JP2000345492A - Coated paper for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a coated paper having an excellent white paper appearance with especially a high white paper glossiness, degree of whiteness and opacity and a high printing glossiness and further an excellent printing surface feeling regardless of a low basis weight. SOLUTION: This coated paper has a coating layer containing titanium dioxide as a filler for a base paper in an amount of 1-12 wt.% based on the paper weight and having >=60% of the volume distribution particle diameter of the coated pigment included within the range of 0.1-1.0 μm in the coated paper for printing having the coating layer containing the pigment and an adhesive on the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coated paper for printing, and more particularly to a coated paper having excellent white paper appearance and printability.

[0002]

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

[0003] Among the qualities of coated paper, important ones are whiteness, opacity, blank gloss, print gloss, and stiffness. Whiteness is contrast, opacity is strikethrough,
The glossiness is related to the luxurious appearance of the printed matter, and it is important that these are all satisfied in a good balance. The stiffness mainly relates to the printing workability, and is also an important factor for the page turning property of the printed matter.

[0004] As described above, to reduce the weight, it is necessary to make the base paper a low basis weight and a coating layer having a low coating amount.
However, if the paper is simply made of a low basis weight without changing the composition of the stock, the paper thickness becomes thinner in proportion to the weight reduction, and the opacity and 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 low basis weight,
Opacity and stiffness are rather impractical because they decrease. Conversely, if a low coating weight coating layer is provided on high basis weight base paper,
Although the opacity and rigidity are sufficient, the amount of coating must be reduced more than necessary to reduce the basis weight, resulting in insufficient print quality, which is not practical. Therefore, a certain balance is required between the basis weight and the coating amount, and the low-weight basis paper is a coated layer with a low coating amount and the high-basis base paper is a coated paper with a high coating amount. In general, a low basis weight product is inferior to a high basis weight product in whiteness, opacity, blank gloss, print gloss, and rigidity. Generally, the opacity sharply decreases when the grammage is 80 g / m ² or less. To minimize the decrease in stiffness and opacity even if the basis weight is reduced to a certain extent, use low-density, bulky paper, and use mechanical pulp of a specific tree species such as gumwood, maple, birch Although it is effective, it is not practical to use only specific tree species because of resource saving and cost. However, the use of mechanical pulp for any species is effective for stiffness and opacity. In order to reduce the density and improve the opacity, a hollow synthetic resin capsule is internally added (Japanese Patent Publication No. 52-118116), and a synthetic organic foaming filler (for example, trade name: EXPANCEL, manufactured by Nippon Philite Co., Ltd.) Is known to be internally added and foamed during drying. 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. Also, it is known that the opacity is improved when a filler, especially titanium dioxide, is mixed into the base paper.However, the density is rather increased, the rigidity is reduced, and the paper strength is weakened. Cannot be blended.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a coated paper having a quality exceeding the grade wall.
Specifically, whiteness, opacity, blank gloss, print gloss, and stiffness are improved compared to conventional coated paper with the same coating amount as the base paper, and the surface strength suitable for printing work is improved. The purpose of the present invention is to provide a coated paper for printing.

[0006]

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

In the present invention, by containing titanium dioxide as a filler in an amount of 1 to 12% by weight based on the weight of paper, it is possible to obtain a coated base paper having high opacity.
When a low basis weight coated paper is manufactured by using base paper containing less than 1% by weight of titanium dioxide as a filler, the opacity of the coated base paper is low, and when the pulp mixing and the calendar conditions are optimized. However, a coated paper having low density and high opacity cannot be obtained. 12% by weight of titanium dioxide
If the amount is more, the number of particles per unit weight increases, inter-fiber bonding is inhibited, and a constant surface strength cannot be maintained even after the coating layer is applied.

