JP2008196056A - Coated paper using calcium aluminate compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper having high whiteness and glossiness of white paper and excellent coating properties, opacity and aspects of cost. <P>SOLUTION: The coated paper is obtained by using an entirely new pigment represented by calcium aluminate monocarbonate of chemical formula: 3CaO-Al<SB>2</SB>O<SB>3</SB>-CaCO<SB>3</SB>-11H<SB>2</SB>O as a coating pigment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to providing a coated paper excellent in whiteness, white paper glossiness, and opacity by using calcium aluminate monocarbonate, which is one of calcium aluminate compounds, as a pigment for paper coating. Is.

  The expansion of the information society represented by the spread of the Internet in recent years requires a large amount of information for printed matter, and is also becoming more colored and visualized with the improvement of printing technology. Along with this, the demand for coated paper for printing is not only severe, but also various in terms of price, printing workability (suitable for high-speed printing), high quality, light weight, bulkiness, thinning, and the like. In response to this trend, paper manufacturers have classified conventional grades: cast coating, A0 (high quality art paper), A1 (art paper), A2 (high quality coated paper), A3 (high quality lightweight coated paper), fine coating In addition to the increased production of special grades and custom-made products that are not bound by the category of paper, there is a demand for the shift of cast, A0 and A1 users to A2, and the improvement of A2 coated paper quality.

The A2 coated paper, since the paper which has been subjected to essentially about 20-25 g / ^{m 2} of the coating at both surfaces kraft pulp 100% of the base paper, A0, A1 coated paper coating amount than A2 coated paper In many cases, both sides are about 40 g / m ² , while A3 coated paper is less on the both sides, and both sides are about 15 g / m ² . The cast coat is a particularly high-grade coated paper in which one or both sides of A1 and A2 coated paper are further mirror-coated, and is used for the covers of various labels and publications.

  A2 coated paper, which is the middle grade of such a grade, has strong quality requirements similar to A1, has a high-grade feeling, and is typically representatively an improvement in whiteness and gloss. In order to improve the whiteness, on-site measures to deal with them include blending kraft pulp, improving pulp bleaching method, increasing the amount of filler, selecting a filler with high whiteness, increasing the coating amount, whiteness In order to improve glossiness, selection of pigments with high grades, blending of fluorescent dyes, etc., to increase the coating amount, selection of pigments with high glossiness, selection of binders (adhesives) with high glossiness Especially in the super calendar, the number of nips is increased, the line pressure is increased, the speed is decreased, the roll temperature is increased, and a humidifier is installed. However, there are limitations and limitations in terms of price, facility capacity, and quality specifications. Therefore, research is being conducted in various directions.

  As an approach to coating pigments to achieve both high whiteness and high gloss, one or two coating layers containing one or more pigments with a specific particle size are provided, and the particle size of the coating layer is adjusted. A method of proposing slope distribution and optimization is shown. (See Patent Documents 1 and 2) However, this method is a technique using existing pigments and is easy in cost, but it is difficult to expect a large quality change. Several reports using plastic pigments are also shown. (See, for example, Patent Document 3, Patent Document 4, and Patent Document 5) Plastic pigments are relatively new pigments that have light weight and thermoplasticity that inorganic pigments do not have, but they require advanced synthesis techniques and are therefore costly. There are challenges. On the other hand, as a new attempt for inorganic pigments, there has been proposed a blade coating method for hydrous silicate and hydrous aluminum silicate used in ink jet paper and thermal paper for offset printing or gravure printing paper. (See Patent Document 6) The method is interesting as an application example of inorganic pigments, but the raw materials are relatively expensive, that sodium sulfate as a by-product must be sufficiently washed, synthesis efficiency, wastewater treatment, etc. There is still a problem in terms of cost.

  As countermeasures from coating binders, many have devised the thermal behavior of latex. (For example, see Patent Document 7 and Patent Document 8) However, binders are basically obstructive factors in terms of gloss and other color reproducibility during printing, and latex is expensive, so that the strength of the coating layer is allowed. As few as possible is better.

