JP3458896B2 - Coated paper for printing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for printing, and more particularly to a coated paper having an excellent white paper appearance and printability.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand (hereinafter referred to as "visualization") to strongly convey the content visually to printed matter by making extensive use of photographs and patterns and further colorizing the same. On the other hand, there is a strong demand for reducing the weight of printed matter in terms of resource saving and transportation cost. These two demands are contradictory, and a high-grade coated paper suitable for visualization has both a high basis weight and a large coating weight, is expensive, and is lightweight.
Not suitable for low price. Therefore, there is a demand for a technique for realizing higher grade quality with so-called lower grade coated paper having a low basis weight and a low coating amount.

Of the qualities of coated paper, the most important ones are whiteness, opacity, white paper gloss, print gloss, and stiffness. Whiteness is contrast, opacity is strikethrough,
Glossiness is related to the high quality of printed matter, and it is important that they are all satisfied with a good balance. Rigidity is mainly related to print workability and is also an important factor for page turning of printed matter.

As described above, in order to reduce the weight, it is necessary to make the base paper have a low basis weight and a coating layer having a low coating amount.
However, if a paper having a low basis weight is simply used without changing the composition of the stock, the paper thickness becomes thin in proportion to the weight reduction, and the opacity and the rigidity become insufficient. If a thick coating layer is provided on the low basis weight base paper, the printability can be maintained at the level before the reduction of the basis weight.
The opacity and the rigidity are rather reduced, which is not practical. Conversely, if a coating layer with a low coating amount is provided on the high basis weight base paper,
Although the opacity and rigidity are sufficient, the coating amount is unnecessarily reduced to reduce the basis weight, resulting in insufficient print quality, which is also impractical. Therefore, it is necessary to have a certain balance between the grammage and the coating amount. It means that the low grammage base paper has a low coating weight coating layer and the high grammage base paper has a high coating weight coating layer. In general, low basis weight products are inferior in whiteness, opacity, white paper glossiness, printing glossiness, and rigidity to high basis weight products. Generally, the opacity sharply decreases when the basis weight is 80 g / m ² or less. Low density bulky paper can be used to minimize stiffness and opacity loss even if the basis weight is reduced to some extent by using mechanical pulp of a specific tree species such as gumwood, maple or birch. Is effective, but it is not practical to use only specific tree species for resource saving and cost. However, the use of mechanical pulp is effective for stiffness and opacity for all tree species. Further, in order to reduce the density and improve the opacity, a hollow synthetic resin capsule is internally added (Japanese Patent Publication No. 52-118116), a synthetic organic foaming filler (for example, trade name: EXPANSEL, manufactured by Nippon Philite Co., Ltd.) It is known to internally add and foam when dried. However, hollow synthetic resin capsules and expandable fillers are not practical means at present because mixing and foaming conditions are difficult and the price is high. It is known that when a filler, particularly titanium dioxide, is added to the base paper, the opacity is improved, but the density rather increases, the rigidity decreases, and the paper strength becomes weaker. Cannot be blended.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a coated paper having a quality that exceeds the grade wall.
Specifically, whiteness, opacity, white paper glossiness, printing glossiness, and rigidity are improved compared to conventional coated paper with the same coating amount as the base paper, and surface strength suitable for printing work is improved. It is to provide a printing coated paper having the same.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, in a coated paper for printing having a coating layer containing a pigment and an adhesive on the base paper, Titanium dioxide is contained as a filler in an amount of 1 to 12% by weight based on the weight of paper, and the volume distribution particle diameter of the coating pigment is 0.1 to 1.0.
It has been found that the subject coated printing paper can be obtained by having a coating layer containing 60% or more in the range of μm, and completed the present invention.

In the present invention, by containing 1 to 12% by weight of titanium dioxide as a filler per weight of paper, it becomes possible to obtain a coated base paper having high opacity.
When a low basis weight coated paper is produced by using a base paper with less than 1% by weight of titanium dioxide as a filler, the coated base paper has a low opacity, and the pulp composition, the calendar conditions, etc. are optimized. However, it is not possible to obtain coated paper with low density and high opacity. 12% by weight of titanium dioxide
When it is added in a larger amount, the number of particles per unit weight increases, interfiber bonding is hindered, and a constant surface strength cannot be maintained even after applying the coating layer.

