RI tester, water is allowed to flow with a slight gap between the metal roll and the rubber roll, and then black ink for newspaper is solid printed. The degree of black ink arrival is measured with an ink densitometer. Larger numbers are better. (Ink set) After indigo blue ink for newspaper is solid printed using an RI tester, coated paper is overlaid and pressed, and the degree of transfer of the ink to the coated paper is measured with an ink densitometer. The lower the number, the better. (Surface strength) Dry pick: Using an RI tester, the state of peeling of the paper after several times of overprinting using a picking test ink (TV (tack value) 16) is visually determined.
The larger the number in the five-point evaluation, the better. Wet pick: After using a RI tester and moistening with water with a Molton roll, ink for picking test (TV
In step 16), solid printing is performed, and the state of paper peeling is visually determined.
The larger the number in the five-point evaluation, the better.

REFERENCE EXAMPLE (Production of copolymer latex) In an autoclave equipped with a stirrer, 32 parts of water, 1.1 parts of tetrasodium ethylenediamine / tetraacetate, 1.1 parts of sodium lauryl sulfate and 0.2 part of potassium persulfate were placed. Then, 10% of the monomer mixture emulsion (a) having the composition shown in Table 1 prepared in another tank equipped with a stirrer was added. Next, the reaction system was
The mixture was heated to ℃ and reacted for 1 hour. Next, after adding 0.8 parts of potassium persulfate together with 20 parts of water, the remaining 90% of the monomer mixture emulsion (a) was continuously fed into an autoclave for 4 hours. During this time, the autoclave was kept at 80 ° C. Thereafter, the reaction system was maintained at 80 ° C. for another 2 hours to obtain a copolymer latex. The copolymer latex has a polymer Tg of -1.
It is a carboxy-modified styrene-butadiene copolymer latex of 0.7 ° C., a gel fraction of 85%, and a particle size of 120 nm. Similarly, the monomer mixture emulsion shown in Table 1 (b)
And (c) were used to obtain a copolymer latex and a copolymer latex, respectively. The copolymer latex is a carboxy-modified styrene-butadiene copolymer latex having a different carboxylic acid from that of the latex.
Is + 2.2 ° C., the gel fraction is 45%, and the particle size is 150 nm. The copolymer latex is a carboxy-modified styrene-butadiene copolymer latex in which the type of carboxylic acid is further different, and the Tg of the polymer is + 6.8 ° C., the gel fraction is 80%, and the particle size is 130 nm.

After adding 10% of the monomer mixture emulsion (d) shown in Table 1 in the same manner, the reaction system was heated to 80 ° C. and reacted for 1 hour. Next, potassium persulfate 0.8
After the addition of 20 parts of water together with 20 parts of water, the remaining 90% of the monomer mixture emulsion (d) was continuously fed into the autoclave over 4 hours. During this time, the autoclave
It was kept at 0 ° C. Maintaining the reaction at 80 ° C. for an additional hour,
8. Add ammonia water to adjust the pH of the copolymer latex to 9.
Adjusted to zero. Next, 4.0 parts of water, 2.5 parts of N, N-dimethylaminoethyl methacrylate and 0.1 part of ammonium persulfate were added and reacted at 80 ° C. for 2 hours to obtain a copolymer latex. Latex is polymer Tg
Is an amphoteric latex having -6.1 ° C., a gel fraction of 82%, a particle size of 120 nm, and a gel point of pH 5.0.