  By the way, as a trend in recent years, development of paper characterized by bulkiness is thriving, and bulky paper is steadily increasing in non-coated paper. This is because the bulky paper can be used to increase the thickness of the book without changing its weight, and therefore the book looks better and meets the new need for a sense of readability. The center of the bulking technology is the good inhibition of the bond between fibers of the base paper, and bulking chemicals for this purpose are sold by various companies. The need for such bulky paper is the same for coated paper, but simply by making the coated base paper bulky, the surface of the base paper is rougher than usual, so there is no coating pigment coverage failure. It is difficult to get the expected specs. (See Non-Patent Document 1)

  As described above, with the conventional technology, there are still problems in terms of cost and performance in order to improve whiteness, white paper glossiness, and opacity at the same time. In addition, new technologies such as bulky coated paper are used. It is difficult to respond to various needs, and the appearance of a new method completely different from the conventional one has been desired.

JP 2006-257581 A JP 2006-132024 A JP-A-2004-091997 JP 2004-076216 A JP 2000-336593 A JP-A-2005-036334 JP H10-168358 JP H07-173793 A 2006 “Paper Technology Association Annual Conference” Abstracts P33-39

  In view of the circumstances as described above, an object of the present invention is to provide a coated paper having high whiteness and white paper glossiness and excellent in covering property, opacity and cost.

As a result of intensive studies on the above-mentioned problems, the present inventor has obtained a completely new pigment represented by calcium aluminate monocarbonate (hereinafter referred to as monocarbonate), chemical formula 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O. They have found that they can be achieved at a high level by using them on coated paper.

Monocarbonate is a crystalline substance having a layered structure and is in the form of a fine hexagonal plate similar to kaolin. Since monocarbonate does not exist in nature and is synthesized by a chemical reaction from slaked lime and aluminum hydroxide, it can be obtained with the highest whiteness without impurities. Monocarbonate has a long history as satin white, 3CaO · Al ₂ O ₃ · 3CaSO ₄ · 31 to 32H ₂ O, and has a very similar chemical formula (composition formula) as a high gloss pigment. It also has the same glossiness and lightness suitability derived from the properties. Incidentally, the true specific gravity of monocarbonate by the pycnometer method is 2.1 g / cc, which is considerably smaller than 2.6 g / cc of kaolin and 2.7 g / cc of calcium carbonate, and the pigment itself is bulky.

  Since the present invention uses a completely new pigment that has not been attempted in the past as a pigment for paper coating, it not only provides a high-white, high-gloss coated paper but also realizes a high-quality bulky coated paper. It is effective for building distinctive products and differentiating quality. Further, the present invention can of course be used for the purpose of reducing the burden on finishing equipment such as a super calendar and a soft calendar and reducing the amount of coating. The reduction in coating amount leads not only to the cost of raw materials but also to the relative increase in dispensing equipment capacity and drying equipment capacity, facilitating speeding up of the coater machine.

  The monocarbonate used as a pigment for the coating layer in the present invention may be any production method as long as it achieves the object of the present invention. The use of monocarbonate produced by a production method characterized by using aluminum hydroxide that has been mechanochemically activated by grinding treatment as described in 209913 is inexpensive in terms of dispersion of particles It is most desirable because of good properties, uniform particle size and aspect ratio.

  The particle size of the monocarbonate obtained by the above method is usually 0.5 to 1.5 μm and hardly aggregates. After production of monocarbonate, after dehydrating and concentrating with the same technique as general light calcium carbonate for coating, it is liquefied again using a powerful shear stirrer with the addition of polyacrylic dispersant, and has a solid content of 50% or more. It is desirable to finish as a high concentration slurry.

  The present invention is characterized in that monocarbonate, which is a completely new pigment, is used for coated paper, and exhibits an effect corresponding to any number of blending parts of 1 to 100 parts with existing pigments. Examples of the existing pigment include kaolin, heavy calcium carbonate, light calcium carbonate, talc, plastic pigment, titanium oxide, aluminum hydroxide, and satin white, and one or more of them may be used in combination.

  As the adhesive used in the coating layer of the present invention, styrene / butadiene copolymer latex and modified starch used for the production of general coated paper are suitable. Either of them may be used, but it is usually better to use them together. Chemically modified starch not only serves as an adhesive, but also has the role of imparting water retention to paints, suppressing migration (inhibiting fluidization), and imparting rigidity to coating layers. Phosphate-starch is suitable for coating. It is also possible to use oxidized starch, etherified starch, enzyme-modified starch and the like. These adhesives are preferably used in an amount of 8 to 15 parts by weight for latex and 1 to 10 parts by weight for modified starch with respect to 100 parts by weight of pigment.