In the present invention, the coating pigment in the coating layer has a volume distribution particle size of 60% in the range of 0.1 to 1.0 μm.
It is important to include the above. When the volume distribution particle size of the coating pigment is out of this range, the glossiness is poorly developed. The volume distribution particle size of the coating pigment is 0.1
If the amount of the pigment having a thickness of 1.0 μm is less than 60% and the amount of the pigment having a thickness of more than 1.0 μm increases, the glossiness of the coating layer becomes insufficient.

It is generally said that pigments having a small volume distribution particle size tend to exhibit excellent glossiness. When the volume distribution particle size of the coating pigment is smaller than 0.1 μm, the contribution rate of the glossiness to the developability is low. Therefore, the volume distribution particle size of 0.1 to 1.0 μm is less than 60%,
The larger the amount of the pigment smaller than 0.1 μm, the less the development of the white paper gloss and the print gloss.

The papermaking pulp of the present invention preferably contains mechanical pulp in an amount of 10% by weight or more, particularly 15 to 60% by weight. By using one in this range,
Furthermore, it becomes easy to obtain a low-density coated base paper. When mechanical pulp is blended in an amount of less than 10% by weight, it is difficult to obtain a sufficient bulking effect, and even when the filler, calendar conditions, etc. are optimized, the coating is further reduced in density and has high opacity. Getting paper is difficult. Further, as the mechanical pulp, mechanical pulp obtained from recovered waste paper such as used newspapers, used magazines and the like can also be used.

Further, it is desirable to obtain a printing coated paper provided with a coating layer containing 2 to 20% by weight of a plastic pigment with respect to 100% by weight of the coating pigment. 2 to 20% by weight of plastic pigment for 100% by weight of coating pigment
When a coating layer containing it is provided, the glossiness of the coating layer is improved, and even if it is unavoidable to reduce the coating amount by trying to reduce the weight, the glossiness of white paper and printing glossiness is further expressed. It becomes possible to obtain a coated paper having improved properties. 2% of plastic pigment to 100% by weight of coating pigment
In the case of the coating layer containing less than 5% by weight, the effect of expressing the glossiness of the coating layer is low, and it is possible to obtain only the white paper glossiness and the printing glossiness almost equal to those of the coated paper in which the plastic pigment is not mixed. When the amount of the plastic pigment is more than 20% by weight based on 100% by weight of the coating pigment and the coating is applied, the glossiness of the coating layer is high, but the surface strength is low and the blanket is not printed during offset printing. When the ink is transferred, the surface peeling trouble of the coating layer is likely to occur. As for the plastic pigment, the hollow type has better opacity and glossiness than the solid type, and it is preferable to blend the hollow type.

The calendering is preferably carried out with a high temperature calender comprising an elastic roll and a metal roll heated to 150 ° C. or higher. If the water content of the coated paper is appropriate, the higher the metal roll temperature, the lower the nip pressure or the shorter residence time to smooth the base paper or coating layer,
It is possible to obtain glossiness without increasing the density, but 1
If the temperature is lower than 50 ° C, this effect cannot be obtained. When high temperature calendering is performed under the conditions for obtaining white paper gloss and printing gloss obtained using a conventional super calender, that is, by lowering the calender pressure or by high-speed treatment to shorten the residence time, The density of the coating layer and the base paper is low, the opacity is improved, and the rigidity is high. Further, the processing speed is faster than that of the conventional super calendar processing, and the change of the winding frame can be omitted, so that the production can be efficiently performed and the operability is excellent.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Titanium dioxide which is a filler used in the present invention is so-called titanium oxide, and its crystalline form is classified into rutile type, anatase type and brookite type. As titanium dioxide for paper coating, rutile type and anatase type are generally used, but various titanium dioxides are used singly or in a mixture. As titanium dioxide, it is preferable to use rutile type which has a particularly high yield. Further, other fillers such as talc other than titanium dioxide, kaolin, heavy calcium carbonate, light calcium carbonate, titanium oxide, and amorphous silicate may be mixed.