(Production of Organic Pigment) As an organic pigment, a binder pigment latex was produced in the following manner in accordance with JP-B-62-31115. The following composition was charged into a tank equipped with a stirrer to prepare Monomer Emulsion-1. Water 27 parts Sodium lauryl sulfate 0.05 part Sodium bicarbonate 0.2 part Styrene 48 parts Itaconic acid 1.0 part Acrylamide 1.0 part The following composition was charged into another tank equipped with a stirrer to prepare monomer emulsion-2. did. Water 27 parts Sodium lauryl sulfate 0.05 parts Sodium bicarbonate 0.2 parts Styrene 20 parts Methyl methacrylate 5.0 parts Itaconic acid 1.0 parts Acrylamide 1.0 parts Butadiene 20 parts T-dodecyl mercaptan 0.15 parts Water in an autoclave 30 parts, 0.05 parts of tetrasodium ethylenediaminetetraacetate and 0.2 parts of potassium persulfate were heated to 80 ° C., and then 5 parts of the monomer emulsion-1 were added.
% Was sent to an autoclave and reacted for 1 hour. After 1 hour, 0.6 part of potassium persulfate was sent to the autoclave together with 12 parts of water. During this time, the autoclave was kept at 80 ° C. After an additional 15 minutes, 0.2 parts of ammonium persulfate were charged into an autoclave together with 4 parts of water, and then the monomer emulsion-2 was continuously sent to the autoclave for 2 hours, and the temperature was increased to 85 ° C. and stirred for another 3 hours. Continued. After the completion of the reaction, steam distillation was performed, and the pH was adjusted to 7.5 with caustic soda to obtain a binder pigment latex. The average particle size of the obtained latex is 350 nm.
And a continuous film was formed at room temperature.

(Production of a hollow polymer latex) A hollow polymer latex having one or two or more hollow portions separated from each other was obtained as follows in accordance with JP-A-1-162131. 95 parts of styrene, 5 methacrylic acid
Parts of seed latex, water 518 in a reaction vessel.
And 3.4 parts of seed latex were charged and heated. After the internal temperature reaches 80 ° C., a 3% aqueous potassium persulfate solution 30
Was added to the flask from the dropping funnel. Next, after the dropping funnel was washed with 20 parts of water, a monomer mixture consisting of 94 parts of styrene and 6 parts of acrylic acid was added from the dropping funnel over 6 hours. Thereafter, the temperature was maintained at 80 ° C. for 2 hours to complete the polymerization reaction, and the polymerization conversion rate by a weight method was 97%.
Thus, a latex having a solid content of 15% was obtained. 100 parts of this latex, 870 parts of water, 1 part of sodium dodecylbenzenesulfonate, 30 parts of toluene and 33 parts of a 10% aqueous sodium hydroxide solution were charged into a container, stirred at 80 ° C. for 3 hours, and cooled to room temperature. The organic solvent was removed under reduced pressure to obtain a hollow polymer particle latex. The latex had a pH of 2.3, a particle diameter of 530 nm, a small pore diameter in the polymer of 150 nm, the number of small pores was 1 to 2, and Tg was 100 ° C.

[0031]

[Table 1]

(Production of Plastic Pigment) The inside of a 2-liter reactor equipped with a stirrer, a cooling condenser, a nitrogen gas inlet tube and a thermometer was purged with nitrogen, and 360 g of deionized water and 84 g of ethyl alcohol were placed in the reaction vessel.
0 g, methacrylic acid 13.3 g and potassium persulfate 0.1 g.
95 g was added and stirred for 30 minutes to obtain a homogeneous mixed solution. Next, after bubbling the mixed solution with nitrogen,
The reactor was heated to start the reaction, and kept for 6 hours to complete the polymerization of methacrylic acid. The polymerization conversion was about 100%. Next, 66.7 g of styrene was added to the reactor.
And 0.5 g of potassium persulfate were added, polymerization of styrene was carried out at the same temperature for 16 hours, and the reaction mixture was cooled to room temperature. The polymerization conversion was 98.3%. The obtained polystyrene suspension was centrifuged to precipitate polymer particles, and the polymer particles were separated by decantation. The polymer particles were put into distilled water, sufficiently stirred, and then subjected to centrifugal separation again twice to obtain polystyrene particles (plastic pigment).
The obtained polystyrene particles had a weight average particle size of 470 n.
m, spherical particles having a monodisperse particle size distribution with a number average particle size of 440 nm.

[Examples] (Example 1) Coating compositions A to K for newsprint paper having a solid content of 20% and a pH of 6.5 using the copolymer latex and having the formulation shown in Table 2 were prepared. Created.