[0008] In the present invention, the volume distribution particle size of the coating pigment in the coating layer is 60% within the range of 0.1 to 1.0 µm.
It is important that this is included. When the volume distribution particle diameter of the coating pigment is out of this range, the expression of glossiness is deteriorated in any case. The volume distribution particle size of the coating pigment is 0.1 to
The pigment having a thickness of 1.0 μm is less than 60%, and the more pigments larger than 1.0 μm, the more insufficient the glossiness of the coating layer becomes.

It is generally said that pigments having a small volume distribution particle size tend to have excellent glossiness. When the volume distribution particle size of the coating pigment is smaller than 0.1 μm, the contribution to the development of glossiness is low. Therefore, those having a volume distribution particle size of 0.1 to 1.0 μm are less than 60%,
As the amount of the pigment smaller than 0.1 μm increases, the glossiness of the white paper and the glossiness of the print become poorer.

The paper 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 this range,
Further, it becomes easy to obtain a low-density coated base paper. When the mechanical pulp is blended in less than 10% by weight, it is difficult to obtain a sufficient bulking effect, and even when the filler, the calendar conditions, etc. are optimized, the coating with further lower density and higher opacity is obtained. It is difficult to get paper. Further, as the mechanical pulp, mechanical pulp obtained from recovered waste paper such as newspaper waste paper and magazine waste paper can also be used.

Further, it is desirable to obtain a coated paper for printing provided with a coating layer containing 2 to 20% by weight of a plastic pigment with respect to 100% by weight of a coating pigment. 2-20% by weight of plastic pigment based on 100% by weight of coating pigment
When a coating layer including the coating layer is provided, the glossiness of the coating layer is improved, and even when the weight of the coating layer has to be reduced and the amount of coating has to be reduced, the white paper glossiness and the printing glossiness are further expressed. It is possible to obtain a coated paper having improved properties. 100% by weight of coating pigment and 2 parts of plastic pigment
In the case of a coating layer containing less than% by weight, the effect of expressing the glossiness of the coating layer is low, and only a white paper glossiness and a printing glossiness substantially equivalent to a coated paper containing no plastic pigment can be obtained. 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 effect of expressing the glossiness of the coating layer is high, but the surface strength is low, and the blanket is removed from the blanket during offset printing. When the ink is transferred, the surface peeling trouble of the coating layer is apt to occur. As for the plastic pigment, the hollow type is more excellent in expressing opacity and glossiness than the solid type, and it is preferable to mix the hollow type.

The calendering treatment is desirably performed with a high-temperature calender comprising an elastic roll and a metal roll heated to 150 ° C. or higher. If the moisture content of the coated paper is appropriate, the higher the metal roll temperature, the lower the nip pressure or the shorter the residence time, the smoother the base paper or the coated layer,
Glossiness can be obtained without increasing density.
Below 50 ° C., this effect cannot be obtained. When high-temperature calendering is performed under the conditions for obtaining blank gloss and print gloss obtained using a conventional super calender, that is, if the calender pressure is reduced or the high-speed processing is performed to reduce the residence time, The density of the coating layer and the base paper are reduced, the opacity is increased, and the stiffness is increased. Further, the processing speed is higher than that of the conventional super calender processing, and the change of the winding frame can be omitted, so that the production can be performed efficiently and the operability is excellent.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Titanium dioxide as a filler used in the present invention is a so-called titanium oxide, and its crystalline form is classified into rutile type, anatase type and brookite type. As the titanium dioxide for paper coating, it is common to use rutile type and anatase type, but various titanium dioxides are used alone or in combination as appropriate. As the titanium dioxide, it is preferable to use a rutile type having a particularly high yield. Further, other fillers such as talc, kaolin, heavy calcium carbonate, light calcium carbonate, titanium oxide, and amorphous silicate other than titanium dioxide may be mixed.