The method for making the base paper is not particularly limited.
Not a thing, long wire machine including top wire, circle
Net machine, two-sided machine, Yankee dryer
Machine, etc. are used to make acidic paper, neutral paper, alkaline paper
Any of the base paper made by the paper method may be used.
It is also possible to use medium-quality base paper containing recovered waste pulp obtained from paper.
Wear. In addition, size press, bill blade, gate low
Using a le coater, pre-metering size press,
Base paper precoated with starch, polyvinyl alcohol, etc.
Or more than one layer of coating liquid containing pigment and adhesive
Coated base paper can also be used. For coating base paper, general coating
The basis weight used for paper is 30 to 400 g / m ^TwoUsing degree
You can However, if the basis weight of the base paper is large,
The effect of the invention is small, and the basis weight of the base paper is 20 to 70 g / m.^Twoof
This is especially effective in the case.

There is no particular limitation on the pigment used in the present invention, and kaolin, clay, delaminated clay, ground calcium carbonate, which are conventionally used for coated papers,
Light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate,
Inorganic pigments such as colloidal silica and satin white, and organic pigments such as plastic pigments, and these pigments can be used alone or in combination of two or more as required. It is preferable to use a plastic pigment having a high hollow ratio and an average particle diameter of 0.6 to 1.5 μm. In the present invention, in order to obtain desired properties such as coating suitability of paint and quality of coated paper, it is usually preferable to use a plurality of pigments in combination. 60 in the range of 1.0 μm
It is important that the particle size distribution contains at least%. The pigment of the present invention is characterized by a particle size distribution, and compared with a commonly used coating pigment, there are many particles having a small particle size, and a pigment having these distributions in advance is selected. Or classified and used as a product within the range specified in the present invention.

There is no particular limitation on the adhesive used in the present invention, and styrene / butadiene type, styrene / acrylic type, ethylene
Vinyl acetate type, butadiene / methyl methacrylate type,
Synthetic adhesives such as vinyl acetate / butyl acrylate-based copolymers and polyvinyl alcohol, maleic anhydride copolymers, acrylic acid / methyl methacrylate-based copolymers, proteins such as casein, soybean protein, and synthetic proteins;
Oxidized starch, positive starch, esterified starch such as urea phosphate esterified starch, hydroxyethyl etherified starch, starches such as dextrin; Adhesion of ordinary coated paper such as cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, etc. One or more agents are appropriately selected for use. These adhesives are used in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the pigment. Further, if necessary, various auxiliaries which are added to ordinary coated paper pigments such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistance agent, and a colorant are appropriately used.

The prepared coating solution is a blade coater,
Bar coater, roll coater, air knife coater,
A reverse roll coater, curtain coater, size press coater, gate roll coater or the like is used to coat both sides of one or more layers on the base paper. The coating amount of the coating layer of the present invention is 5 to 15 per one side in double-sided coating.
g / m ² is preferable in order to obtain sufficient whiteness, opacity, white paper gloss, printing gloss and rigidity.

As a method for drying the wet coating layer, various methods such as a steam superheated cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer and an infrared heater dryer can be used alone or in combination.