[0034]

[Table 2]

The above coating composition was coated on newsprint base paper under the following conditions, and humidified in a constant temperature and humidity room at 20 ° C. and a relative humidity of 65 ± 5%, and subjected to various characteristic tests. Table 3 shows the results
Shown in Coater: Manual blade coater Drying conditions: Use hot air oven. 130 ° C x 20 seconds Calendar: Use super calendar. 40 ° C, 55k
Pass twice at g / cm. Base paper: Newspaper base paper (46 g / m ² ) Coating amount: 2.0 g / m ^{2 on} one side

[0036]

[Table 3]

From the results shown in Table 3, it can be seen that the newsprint obtained using the coating composition of the present invention is excellent in whiteness, opacity, surface strength, print gloss, ink setting and ink deposition. (Composition numbers AF). Particularly, by mixing an organic pigment, the improvement in whiteness and opacity is remarkable (composition numbers C to D). For ink set,
The starch / copolymer latex combination system tends to be slightly faster (composition number A, B, E, F) than the case of using only starch (composition number G). It tends to be much faster (Composition Nos. C, D). When the proportion of the copolymer latex in the binder exceeds 60% by weight (composition Nos. I and K), the oil absorbency obviously decreases, and the ink setting becomes slow. In addition, the blocking resistance is greatly reduced. As the proportion of the copolymer latex increases, the coated paper becomes less likely to absorb water, and the fact that starch is extremely easy to absorb water, resulting in a significantly improved swimsuit meat, is greatly improved (composition numbers AF). However, since the water absorption is appropriately required in the offset printing, a problem occurs in the offset printing if the water absorption is too low.

Example 2 A coated paper was prepared in the same manner as in Example 1 except that the amount of coating was changed using the composition C in Table 2.
The various property evaluation tests were performed in the same manner as in Example 1.
Table 4 shows the results.

[0039]

[Table 4]

From the results shown in Table 4, the amount of coating when the coating composition of the present invention is coated on newsprint base paper is as follows. From this, it can be seen that there is a desired coating amount. That is, when the coating amount per one side of the base paper exceeds 4 g / m ² , the ink set starts to decrease, and
If it exceeds g / m ² , the decrease will be significant. When the coating amount exceeds 5 g / m ² , the print gloss, dry pick and wet topic improve with the increase in the coating amount, but the whiteness,
The opacity, oil absorbency and water absorbency decrease undesirably. Therefore, in high-speed offset printing using a cold-set type ink, an extremely excellent newsprint is obtained by coating the coating composition of the present invention at a coating amount of 0.5 to 3.5 g / m ^2. Is obtained.

Example 3 The procedure of Example 1 was repeated except that the type and the mixing ratio of the water-soluble polymer compound, the copolymer latex or the organic pigment were changed as shown in Table 5 using the copolymer latex. Coating composition L prepared in the same manner as
A coated paper was prepared using V, and various characteristics evaluation tests were performed. Table 6 shows the results.

[0042]

[Table 5]

[0043]

[Table 6]

From the results shown in Table 6, the coating composition of the present invention was
Even if the type of starch, which is a water-soluble polymer compound, is changed, it shows an effect on improving whiteness, opacity, surface strength, print gloss, ink setting, and ink adhesion (compositions L and M), and the same applies to polyvinyl alcohol (Composition N). Although there are slight differences due to differences in the composition, particle size, gel fraction, and the like of the copolymer latex, it can be seen that all of the above properties are excellent (compositions O to Q). When the hollow polymer latex and the plastic pigment latex are used as the organic pigments, the whiteness, the opacity, and the ink setting are excellent (compositions R and S).

[0045]

As described above, according to the present invention, whiteness, opacity, surface strength (particularly wet surface strength), print gloss, and the like as high-speed offset rotary printing suitability using a cold-set type ink as compared with the prior art are improved. A coating composition for newsprint paper excellent in ink setting and ink deposition can be obtained.

Claims (4)

(57) [Claims] Respect 1. A water-soluble polymer compound 90 to 40 wt% of a copolymer latex of 10 to 60 wt% (solid basis) consisting of a binder to 100 parts by weight of a pigment
And 30% by weight or less of an organic pigment. Respect 2. A water-soluble polymer 90 to 40 wt% of a copolymer latex of 10 to 60 wt% (solid basis) consisting of a binder to 100 parts by weight of a pigment
And 15 to 30 parts by weight of an organic pigment. 3. The organic pigment according to claim 1, wherein the organic pigment is a plastic pigment, a binder pigment, or a hollow polymer particle.
Or the coating composition for newsprint paper according to 2 above. 4. The coating composition for newsprint paper according to claim 1, wherein the coating composition is 0.5 to 3.5 g / m ² per one side of the base paper.
Newsprint paper coated.