The method of making the base paper is particularly limited.
Not a thing, fourdrinier machine including top wire, round
Netting machine, machine that combines two people, Yankee dryer
Acid paper, neutral paper, alkaline paper
Any of the base papers made by paper method may be used.
Uses medium-grade base paper containing recovered paper pulp obtained from paper.
Wear. In addition, size press, building blade, gate row
Le Coater, using a pre-metal ring size press
Base paper pre-coated with starch, polyvinyl alcohol, etc.
And, more than one pre-coating coating liquid containing pigment and adhesive
Coated base paper can also be used. As a coating base paper, general coating
The basis weight used for paper is 30 to 400 g / m ²Using degree
Can be However, if the base paper weight is large,
The effect of the invention is small, and the basis weight of the base paper is 20 to 70 g / m.²of
This is particularly effective in the case.

There is no particular limitation on the pigment used in the present invention, and kaolin, clay, delaminated clay, heavy calcium carbonate, and the like conventionally used for coated paper.
Light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate,
These are inorganic pigments such as colloidal silica and satin white, and organic pigments such as plastic pigments. These pigments can be used alone or in combination of two or more as necessary. 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 applicability 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
% Is important. The pigment of the present invention is characterized by a particle size distribution, compared to a commonly used coating pigment, has a large distribution of particles having a small particle size, and selects a pigment having these distributions in advance. Or classified and used as in the range specified in the present invention.

There is no particular limitation on the adhesive used in the present invention, and styrene-butadiene-based, styrene-acrylic, ethylene-based adhesives conventionally used for coated papers are used.
Vinyl acetate, butadiene / methyl methacrylate,
Various copolymers such as vinyl acetate / butyl acrylate and synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer; proteins such as casein, soy protein, synthetic protein;
Oxidized starch, positive starch, urea phosphorylated ester, etherified starch such as hydroxyethyl etherified starch, starches such as dextrin; ordinary adhesives for coated paper such as carboxymethylcellulose, hydroxyethylcellulose, and cellulose derivatives such as hydroxymethylcellulose One or more agents are appropriately selected and used. These adhesives are used in an amount of 5 to 50 parts by weight, more preferably about 10 to 30 parts by weight, per 100 parts by weight of the pigment. If necessary, various auxiliaries to be added to ordinary pigments for coated paper, such as a dispersant, a thickener, a water retention agent, a defoaming agent, a waterproofing agent, and a coloring agent, are appropriately used.

The adjusted coating liquid is supplied to a blade coater,
Bar coater, roll coater, air knife coater,
Using a reverse roll coater, curtain coater, size press coater, gate roll coater, or the like, one or more layers are coated on both sides of the base paper. The coating amount of the coating layer of the present invention is 5 to 15 per side in double-side coating.
g / m ² is preferable for obtaining sufficient whiteness, opacity, blank gloss, print gloss and rigidity.

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

In the present invention, the coating liquid is applied to the above-mentioned base paper, dried and then press-finished with a high-temperature calender at 150 ° C. or higher, thereby further improving the effects of the present invention, ie, whiteness and glossiness. A high-temperature soft nip calender capable of high-speed finishing using an elastic roll having high hardness and a metal roll is suitable as such a calender. In a high temperature soft nip calender, not only the temperature but also the nip residence time is important. From this point, in actual operation, the equivalent roll diameter is 300 mm or more, and the Shore D hardness of the elastic roll is 80 to 100 (preferably 85 to 95).
The treatment is preferably performed at 3000 m / min, a linear pressure of 30 to 500 kg / cm, a calender nip number of 2 nips or more at a calender pre-coated paper moisture of 5 to 8%. The equivalent roll diameter was shown by the following formula by AVLyons et al. (1990 TAPPI F
inishing and Converting, P5) Roll equivalent diameter (equivalen
t diameter). (Roll equivalent diameter) = (soft roll diameter) x (chilled roll diameter) / ｛(soft roll diameter) +
(Chill roll diameter)｝ In the present invention, the basis weight is 80 g.
/ M ² or less, or a product having a density of 1.2 g / cm ³ or less is remarkable.