In the present invention, after the coating liquid is coated and dried on the above-mentioned coated base paper, it is subjected to pressure finishing with a high temperature calender of 150 ° C. or higher, whereby the effect of the present invention, that is, whiteness and glossiness is further enhanced. A high-temperature soft nip calender capable of high-speed finishing using an elastic roll having a high hardness and a metal roll is suitable for such a calender. In the high temperature soft nip calender, not only the temperature but also the nip residence time are important. From this point, in actual operation, the equivalent roll diameter is 300 mm or more, the Shore D hardness of the elastic roll is 80 to 100 (preferably 85 to 95), and when converted to the equivalent roll diameter of 500 mm, the sheet passing speed is 400 to
It is preferable to perform the treatment at 3000 m / min, a linear pressure of 30 to 500 kg / cm, a calender pre-coated paper water content of 5 to 8%, and a calender nip number of 2 nip or more. The equivalent roll diameter was shown by AVLyons et al. In the following formula (1990 TAPPI F
inishing and Converting, P5) Equivalent roll diameter (equivalen
t diameter). (Roll equivalent diameter) = (Soft roll diameter) × (Chilled roll diameter) / {(Soft roll diameter) +
(Chilled roll diameter)} In the present invention, the basis weight is 80 g.
/ M ² or less, or a density of 1.2g / cm ³ or less of the product is remarkable effect.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples mean parts by weight and% by weight, respectively. The obtained coated paper was tested based on the evaluation method shown below. <Evaluation method> (1) Volume distribution particle size: MALVERN Instrument
The volume distribution particle size was measured by using a Lent Diffraction particle size distribution analyzer manufactured by ents. (2) White paper glossiness: Measured according to JIS P 8142. (3) Printing gloss: Using a RI-II type printing tester, sheet-fed process ink manufactured by Toyo Ink Mfg. Co., Ltd. (trade name T
K high echo red MZ) was printed using 0.30 cc, and after leaving it for 24 hours, the print glossiness of the obtained printed matter was set to J
It was measured according to ISP 8142. (4) Opacity: Measured according to JIS P8138. (5) Density: Measured according to JIS P 8118. (6) Surface strength: Using a RI-II type printing tester, 0.40 cc of a special ink manufactured by Toyo Ink Mfg. Co., Ltd. (product name SMX Tack Grade 15) was used for printing, and then lined, The peeled state was visually evaluated according to the following criteria. ⊚: Very good, ◯: Good, Δ: Slightly inferior, ×: Inferior (7) Stiffness: Measured according to JIS P8143, and evaluated according to the following criteria. ⊚: Very good, ◯: Good, Δ: Slightly inferior, ×: Inferior [Example 1] [Preparation of coating liquid] 100 parts of a pigment consisting of 70 parts of fine kaolin and 30 parts of fine heavy calcium carbonate (volume distribution) 0.2 parts of sodium polyacrylate as a dispersant was added to a particle size of 0.1 to 1.0 μm: 65.0%) and dispersed by a serie mixer to prepare a pigment slurry having a solid content concentration of 70%. did. 4 parts of a hollow plastic pigment, 10 parts of a non-thickening type styrene-butadiene copolymer latex (glass transition temperature 15 ° C, gel content 75%), and hydroxyethyl etherified starch were added to the pigment slurry thus obtained. 6 parts was added and further water was added to obtain a coating solution having a concentration of 60%. [Base paper] Titanium dioxide as a filler is contained in an amount of 4% by weight and talc is included in an amount of 4% by weight, and mechanical pulp is used as a pulp for papermaking in a basis weight of 44 g / m ² as a coated base paper. Using. [Production of coated paper] The above base paper is coated on both sides with a blade coater at a coating speed of 800 m / min so that the coating amount per one side is 8 g / m ² . The paper was dried so that the water content was 5.5%. [Calendar] Next, a roll equivalent diameter of 400 mm, a metal roll temperature of 160 ° C., an elastic roll Shore hardness of 85,
Soft nip calendering was performed under the conditions of a paper passing speed of 650 m / min, a linear pressure of 230 kg / cm and a calender nip number of 2 to obtain a coated paper for printing. Example 2 In Example 1, as the pigment, 100 parts of a pigment consisting of 80 parts of fine kaolin and 20 parts of coarse heavy calcium carbonate (volume distribution particle size 0.1 to 1.0 μm: 80.
0%), 0.2 parts of sodium polyacrylate as a dispersant was added and dispersed by a serie mixer to obtain a solid content concentration of 70%.
%, A coated paper was obtained in the same manner as in Example 1 except that the pigment slurry was prepared. [Example 3] In Example 2, titanium dioxide was used as a filler in an amount of 8% by weight, and talc was included in an amount of 2 parts by weight.
A coated paper was obtained in the same manner as in Example 2, except that a medium-quality paper having a basis weight of 44 g / m ² containing 30% by weight of mechanical pulp was used as the coating base paper. [Example 4] The same as Example 1 except that, in place of the soft nip calender, roll temperature was 70 ° C, 2 nip, calender linear pressure was 200 kg / cm, and paper passing speed was 10 m / min. A coated paper was obtained by the method. [Example 5] A coated paper was obtained in the same manner as in Example 4, except that the pigment slurry was used to adjust the paint without adding plastic pigments. [Example 6] In Example 5, except that a medium-quality paper containing 4% by weight of titanium dioxide and 4% by weight of talc as a filler and 8% by weight of mechanical pulp as a pulp for papermaking was used as a coated base paper. A coated paper was obtained in the same manner as in Example 5. [Comparative Example 1] In Example 1, as the pigment, 100 parts of a pigment composed of 25 parts of fine kaolin, 25 parts of secondary clay, 25 parts of delaminated kucre, and 25 parts of coarse ground calcium carbonate (volume distribution particle size) 0.1-1.0 μm: 52.
2%) to which 0.2 part of sodium polyacrylate as a dispersant was added and dispersed by a serie mixer to obtain a solid content of 70%.
%, A coated paper was obtained in the same manner as in Example 1 except that the pigment slurry was prepared. [Comparative Example 2] In Example 1, a medium-quality paper containing 0.5% by weight of titanium dioxide as a filler, 7.5% by weight of talc and 30% by weight of mechanical pulp as a pulp for papermaking was used as a coated base paper. A coated paper was obtained in the same manner as in Example 1 except that it was used. [Comparative Example 3] In Example 1, except that a medium-quality paper containing 13% by weight of titanium dioxide as a filler, 2% by weight of talc and 30% by weight of mechanical pulp as a pulp for papermaking was used as a coated base paper. A coated paper was obtained in the same manner as in Example 1. The above effects are shown in Table 1. [Comparative Example 4] [Preparation of coating liquid] 20 parts of finely divided kaolin, secondary clay 40
100 parts, 40 parts of fine ground calcium carbonate
Part (volume distribution particle size 0.1 to 1.0 μm: 57.0%)
Then, 0.2 part of sodium polyacrylate as a dispersant was added and dispersed by a serie mixer to prepare a pigment slurry having a solid content concentration of 70%. A non-thickened styrene-butadiene copolymer latex (glass transition temperature 15 ° C, gel content 75%) 1 was added to the pigment slurry thus obtained.
0 part and 6 parts of hydroxyethyl etherified starch were added, and water was further added to obtain a coating solution having a concentration of 60%. [Base paper] A grammage containing talc of 8% by weight as a filler and not containing mechanical pulp as a pulp for papermaking 44 g / m ²
High quality paper was used as the coated base paper. [Production of coated paper] The above-mentioned base paper is coated on both sides with a blade coater at a coating speed of 800 m / min so that the coating amount per one side is 10 g / m2. It was dried so that the water content was 5.5%. [Calendar] Next, roll temperature 70 ℃, 2 nip,
Supercalendering was performed at a calender linear pressure of 200 kg / cm and a sheet passing speed of 10 m / min to obtain coated paper.