  In the coating material of the present invention, various auxiliary agents such as a dispersant, an antifoaming agent, a water-resistant agent, a water retention agent, a thickening agent and the like are suitably used as in the case of a normal coating paper coating.

  The coating material thus adjusted can be applied in the same manner as ordinary coated paper by various coating methods such as a blade coater, an air knife coater, a roll coater, a rod coater, and a curtain coater. When the coating layer has a multi-layer structure, it is desirable to mix it with the outermost layer in order to efficiently exhibit the optical properties of monocarbonate.

  Other conditions such as base paper conditions, paint concentration, pigment dispersion conditions, coating speed, drying conditions, supercalender or soft calender conditions may be appropriately adjusted within the range of normal coated paper manufacturing conditions. The paint containing the monocarbonate of the invention does not require any special consideration at all, and exhibits excellent effects only when used under ordinary conditions.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the following Example. Unless otherwise specified, “parts” and “%” in the examples represent “parts by weight” and “% by weight”, respectively, and are values in terms of solid content. In addition, it evaluated based on the test method as shown below about a coating liquid and the obtained coated paper.
(Test method)
Whiteness (ISO whiteness): Measured based on JIS P8148.
Blank paper glossiness: measured based on JIS P8142.
Opacity (hunter opacity): Measured based on JIS P8138.
Gloss of printing: Using RI printing tester (manufactured by Meisei Seisakusho), using printing test exclusive ink (manufactured by Toyo Ink, SMX, Red, TV15), printing at a constant 0.5 ml, 30 rpm, temperature 23 ° C, After drying for 15 to 20 hours in an environment of 50% humidity, the measurement was made based on JIS P8142.

[Example 1]
Monocarbonate slurry with a solid content of 57% (manufactured by Kotegawa Sangyo, particle distribution of 0.5 to 1.5 μm), 11 parts of latex (Nipol LX407G: manufactured by Nippon Zeon) and phosphated starch (Star Coat # 16: manufactured by Nippon Shokuhin Kako) ) 3 parts were mixed and mixed with a centrifugal defoaming stirrer to prepare a coating solution having a solid content of 48%. This was coated on one side of a high-quality paper of 85 g / m ² with a wire bar so that the coating amount was 12.5 g / m ² , dried in a shelf dryer at 110 ° C. for 2 minutes, and then subjected to soft calendering. . The elastic roll of the soft calender was rubber, the processing conditions were a linear pressure of 100 kgf / cm, a roll temperature of 150 ° C., a processing speed of 10 m / min, and the number of paper passes twice. The results are shown in Table 1.

[Example 2]
The same procedure as in Example 1 was performed except that the soft calendar process was changed to the super calendar process. The elastic roll of the super calender was cotton, the processing conditions were a linear pressure of 100 kgf / cm, a roll temperature of 60 ° C., a processing speed of 10 m / min, and the number of paper passes twice. The results are shown in Table 2.

[Comparative Example 1]
It carried out similarly to Example 1 except having used the typical fine grain kaolin for paper coating (UW90: Engelhard make, particle distribution 0.2-0.8 micrometer) instead of monocarbonate. The results are shown in Table 1.

[Comparative Example 2]
It carried out similarly to Example 2 except having used the typical fine particle kaolin for paper coating (UW90: Engelhard make, particle distribution 0.2-0.8 micrometer) instead of monocarbonate. The results are shown in Table 2.

[Comparative Example 3]
It carried out similarly to Example 1 except having used the acicular calcium carbonate for paper coating (TP-123: Okutama Kogyo make, particle distribution 0.5-1.5 micrometers) instead of the monocarbonate. The results are shown in Table 1.

[Comparative Example 4]
It carried out similarly to Example 2 except having used the acicular calcium carbonate for paper coating (TP-123: Okutama Kogyo make, particle distribution of 0.5-1.5 micrometers) instead of monocarbonate. The results are shown in Table 2.

From Table 1 and Table 2, the paper coated with monocarbonate is superior in whiteness and white paper glossiness to paper coated with typical existing pigments, and forms a bulky coating layer, which is advantageous for opacity. I know that there is.

Claims (1)

In a coated paper on which a paint mainly composed of a pigment and an adhesive is applied on a base paper, the pigment contains calcium aluminate monocarbonate, chemical formula 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O of 1 to 100 Coated paper, characterized by blending parts by weight.