[0020]

The present invention will be described in more detail with reference to the following examples, but it is needless to say that the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples indicate parts by weight and% by weight, respectively. In addition, the obtained coated paper was tested based on the following evaluation method. <Evaluation method> (1) Volume distribution particle size: MALVERN Instrument
The volume distribution particle size was measured using a Last Diffraction particle size distribution analyzer manufactured by ents. (2) Blank glossiness: Measured according to JIS P8142. (3) Print gloss: Using a RI-II print tester, a 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 standing overnight, the print gloss of the obtained printed matter was J
It was measured based on ISP8142. (4) Opacity: Measured based on JIS P 8138. (5) Density: Measured according to JIS P 8118. (6) Surface strength: After printing with 0.40 cc of a special ink (trade name: SMX Tack Grade 15) manufactured by Toyo Ink Mfg. Co., Ltd., using a RI-II type printing tester, The peeled state was visually evaluated according to the following criteria. ◎: extremely good, ：: good, Δ: slightly poor, ×: poor (7) Stiffness: Measured based on JIS P8143, and evaluated according to the following criteria. ：: extremely good, ：: good, Δ: slightly poor, ×: poor [Example 1] [Preparation of coating liquid] 100 parts of pigment consisting of 70 parts of fine kaolin and 30 parts of fine heavy calcium carbonate (volume distribution) (Particle size: 0.1-1.0 μm: 65.0%), 0.2 parts of sodium polyacrylate as a dispersant is added and dispersed by a Serie mixer to prepare a pigment slurry having a solid content of 70%. did. 4 parts of hollow plastic pigment, 10 parts of non-thickening styrene-butadiene copolymer latex (glass transition temperature 15 ° C., gel content 75%) and 10 parts of hydroxyethyl etherified starch were added to the pigment slurry thus obtained. 6 parts were added, and water was further added to obtain a coating solution having a concentration of 60%. [Base paper] Medium-weight paper containing 4% by weight of titanium dioxide and 4% by weight of talc as filler, and 30% by weight of mechanical pulp as papermaking pulp, and a basis weight of 44 g / m ² as coating base paper Using. [Production of coated paper] The above-mentioned base paper was coated on both sides with a blade coater at a coating speed of 800 m / min so that the coating amount per side was 8 g / m ² , The paper was dried so that the paper moisture became 5.5%. [Calendar] Then, the roll equivalent diameter was 400 mm, the metal roll temperature was 160 ° C., the shore hardness of the elastic roll was 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 nips, to obtain a coated paper for printing. [Example 2] In Example 1, as a pigment, 100 parts of a pigment composed 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 the mixture was dispersed with a serie mixer.
%, A coated paper was obtained in the same manner as in Example 1 except that a pigment slurry was prepared. [Example 3] In Example 2, 8 wt% of titanium dioxide and 2 wt% of talc were contained as fillers per paper weight.
A coated paper was obtained in the same manner as in Example 2 except that a medium-grade paper containing 30% by weight of mechanical pulp and a basis weight of 44 g / m ² was used as a papermaking pulp. Example 4 Example 1 is the same as Example 1 except that the soft nip calender was replaced with a roll calender at 70 ° C., 2 nips, a calender linear pressure of 200 kg / cm, and a paper passing speed of 10 m / min. To obtain a coated paper. Example 5 A coated paper was obtained in the same manner as in Example 4, except that the paint was adjusted without adding plastic pigment to the pigment slurry. [Example 6] In Example 5, a medium paper containing 4% by weight of titanium dioxide, 4% by weight of talc as a filler, and 8% by weight of mechanical pulp as a papermaking pulp was used as a base paper for coating. A coated paper was obtained in the same manner as in Example 5. [Comparative Example 1] In Example 1, as a pigment, 25 parts of fine kaolin, 25 parts of secondary clay, 25 parts of delaminated clay, and 25 parts of coarse heavy calcium carbonate (100 parts by volume) 0.1-1.0 μm: 52.
2%), 0.2 parts of sodium polyacrylate as a dispersant was added and dispersed by a Serie mixer.
%, A coated paper was obtained in the same manner as in Example 1 except that a pigment slurry was prepared. [Comparative Example 2] In Example 1, a medium paper containing 0.5% by weight of titanium dioxide and 7.5% by weight of talc as filler and 30% by weight of mechanical pulp as papermaking pulp was used as a coating base paper. Except for using, a coated paper was obtained in the same manner as in Example 1. [Comparative Example 3] In Example 1, a medium paper containing 13% by weight of titanium dioxide and 2% by weight of talc as a filler and 30% by weight of mechanical pulp as papermaking pulp was used as a base paper for coating. 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 fine kaolin, second grade clay 40
100 parts by weight of pigment 100 composed of 40 parts of fine heavy calcium carbonate
Part (volume distribution particle size: 0.1 to 1.0 μm: 57.0%)
Then, 0.2 parts of sodium polyacrylate as a dispersant was added and dispersed by a Serie mixer to prepare a pigment slurry having a solid concentration of 70%. A non-thickening styrene-butadiene copolymer latex (glass transition temperature: 15 ° C., gel content: 75%) was added to the pigment slurry thus obtained.
0 parts and 6 parts of hydroxyethyl etherified starch were added, and water was further added to obtain a coating solution having a concentration of 60%. [Sheet] as a filler, talc containing 8 wt%, a basis weight of 44 g / m ² not containing mechanical pulp as a papermaking pulp
High quality paper was used as the coating base paper. [Production of coated paper] The above-mentioned base paper was coated on both sides with a blade coater at a coating speed of 800 m / min so that the coating amount per one side was 10 g / m2. It dried so that moisture might be 5.5%. [Calendar] Then, roll temperature 70 ° C, 2 nips,
Supercalendering was performed at a calender linear pressure of 200 kg / cm and a paper passing speed of 10 m / min to obtain a coated paper.