The results of the above evaluations are shown in Table 1.

[0022]

[Table 1] As is clear from Table 1, Examples 1 to 6 have white paper glossiness,
It is possible to obtain a coated paper for printing which has an excellent white paper appearance with high whiteness and opacity, a high printing glossiness, and an excellent printed surface feeling. Comparative Example 1 is inferior in white paper gloss and print gloss. Comparative Example 2 is inferior in opacity. Comparative Example 3
Has poor surface strength. Comparative Example 4 has white paper glossiness, opacity,
Inferior in rigidity.

[0023]

EFFECTS OF THE INVENTION According to the constitution of the present invention, an excellent white paper appearance having a particularly high white paper glossiness, whiteness and opacity, and a high printing glossiness and a good printing surface feeling are obtained despite the low basis weight. It is possible to obtain a coated paper that also has a combination.

─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Shinobu Kajiyama 1551 Todaira, Higashimatsuyama City, Saitama Prefecture Higashimatsuyama Works, Nippon Paper Industries Co., Ltd. (56) Reference JP-A-5-148796 (JP, A) JP-A-6-294100 (JP, A) JP 4-370299 (JP, A) JP 9-256296 (JP, A) JP 61-275497 (JP, A) JP 55-163298 (JP, A) Kaihei 7-238497 (JP, A) JP 2000-110093 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (4)

(57) [Claims] 1. A coated paper for printing having a coating layer containing a pigment and an adhesive on the base paper, wherein titanium dioxide as a filler for the base paper is contained in an amount of 1 to 12% by weight based on the weight of the paper, and the volume distribution of the coated pigment is A coated paper for printing, which has a coating layer containing 60% or more of a particle diameter in the range of 0.1 to 1.0 μm. 2. The coated paper for printing according to claim 1, wherein the mechanical pulp in the base paper is contained in an amount of 10% by weight or more based on the weight of pulp. 3. The coated paper for printing according to claim 1, which comprises 2 to 20% by weight of a plastic pigment with respect to 100% by weight of the coating pigment. 4. The coated paper for printing has a metal roll temperature of 15
The coated paper for printing according to any one of claims 1 to 3, which has been treated with a soft calender at 0 ° C or higher.