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

[0022]

[Table 1] As is clear from Table 1, Examples 1 to 6 have blank gloss levels,
A coated paper for printing having excellent white paper appearance having high whiteness and opacity, high printing glossiness, and excellent print surface feeling can be obtained. Comparative Example 1 is inferior in blank gloss and print gloss. Comparative Example 2 is inferior in opacity. Comparative Example 3
Is inferior in surface strength. Comparative Example 4 has blank gloss, opacity,
Poor rigidity.

[0023]

According to the constitution of the present invention, in spite of a low basis weight, particularly, an excellent white paper appearance having high blank gloss, whiteness and opacity, and an excellent print surface feeling having high print gloss are obtained. It is possible to obtain a coated paper that has both functions.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Hayasaka 505-1, Pulp-cho, Asahikawa-shi, Hokkaido Nippon Paper Industries Co., Ltd. Asahikawa Mill (72) Inventor Shinobu Kajiyama 1551 Higashidaira, Higashimatsuyama-shi, Saitama Prefecture Nippon Paper Industries Higashi-Matsuyama In-house F-term (reference) 4L055 AC01 AG19 AH01 AH02 AJ04 BE08 BE20 EA16 EA32 GA19

Claims (4)

[Claims] 1. A coated paper for printing having a coating layer containing a pigment and an adhesive on a base paper, wherein titanium dioxide is contained as a filler of the base paper in an amount of 1 to 12% by weight per paper weight, and a volume distribution of the coating pigment. A coated paper for printing, characterized by having a coating layer containing 60% or more in a particle size range of 0.1 to 1.0 [mu] m. 2. The coated paper for printing according to claim 1, wherein the mechanical pulp in the base paper contains at least 10% by weight based on the weight of the pulp. 3. The coated paper for printing according to claim 1, wherein the coating pigment contains 2 to 20% by weight of the plastic pigment based on 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, wherein the coated paper is processed by a soft calender at 0 ° C or higher.